True/Common Armyworm (Pseudaletia unipuncta) Alert – Northern NY

From Ken Wise: Eastern NYS Extension IPM Specialist- Livestock and Field Crops

Mike Hunter (CCE Northern NY) is finding a lot of true armyworm in grass hay fields in Northern NY. He states the larvae are still very small (1 mm to 1.5 mm) and are in the 1st instar. These armyworm moths most likely have come on the recent storms from the south and laid their eggs in hay fields.  If there is a lot in the field you will not see much damage until they reach the later instars. True armyworm larvae in their (6th) final instar will eat 80% of  all the forage they will consume. Many times a hay field can look great in the evening and gone the next day if they all reach the 6th instar about the same time.

It is best to scout your fields ASAP and look for smaller larvae. Be proactive make sure you know if your fields are infested. True armyworm will feed on grasses, corn and small grains. There are economic thresholds  for corn and small grains.

Recommended economic thresholds for corn:

  • seedling: 10 percent or more plants show damage and larvae are still present.
  • whorl-stage: apply an insecticide when there are three or more larvae per plant.
  • Tall corn seldom needs treatment unless the leaves above the ear are also damaged.

Recommended economic thresholds for small grains:

  • Wheat/small grains – 5 or more larvae per linear ft of row, larvae less than 1.25 inches and not parasitized, watch for flag leaf reduction or if grain heads clipped off – yield losses, a spray before soft dough to save the remaining 3 upper leaves is generally beneficial since these tissues are still important to grain filling

Recommended economic thresholds for grasses:

  • Grasses – no specific guidelines available, need for treatment based on the level of damage observed in relation to the expected value of grass harvest

Most years, natural enemies—various fungal and viral diseases as well as parasites such as tachinid flies—help suppress armyworms. You cannot be sure when and where they occur.

Sometimes when armyworms are at very high populations they will march to new fields. They can be in a hay field and move to a corn or small grains field.

SPECIAL NOTE: if you spray for armyworm the CROP and True/Common Armyworm has to be on the label! READ THE LABEL!!!!!

Check the Cornell Guide for Integrated Crop Management for an insecticide labeled for use.

I have added some web links that have specific armyworm information:

Armyworm (Pseudaletia unipuncta Haworth)

Armyworm as a Pest of Field Corn

Cornell Guide for Integrated Field Crop Management

Armyworm Damage to Field Corn and Grass Hay and Pasture

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NYS IPM Weekly Field Crops Pest Report – July 2, 2018

NYS IPM Weekly Field Crops Pest Report – August 18, 2017

The Capital Area Ag Report – August 15, 2017

Here is this week’s Ag Report: The Ag Report, 8-15-2017

Topics in this issue:
Advice for a difficult crop year.
Grain Bin Safety
Winter Rye Varieties
Fall Forages

Aaron Gabriel
Sr. Extension Resource Educator, Agronomy
Cornell Cooperative Extension
415 Lower Main St.
Hudson Falls, NY 12839
518-380-1496 cell
518-746-2560 office

Cornell Cooperative Extension
Capital Area Agriculture and Horticulture Program

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Oneida County Weekly Crop Report – 7/28/2017

PLH numbers have softened a bit…. Growers harvested and some fields were treated.

Soy bean aphid numbers remain low in most fields.

Big flight of western bean cutworm  identified in southern Oneida county.

Wheat harvest continues with good reports on both yield and quality.

Oat crop is starting to turn

Early planted corn fields are tasseling

Many soybeans are at full flower.

Some growers are preparing fields for summer seedings.

See the full Crop Report for more details.

Jeffrey J. Miller
Cornell Cooperative Extension Oneida County
Ag Program Leader
121 Second St., Oriskany, NY 13424

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