Tag Archives: peach leaf curl

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.



March 30, 2017 Volume XIII No. 1

Fruit Bud Stages

As I write this in late March, all fruit buds in the Durham area seem dormant: apple, peach, blueberry, raspberry.

NEWA Weather Station Setup & Info Retrieval

Some of you know that Cheryl Smith, Becky Sideman and George Hamilton wrote and received a Specialty Crop block grant last year from the NH Department of Agriculture, Markets and Food. The purpose was to bring NEWA [Network for Environment and Weather Applications] weather stations to New Hampshire. The money arrived well into the growing season, and by December 31, Cheryl Smith had received equipment and set up stations in six counties:

Belknap (Moulton farm, Meredith)

Carroll (County farm, Ossipee)

Merrimack (State forest nursery, Boscawen)

Rockingham (County farm, Brentwood)

Strafford (UNH Woodman farm, Durham)

Sullivan (Alyson’s orchard, Walpole)

There is already one NEWA site that Brookdale Fruit Farm (Hollis) bought and installed in their orchard earlier. There is another privately-owned system on River Road in Bridgewater. Cheryl hopes that the equipment will be set up in Cheshire, Coos, Grafton and Hillsborough counties by some time in April-May (depending on snow cover and frozen soils).

Why were those sites chosen? We wanted one site per county, a mix of county farms and growers, a mix of crops, and the sites must have certain data access and transmission requirements (basically, fast, reliable access to internet).

If you haven’t tried accessing information from these sites, you ought to try it now, before the growing season gets too busy. The six sites are up and running. In addition to seeing what the weather information was for your site(s) of interest, you can learn how many degree days have accumulated (set the biofix first) for various insect or pathogen models.

Last year we had significant problems with fireblight in New Hampshire orchards. The NEWA system has a FB predictive model to assess risk. Cheryl uses this information to send out alerts. A few NH orchards had codling moth problems last year. NEWA can predict when each codling moth generation begins, to help you determine when risky periods occur. Some of you would benefit from knowing when San Jose scale crawlers emerge. The site can predict that as well. Cheryl and Alan already use NEWA to look at apple scab risk.

To begin using the system, point your computer’s internet browser to NEWA’s home page www.newa.cornell.edu  On the screen you’ll see a map with lots of green “leaf” icons. Those are weather stations. Use the + and – buttons on the lower right of the map to enlarge or shrink the map, to find the sites of interest to you. (You could use an airport if that is nearby, but a station next to the tarmac might not be the best for some applications… like determining how long leaves were wet.)

Do you need to set biofixes?  Yes, for some models, you’ll have to do that. For example, last week when Alan clicked on the Durham station and selected apple scab, the system gave him the opportunity to enter the date for green tip stage. Since this was before green tip had occurred, he switched tasks and asked to look at the weather data. It has lots of options to explore.

Take a look, and we think you’ll find it easy and helpful

Written by Alan Eaton and Cheryl Smith

Higher-Than Average Gypsy Moth Numbers for 2017

Formerly, gypsy moth populations in New England followed rough cycles of highs and lows, with about 10 to 11 years between high points. Then the fungus Entomophthora entomophaga (a pathogen that hits mostly gypsy moth and other caterpillars in its family) took hold, and we no longer had enough gypsy moth caterpillars to cause widespread defoliation. But in really dry years, the fungus does poorly. So I anticipate that we will see some individual spots with gypsy moth buildup, especially in Rockingham and eastern Hillsborough Counties. That is, unless the rains return and knock down larval numbers in June. If you see the egg masses, that suggests you’ll have caterpillars this year. Egg masses should hatch in late April.

Another Prediction: High Peach Leaf Curl Incidence in 2017

We had almost no peach crop last year, so that means there were relatively few fungicides sprayed on peach trees last year. Those conditions cause an increase in problems with peach leaf curl. If done at the correct time, spraying certain fungicides (Bravo, C-O-C-S, Echo, Ferbam, Kocide, Badge, Ziram…) will control the disease. One time to have done that was last fall, at the time of leaf fall. If you did not make an application then, and you’ve had peach leaf curl problems before, you should consider a spring application this year, before bud swell. Sprays made shortly after buds started swelling might provide partial control. My photo shows the distorted, thickened & discolored leaves affected by peach leaf curl disease.

Prune off Peach Mummies?

I asked David Rosenberger if it was worthwhile to prune off peach mummies, while I was pruning my apple trees. I don’t have many, so it would be easy. He said that on the cruel, frozen tundra of New Hampshire, Brown rot fungus does not overwinter well in fruit mummies, so dropping them might help, but probably isn’t necessary.

Prune off Cedar-Apple Rust Galls?

The fungus that causes cedar-apple rust has to switch hosts each year. Spores from rust lesions on apple leaves infect redcedar, and spores from redcedar infect apples. So if you have a redcedar tree with galls on it, and you also grow apple varieties that are susceptible to the disease, it is worthwhile to remove & burn or bury the galls, before much apple leaf tissue emerges. But you may consider just cutting down the redcedar tree, especially if it is tall and has a lot of galls. Either way works to break the infection cycle. The manuals say that the spores from galls on redcedar can travel a long ways. If you grow susceptible varieties such as Gala, Golden delicious, Jonathan, Jonagold, Mutsu, Prima or Rome, we often suggest removing any red cedar trees (even tiny ones) within 500 feet of your apples.

Winter Moth

In New Hampshire, the seacoast region has the greatest risk of winter moth problems. Elsewhere, a close relative (bruce spanworm) is common, but rarely causes serious problems. Winter moth overwinters as eggs on trees (esp oaks, maples). The eggs turn blue just before they hatch. The tiny caterpillars that hatch out of the eggs feed on leaves, and often they spin out long strands of silk, and get blown into other trees & bushes nearby… like your apples or blueberries. The insects are not particularly difficult to kill, but they often escape our notice before they cause damage. Egg hatch usually occurs as buds are swelling open and the first tiny leaves are emerging.

Another New Insect

It has been a few months since we had an announcement about a new insect, so I guess we are overdue. A European fly that attacks cherries (wild and domestic) was detected in Missisaugua, Ontario in 2016. It is called the European cherry fruit fly. Yes, it is similar to our native cherry fruit fly, but has a slightly different wing band pattern, and a yellow dot on its thorax. To my knowledge it has not yet been found in the USA, but we have the climate and hosts for it to thrive in New England. For cherry growers, its appearance will change a few things. Our State Entomologist Piera Siegert and her staff at the New Hampshire Department of Agriculture, Markets and Food are planning to set traps for it at several NH sites this year. The insect hits mid and late season cherries, and prefers fruit that are in full sun.

2017 New England Tree Fruit Management Guide

We do not plan to print and distribute the 2017 guide. Instead, we have been working on creating an on-line version, which is mobile-friendly. I wrote a chapter on vertebrate pests, and George Hamilton wrote one on sprayer calibration. Our New England colleagues have been busy writing about pathogens, insects and other concerns. We hope that it will be ready for you and accessible soon. When it is ready, I’ll provide you a link. Until then, we’ll depend on the older version.

Just announced! The guide should be ready next week. Read it here: http://netreefruit.org

Fruit Pest Update Telephone

I plan to set up the first message March 28th to 30th, and expect to record a new message every Tuesday. Most messages last three minutes, but sometimes when things are really busy, one stretches to four minutes. The telephone number is unchanged (862-3763) and you can call it any time of day or night that interests you. As usual, I’ll cover fruit pest information and will include announcements of events that might be of interest. I’ll keep it running continuously through mid-September, possibly later. I started this service in 1979, when the NH fruit growers’ association purchased equipment to get it started.

2017 Fruit-Related Events:

There are many events that might be of interest on our events calendar. Among them are our usual mix of spring pruning demonstrations, some of which have already gone by. 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.