Tag Archives: bud stages

May 11, 2017 Volume XIII No. 3

Fruit Bud Stages

In the Durham area, McIntosh and Cortland apple fruit buds were at late pink stage on Monday morning May 8th. A couple of king blossoms were threatening to open. Peaches still had petals… about 70% of the petals had dropped. Blueberries were at pink bud stage. Raspberries have some new primocanes emerging from the ground up to 4 inches high, and the very first flower buds were visible on the bearing canes.

Apple Scab

The largest ascospore releases during primary apple scab season usually occur around the time of pink or bloom. The rate of spore maturation is high then, and we have lots of exposed tissue available for infection. As of Monday May 8, the apple scab model forecasted 66% of the season’s spores were ready for release and 55% had already been released. Meanwhile, any spores that had started new infections this year have grown into lesions that soon will be producing conidia, which are infective spores that get spread by splashing. Conidia can be spread at night, but ascospores only get released by rains that fall during the daytime. You knew that, right?

Monitoring Leafminers in Apple Orchards

Not every apple grower sets out red sticky rectangle traps to monitor leafminer adults. For those who did not use the sticky traps, there is another way to monitor leafminer populations. It involves looking at the undersides of leaves, for the sap-feeding mines. You have to wait until about a week or so after petal fall for the mines to show up. They remain in this stage for perhaps a week to 10 days. So I’m showing this photo now, since I might not have a newsletter issue that comes out right at that time. Turn the leaf over and look at the undersides. Sap feeding mines show up as slightly silvery areas. Basically, the miners have severed the lower epidermis from the spongy palisade layer of the leaf. If you see 13  or more mines out of 100 CLUSTER leaves, it is worthwhile to apply an insecticide to control them.  Once the miners get bigger, they begin feeding on the spongy layer in little clusters. That creates spots that soon become visible on the upper side of the leaf. That signals the end of the period when the caterpillars are vulnerable to insecticides. By the way, in this photo I see 4 sap-feeding mines on the same side of the mid-vein as my thumb. In real life, tilt the leaf a bit, if you are unsure. Another trick is to use a pin or knife tip to try & peel away the epidermis. The tint, translucent caterpillar should be there somewhere.

Tent Caterpillars and Gypsy Moths

Both of these are common backyard tree fruit pests that are easily controlled if you act early. The larger the caterpillars get, the more damage they have already done, and the harder they are to control. There are actually two species of tent caterpillars, forest tent caterpillar and Eastern tent caterpillar. Both are easily controlled with Bacillus thuringiensis-based insecticides, but could use synthetic chemicals too. Not only are they easier to control when small, they have also done less damage then.

Gypsy moth is usually held in check by an insect-killing fungus. But the southeastern part of our state has experienced drought the last two growing seasons, so gypsy moths are building up there. Gypsy moths are tougher to kill with B.t.- based insecticides, but they work if the caterpillars are small… perhaps shorter than 1 inch. By the way… B.t.-based materials must be sprayed on the leaves the caterpillars eat. They do not work by contact action. Most chemical insecticides work both ways… both as stomach poisons and as contact poisons.

Insect Pest Activities in Apples During Bloom

Adults of codling moth begin laying eggs about the time of full bloom to petal fall. That’s also the same time that males of San Jose scale do their flying. Since a couple people are trying pheromone traps to monitor SJS this year, I include this old drawing of a male from a USDA bulletin over 70 years ago. They are only 1 millimeter (1/25 inch) long. For those of you monitoring SJS with these traps, the number of males you find is not very important. It is WHEN they appear, so I’d check my traps every day or two. That starts the clock ticking to predict crawler emergence by calculating degree days. What else is happening then?  Eggs of European apple sawfly are beginning to hatch. Lesser appleworms should start flying. Plum curculios should start moving into orchards, if the weather is favorable. They won’t begin attacking the fruit until the first fruit reach ¼ inch size. Then, they attack heavily, usually for about 3 weeks. They can totally eliminate your crop.

Mummyberry Disease of Blueberry

The fungal cups that I showed in the last newsletter produce ascospores that are released in rainy weather and infect young blueberry leaves. Now it is time to show the next part of the cycle. Those primary lesions (photo below) produce fungal spores that are splash spread and infect the green fruit. At first, there is no outward sign that the fruit are infected. But eventually they start turning a salmon color, and then start becoming ridged, like a pumpkin, and drop to the ground. The fruit stay on the ground all season, becoming black, dry and ridged. Then the following spring, fungi grow from them and the cycle repeats.

Blueberry Pollinators and “Cheaters”

Since the large carpenter bee reached New Hampshire a few years ago, we have seen more blueberry corollas with holes in the base. What’s going on?  Large carpenter bee has strong jaws, and often chews a shortcut to reach the nectar. That means that it doesn’t really contribute much to pollination, when it does this to reach nectar. Other bees don’t seem to do this. What can you do about it? Probably nothing, so don’t worry. Carpenter bee looks just like several species of large bumble bees (which are good blueberry pollinators by the way) except that it has a SHINY black abdomen.

Strawberry Clipper

This tiny (2mm long) weevil is also known as strawberry bud weevil. It overwinters as an adult, and usually appears in May, just as the first fruit buds of its major host plants (strawberries, raspberries and blackberries) are appearing. The female beetles attack the unopened flower buds by laying an egg inside. Then they sever the petiole, and that bud will never produce fruit. Damage is typically worst at the edges of a bed, especially if woodland is on that side. Sometimes we can see a significant amount of injury, and in other spots or other years, there is very little. If you look at the New England Small Fruit Management Guide, you’ll see a sampling procedure and thresholds to help you determine if it is worthwhile to treat a bed for this insect. It is worthwhile to do the monitoring, rather than guessing if there will be a problem… or just automatically treating.

Organic Weed Control in Lowbush Blueberries

My colleague Olivia Saunders finished a SARE grant on this subject, and recently placed a report you could read, if you’re interested. Bill Lord assisted setting up this project, which especially focused on poverty grass. Here is a link to that report https://extension.unh.edu/resources/files/Resource006566_Rep9432.pdf

We thought that lowbush people might like to learn more, so Olivia has set up a meeting at a lowbush site in Milton, on May 31st. See the UNH Cooperative Extension events calendar for more details.

Raspberry Fruitworm

Do you ever find a small, tan, segmented “worm” in the raspberries you picked? Those are most likely raspberry fruitworms. Usually they are not a significant problem, but in some plantings there are a lot of them… enough to discourage customers. The problems from this insect begin early, and the adults are tiny (3mm) oval, tan beetles. They are active on opening raspberry and blackberry vegetation, and sometimes they chew up the opening fruit buds. If you see what you think are a significant number of them, you might consider applying an insecticide before bloom to kill them. After bloom, the females lay eggs inside the green fruit. The eggs hatch into the segmented tan larvae, which feed on the receptacle. When the ripe berry is picked, the larva often ends up inside.

Alan T. Eaton
Extension Specialist
Integrated Pest Management

UNH Cooperative Extension programs and policies are consistent with pertinent Federal and State laws and regulations, and prohibits discrimination in its programs, activities and employment on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sex, sexual orientation, or veteran’s, marital or family status. New Hampshire counties cooperating.

April 18, 2017 Volume XIII No. 2

Fruit Bud Stages

In the Durham area, McIntosh and Cortland apple fruit buds are mostly at half inch green stage, with a few buds still at quarter inch green. Peaches are at pink stage, with a few buds still at half inch green. Blueberry fruit buds have loose scales, with one variety at early tight cluster. Raspberries show ½ to ¾ inch of growth from the fruit buds.

Apple Damage Photograph

The photo used for the header in this year’s newsletter shows a certain type of injury to apples. Can you tell what it is?  I’ll reveal the answer later in the season.

Tarnished Plant Bug

A few growers still monitor for tarnished plant bug, using the white sticky rectangle traps (still available from Great Lakes IPM). The traps can tell you whether or not it is worthwhile to apply an insecticide for this insect. Place the traps at knee height, towards the tip of a low branch. Yes, that’s at KNEE height. The trap should be over a grassy (not bare) part of the orchard floor. I tend to hang them relatively close to the orchard periphery, but that’s not essential. When?  Hang at silver tip stage. Then you check them weekly and count (then remove) any tarnished plant bugs you catch. Some growers use these to compare differences block-to-block. I’d expect more TPB injury in a block that was adjacent to hay fields or clover, compared to one that was surrounded by woods.

There are several thresholds. For people with a strong market for #1 fruit (like pick-your-own growers), it is worthwhile to apply an insecticide for TPB if the cumulative catch (from silver tip to tight cluster stage) per trap is 5.5 or more by the time of tight cluster. If you haven’t reached that threshold by TC stage, keep the traps up and check again at late pink stage. The cumulative threshold from ST to late pink is 8 or more per trap.

If you are aiming for extra fancy fruit, the threshold is from ST to TC is 3.5 per trap, and ST through late pink is 5 per trap.

Identifying the insects: tarnished plant bugs are 3/16 inch long, with long, thin antennae. Overwintered adults are dark brown. The body is shield-shaped.

Monitoring Leafminers in Apple Orchards

We have two species of leafminers that are difficult to tell apart… apple blotch leafminer and spotted tentiform leafminer. Both can cause premature fruit drop, usually just as you are setting out bins in your McIntosh block. McIntosh is the variety most sensitive to this injury. We can monitor populations of these leafminers by two methods: red sticky traps or counting the tissue-feeding leaf mines. If you choose to use the traps, they need to go up soon. The red sticky traps are available from Great Lakes IPM www.greatlakesipm.com I’d place them in blocks where leafminers have been a problem in the past. Attach one at knee height to the south side of the tree trunk. Some growers use a stapler for this, while I use four push pins. When do you set them up?  Do this at green tip stage. Sometimes you can delay until ¼ inch green. The moths start emerging just after QIG stage, and you check the traps weekly for the tiny moths. Don’t check your traps over a longer interval than 1 week, or the insects will turn black and you won’t be able to identify them. Count and remove the moths each week. The moths are almost 2/16 inch long, with dark silvery marks on white, elongated wings.

In a McIntosh block, the threshold is 3-4 moths or more by early pink stage. In all other varieties, the threshold is 6-8 or more by early pink stage. If the leafminer population is below the threshold, I suggest that you NOT spray an insecticide for them.

These thresholds tell you IF it is worthwhile to apply a leafminer treatment. WHEN you treat is up to you. You have 2 generations that could be targeted, with multiple windows of opportunity before mid-summer. Generally, treating for the first generation is more effective than the second, because it is more synchronous than the second. I NEVER recommend treating for the 3rd generation, because it is too late to prevent the fruit dropping, and the third leafminer generation is heavily parasitized by tiny wasps.

Winter Moth

Winter moth eggs hatch when the buds are opening, and the tiny caterpillars sometimes balloon into the edge of your orchard or blueberry planting, from adjacent oak or other trees. They are not very difficult to control, but timing is important. If your blueberries/apples are in the seacoast region, you have a greater risk of a problem than people who are located farther inland in New Hampshire. Make a note on your calendar to check for these insects, especially at the edges of your planting.

Eastern Tent Caterpillars

Eastern tent caterpillar eggs are in a shiny mass that usually encircles a twig. I rarely see them in conventional commercial orchards, but they are very common in organic blocks and backyard trees. Apples, cherries, peaches and pears seem to be the most frequently attacked. The insects are easy to control (even with Bacillus thuringiensis), unless you wait until they are huge. For many years I could accurately say that they hatched about April 15th. In recent years, it has been significantly earlier. The tiny caterpillars feed on the leaves, and begin to construct a silk tent in a nearby crotch. In most orchards, they are controlled by insecticides directed at other insects. If you see the egg masses before they hatch, you can avoid damage to your tree by removing and burning the egg masses. Just peel them off the twigs. My photos show an egg mass in early March and some very young ETC caterpillars in April.

Apple Scab

The biofix (starting point) for the apple scab fungus spore maturation model is when 50% of the McIntosh buds have reached green tip stage. Really early in the season, there is relatively little host tissue that is exposed, and a small % of the season’s supply of spores that are ready for release. As the season progresses, more vulnerable tissue is exposed. Typically we have the largest spore releases around the period of pink or bloom stage. Then, the primary infection season winds down, often in early or mid-June. It ends because the ascospore supply gets exhausted, and the dead apple leaves from last year are breaking down. But the lesions that result from primary infection enlarge and start producing infective spores called conidia, which get spread by rain splashing. So we can have many cycles of the disease by the time the season ends. If growers get through primary season with few or no lesions, they can relax spraying quite a bit (for scab anyway) after that.

So, we are at the beginning of primary scab season, and growers need to think about if & when to apply a protectant fungicide. We want to apply the fungicide long enough before a rain so that the residue dries onto the leaves and fruit. Then, rain can come after that, and the fungicide can protect from any rain that falls. Generally, a good protectant fungicide that is allowed to dry onto the foliage will protect for 7 days, no matter how much rain falls. Occasionally we get real deluges that test this theory. There are also “eradicant” fungicides that can be applied after a rain, and they can stop an infection even up to X hours after the rain started. In some cases X is as high as 48 hours!  Of course, these tools are usually more expensive than the protectant fungicides. It is nice to know that they are available, so if your sprayer breaks down at a critical time, an eradicant fungicide can serve as a safety net.

As of Monday April 17, 4% of the season’s supply of ascospores were ready for release in the Durham area.

Peach Leaf Curl

It is too late to control peach leaf curl this year. You’ll have to live with it.

Cedar-Apple Rust and Quince Rust

In the last issue, I showed a photo of the galls on a red cedar tree during the quiet winter. Once spring arrives, things start to change. During rainy weather, orange, fleshy telial horns project from the galls, and release the telial spores that infect apple foliage. One co-worker said the galls looked like bright orange Christmas ornaments. I thought that was a good description. The very first spore releases are around the time of tight cluster stage, and the major releases are at pink and bloom period. Quince Rust shows a similar pattern, though the galls (which are on common juniper) are difficult to spot. They are swellings in the juniper branches. To me, they are almost impossible to find, except when the fleshy orange telial horns are projecting. This photo shows them on a common juniper in Durham, on a rainy May 9th morning, 2013.

There are three ways to fight rust diseases on apples. One is to grow varieties that are not very susceptible to them. Another is to apply protectant fungicides during the period when spore releases are likely to occur. A third way is to remove all alternate hosts within 500 feet or so of your apples. With the exception of rusts that attack apple fruit, I don’t see enough injury to worry too much about them. The bright orange spots on apple leaves are easy to identify as rust lesions.

Mummyberry Fungus

Blueberries get attacked by fungi, too. The most serious disease I see is mummyberry, and the tiny fungal stipes should start growing from last year’s mummified berries (on the ground) soon. They begin as a dark brown stalk. Then the tip swells slightly, and a dimple appears at the tip, so it looks a bit like the head of a finishing nail. Then the tip expands still further into a tiny mushroom, and the color is light brown. These are the source of the spores that infect shoots this spring.

We manage mummyberry with several methods. One method is to bury last year’s mummies with at least 2 inches of mulch. That can be difficult to do if you have a large planting. You have to be sure you finish applying the mulch before green tissue appears (= before spores start getting released).

Another method is to apply a burning agent (urea) when the fungal stipes have started elongating, but before the fungal cups have opened. A third method is to apply protectant fungicides. For some growers with very small plantings, there is another option: Collect and deeply bury all fruit affected by this disease. The New England Small Fruit Management Guide has details on all of these options.

2017 Fruit-Related Events:

There are many events that might be of interest on our events calendar. Some events require registration or have fees, so you can see more details on our  events calendar.

Alan T. Eaton
Extension Specialist
Integrated Pest Management

UNH Cooperative Extension programs and policies are consistent with pertinent Federal and State laws and regulations, and prohibits discrimination in its programs, activities and employment on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sex, sexual orientation, or veteran’s, marital or family status. New Hampshire counties cooperating.

 

May 25, 2016 Volume XII No. 3

 Fruit Bud Stages

In Durham and Madbury, McIntosh apple buds were at fruit set on Monday May 23rd. Blueberries were in bloom. Raspberries had many flower buds visible, but unopened.

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Apple Scab

We usually expect the primary apple scab season to start winding down now, but will not end for a while… probably early June. It is a good time now to do a check for apple scab lesions, and it would be very important to do that again about 10 days after primary season ends. The 10 days allows enough time for the latest lesions to become visible.

Weather Data, Prediction Models

Although the riskiest time for fireblight has ended for some NH orchards, I’ll give links I have been mentioning at twilight meetings and orchard visits. They can help with a number of pest events. One is Glen Koehler’s Orchard Radar. This link takes you to the radar page, and there may be sites relatively close to you that are worth checking out. Groton Massachusetts or Sanford Maine may be relatively close to some NH growers.

A second source of information is NEWA, the Network for Environmental and Weather Applications. We have one NH orchard with a NEWA station, Brookdale in Hollis. You can view the data and predictions for fireblight, (and apple scab, curculio, potato late blight and lots of other pests). Look at the map, and enlarge it to find the icon for Hollis, then clicking on it to get predictions for that site. If you’re far from Hollis, another option (maybe not quite as accurate) is to click on an icon for a nearby airport, on the NEWA map. Eventually we hope to have more NEWA sites in NH. Funding for some of that equipment is anticipated soon. We’re still waiting to hear on a second grant proposal.

Plum Curculio: Most Important Apple Insect Pest?

Plum curculios overwinter as adults, in leaf litter in the woods. They become active about when apple blocks are in bloom. They heavily depend on odor to find apple trees. Once there, attack must wait until the fruit reach 6mm in size. Then the females cut a shallow curved scar into the fruit, and lay an egg under the flap. Fruit that are attacked usually drop to the ground, and in some spots there are enough curculios to attack nearly 100% of the crop. The larva hatches from the egg and tunnels through the fruit. When mature, it drops to the ground and pupates in the soil.

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The attack period generally lasts about 3 weeks, but in sites with lots of nearby wild apples, it can extend longer. Basically, we use insecticides to control this insect. The insecticides are harmful to pollinators, plus parasites and predators of leafminers, aphids, caterpillars and mites. If we can minimize spraying, it helps preserve populations of these beneficial organisms and save money.

One way to minimize spraying is to wait to apply the first one until just before the first fruit reach 6mm size. Another option is to time your applications with the aid of a degree day model. My colleagues in New York developed one that some NH growers find useful… and others say it doesn’t work so well for them. It says to keep apples protected through 340 degree days (base 50) after petal fall. [By the way… petal fall in Durham was Friday May 20th. Did you write down your PF date?] We expect that some pesticide residue will continue to control them for a little while past that. This model doesn’t work too well in blocks with a history of heavy, long-lasting pressure. I would not rely on it completely, but it might help you determine when you can stop. In most blocks, three weeks after the first fruit reached 6mm size, there should be no significant immigration of new adults, and spraying can cease.

The insecticides we target for curculio also control the first generation of several other fruit-attacking insects: codling moth, lesser appleworm, and redbanded leafroller. They also control insects that rarely are a problem in commercial blocks, but can be serious in backyard trees: tent caterpillars, gypsy moths, winter moth, green fruitworms. The most effective for curculio: probably (alphabetically listed) Actara, Avaunt, Calypso, Imidan, Leverage and Voliam Express. The last two are combination products. For backyard growers, Sevin is probably the best alternative, in part because it is packaged in appropriate sizes. All-purpose fruit sprays are too drastically diluted to control curculio. For organic growers, Surround is the best choice, but it has to be applied very carefully to work properly. That means you need several thorough but dilute applications. Surround doesn’t kill them. It just interferes with their host recognition (and thus, attack).

European Apple Sawfly

This is now a relatively minor pest, but fruit that are attacked have a long, curved scar that greatly reduces the fruit’s value. EAS adults emerge from the soil during pink stage. The females are very active in the flowers during bloom. That’s when they insert their eggs singly into the tiny fruitlets at the calyx end. In a few orchards, growers have enough trouble with this insect that they apply an insecticide at pink to control it, knowing that the first curculio spray will also help. But in blocks that have varieties with a range of petal fall dates, that curculio spray is slightly late to stop some EAS damage. My data shows that the incidence of EAS injury at harvest in NH (25 year average) has been below 3/10ths of 1 percent… so not very serious.

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Blueberries: Mummyberry and Fruitworms

Blueberry growers take note: the fungal stipes of mummyberry fungus should be releasing ascospores now during rainy periods. The spores infect tiny opening blueberry leaves, where the fungus grows and produces conidia. The conidia are splash-spread spores, and they infect the fruit, while it is still green. At first, infected fruit are symptomless, but when ripening time arrives, they turn tan and shrivel up. Some of our varieties that are especially susceptible to the disease are Bluecrop, Blueray, Earliblue, Jersey and Berkeley.

We have two species of fruitworms that attack blueberry. One is called the cherry fruitworm, and the other is cranberry fruitworm. I see a lot of highbush plantings, and in a few of them there is enough fruitworm attack to consider an insecticide treatment. In most, the attack rate is so low, the cost of treatment is probably higher than the value of the damage it would prevent. If you do decide to apply an insecticide, the timing is right after bloom ends. Usually one treatment is enough. It is designed to kill the just-hatched caterpillars.

Clipper in Brambles and Strawberries

Strawberry bud weevil is also known as “clipper”, because it attacks the unopened flower buds of brambles and strawberries, then chews off the buds in which it laid an egg. There is only 1 generation per year, and they overwinter as adults. When flower buds are present but unopened (= NOW), that is when this insect attacks. Attack rate is usually the highest in the edges of the fields, and lower in the interior of the plantings. In strawberries there are thresholds established, and you can read about them in the New England Small Fruit Management Guide. Thresholds have not yet been determined for brambles. Notice in my blackberry photo that all of the brown fruit buds are the ones that have been attacked, and are dangling.

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Alan T. Eaton
Extension Specialist
Integrated Pest Management

The University of New Hampshire Cooperative Extension is a public institution with a longstanding commitment to equal opportunity for all. It is the policy of UNHCE to abide by all United States and New Hampshire state laws and University System of New Hampshire and University of New Hampshire policies applicable to discrimination and harassment. It does not discriminate on the basis of race, color, religion, sex, national origin, age, veteran’s status, gender identity or expression, sexual orientation, marital status, or disability in admission or access to, or treatment or employment in, its programs, services, or activities.

 

May 3, 2016 Volume XII No. 2

 Fruit Bud Stages

In Durham and Madbury, McIntosh apple buds were in late tight cluster stage on Monday May 2nd.  Almost all of our peach buds appear dead.  Blueberries are at pinkbud stage.  Raspberries and thornless blackberries are still ½ to 1 inch of growth from the buds.

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Apple Scab

We are at the part of the season when we normally expect high numbers of ascospores to be ready for release, and there is a lot of susceptible apple tissue. That makes it a high risk period for apple scab. The spring has been fairly dry, and that might affect ascospore maturation, but for now, I’d assume the risk is high, whenever that next daytime rain falls.

Fireblight

As we approach the bloom period, remember that warm (60F or higher) rains when flowers are open means high risk for fireblight. We had a number of NH orchards with LOTS of FB strikes last year, so there is potential for a lot of inoculum being present. Remember that there are a couple of sources that run weather models to predict fireblight risk. It may be worthwhile to check these sites as we approach & enter the high risk time for FB. One is Glen Koehler’s Orchard Radar. There may be sites relatively close to you that are worth checking out. Groton Massachusetts or Sanford Maine may be relatively close to some NH growers.

A second source of information is NEWA, the Network for Environmental and Weather Applications. We have one NH orchard with a NEWA station, Brookdale in Hollis. You can view the data and predictions for fireblight, (and apple scab, curculio, potato late blight and lots of other pests) here. Look at the map, and enlarge it to find the icon for Hollis, then clicking on it to get predictions for that site. If you’re far from Hollis, another option (maybe not quite as accurate) is to click on an icon for a nearby airport, on the NEWA map. Eventually we hope to have more NEWA sites in NH. Funding for some of that equipment is anticipated soon. We’re still waiting to hear on a second grant proposal.

Thresholds for TPB and Leafminers in Apples

If you have a good market for #1 fruit (like pick-your-own blocks), then the threshold for tarnished plant bug in apples is a cumulative catch of 5 TPB’s caught per trap from silver tip to tight cluster stage. If  tight cluster stage comes and you still have not reached the threshold, look at the traps again at pink stage. A cumulative average of 8 or more per trap by pink would warrant control. For apple growers who aim to produce extra fancy apples, the thresholds are a cumulative catch of 3 per trap (ST to TC) and 5 per trap (ST to pink).

I’m happy that many apple growers don’t bother to spray for TPB any longer. Once bloom arrives, there’s no point to spray for TPB.

Leafminers: The red rectangle traps are very effective to predict whether or not you need an insecticide this year for these pests. Please remember they tell IF you need to treat. You’ve got a wide window for timing sprays if they are needed. The threshold varies with apple variety, because apples vary in their likelihood to drop fruit just before harvest, in response to leafminer damage. For McIntosh, it is a cumulative catch of 4 or more moths from quarter inch through tight cluster stage. For other varieties, the threshold is 9 or more moths, because other varieties are much less sensitive to leafminer damage. Now back to my point about when to treat. Some insecticides would be aimed at the eggs or very young larvae. They’d go on at pink stage. Examples: Esteem, Intrepid, Aza-direct, Assail. Others would be applied a while after petal fall, when sap-feeding stage of miners are visible. Examples: Altacor, Belt, Calypso, Lannate, Leverage, Proclaim…

There is another monitoring option. You could wait and count the sap-feeding mines shortly after petal fall. This is a trickier monitoring method than using the sticky red rectangle traps. Starting about 5 days after petal fall (try again 5 days later if find no mines) you examine the UNDERSIDES of CLUSTER leaves. You look for a slightly silvery patch on the leaf undersides. That’s where the tiny caterpillars have separated the lower epidermis layer from the internal spongy layer of the leaf. If you find 13 or more mines out of 100 leaves, it is worthwhile to treat for leafminers. I’ll show my sap-feeding mine photo now, but it should be a while before they appear.

 Green Pug Moth in Apples: Maybe a Bad Surprise?

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The caterpillars of green pug moth are tiny yellow-green loopers that start feeding on expanding tissue soon after the buds open. The older ones often have a red-brown stripe down their backs. Normally a little foliage feeding would not be too bad. But as soon as the flowers open, the caterpillars feed on their most preferred tissues: the pistils of the flower buds. Chomping down the pistil results in no fruit from that bud. Sometimes the caterpillars are in very high numbers, and in other blocks (or years) they are in very low numbers, and do no significant injury. No one has determined how many caterpillars it takes to warrant a spray, but we do know a simple way to check: at pink stage, firmly tap the branches with flower buds over a white inverted frisbee or pie plate. Check a number of spots and see if you find what you think are significant numbers. If you find enough to worry you, apply an insecticide right away… before bloom. A few New Hampshire growers have had bad surprises in recent years. My photos show the technique (above) and the tiny caterpillar (below).

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Rosy Apple Aphid Can Harm Cortland Fruit

If you have a lot of Cortland apples, it is worthwhile to check those trees at pink stage, to see if you have many colonies of rosy apple aphid. As the aphids feed on leaves, the leaves begin to curl up. Quickly they curl so tightly that they protect the colony from pesticides. As the insects keep feeding & growing, they produce a toxin that stunts the growth of the apple(s) adjacent to that spur. Affected fruit are puckered, and often are not marketable. The vast majority of varieties are not susceptible to the damage. Why check at pink stage? That’s the last opportunity to hit them with an insecticide, before leaf curling proceeds too far. Rosy aphids can appear yellowish, but older ones are pinkish or purple with a powdery exterior. The photo that shows one just starting to turn powdery was taken in early May, while the red ones were photographed in July. When you check, search for curled leaves. THRESHOLD??

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Pink Stage is an Important Time for Apple Rust Diseases

Rusts are fungi that have two different species as hosts, and keep switching from one to the other. Galls or lesions on host 1 produce spores that infect species 2, and simultaneously, spores from species 2 infect species 1. We have several types of rust that affect apples. If you have problem with them, and have not been able to eliminate the nearby sources of spores, remember that the pink stage is usually when a significant number of infections occur. Cedar-apple rust usually hits apple foliage, while quince rust can affect the fruit. Japanese rust primarily hits apple foliage. Red cedar and some other junipers are key hosts. Even a tiny red cedar tree can produce enough spores to create problems. During rainy periods in the spring, the galls swell, and orange, fleshy telial horns appear. They are the source of the infective spores. I’ve got photos from previous years here. The round gall was on red cedar and is from cedar-apple rust. The other photo shows branches of common juniper, with slightly swollen spots from which long telial arms have appeared. They are from quince rust. The spores get released during rainy periods. My neighbor thought they looked like orange Christmas tree ornaments.

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 Mummyberry

Blueberry growers take note: the fungal stipes of mummyberry fungus should be releasing ascospores now during rainy periods. The spores infect tiny opening blueberry leaves, where the fungus grows and produces conidia. The conidia are splash-spread spores, and they infect the fruit, while it is still green. At first, infected fruit are symptomless, but when ripening time arrives, they turn tan and shrivel up. Some of our varieties that are especially susceptible to the disease are Bluecrop, Blueray, Earliblue, Jersey and Berkeley.

Pollination Time for Apples, Blueberries

Many commercial orchards in New Hampshire bring in honeybee hives for pollination. To get the most out of them, here are some points. Honey bees require fairly warm temperatures (60F or higher) for foraging. If there is much of a breeze, foragers huddle close to the ground, or in other sheltered spots. If the wind picks up, honey bee foraging stops. Rain stops honeybee foraging, too. Apple blossoms have a relatively high sugar concentration in their nectar, so they are readily pollinated. Pear nectar has much less sugar, so it is really difficult to attract honey bees to pollinate them, especially when there are other choices, like dandelions in the orchard floor.

Put hives in groups across the orchard, rather than set them all at one end. Place hives on pallets or boards, rather than directly on the ground. This reduces the chances of cool water soaking into the bottom, cooling & slowing down activity. Try to put them in sheltered spots, out of the wind. If you can, place them facing southeast or east, so the morning sun warms it up early in the day.

It has been pretty dry this spring. If there is no clean water within a hundred yards of the hives, consider placing shallow trays of water nearby, with rough pine boards in them (drinking bees can grip well & not fall in).

We are lucky. In many New Hampshire orchards there are lots of native bees, and they pollinate the crop well by themselves (no need to introduce honey bees). We have over 120 species of them in NH. Most live singly, not in nests with hundreds of companions. A few (bumble bees for example) live in nests with a few—perhaps as many as a couple dozen — in a colony. Many of our natives fly in relatively cool, even wet weather. If you have active bees that are not honey-colored, they may very well be natives. Please remember that significant pollination from native bees requires nesting habitat in or close to the orchard. So it pays to protect that habitat. Some bees nest in tunnels in stems, stumps and twigs. Many bumble bees nest in old chipmunk, mouse or vole nests. About 70% of our native bees nest in the ground. Most of them prefer bare, undisturbed soil to dig their nest tunnels.

 

Alan T. Eaton
Extension Specialist
Integrated Pest Management

The University of New Hampshire Cooperative Extension is a public institution with a longstanding commitment to equal opportunity for all. It is the policy of UNHCE to abide by all United States and New Hampshire state laws and University System of New Hampshire and University of New Hampshire policies applicable to discrimination and harassment. It does not discriminate on the basis of race, color, religion, sex, national origin, age, veteran’s status, gender identity or expression, sexual orientation, marital status, or disability in admission or access to, or treatment or employment in, its programs, services, or activities.

May 19, 2015 – Vol. XI No. 4

Bud Stages

On Monday May 18th, McIntosh apples in Durham & Lee were at bloom stage. Peaches and blueberries: also in bloom. Kilarney Raspberries: flower buds were visible but not open.

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In the southern half of New Hampshire we are in the rapid ascospore maturation phase now. Some places (like Durham) have had no daytime rain for quite a while. When we do get daytime rain, we should see major spore releases, even in spots that did get rain on May 12th, 13th or 16th. Be sure your trees are protected with fungicides.

In the southern half of New Hampshire we are in the rapid ascospore maturation phase now. Some places (like Durham) have had no daytime rain for quite a while. When we do get daytime rain, we should see major spore releases, even in spots that did get rain on May 12th, 13th or 16th. Be sure your trees are protected with fungicides.The Durham area had spotty light drizzle in late morning on the 16th. It should have triggered the release of ascospores, but probably dried too quickly to cause infection. At those temperatures, we need 7 to 8 hours of leaf wetness to cause infection, and things dried much faster than that.

Fireblight

Temperatures in southern NH on Tuesday 19th are predicted to be in 60’s and 70’s when the rain comes. If your orchard is also in bloom, that is a high risk situation for orchards that either have FB in orchard or within 1 mile of the orchard this year. As last week, caution is advised for those where there is no active FB this year, but did have strikes in the last 2 years (or within 1 mile).

Cedar-Apple Rust

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May is the month when the galls of cedar apple rust (on red cedar trees) release a lot of their spores. This happens during rainy periods. The telial arms on the galls expand, and turn orange & fleshy, almost jelly-like. By June, tiny orange spots appear on foliage where infections were initiated. The disease requires that both hosts [apple and red cedar] be present and relatively close to each other. Spores from the lesions on apple foliage infect red cedar, and vice versa. Even a very small, wimpy red cedar sapling is enough to keep the disease cycle going in your orchard. If you remove all of the red cedars within 500 feet of your apples, the cycle stops. Are the red cedars on your neighbor’s property? Maybe he/she will agree to have the tree cut down. Maybe a bribe of some fresh fruit would help.

Bird Repellant: Fogging

One of our alert apple growers asked me about a product whose name was somewhat new to me: Avian Control. The active ingredient has more than one chemical name. I know the active ingredient as methyl anthranilate, the artificial grape flavor we have seen used before as a taste repellant to be sprayed on certain plants. The label also lists the active ingredient by another chemical name: methyl 2-aminobenzoate. The product is registered in NH, and the label includes an application method I had not noticed before: using a fogger to send a fog of methyl anthranilate into flocks of birds that are in or on buildings, on (non-fish-containing) water, on in vegetation. I don’t know how many growers have thermal or mechanical fogger equipment, or ULV spray applicators, but they would be necessary to get the tiny droplet sizes required for fogging. Such equipment is regularly used for mosquito spraying. I’m guessing that inhaling the fog is not pleasant for the birds, and they leave immediately. I’m guessing it is not intended to leave a residue. But it might still have relatively long lasting effects, because birds remember negative experiences, and change their behavior (go elsewhere).

White Apple Leafhopper on Apples

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Occasionally this insect is a pest in apple orchards. It overwinters as eggs laid in the twigs. If you had problems with it last August or September, it is worth checking those blocks for the insect this spring. Checking is simple. About 4 to 6 days after petal fall, go to the blocks where you had a problem last year, and search the undersides of CLUSTER leaves, in a number of trees. Search for the tiny, elongated leafhopper nymphs. They can’t fly away, because they don’t have wings yet. Just-hatched ones will be almost transparent, perhaps 2mm long. Older ones will be yellow-green and a bit larger. If you find 25 or more, out of 100 cluster leaves, it is worthwhile to treat them with a leafhopper insecticide. They remain vulnerable to sprays for a couple of weeks, so if you are planning to use Sevin as a thinner, it will also control the leafhoppers. There are quite a few insecticide options listed in the 2015 New England Tree Fruit Management Guide.

There is more than one generation per season, and this first one is the easiest to control, since it is fairly synchronous. Later on, the insects are really spread out in age. Typically, if you need to treat now (and do so), the insects don’t build up to high enough numbers to require treatment later this year. The significant problems come later in the season:  stippling the leaves, dropping brown poop splatters on fruit (and anything else underneath), and flying in the faces of pickers, annoying them and slowing their work.

Don’t confuse WALH with a second leafhopper that we have, called potato leafhopper. That one overwinters along the Gulf of Mexico, and migrates back to New England each year. In some years we have a lot of them, and few in other years. They damage shoots, suckers and water sprouts. They can stunt the growth of young trees, but are rarely a problem on mature trees.

Plum Curculio

Once apple fruitlets reach 6mm in diameter (that’s ¼ inch) they are vulnerable to attack by plum curculio. That insect typically attacks for 3 weeks, sometimes longer, and it has the ability to remove most of your crop if you let it. Insecticide options are listed in the New England Tree Fruit Management Guide. My photos show a fruit cut open to reveal the curculio egg laid under the flap.

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Strawberry Bud Weevil a.k.a. Clipper

This tiny weevil (1/16 inch long) overwinters as an adult, and should be appearing in your plantings shortly. It attacks strawberry, raspberry and blackberry flowers when the flower buds are visible but have not yet opened. They are worst at the edges of plantings beside woods or shrub borders. The females lay an egg in a flower bud, then clip it and move on to another. The clipped buds drop to the ground, and the tiny larvae grow inside each one. Eventually a weevil emerges from each one, in mid-summer. Some varieties of strawberries can compensate quite a bit for clipped buds by making the remaining fruit grow larger. Others have moderate or no ability to compensate. Insecticides are recommended as controls, and the New England Small Fruit Management Guide lists the sampling methods & thresholds to determine if it is worthwhile to treat your plantings. Although I see some strawberry beds with significant injury, I see more in brambles, probably because growers don’t think to check them. We have not developed sampling methods & thresholds for brambles.

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Alan T. Eaton
Extension Specialist
Integrated Pest Management

April 28, 2015 – Vol. XI No. 3

Bud Stages

On Monday April 20, almost 50% of the McIntosh apple buds in Durham/Lee were at silver tip and 50% were at early green tip. Peach buds were almost all dead. Blueberries were all swelling. Raspberries showed about ¼ to ½ inch of growth. On Wednesday 22nd, McIntosh buds in Derry & Londonderry were mostly at ¼ inch green stage. There were lots of peach buds swelling.

On Monday April 27th, 95% of McIntosh apple fruit buds in Durham/Lee were at the half-inch green stage.  There were many more live peach buds than I thought earlier.  Blueberry buds were swollen (tight scales), and raspberries showed ½ to 1 inch of growth from the buds.

Setting up Traps for TPB & Leafminers in Apples

If you monitor tarnished plant bugs in your apples with white sticky rectangle traps, the time to hang them up is at silver tip stage. If you have passed that stage, it is too late to get an accurate assessment of TPB numbers. The traps are mimics of a cluster of opening foliage (works on the TPB’s anyway), so they should be hung towards a branch tip. Also important: hang them at knee height, over a grassy (not bare) part of the orchard floor. IMG_1769

Are you monitoring leafminers? The red sticky rectangle traps for those go up at ¼ inch green stage. They get stapled to the south or southeast side of the trunk, at knee height. As with TPB traps, you check them every week and write down the numbers caught. I’ve had growers ask me if they could stretch out the interval, and check after 10 to 14 days. I don’t recommend that, because the trapped insects gradually turn black, and get very difficult to identify if they’ve been caught a long time.

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Recognizing the catch is relatively easy for both. Leafminer moths are narrow, about 3mm long (slightly over 1/16 inch). Their wings are bright silvery white, with dark markings. Overwintered tarnished plant bugs are dark, almost black, and shield-shaped. They are 4 to 5mm long (almost ¼ inch), with long, thin antennae.

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Threshold for TPB’s in Apples

If you have a good market for #1 fruit (like PYO blocks), a cumulative catch of 5 TPB’s caught per trap from silver tip to tight cluster makes it worthwhile to spray. If you haven’t reached threshold by tight cluster stage, wait and look again at pink stage. A cumulative average of 8 or more per trap by pink would warrant control. For apple growers who aim to produce extra fancy apples, the thresholds are a cumulative catch of 3 per trap (ST to TC) and 5 per trap (ST to pink). Many apple growers don’t bother to spray for TPB any longer. I think that’s great!!

Threshold for Leafminers on Apple

The traps are very effective to predict whether or not you need an insecticide this year for these pests. Threshold varies with apple variety. For McIntosh, it is a cumulative catch of 4 or more moths from quarter-inch through tight cluster stage. For other varieties, the threshold is 9 or more moths, because other varieties are much less sensitive to leafminer damage.

Insecticide Options for Leafminers on Apples

Once you have determined that you do need to control leafminers this year, There is a really wide range of insecticide options & times.

1) Insect growth regulators (Esteem and Intrepid for example) are most effective on eggs and very young larvae, so if you need to spray, and wanted to use them, spray at late tight cluster (pre-pink) or pink stage. Organic growers don’t usually have leafminer problems, but if they do, Aza-direct is OMRI listed, and would be used then.

2) Vydate is an organophosphate insecticide, rough on beneficials, but effective on leafminers. The preferred timing for that would be at pink, because spraying Vydate soon after pink can cause erratic fruit thinning.

3) Materials that are effective on the young larvae (sap-feeders) come next. That should be soon after petal fall. Proclaim is one example. You use it with a surfactant, and it has some translaminar (foliage penetrating) action. Exirel is a new one that would be used at that time. Gladiator and Tourismo are both relatively new combination products that would be used then. The Voliam flexi and Actara labels have similar language — apply right after petal fall. Other labels say just during the sap-feeding stage, so that could be a little bit later (watch for signs on your leaves). Agri-Mek, Altacor, Assail, Belt, Calypso, Delegate, Lannate, Leverage, Provado, Entrust and SpinTor are in this category. Some Insecticides require a surfactant or horticultural oil be added to the tank, to penetrate properly and be effective. Be sure to check the labels!! Agri-Mek, Delegate, Agri-Flex and SpinTor are in this group that need to be tank mixed with a surfactant or oil.

4)  We have a number of pyrethroid insecticides that also work on leafminers. I believe they affect adults (or eggs, if you have high enough gallonage to hit them), not the immatures, which are inside the leaf layers. Pyrethroids (in general) are quite persistent and broad spectrum, so they can be very harmful to beneficial insects. I downplay them as an option for leafminers. Examples include Asana, Baythroid, Delegate, Warrior.

Label language: Avaunt is registered to suppress leafminers, which to me means it doesn’t work too well. Watch out for this phrase. Repeat sprays: If you apply an insecticide for this generation of leafminers, you should need only one treatment. If you treat (correctly) for the first generation, it would be rare to require a leafminer treatment later in the season. Later in the season, if you do find out that you need to treat for leafminers, generally it would take two applications to provide control, while controlling this first generation would require only one.

Apple Scab Update — Cheryl Smith

SARE project collaborators are still monitoring ascospore maturity in New England. Massachusetts people are doing petri dish and squash mounts (a graduate student project). In New Hampshire and Maine, spore trapping is going on [MacHardy, Smith, Schneider]. We will know the actual start and true end of the ascospore season. In Durham on April 20th, 45% of the McIntosh buds were at green tip stage. By April 22nd, it was probably over 80%.

There is now a NEWA weather station in Hollis. The model says there was an infection period Monday-Tuesday. It was wet long enough, though cool. Only 3% of the ascospores were mature, but we don’t know how many (if any) got released. In Durham, there were none trapped. The Durham weather station showed 39 Apple scab ascospore degree days accumulated since 4/15, but the 15th was before our biofix. Soooooo, very southern NH may have had an infection period. The scab model on the NEWA website (for Hollis NH) estimated 3% of the ascospores were mature, and we had an infection period then. It predicts 15 days (after the Mon-Tues wetting period) for any symptoms to show up. If you have blocks of apples that you are SURE have very low inoculum (urea spray, leaf-chopping, or passed a PAD count in the Fall) you don’t need to worry about a few percent of spores being mature (prob. below 8-10%). But, if you’re not sure, it would be wise to be covered before the next significant rainfall (the next infection period). If you are beyond green tip stage and are not covered, it may be good to apply a kickback fungicide. Check Alan’s Fruit pest update telephone (862-3763). I or Bill MacHardy or Deb Schneider will be giving spore maturity info.

Cedar-Apple Rust — Cheryl Smith

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We had lots of cedar-apple rust [CAR] in 2014, with great jelly horns visible. So far, no horns are visible on galls, but they will begin releasing spores soon (during rainy periods), through May. Leaf spots should be visible by June. Some varieties are really susceptible, such as Braeburn, Fugi, Gala, Ginger Gold, Golden Delicious, Idared, Mutsu, Rome, and others. Remember that the best management practices for CAR are to grow resistant varieties, and separate apples from the alternate hosts, redcedar.

Oil for Red Mite Eggs

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The easiest time to smother mite eggs with oil is when they are respiring the most rapidly. That occurs just before they hatch, so the ideal time on apple is during the tight cluster stage. In the past I’ve shown tentative sampling procedures and thresholds for ERM eggs in early spring. But I’ve found no one that used them. I’ll offer some added, easy guidance: If you have a block where your pruning gloves got orange streaks after handling the branches, that’s a block to be sure you treat with oil. Some growers have so much acreage to cover, that they have to begin before TC stage. You want to get this treatment done before pink stage, because that’s when the eggs start hatching, and the motile mites can just walk out of the oil.

Be careful about temperatures, when applying oil on apples. Try to apply it when the temperature won’t dip down into the 30’s within 24 hours of application. Also, don’t mix it with Captan, and don’t use Captan as the next fungicide after applying oil. Getting Captan and oil too close (or mixing them) results in brown phytotoxic spots on the foliage.

Winter Moth Update

There is very little risk of winter moth injury here in NH, except in southeast Rockingham County. But we do have another species that is very closely related, with nearly identical biology, which hybridizes with winter moth. So you might experience problems from a very early season, green looper that chews holes in foliage. Damage is worst on oaks, maples, blueberries and sometimes apple, especially bordering woods. The moths lay eggs in late fall and early winter, in bark crevices of trees. Winter moth eggs hatch very early, as buds are swelling and beginning to open. One odd quirk: the (orange) eggs turn blue just before they hatch!  When we see problems, it is usually due to a gradual buildup, rather than sudden appearance of a problem. Yes, chemical insecticides work on the caterpillars, but so do biological insecticides like those based on the caterpillar strains of Bacillus thuringiensis. Trade names include Dipel, Biobit, Deliver, Javelin. Timing? Often that’s pre-bloom.

Stem Galls on Blueberry

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I received these galls just after the last newsletter was issued. They were created last year, by a wasp named Hemadas nubilipennis Ashmead. No, there is no common name, but you could call it blueberry stem gall wasp, and entomologists and blueberry growers would both understand you. I see these mostly on wild and backyard blueberry bushes. The adults are tiny black wasps, and they fly in June or early July. If you see old galls in mid-summer, with tiny holes in them, the wasps have already emerged. If there are really high numbers of galls on a bush, they can reduce fruit production. That is rare, by the way.

In my backyard, I prune these out during the dormant season, and burn them. If you see low or moderate numbers of them, I wouldn’t worry. The species is heavily parasitized by other wasps, and that may be one reason that I rarely see high numbers of these galls.

Girdled Grapes

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I pruned my grape vines before the snow had fully melted. A week later the rest of the snow melted, and revealed that both vines had been girdled by voles over the winter. I asked George Hamilton if some latent buds might break below the girdle point, and save the vines. He said that might happen, so I’ll wait and see. In the meantime, there is a lesson. Meadow voles are the most common cause of this girdling, and two things made it more likely for this problem to occur. One was that I did not keep the weeds down under these vines. The other is that the previous owner had piled small rocks (4″ to 9” in diameter) under the vines and bordering the entire garden. I guess this was to create a visual border. Meadow voles really like both situations, because they get protected from most of their enemies by thick grass or weeds, and rock piles. When the snow fully melted, I found a vole nest only 3 feet from one girdled grape vine, and another nest 5 feet away. I suppose I could have installed vole (“mouse”) guards of ¼ inch mesh hardware cloth around each vine. But George sent me photos of one vineyard where the girdling was very high on the plant. It would have been difficult to construct guards to prevent that. My future efforts will be on removing the rock piles, and keeping weeds controlled or mowed.

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Brown Rot on Stone Fruit — Cheryl & Alan

Brown rot hits our stone fruit, and is most favored by rain and cooler temperatures during bloom. Removing mummies from the trees will help in managing this fungal disease. Insect control can help, too, by eliminating insect injury on the fruit as a point of entry for the fungus.

Alan T. Eaton
Extension Specialist
Integrated Pest Management

May 28, 2014 – Volume X No. 4

Fruit Bud Stages In Durham

At the Woodman Horticulture farm in Durham, fruit buds on Monday May 26 were: Pioneer McIntosh Apple: fruit set. Japanese plums: fruit set. Peach: petal fall. Blueberry: bloom.

Apple Scab

In Durham, we are at the end of the rapid maturation phase of ascospore development, and now spore maturation slows down as we enter the final phase. Cheryl Smith did squash counts on May 28th in Durham and found 17% of ascospores were immature; 12% were mature, and 71% had already been released.  These figures might be off a bit, since some of the empty asci shrivel and are difficult to spot. Also, some of the “immature” spores will never finish development.

The apple scab degree day models for Durham as of the morning of May 28th show 730 DD accumulated; equivalent to about 94% spore maturation. Cold temperatures and daytime rain are forecast for today, and warm temperatures & showers are predicted Friday May 30th, and possibly Saturday 31st. Primary apple scab season will be over soon. Remember that it takes 10 days (longer in cold temperatures) for infections to become visible on the leaves.

Plum Curculio Injury

Expect plum curculio injury to begin any time after the first apple fruitlets reach 6mm (1/4 inch) size. They may enter the orchard before that, but can’t begin fruit attack until then. If we have warm temperatures (70F or higher), that really helps kick-start activity, and if we have a warm night (70F or higher) with rain, that really gets them going, too. Typically they stay active for about 3 weeks, but that varies. Some spots have lots of wild apple trees nearby, and thus have a longer PC risk period than average. A few lucky spots have slightly shorter period of activity. Some growers look at nearby unsprayed apples, to see if they have fresh PC scars. I have a close up photo of really fresh injury, to help. Notice that the cut is slightly curved, about 2 – 3mm long. If it is really fresh, then there is no discoloration or healing of the exposed surface.

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My colleagues in New York developed a predictive model to tell when to apply last PC spray: keep apples protected through 340 degree days (base 50) after petal fall. We expect that some residue will continue to control them for a little while past that. This model doesn’t work too well in blocks with a history of heavy, long-lasting pressure. I would not rely on it completely.

For conventional growers, the most effective PC insecticides: Actara, Avaunt, Calypso, Imidan, Leverage and Voliam Express. The last two are products that combine two different insecticides. For backyard growers, Sevin is the best material that is available and packaged in backyard-garden sizes. Most backyard fruit spray mixtures are much too diluted to control plum curculio. For organic growers, Surround is the best choice, but it has to be applied very carefully to work properly. You start right at petal fall, and make a dilute, thorough application. You don’t want bright white splotches on the leaves, separated by gaps. You want a very thin, translucent coating. Then you apply another perhaps 2-3 days later. Good protection starts with the second or third application, provided rain doesn’t wash everything off. Surround doesn’t kill PC’s… it just stops them from attacking. That means the attack period is longer than with conventional insecticides… about a month.

Caterpillars Inside Apple Fruit

Codling moth and lesser appleworm are two species that bore inside the fruit. They are both common here. Look at fruit from wild trees, and you’ll find plenty of examples. In most New Hampshire commercial apple orchards, these two species plus redbanded leafroller (feeds externally on the fruit) are controlled by insecticides directed at plum curculio and apple maggot. All three caterpillar species have two generations per year here. The first generation is usually well controlled by our curculio sprays, except in some organic orchards. If a Bacillus thuringiensis-based spray is used, the timing for CM and LAW is 2-3 days after fruit set. Often, a second treatment is required perhaps 5 days later. These usually work well on redbanded leafroller and various foliage feeders: tent caterpillars (a bit late for them), white-marked tussock moth, green fruitworms and gypsy moths too.

The second generation is more likely to be troublesome, partly because it is not as synchronous as the first. For either generation, a hole in the fruit, together with some fine dry brown frass is a likely sign of attack. CM seems to prefer to attack via the calyx end (as in my photo), while the others are a bit more variable in their attack sites. Telling the larvae apart usually requires a microscope. One fairly reliable sign: if the caterpillar fed on the seeds, it is likely to be codling moth.

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In June, you might find a fruit with European apple sawfly larva inside. They look a lot like caterpillars (read below).

European Apple Sawfly

In the last issue, I showed injury from the first instar of European apple sawfly (EAS). It has the classic curved shape, beginning at the calyx end of the fruit. The adult sawfly flies during bloom, and lays her egg in the calyx. The tiny larva hatches a few days later and feeds just barely below the skin of the fruit for several days. That makes the long, curved scar. Next, it usually moves to an adjacent fruit and bores a hole inside. That’s where it completes its feeding for a couple weeks. Fruit infested with these later stage larvae have an orange stain and messy, wet reddish-brown frass coming from the hole. The fully grown larvae drop from the fruit during the last days of June, and overwinter in the soil.

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Although the larvae look like caterpillars, you can tell them from caterpillars by counting legs and body segments. Behind the head are three body segments (the thorax), each of which has a pair of legs. That’s true for both caterpillars and sawfly larvae. But here’s where it is different. In caterpillars, the next two body segments behind the thorax NEVER have legs attached. In sawflies, either one of those segments, or both of them have a pair of legs. My photo of a nearly mature EAS larva is below. Because of the way it is curled up, it is a little difficult to count the legs, but it is the best I’ve got.

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Before I move on to insecticides for EAS control, I’ll answer another common question. How do I tell EAS larvae apart from plum curculio larvae? It is easy. PC larvae have no legs.

The insecticides that control most European apple sawflies are applied at or right after petal fall. If the material is sprayed right at petal fall, it stops the first instar larvae so quickly that there are few or no long, curved scars. If the grower decides to delay the petal fall spray, to wait until fruit have reached 6mm size (therefor aiming primarily at plum curculio), then the EAS larvae aren’t killed until after they have made their curved scars. More growers seem to be delaying the spray, and accepting a little bit of EAS injury now, hoping to control curculio with fewer sprays. In most sites, that seems to be a good decision, since I find well under 1% of the fruit at harvest with EAS scars.

White Apple Leafhoppers — Check Soon After Petal Fall

White apple leafhoppers lay their eggs in the fall, inside apple twigs. The eggs hatch at petal fall. Three to five days after petal fall is a good time to search for the just-hatched nymphs. If you had any spots in the orchard with WALH problems last year, you may want to check (especially those hot spots) before you plan to spray for plum curculio. If you find 25 or more nymphs on 100 leaves, it is worthwhile to apply an insecticide for leafhopper. Some insecticides will get both WALH and curculio.

To check, look at the undersides of CLUSTER leaves. Leafhopper nymphs are translucent when first hatched, and after a couple of days begin to look greenish yellow.

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Blueberry Pollinators and Cheaters

Blueberry flowers have long, narrow corollas, so bees that want to reach the nectar need long tongues. Some species “cheat” and cut a hole through the side of the corolla, therefor bypassing the anthers, and not helping to pollinate that blossom. I understand that some carpenter bees do this, but there may be others as well.

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Strawberry Clipper Also Attacks Bramble Fruit

Strawberry bud weevils, a.k.a. “clippers” attack strawberries, raspberries and blackberries. The tiny female weevils search these plants when the flower buds have appeared but have not yet opened. When they find a suitable one, they lay an egg inside the bud, then sever it at the pedicel. The buds sometimes dangle for several days before they drop off.

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Inside each attacked bud is a tiny egg that hatches and the tiny legless larvae feed for a couple of weeks, then pupate inside the bud, like in my photo. Later in the summer, the adult weevils emerge, leaving a hole in the dropped buds on the ground. They feed for a while before preparing for winter. There is only one generation per year, and the attack period is May to early June. Flowers that appear in July, August or September are not attacked.

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I have not seen any threshold published, to tell us how many clipped buds, or how many active adults per row foot make it worthwhile to spray for clipper on brambles. I have noticed that damage can be severe, especially on blackberries. I find that it is often worse on rows that border brush or woods. When the fruit buds appear, they are vulnerable to clipper until the flowers open. Checking just before the first flowers open is a good time… you could apply an insecticide (if you wished) before pollinators started visiting.

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On strawberries, thresholds are listed in the New England Small Fruit Management Guide. In strawberry beds, usually clipper damage is less severe on new beds, compared to older ones. As in brambles, it is usually worse in the rows next to woods or fallow fields. Some strawberry varieties have been shown to compensate for clipper damage by having the remaining fruit get larger. Unfortunately, most varieties haven’t been evaluated for this trait, so we only know about a few. Varieties that compensate well (therefor clipper damage isn’t much of a problem): Jewell and Senecca. Primetime and Lateglow are varieties that compensate somewhat, so clipper can be more of an issue. Cavendish, Earliglow, Honeyoe and Northeaster show no compensation for clipped buds.

Updated Directories from NH Department of Agriculture, Markets & Food

Gail McWilliam-Jellie just advised me of their recently updated directories, now available:

Harvest Your Own and Farm Stand

She says, “These do not include every farm that could possibly be listed, but includes a fair representation. We would like to make this as comprehensive a list as possible and can add farms at any time. We welcome you to spread the word among the farms you work with about the directories and the opportunity to be listed (for free). We will be promoting these throughout the season through various channels, so it’s another marketing avenue for the participating farms.”

Farm Stand and/or Harvest Your Own Sign-up Form

“Additionally, our 2014 Summer Season Farmers Market Directory is also on line. The directory currently has about 2/3 of the markets that were operating last year. Frequently, market contact information changes from one year to the next and the new year sign-up doesn’t get to the right person. If you don’t see markets from your area on the list. Please pass this on to the market organizers so we can make this as complete a list as possible.”

2014 Summer Season Farmers Market Directory

Market Registration Form

 

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Alan T. Eaton, Extension Specialist, Integrated Pest Management

Visit the Extension IPM page.

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