Tag Archives: plum curculio

June 6, 2017 Volume XIII No. 4

Fruit Bud Stages

In the Durham area on June 5th, McIntosh and Cortland apples both had some fruit at 3/4 inch size. Peaches: fruit size 3/4 inch. Blueberries: bloom almost over. Raspberries: bloom. Grapes had flower buds visible, shoots up to 18 inches long.

Apple Scab

The primary apple scab season is over for much of the southern part of New Hampshire. If you are using the NEWA system data from a site close to you, it should predict the end relatively  accurately, provided that you had correctly entered the apple scab biofix (date when 50% of McIntosh buds are at green tip). The primary season ends with the next daytime rain, after all the spores have matured. Ten days after the end of primary season is an excellent time to do a final assessment (we often call it indexing) to see how well you did at managing the primary phase of the disease. All the lesions resulting from ascospore infection should be visible by that time. If you find no or very few lesions, you can relax scab management for the remainder of the season, and focus on bitter rot, flyspeck, sooty blotch and others. If you find a significant number of scab lesions, you may wish to make two back-to-back captan treatments to “burn out” those spore-producing lesions.

As a test, on June 2nd I looked at the NEWA data for Ossipee, and used April 14th as the date of green tip. That is two days later than we observed at the UNH Kingman farm in Madbury, and was my best guess for Ossipee. The model then predicted that all ascospores were mature June 1st, and primary season would end with the next daytime rain after June 1st.

Flyspeck and Sooty blotch of Apple

These “summer diseases” are caused by fungi that grow on the surface of the fruit, and on stems of LOTS of other hosts, including brambles, maples, wild apples & relatives. When the fungi grow on the surface of apples, they create cosmetic blemishes that lower the value of the fruit. So, many growers think about how to manage these fungi. They grow very slowly. The number of hours of leaf wetness after petal fall (I’ll abbreviate that & call it HLWAPF) is a critical measurement in managing the disease. Basically, we need 270 HLWAPF (if you are using old-style leaf wetness equipment) or 200 HLWAPF (of you are using the latest equipment) for each cycle of the fungus to grow and produce spores. We want to apply a fungicide that works on summer diseases at least once every cycle. In the early part of the year, we are usually focusing on apple scab, and often the fungicides we use also control summer diseases. We have the NEWA system to help monitor the weather. If you turn on your computer and visit the NEWA page for the weather station closest to you, it will predict where we are in the Sooty blotch/flyspeck cycle. First, it asks you to confirm the petal fall date for that site. For Durham/Madbury, petal fall on McIntosh was May 21-22. The model said that on June 2nd, we had accumulated 132 hours of leaf wetness after petal fall. If you enter when your last fungicide was, the model will predict the risk level you have for summer diseases. By the way, fungicides that are really effective on summer diseases include materials like Cabrio, Dithane, Flint, Manzate, Inspire, Penncozeb, Polyram, Pristine, Sovran and Topsin-M. Remember to rotate fungicides between activity groups, to reduce the risk of the fungi becoming resistant to the fungicides.

Summer diseases show up especially on varieties that are light, such as golden delicious and gingergold. The growth is less obvious on dark red fruit. A low incidence of these is probably not a problem on pick-your-own blocks.

Got Cherries and Peaches?

I haven’t said anything about cherries this year, because things were so busy on the other fruits we grow. Brown rot can be a serious problem on cherries and peaches, and we have two phases where we focus attention. One is the blossom and shoot phase, mostly passed now. The second phase is attacking the fruit. Fruit become very susceptible as they begin to ripen. A second risk factor (especially for cherries) is splitting and cracking. This opens up infection routes for the fungus to attack. Bird attack also threatens when the fruit turn color. Are your bird protection methods ready?  The time will arrive before you know it.

San Jose Scale   

If you have a block of apples with SJS in them, you’ll probably want to consider making an insecticide application for the crawlers. The timing is important, and we use degree days to predict when the crawlers emerge. The NEWA system doesn’t currently include an SJS model, but it will compute degree days for you. You have to feed it information. It will need to know what base temperature you’re using [50F for SJS]. It will need to know the starting date (“biofix”). That’s when you captured your first SJS male in a sticky trap. Don’t use those traps?  Then substitute the full bloom date. We expect SJS crawlers to appear 310DD after full bloom. Usually that is in mid to late June.

Plum Curculio Time

Plum curculio attack is heaviest from the time apples are 6mm in size, through the next 3 weeks or so. PC is abundant enough and active enough to reduce your apple crop by 75 to 100%, if you do nothing to control it. The early injury (see my photo) looks like tiny c-shaped scars. Soon, the eggs laid in those scars hatch, the larvae bore through the fruit, and the affected fruit usually drop to the ground.

Blueberries: Mummyberry Disease and Fruitworms 

We had really good conditions for primary mummyberry infection this year. The risk of infecting the tiny green berries continues, and can be reduced by fungicide application. When bloom ends is the time to consider an insecticide for cherry fruitworm and cranberry fruitworm, both of which attack blueberries. Many plantings can go without this treatment, but some sites are prone to repeated attack. Both fruitworms are tiny caterpillars that bore inside the fruit. There are other caterpillars that eat the leaves, but most of them occur a little later in the year… usually July or August. One exception (on lowbush fields) is blueberry spanworm, which is feeding now.

Strawberry Clipper in Blackberries

I covered this tiny weevil in the last issue, and pointed out that it was attacking Strawberries and Raspberries. Blackberries are in perfect stage for attack as I write this, and the process is the same. The weevils hit the unopened flower buds. Damage is typically worst at the edges of a bed, especially bordering woods.

 Slime Mold  —  Yuck – In Strawberries

 We have had so much cool, wet weather this year, I’m anticipating that we will see a significant amount of slime mold this year. I hope it will get drier and I’ll be wrong. But in case that’s not correct, I’ll show a photo. Strawberry fields seem especially good places to find slim mold. Maybe it is our use of mulch that helps keep the soil at the right temperature and moisture for slime mold. Whatever it is, slime mold doesn’t actually attack the plant… it just grows over it. Typically it appears as blackish stubble growing on a nice, healthy green plant. It changes/moves quickly. Customers do not like it, and the best advice I can give is to assure them that it is not dangerous, and there’s not much we can do to avoid it.

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.


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.


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.


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.



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.

Apple scab

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.


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


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


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.



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.



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.


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.


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.


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.

ATEApples 2enlarged

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.


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.


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.


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.


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.


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



Alan T. Eaton, Extension Specialist, Integrated Pest Management

Visit the Extension IPM page.

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 13, 2014 – Volume X No. 3

Fruit Bud Stages Now

At the Woodman Horticulture farm in Durham, fruit buds on Monday May 12th were: Pioneer McIntosh Apple: pink. Japanese plums: bloom. Peach: bloom. Blueberry: loose clusters to pink bud.

Rosy Apple Aphid: Look During Early Pink Stage

This isn’t a problem for everyone, but might be a slight concern for a few. One apple variety that we grow is very sensitive to rosy apple aphid: Cortland. If a colony of only a few RAA’s establishes on one or more of the cluster leaves, the fruit in that cluster can be ridged and stunted, sometimes severely. My photo was taken in late August, when that fruit should have been MUCH bigger.


The saliva secreted by the aphids somehow causes this. Leaves also respond to feeding by this species. They strongly curl up, and that makes it extremely difficult to reach them with an insecticide. Do you see the curled up leaf at lower right of the photo below? So, if you have Cortland trees that showed this symptom last year, it might be worthwhile to look for RAA colonies at the late tight cluster or early pink stage.


If you find some, it might be worthwhile to treat your Cortland trees with an insecticide. You recognize the colonies from the curled up apple leaves. Inside each one will be 1 or more aphids. The aphids could be dark green, yellow, powdery blue, or pink. The New England Fruit Management guide has details on insecticide options, but the critical thing (if you decide to treat) is to do so no later than pink stage. After that, the leaf curling is so strong, it encircles and protects the aphid colonies. Below is a photo of one of the aphids in May, after I uncurled a leaf.


Green Pug: Check Apples at Pink Stage

Green pug caterpillars are tiny yellow-green loopers, which sometimes show a red-brown line down the back. They hatch in early spring, and the caterpillars feed on young opening tissues. They strongly prefer to feed on the pistil & style of the flowers, which means you get no fruit from those flowers they attack. They pupate during bloom. The time to search for them is at early pink stage. No one has figured out a threshold for them, so if you find what you think is a significant number of them, you might want to apply an insecticide. Each caterpillar can feed on more than one blossom. The time to spray is during pink stage. I like the idea of using Bacillus thuringiensis-based sprays for this insect, but you could also try Imidan, Calypso, Avaunt, Proclaim, Altacor, or I suppose a pyrethroid (I don’t like recommending them for this). The catch? If you do not have a NH private pesticide applicator’s license, your only legal choice is one of the B.t. products (Dipel, for example). That’s because the name green pug moth doesn’t appear on most labels.


Pink Stage: Key Time for Management of Apple Rust Diseases

We have several types of rust that affect apples, and all of them have two different hosts. The spores from infections on one host infect the other, and vice versa. If you have problem with rusts on apples, 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. I think the “new” 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. If the infection sources are on your neighbor’s property, besides asking if it would OK to remove it/them, maybe you could offer a bribe. How would you like some nice fruit in exchange for cutting down an important source of rust spores?

Exirel: New Insecticide for SWD & Others

Exirel is a DuPont product, just recently registered with the EPA. It is effective on (and registered to control) spotted wing drosophila, and has a unique mode of action. That means it is a strong addition to our SWD arsenal, allowing us to rotate materials between different modes of action, and therefor reduce the risk of SWD developing resistance to any of our insecticides. It is registered for use on many vegetables and small fruits. Looking at the label, I see lots of caterpillars listed, but also aphids and a few beetles (including plum curculio).

Raspberries: Crown Borer Drench

If your bramble planting has been hit hard by crown borer, one option (in addition to destroying nearby unmanaged brambles) is to consider an insecticide drench before bloom. Not too many plantings would need this, but if yours is one of them, timing is critical.

Airblast Sprayer Calibration On Line

George Hamilton has been doing a lot of work on sprayer calibration, and in particular has partnered with Jason Deveau from Ontario Ministry of Agriculture and Food. George suggests that growers visit Airblast 101 to learn more about airblast sprayer calibration. If you follow the link on “new presentations”, you’ll note that George’s presentation is #17 on the list, and there are various others on drift and other aspects of spraying. You can pick & choose from among a wide range of topics, and look at them when it is convenient for you.

Thresholds for Leafminer Traps, Apples

For McIntosh, the threshold for Spotted tentiform leafminers on the red rectangle traps 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. Since we went over threshold at the UNH Woodman farm, we are planning a leafminer spray for the young larvae in 2-3 weeks or so.


When Does Plum Curculio start Attacking Apples?

It is when the first fruitlets are 6mm in diameter; ¼ inch. Until the fruit get that big, they can’t do anything but lurk in the trees, waiting. Odor plays an important role in host-finding for this species, and once there are a lot of small fruitlets, they add their odor to other volatiles released by the bark, twigs and flowers. Many growers delay their “petal fall” insecticide a bit, until this point arrives. If the weather cooperates, that’s great. One negative effect of delaying that treatment is that you’ll get more European apple sawfly [EAS] damage if you delay. For many growers, that’s not a real concern, since EAS injury level is fairly low. In case you forgot what EAS injury looks like, here’s one of my photos. The injury is only skin deep, but is very obvious, and throws that fruit out of the high grades.


Apple Scab

Pink to bloom is when we expect the big spore releases of primary apple scab season. Ascospore maturation is in its rapid phase, and there is usually plenty of tender, exposed tissue available for infection. We had some daytime rain Friday/Saturday, and we should see some daytime rain (and therefor spore release) coming this week. The temperatures may be warm, so that the number of hours of leaf wetness required for infection will be relatively short. I hope you are prepared.


Alan T. Eaton, Extension Specialist, Integrated Pest Management

Visit the Extension IPM page.

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.