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Eastern New York Field Crops Pest Report, 2002

For 7/31/02:

Alfalfa

General: Alfalfa was 3 to 18 inches tall this week at the SUNY Cobleskill Farm. All of the new seedings appeared drought stressed with high potato leafhopper infestations (July 26).

Potato Leafhopper: Many counties report infestations of potato leafhopper over threshold in several alfalfa fields. Many of these fields are new seedings. Remember new seedings are quite susceptible to potato leafhopper. When there are multiple stresses (such as drought and potato leafhopper) affecting stands consider reducing the potato leafhopper action threshold by half.

At the SUNY Cobleskill Farm this week, potato leafhopper infestations were over threshold in all 5 new seedings (3-6 inches), while the established stands (16-18 inches) were far below threshold (July 16).

Jeff Miller (Oneida County) reports two new seedings over threshold for potato leafhopper (July 25).

Raymond Kennett (Dutchess and Columbia Counties) reports one field over threshold for potato leafhopper and was treated with an insecticide.

Kevin Ganoe (Chenango, Otsego, Herkimer, Fulton & Montgomery Counties) reports several new seedings over threshold for potato leafhopper (July 29).

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

Field Corn

General: Field corn is between the V6 and R1 stage of development this week at SUNY Cobleskill. Conventionally tilled fields were very uneven in corn development ranging from V6 to R1 and was drought stressed. No-till corn was uniform and ranged from V6-V8 and showed no signs of drought stress (July 26).

Corn Rootworm: I have seen both northern and western corn rootworm at the SUNY Cobleskill farm (July 26). Many of the cornfields I looked at this week had uneven pollination. In these situations, corn rootworm beetles - pollen feeders that they are - tend to concentrate in the pollinating areas while the rest of the field has a low infestation. Remember that the sequential sampling method is based on the assumption that the field will be at reasonably uniform growth and development. If a field clearly has large differences in crop maturity throughout the field, sequential sampling may not provide an accurate CRW assessment.

In these situations if you happen to monitor an area shedding pollen and has many beetles, it may bias your decision making. The sampling may show that you are over threshold when the majority of the field may not have that many beetles. So, in field's with uneven crop maturity, check 55 plants (at random) for corn rootworm keeping track of western and northern species. Remember northern corn rootworm count as a 0.5 and western corn rootworm count as 1. The action threshold is one corn rootworm per plant thus; you need an average of 55 beetles or more per 55 plants. Also make sure the beetles are ready to lay eggs (gravid). How do you tell if a corn rootworm beetle is ready to lay eggs? Capture the beetle between your thumb and forefinger and squeeze the contents of the beetle out of the abdomen. Mature eggs are white and about the size of a pin head and shaped like footballs.

Raymond Kennett (Dutchess and Columbia Counties) reports two fields over the action threshold for corn rootworm (July 23).

Peter Carey (Sullivan County) reports many fields are approaching the action threshold for corn rootworm (July 26).

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

Soybeans

Soybean Aphids: Keith Waldron and his soybean aphid crew are finding low to high infestations of soybean aphids in some fields in Central New York.

Raymond Kennett (Dutchess and Columbia Counties) reports that a few soybean aphids were found in a soybean field this week (July 23).

What do ants and soybean aphids have in common? See next week's report for the answer!