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Eastern New York Field Crops Pest Report, 2003

For 7/8/03:

Alfalfa

General Crop Condition
Alfalfa at the Cornell/Valatie Research Farm was about 38 to 40 inches tall and lodged over (July 1). Alfalfa at the SUNY Cobleskill Farm was 10 to 15 inches tall (July 2).

Alfalfa weevil over?
Yes, there are very few reports of alfalfa weevil still feeding on alfalfa. This means most of the larvae have pupated and they will not continue to be a problem this growing season.

Potato Leafhopper might be increasing!
Potato leafhopper infestations are at moderate levels across Eastern New York (July 3).

Do you know what potato leafhopper looks like and can do to alfalfa?
Potato leafhopper is a lime-green insect about 1/8 inch long and rides the storms that come from the south, looking for alfalfa and other host plants. The adult females are strong flyers and move from plant to plant laying 2-3 eggs per day. Bright yellow-green nymphs (looking much like adults, but smaller and wingless) hatch from the eggs to feed on plant juices. Nymphs and adults alike use their needle-like mouthparts to suck juices, replacing them with toxic saliva. Once you see V-shaped yellowing on the tips of the leaves it's too late. Potato leafhopper has likely reduced plant protein by 5% and yield by about .10 - .25 ton per acre pre cutting. New seedings are at higher risk to potato leafhopper damage. Crop stress from this insect can impact production this season as well as affect production potential for subsequent years. The key is to scout fields before the damage has already occurred.

For more information, see Potato Leafhopper on Alfalfa Management Guide, 302k pdf file

Picture of potato leafhopper

Field Corn

General Crop Condition
Field corn this week was between the 4 and 8 leaf stage across many regions of Eastern New York (July 3). In one field at the SUNY Cobleskill farm I noticed patches of drought stressed corn (July 2).

Western Corn Rootworm Vs Striped Cucumber Beetle
Have you ever gotten western corn rootworm confused with the striped cucumber beetle? Do you know the difference between corn rootworm and striped cucumber beetle? Striped Cucumber Beetle and Western Corn Rootworm look similar but are two different species of insects.

Striped Cucumber Beetle, Acalymma vittatum
The Striped Cucumber Beetle adult is about 1/4 inch long and the upper body surface is about equal black and yellow, the folded wing covers forming three longitudinal black stripes. The adult beetle starts appearing on several vegetable crops starting in mid-June.

Western Corn Rootworm, Diabrotica virgifera virgifera
Female Western Corn Rootworm is 5/16 inches long with three black strips alternating with yellow. Male Western Corn Rootworm is mostly black with a small area on the poster end that is yellow-green.

 

Female Western Corn Rootworm

Striped Cucumber Beetle

Insect Markings

Stripes are less distinctive and do not extend to the tip of the abdomen

Both sexes have stripes, are clearly defined, and extend to the tip of the abdomen.

Insect size

5/16 inches long

1/4 inch long

Host range

Primarily Corn
Secondary Cucurbits

Primarily Cucurbits
Secondary beans, corn, potatoes and other crops

Emerge

July

June

Life cycle

1. Over-winter as eggs in the soil in the field
2. Eggs hatch and larvae feed on the corn roots starting in late May
3. Adults emerge at time of corn pollination. Males emerge first
4. Adults lay eggs in cornfields mid to late pollination
5. Adults die, eggs overwinter

1. Over-winter as adults in woodland litter or in the soil.
2. Lay eggs at the base of the plant in mid-June through mid-July
3. Larvae develop for 2 to 4 weeks on the roots, pupate in the soil.
4. Adults appear in early to mid-August
5. Adults produced this season overwinter

Learn more about the differences between Western Corn Rootworm and Striped Cucumber Beetle:
Cucumber Beetles, Corn Rootworms, and Bacterial Wilt in Cucurbits

How to Monitor for Corn Rootworm

What are the other species of corn rootworm in New York? See next week's report for the answer.

Last week's IPM Question!
What are the weeds in New York that are resistant to triazine herbicides?
1. Common Lambsquarter
2. Common Ragweed
3. Smooth Pigweed
4. Common Groundsel

Weed question of the week!
Why is it important to change the families of herbicides used on fields from year to year?

Do you know the number of growing degree-days in your region today?
Check this website: NEW YORK GROWING DEGREE-DAY TRACKER
(Base Temp. 50F)

Contributors to this week's pest report!
Beth Spaugh, (Clinton County)
Jeff Miller, (Oneida County)
David Norton, (TAg Scout: Chenango, Fulton, Montgomery, Herkimer, Otsego, Madison, Oneida Counties)
Kathryn Evans, (Madison County)
Kevin Ganoe, (Chenango, Fulton, Montgomery, Herkimer, Otsego Counties)
Richard Gast, (TAg Scout: Franklin County)
Ken Wise, (Eastern New York)

Happy Scouting!
Ken Wise