Tag Archives: Leafminers

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.


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.


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.


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


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


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


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


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.


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