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Fall Armyworms Have Arrived Early in Oklahoma Pastures Featured

Written by  Monday, 10 July 2017 16:17
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News release submitted by Amber Reece, LeFlore County OSU Extension Service


The Fall Armyworm is a tropical insect that overwinters only in the warmest areas of the U.S. As populations build throughout the summer, they move northward on weather fronts often arriving in Oklahoma in late summer. A mature fall armyworm is a large striped caterpillar about 1.5 inches in length, with an inverted “Y” on the front of its head.


This year entomologists are reporting large buildups of Fall Army worms in Wheat, turf, and pastures, these reports serve as an early warning for Oklahoma farmers and ranchers, to be on the lookout for small larvae and monitor the number and the amount of damage they are creating, in an effort to control them in a more cost effective way.


Scouting for caterpillars in a pasture is a relatively easy process. OSU entomologist Tom Royer suggests an easy way to count average larvae numbers. “Get a wire coat hanger, bend it into a hoop, place it on the ground and count all sizes of caterpillars in the hoop. Take samples in several locations along the field margin as well as in the interior. The hoop will typically cover about two-thirds of a square foot, so a threshold in pasture would be an average of two or three half-inch-long larvae per hoop sample, essentially three or four per square foot. If the treatment threshold is exceeded, it is much easier to control them with an insecticide when they are small.” For producers wishing to put up grass hay, the presence of “window paned” or chewed leaves is a tipoff a fall armyworm problem may exist.


If your scouting process determines that a pesticide application is needed there are several insecticides that are registered for use on Fall Armyworms. Control guidelines and information on registered insecticides approved for fall armyworms are available online at http://osufacts.okstate.edu. Remember to always follow label recommendations when applying any insecticide, paying extra attention to the most current rates and restrictions listed on the label. Many pest problems can be avoided by developing an Integrated Pest Management (IPM) plan that includes the use of good pasture management prac¬tices, proper fertilization, mowing and optimal stocking rates.




For more information contact Amber Reece at the Leflore County or Haskell County OSU Extension office or by email at This email address is being protected from spambots. You need JavaScript enabled to view it.

Oklahoma State University, U. S. Department of Agriculture, State and Local governments cooperating; Oklahoma State University in compliance with Title VI and VII of the Civil Rights Act of 1964, Executive Order 11246 as amended, Title IX of the Education Amendments of 1972, Americans with Disabilities Act of 1990, and other federal and state laws and regulations, does not discriminate on the basis of race, color, national origin, gender, age, religion, disability, or status as a veteran in any of its policies, practices, or procedures, and is an equal opportunity employer.

David Deaton

Digital Editor at Oklahoma Welcome

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