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Eastern New York Field Crops Pest Report, 2003

For 5/6/03:

Note: Any Eastern New York Extension Educator who wants to contribute their pest scouting activities to the Eastern New York Field Crops Pest Report, you are more than welcome to join in the fun.

Alfalfa

Alfalfa at the SUNY Cobleskill farm was 6 to 8 inches tall (May 1) and looked to be in very good condition.

Alfalfa Weevil Creeps into Fields, but No Eggs to be Found! Last week (May 1) I discovered a few adult alfalfa weevils. I looked far and wide for eggs in stems of alfalfa and did not find any. Do you know what the eggs look like when the adult female weevil lays them in a stem? Weevils chew a hole and lay up to 25 eggs at one time into an alfalfa stem. Each female weevil can lay from 500 to 2000 eggs during the growing season. When eggs are first deposited into the stem they are yellow and then turn darker as they develop. First instar larvae hatch from eggs at about 280 growing degree-days (48F base temp). Here is a website with great pictures of alfalfa weevil egg development:

Alfalfa Weevil Eggs

Check out our on-line publication, IPM for Alfalfa Weevil. 1.2 Mb pdf file

Field Corn

Corn fields at the SUNY Cobleskill farm were still a little too wet to prepare (May 1st).

When do weeds wakeup in the spring?
It is a good idea to know when certain weeds wakeup in the spring! By knowing when certain species of weeds emerge, selection of the best control measures can be employed. We can break weeds down into the accumulation of growing degree-days (48F Base Temp.) as a means to know when plants might start to emerge:

Group 0 (Emergence occurs in fall or early spring)
Winter annuals normally complete emergence prior to planting of corn.
Examples: horsetails (mares tail), white cockle, field penny cress, shepherd's purse

Group 1 (Emergence begins several weeks prior to corn planting, GDD <150)
Examples: giant ragweed, lambsquarters, Penn. Smartweed, common sunflower

Group 2 (Emergence begins soon, before or at corn planting, GDD 150-300)
Examples: common ragweed, green foxtail, velvetleaf

Group 3 (Emergence begins at the end of corn planting season, GDD 250-400)
Examples: yellow foxtail, black nightshade, common cocklebur, wild proso millet

Group 4 (Emergence begins after corn emergence, GDD 350 >)
Examples: large crabgrass, fall panicum, waterhemp, morning glory species

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)

For more information, check out our on-line publication, Weeds in Corn-Management Guide, 1Mb pdf file

True Armyworm
There have been no advanced warnings of a looming armyworm problem but just incase...we have pheromone traps for true armyworm scattered throughout Eastern New York. As of May 5, we have not detected a migration of armyworm from the Southern United States. While we employ the use of traps they only tell us if there are moths present or not. A pheromone trap can NOT tell us if a field might reach a threshold for armyworm. You still have to get out in the field and scout for larvae. The following are key characteristics of true armyworm larvae identification:

  • Larvae are smooth cylindrical pale green (when young) to brownish.

  • Mature larvae are smooth and marked with two orange, white-bordered strips on each side.

    • Larvae range in size from 1/8 inch to 1.5 inches when fully grown.

    Picture of True Armyworm

    IPM Question of the Week!
    What kind of fields are black cutworm more attracted too?

    See next week's pest report for the answer!
    Have a good week!

    Ken Wise
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