July 1, 2015 Volume XI No. 5

Apple Summer Diseases

The group of diseases that include flyspeck and sooty blotch we refer to as “summer” diseases of apple. One thing we know about them is that the number of hours of leaf wetness after petal fall (we abbreviate this HLWAPF) is a critical factor in growth of the fungi that cause the diseases. Each cycle of the fungus requires 270 HLWAPF to complete. That is a lot of leaf wetness, but recently we have been experiencing wet weather, so we are probably getting closer to the 270 total. We want to apply a fungicide that works on summer diseases at least once during every 270 HLWAPF cycle. In Durham, petal fall was May 21st. When our leaf wetness equipment is working again, I hope to give you some figures. What fungicides are most effective to control these diseases? Cabrio, Flint, Inspire, Luna, mancozeb (Dithane, Manzate, Penncozeb), Polyram, Pristine, Sovran, Topsin-M.

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Potato Leafhopper

This species overwinters along the Gulf of Mexico, and flies back north every year, aided by westerly winds. The feeding damage from this insect is quite different from its close relative, white apple leafhopper. On apple, PLH strongly prefers to feed on shoots, suckers and watersprouts. The saliva it injects during feeding causes the edges of leaves to yellow, then turn brown, and then the leaf forms a cupped shape. The saliva ends up stunting the shoots, too. This isn’t a big problem on mature trees, but can be bad for young trees growing their scaffold branches for future crown development and bearing. PLH creates the same cupping and leaf necrosis on other plants it attacks, including alfalfa, potato, basil, beans, raspberry, cantaloupe. There are a few potato leafhoppers present now.

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Terrestrial Snail… Potential New Hampshire Fruit & Ornamentals Pest

My introduction to this problem came from my former colleague, Dr. John Weaver, now working for APHIS outside of New England. He asked if Cepaea nemoralis [a.k.a. banded garden snail or grove snail] was known to fruit pest management people here. He suggested it had potential as a serious ornamental & fruit pest. I looked into it and found that this foreign species was already established at multiple sites in the Northeast. Next I learned it had just been intercepted at a New Hampshire nursery by Piera Siegert’s staff in the New Hampshire Department of Agriculture, Food and Markets. Thank goodness they do nursery inspections! We may want to be on the lookout for this species, and try to eliminate it as soon as it is detected. Apparently it defoliates a wide range of plant species. Won’t you let us know, if it appears?  It would also be wise to try to control this species quickly, before it spreads far.

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Getting Ready for Apple Maggot and Blueberry Fruit Fly

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These closely related flies are normal summer pests of blueberry and apple. They are highly variable from site to site, both in numbers and in timing. Blueberry fruit fly usually is most serious from July 1 to 20, while apple maggot commonly attacks for a much longer period, sometimes well into September. Both species have similar patterns of black bands on their wings. Both species are reliably monitored by traps. Rather than repeat the details on blueberry fruit fly, you can follow this link  to see photos, look at the pattern of attack, and learn how to set up traps yourself.

Some growers just blanket the summer with pesticides, to protect against these insects. That is easy, but it ends up being very expensive, killing many insect predators and parasites, threatening development of resistance, and exposing the spray person to toxic insecticides. To me, monitoring with traps is much better, and pick-your-own customers notice the traps and appreciate your efforts to minimize spraying. At the UNH apple orchard, trap catches showed apple maggot numbers were so low that we did not need to spray in some years (about half the years), and in others, we needed to spray 1 to 3 times. If you do not monitor on your farm, you might occasionally get a very nasty infestation. Some growers discovered this, but I promised not to say who they are.

My apple maggot fact sheet is no longer on our website, so I’ll go over trapping details for that species:  Red sphere traps are the most effective. Although you can purchase odor lures to add to the trap and enhance the catch, they don’t improve reliability of the traps. Hang your traps about July 1st, in the edge trees. I suggest you put at least 1 in the earliest maturing variety you have, and 1 in the orchard edge nearest to wild or unmanaged apple trees. Hang them in a spot where they are really visible!  That is a key factor. I try to place mine in a spot where fruit is within 18 inches below and/or to the side of the trap. You don’t need a lot of traps; I monitored the UNH Woodman farm trees with only 2 traps, for many years. After selecting the site and hanging the traps, coat them with a thin layer of tangletrap. I use a stout wooden garden stake to do that. Then, to make it easier to find the traps, I hang bright flagging nearby… but not close enough to get stuck in the trap.

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I recommend checking weekly, but in some situations you may want to do it more frequently. Look for flies with the wing band pattern in the upper left of the drawing. When you reach a cumulative average of 1 apple maggot fly per trap, it is time to apply an insecticide. If you use odor-baited traps, the threshold is an average of 5 to 10 per trap. (the big spread in range is one reason I don’t add odor lures for this species). Then, for the next 7-12 days, discount any AMF’s you happen to catch. If I’m using Sevin, I do this for 7 days. If I’m using the labeled rate of a pyrethroid insecticide (Warrior, for example), I discount for 12 to 14 days, since those insecticides have long residual action. When it is time to start harvesting a block, I move the traps to later-maturing trees. At the end of the season, I remove the traps, put them in heavy plastic bags (keeps dirt & dust out) and store them until next July.

SWD: It Has Started…Slightly Early

I was expecting that the first adults of spotted wing drosophila would appear in traps roughly July 1-10th, probably just one or two flies at one or two sites. But the insects surprised me a bit; we captured one in a trap in the edge of the woods in Hillsborough County on June 23rd. Over the next 10 days they should begin to appear at other sites, and numbers will start building, especially if temperatures are warm. Don’t get excited yet… none have been captured in traps in crops as I write this June 30th. If you grow fruit that are attacked, George and I suggest that you put out a couple (or more) SWD traps when your fruit turn color. They are not vulnerable to attack when they are green. On the SWD’s menu are raspberries and blackberries, blueberries, plums, peaches, possibly cranberries. Some varieties of grapes get attacked (especially colored varieties with relatively tender skins), plus August through October-ripening strawberries. Theoretically, cherries are vulnerable, but we have not seen them attacked here. Details on traps, baits, how to hang, etc are on the SWD page. We will update the SWD pesticides list again, for 2015.

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Leaf Tissue Testing for Nutrient Analysis in Tree Fruit

For tree fruit, leaf sampling for nutrient analysis is done in late July through early August. Forms and instructions for doing this can be found on the Problem Diagnosis and Testing page of UNHCE’s website. Look near the bottom of that page, under “Additional Testing Services”.

Over-Use of Entrust:  Beware!

Through emails from colleagues in the northeast region, I became aware that Dow Chemical Corporation (manufacturer of Entrust) is threatening to either pull certain crops or certain pests from the Entrust label. They are concerned that growers (especially organic ones) are over-using the product, without rotating it with other insecticides. They point out the insects could become resistant, and entrust would no longer work. Of course, in addition they wouldn’t be able to sell as much, and get a return on their considerable investment. One of my colleagues pointed out that for certain pest & crop combinations on organic farms, there really is no other alternative for rotation. So, I guess the best way to summarize this is to ask growers to be aware of this situation, and try to not over-use any one chemistry. This lesson applies to many pesticides, not just the insecticide Entrust. Over the time I’ve been employed at UNH, we have seen serious resistance develop in NH in several situations, including apple scab with benomyl and dodine; pigweed with triazine herbicides; European red mites with Plictran. In each case, the pesticide was over-used without rotation. It could happen again if you are not careful.

Viewing Our Vegetable Insect & SWD Trapping Data

If you grow crops attacked by European corn borer, squash vine borer, corn earworm, or fall armyworm, and want to see the current year’s trapping data, that is now possible, if you have access to internet. Point your browser to the IPM Monitoring and Trapping Programs.  Once on that page, you’ll see that one of the options is to view the current data, and it will show you how many insects were captured in traps at various sites. You could look at several weeks of data, if you wish. To help protect privacy, we don’t include farm names on the site, just the town names. The data is ready for you to examine any time you wish, for sweet corn & squash trapping. Shortly we hope to have the spotted wing drosophila trapping data up as well.

Rain and Insecticide Retention on Tree Fruit and Berries.  By Mary Concklin, Visiting Extension Educator, Univ. of CT

Good evening,

You may be wondering after the rain this weekend whether your insecticide application is still working. Dr, John Wise at Michigan State University has developed the following charts for tree fruit and berries which should be helpful as you decide whether a re-application is needed before you had originally planned. There are several so scroll down. SWD is the last one although you do not need that one at this time.

Based on results from current studies, the following charts have been developed to serve as a guide for general rainfastness characteristics and re-application recommendations for certain insect. Note that these recommendations should not supersede insecticide label restrictions or farm-level knowledge based on site-specific pest scouting, but rather are meant to compliment a comprehensive pest management decision-making process.

Rainfastness rating chartHighly rainfast = ≤ 30% residue wash-off, Moderately rainfast = ≤ 50% residue wash-off, Low rainfast = ≤ 70% residue wash-off,  Systemic = Systemic residues remain within plant tissue.

Apple insecticide precipitation wash

Expected codling moth control in apples, based on each compound’s inherent toxicity to codling moth larvae, maximum residual, and wash-off potential from rainfall. * Number of days after insecticide application that the precipitation event occurred. Insufficient insecticide residue = Insufficient insecticide residue remains to provide significant activity on the target pest, and thus re-application is recommended. Sufficient insecticide residue = Sufficient insecticide residue remaining to provide significant activity on the target pest, although residual activity may be reduced.

Grape insecticide precipitation wash

Expected Japanese beetle control in juice grapes, based on each compound’s inherent toxicity to Japanese beetle adults, maximum residual, and wash-off potential from rainfall. * Number of days after insecticide application that the precipitation event occurred. Insufficient insecticide residue = Insufficient insecticide residue remains to provide significant activity on the target pest, and thus re-application is recommended. Sufficient insecticide residue = Sufficient insecticide residue remaining to provide significant activity on the target pest, although residual activity may be reduced.

Blueberry insecticide precipitation wash crabberry fruitworm

Expected cranberry fruitworm control in blueberries, based on each compound’s inherent toxicity to cranberry fruitworm larvae, maximum residual and wash-off potential from rainfall. * Number of days after insecticide application that the precipitation event occurred. Insufficient insecticide residue = Insufficient insecticide residue remains to provide significant activity on the target pest, and thus re-application is recommended. Sufficient insecticide residue = Sufficient insecticide residue remaining to provide significant activity on the target pest, although residual activity may be reduced.

Blueberry insecticide precipitation wash japanese beetles

Expected Japanese beetle control in blueberries, based on each compound’s inherent toxicity to Japanese beetle adults, maximum residual and wash-off potential from rainfall. * Number of days after insecticide application that the precipitation event occurred. Insufficient insecticide residue = Insufficient insecticide residue remains to provide significant activity on the target pest, and thus re-application is recommended. Sufficient insecticide residue = Sufficient insecticide residue remaining to provide significant activity on the target pest, although residual activity may be reduced.

Blueberry insecticide precipitation wash SWD

Expected spotted wing Drosophila control in blueberries, based on each compound’s inherent toxicity to SWD, maximum residual, and wash-off potential from rainfall.  * Number of days after insecticide application that the precipitation event occurred. Insufficient insecticide residue = Insufficient insecticide residue remains to provide significant activity on the target pest, and thus re-application is recommended. Sufficient insecticide residue = Sufficient insecticide residue remaining to provide significant activity on the target pest, although residual activity may be reduced.

Insecticide persistence

Dr. Wise’s work is funded in part by MSU’s AgBioResearch.

 

Alan T. Eaton
Extension Specialist
Integrated Pest Management

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