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Eastern New York Field Crops Pest Report, 2002

For 8/09/02:

Alfalfa

General: Alfalfa was 6 to 24 inches tall this week at the SUNY Cobleskill Farm.

Potato Leafhopper: All 5 new seedings (5-8 inches) at the SUNY Cobleskill farm were sprayed for potato leafhopper last week with Warrior T. The 4 established alfalfa stands (20 to 24 inches) were far below threshold (August 5).

Raymond Kennett (Dutchess and Columbia Counties) reports an alfalfa field was over threshold for potato leafhopper (August 7).

Terry Lavigne (Albany County) reports many new alfalfa seedings are over threshold for potato leafhopper. He states that even new seedings of potato leafhopper resistant alfalfa show symptoms of hopper burn.

Check out our on-line publication, Potato Leafhopper Management in Alfalfa

Field Corn

General: The conventional tilled corn at the SUNY Cobleskill farm is 3 feet to as tall as 9 feet high in the same field. The no-till corn is uniform at 7 feet tall and is pollinating relatively uniformly throughout the field.

Corn Rootworm: At the SUNY Cobleskill farm, 2 of 6 fields were over threshold for corn rootworm this week. 95% of the rootworm monitored were western corn rootworm while the remaining 5% were northern corn rootworm.

When you have a field of corn that is uneven in development it is scouted differently than a field that is uniform. In an uneven cornfield, scout 55 plants randomly through the field for corn rootworm keeping tract of western and northern. Remember northern count as a and a western is equivalent to 1. The action threshold is one corn rootworm per plant thus; you need an average of 55 beetles or more on 55 plants.

Raymond Kennett (Dutchess and Columbia Counties) reports two fields over the threshold for corn rootworm (August 7).

For more information on How to Monitor for Corn Rootworm check out our online publications:

Anthracnose Leaf Blight: Aaron Gabriel (Washington County) reports a cornfield with anthracnose leaf blight (August 6).

Anthracnose leaf blight appears as round to elongate, tan to brown water-soaked lesions, up to inch long and first appear on the lower leaves. Older lesions turn gray with small black specks in the center. Anthracnose inoculum survives on the corn residue left on the surface from the previous season. To control anthracnose leaf blight use resistant hybrids, rotate corn with non-grass crops or cleanly plow under infected residue.

How does European corn borer help anthracnose leaf blight infect corn? (See next week's report for the answer!)

Soybeans

Soybean Aphids: Keith Waldron and his soybean aphid (SBA) crew are finding low to moderate infestations of soybean aphids in fields in Central New York. SBA counts are being taken weekly in five variety trials in central (Waterloo, Interlaken, Aurora) and western (Sonyea) NY. Up to 40 varieties per trial are being monitored. No significant differences have been detected in variety tolerance or resistance to SBA. The Scouting study will continue through the end of this month.

A variety of beneficial insects (adult and nymph stages) can be found feeding on the soybean aphids. These insects include several lady bird beetle species, damsel bugs, lacewings, and minute pirate bugs. The SBA survey team has also found an unknown parasitoid of the SBA aphid which is being identified by USDA experts. No pathogens have yet been found attacking the aphid populations.

What do ants and soybean aphids have in common? In a number of fields Keith and his soybean aphid crew are finding ants on plants with higher soybean aphid infestations. Ants provide protection to soybean aphids from predators and they feed on the honeydew that aphids produce.