May 19, 2015 – Vol. XI No. 4

Bud Stages

On Monday May 18^th, 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 12^th, 13^th or 16^th. 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 12^th, 13^th or 16^th. Be sure your trees are protected with fungicides.The Durham area had spotty light drizzle in late morning on the 16^th. It should have triggered the release of ascospores, but probably dried too quickly to cause infection. At those temperatures, we need 7 to 8 hours of leaf wetness to cause infection, and things dried much faster than that.

Fireblight

Temperatures in southern NH on Tuesday 19^th 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