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Eastern New York Field Crops Pest Report, 2003

For 7/18/03:

Alfalfa

General Crop Condition

Potato Leafhopper infestation high!
Many fields were reported over threshold this week for potato leafhopper on Alfalfa. Some of these fields were starting to show the classic V-shaped yellowing. Once you see V-shaped yellowing on the tips of the leaves it's too late. Potato leafhopper has likely already reduced plant protein by 5% and yield by about .10 - .25 ton per acre pre cutting. So catch them EARLY SCOUT!

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

Field Corn

General Crop Condition
I have seen field corn between the V2 and V9 stage of development this week (July 17).

The Corn Rootworm Saga Still Continues:
During a few TAg meetings this week we discovered corn rootworm larvae feeding on corn roots. Some of the plants exhibited the classic goose necking. Lodging of corn is a symptom of excessive corn rootworm feeding on roots. This type of lodging is sometimes called goose-necking. Goose-necking is an attempt by the plant to straighten up again after it has begun to lean or lodge.

How to determine if your fields are at risk for corn rootworm:
Corn rootworm populations build in a cornfield from year to year. Fields that are not rotated and remain in corn for several years are most at risk from corn rootworm damage. A three to four year rotation reduces the risk that a corn field will reach an action threshold for this pest. This spurs the question, Do you scout a 1st year cornfield after sod for corn rootworm.? Yes, because any pollinating cornfield can attract corn rootworm. Even worse, late pollinating corn can attract many hungry corn rootworm beetles from fields where they did not get enough pollen. After the beetles eat their fill on late season pollen they will lay eggs in the soil. So yes, you have to scout all cornfields for corn rootworm that are going to be planted to corn next year. You do not need to scout fields that will be rotated out of corn next year.

How to Monitor for Corn Rootworm

Anthracnose Stalk Rot
Earlier in the season I reported on anthracnose leaf blight. One point I forgot to mention was that European corn borer can help anthracnose get into the stalk.

Anthracnose stalk rot is the same fungus that causes anthracnose leaf blight. Stalk infection is more severe where there is injury by European corn borer. The holes bored by European corn borer in the stalks provide a means for the anthracnose fungus to enter the plant. Conditions that favor anthracnose stalk rot are continuous corn, surface corn residue (minimum & no tillage) and wet, humid, warm weather. Anthracnose stalk rot symptoms may appear after tasselling as vertical, tan to reddish brown, water-soaked lesions (streaks) in the rind. Lesions become large, dark brown to shiny black. To control anthracnose use resistant hybrids, rotate corn with non-grass crops or cleanly plow under infected residue. Fields with high amounts of anthracnose leaf blight should be checked for indications of anthracnose stalk rot. If stalk rot is found you may wish to target that field for early harvest to avoid losses associated with premature lodging.

Soybeans

Soybean Aphids
Keith Waldron and his soybean aphid crew are finding infestations of soybean aphids in some fields in Central New York (July 17).

What do Ants and Soybean Aphids Have in Common?
Ants provide protection to soybean aphids from predators and they feed on the honeydew that aphids excrete.

 

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
Jeff Miller (Oneida County)
David Norton (TAg Scout: Chenango, Fulton, Montgomery, Herkimer, Otsego, Madison, Oneida Counties)
Kevin Ganoe (Chenango, Fulton, Montgomery, Herkimer, Otsego Counties)
Richard Gast (TAg Scout: Franklin County)
Keith Waldron (NYS Field Crops and Livestock IPM Coordinator)
Ken Wise (Eastern New York)

Happy Scouting!
Ken Wise