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Eastern New York Field Crops Pest Report, 2003

For 8/26/03:

Alfalfa

General Crop Condition
Alfalfa stands ranged between 16 and 24 inches tall this week at the SUNY Cobleskill farm (August 21).

Potato Leafhopper
I found only a few potato leafhoppers in alfalfa fields this last week at SUNY Cobleskill (August 21).

Where do potato leafhoppers go in the fall?
In late summer and early fall, potato leafhoppers migrate back to the southern United States. Potato leafhoppers over-winter on pines and numerous other host plants in the southern and southeastern United States.

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

Picture of potato leafhopper

Fall IPM Alfalfa Assessment
Fall stand counts are an indication of the health of your alfalfa crop. There are a number of pests and crop management issues that can reduce a stand count in alfalfa. The following are guidelines for stand counts in NYS:

Crowns per square foot

Harvest Year

Optimum Stand

Adequate Stand

New Spring Seeding

25-40

12-20

1st hay year

12-20

6-10

2nd hay year

8-12

4-6

3rd and older

4-8

2-5

Fall scouting before the first hard frost can also reveal pest problems. If you find yellow to brown plants it may indicate several different disease problems. These could range from a wide variety of disease problems including, verticillum wilt, leaf spots, fusarium wilt, anthracnose and more. An inspection of the root system can also indicated disease problems. Yellow, reddish-brown to black discolored or damaged roots may indicate disease problems such as phytopthora root rot or verticillium wilt.

For more information, see:
Diseases of Alfalfa (Leaf Spots) Management Guide, 220k pdf file
Diseases of Alfalfa (Wilts and Rots) Management Guide, 216k pdf file

Field Corn

General Crop Condition
Corn at the SUNY Cobleskill farm was in the R2 to R3 stage of development (August 21)

Corn Rootworm differences in Eastern New York
During TAg meetings in the Franklin and Clinton Counties I have seen only northern corn rootworm in fields this year. There have been reports from people finding western corn rootworm in these two counties but the larger percentage of corn rootworms is the northern species. In fields at the SUNY Cobleskill farm I have found 98 percent western corn rootworm this year. Northern corn rootworms tend to emerge from the soil later than westerns. So the population dynamics may change and switch to more northern. 

How to Monitor for Corn Rootworm

Fall Weed Considerations
Do weeds indicate what insect pests may infest a cornfield next year?

Conducting a weed survey may also expose certain insect pests. Some weeds serve as over-wintering sites for common stalk borer, hop-vine borer, and potato stem borer. Black cutworm lays eggs on several species of weeds in the spring. Larvae of these insects migrate from weeds to emerging corn in the spring. Here are some weeds that attract these insect pests:

Insect Pest

Weeds

Common stalk borer

ragweed and other large stemmed broadleaf weeds

Potato stem borer

quackgrass, green foxtail, barnyard grass, and dock

Hop vine borer

quackgrass and other grasses

Black cutworm

grasses, annual broadleaves such as common chickweed

Cheers,
Ken