Insects | Credits
Volume 6, No. 23 August 25, 1997
43F 50F Current DD accumulations (Geneva 1/1-8/25): 2607 1748 Coming Events: Ranges: Apple maggot flight peaks 2033-2688 1387-1804 Spotted tentiform leafminer 3rd flight peaks 2415-3142 1728-2231 Redbanded leafroller 3rd flight peaks 2514-3225 1818-2625 Obliquebanded leafroller 2nd flight peaks 2634-3267 1789-2231 Comstock mealybug 2nd gen. crawlers subside 2740-2766 1818-1934 TRAP CATCHES (Number/trap/day) Geneva: 8/11 8/14 8/18 8/21 8/25 Redbanded Leafroller 0.6 0.3 0 0.3 0 Spotted Tentiform Leafminer 67 112 168 458 363 Lesser Appleworm 0.8 3.3 3.4 4.7 2.4 Oriental Fruit Moth (apple) 2.3 6.0 5.8 4.8 2.0 San Jose Scale 22.8 - 9.9 - 0.8 Codling Moth 17.4 8.3 3.6 2.2 1.6 American Plum Borer 1.8 1.2 1.4 0.5 2.0 Lesser Peachtree Borer 1.4 0.8 2.1 1.2 0.1 Peachtree Borer 0 0 0 0 0 Obliquebanded Leafroller 0.4 0.3 0.1 0.2 0.8 Apple maggot 0.4 0.3 0.1 0.3 0.06
by Art Agnello
By this point, most growers are ready to stop thinking about insects for the year, and we can't really blame you. However, there are a couple of relatively minor pests that can be prevented from becoming a big pain next summer by paying just a little attention to them at the tail end of the season. The number of orchards affected by each is rather small, but you'll thank yourself later if yours is one of them:
Pearleaf Blister Mite
This is a sporadic pest of pears that does not normally show up in commercial pear orchards, but is a fairly common problem in home plantings. The adults are very small and cannot be seen without a hand lens; the body is white and elongate oval in shape, like a tiny sausage. The mite causes three distinct types of damage. During winter, the feeding of the mites under the bud scales is believed to cause the bud to dry and fail to develop. This type of damage is similar to and may be confused with bud injury from insufficient winter chilling. Fruit damage is the most serious aspect of blister mite attack. It occurs as a result of mites feeding on the developing pears, from the green-tip stage through bloom, causing russet spots. These spots, which are often oval in shape, are usually depressed with a surrounding halo of clear tissue. They are 1/4-1/2 inch in diameter and frequently run together. A third type of injury is the blistering of leaves; blisters are 1/8-1/4 inch across and, if numerous, can blacken most of the leaf surface. Although defoliation does not occur, leaf function can be seriously impaired by a heavy infestation.
The mite begins overwintering as an adult beneath bud scales of fruit and leaf buds, with fruit buds preferred. When buds start to grow in spring, the mites attack developing fruit and emerging leaves. This produces red blisters in which female blister mites then lay eggs. These resulting new colonies of mites feed on the tissue within the protection of the blister, but can move in and out through a small hole in its center. The mites pass through several generations on the leaves but their activity slows during the warm summer months. The red color of the blisters fades and eventually blackens. Before leaf fall the mites leave the blisters and migrate to the buds for the winter.
A fall spray is recommended sometime in early October, when there is no danger of frost for at least 24-48 hr after the spray. Use Sevin 50 WP (2 lb/100), or 1-1.5% oil plus either Diazinon 50WP (1 lb/100 gal) or Thiodan 50WP (1/2-1 lb/100 gal). A second spray of oil plus Diazinon or Thiodan, in the spring, just before the green tissue begins to show, will improve the control.
Roundheaded Appletree Borer
There has been a recent increase in complaints about damage by this once-serious pest; it is a cerambycid beetle that attacks young, healthy trees, unlike many other longhorn beetles that are attracted to weak or diseased trees. Although it was once considered the worst enemy of the apple tree next to codling moth, current pest management programs have generally relegated it to a rather minor status among most apple growers, except for homeowners and newer or smaller operations. This insect is also a pest of hawthorn, mountain ash, quince, shadbush, cotoneaster, and flowering crabapple.
The adult is an attractive light brown beetle, approximately 5/8-inch long, and olive brown with longitudinal white stripes. It emerges in N.Y. in June, and is active at night, normally hiding by day. The larva is a pale yellow grub, 1 inch long, and deeply divided between segments, with a dark brown head and blackish mandibles. Eggs are laid mainly from late June through July in the bark near soil level. Two weeks are required to hatch, after which the larvae bore into the sapwood, and create tunnels throughout the lower trunk area. This insect takes 2-3 years to develop, and is closest to the surface during the first and last few months of its life.
Because of its concealed habit and long life cycle, control of this borer is problematic and can be rather labor-intensive. Control recommendations during the spring and summer consist of various physical or chemical methods to deter the females from laying eggs on the trunk (which will be detailed in an early issue next year). However, some important steps can be taken in the fall to help ensure the best success in eliminating this pest:
Scaffolds is published weekly from March to September by Cornell University - NYS Agricultural Experiment Station (Geneva), and Ithaca - with the assistance of Cornell Cooperative Extension. New York field reports welcomed. Send submissions by 3 p.m. Monday to:
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Photographs courtesy of New York State Integrated Pest Management Program