The Arkansas Rambler

True armyworms observed moving
from wheat to rice

By Dr. Gus Lorenz

We have received several reports of true armyworms (Pseudaletia unipuncta) migrating from (Arkansas) wheat fields to adjacent rice fields in several areas throughout the Grand Prairie (Arkansas, Prairie and Lonoke Counties) and in Desha and Lee Counties.

Reports indicate levels up to 25 to 30 armyworm larvae per square foot in wheat. Larvae often become numerous in wheat just before or shortly after heading.

Often, nearly full grown larvae leave wheat fields, especially those fields that are becoming senescent, and move into adjacent rice fields. Damage to rice usually occurs near the border of the two crops and seldom is a rice field completely infested.

Although pupation can occur in the rice field, adults are not known to deposit eggs directly onto rice.

Some level of treatment may by needed
No formal scouting plan is used for armyworm in rice. Growers are encouraged to observe rice fields adjacent to wheat for movement of armyworm between the two crops. This situation can occur in a short amount of time, so watch closely.

Treatment may be necessary if stand reduction is evident. Border treatment of the armyworm-infested wheat fields next to a rice field may prevent populations from crossing over into rice. Also, water in outside levees can serve as an effective barrier to larvae attempting to enter the rice field. Corn and milo adjacent to armyworm-infested wheat can also be damaged.

If treatment is considered, labeled pyrethroids for wheat (Baythroid, Karate, Silencer, Mustang Max, Respect, Proaxis) and rice (Karate, Silencer, Prolex, Proaxis, Mustang Max) may be the most effective choices and provide better residual control than other insecticides. Consult the MP-144 publication for labeled insecticides for control and appropriate rates.

True armyworms are not difficult to control, and high end rates are not needed to achieve control.

Taking a look at Dermacor-treated fields
We are interested in seeing fields treated with Dermacor that may be attacked to ascertain the control of armyworms. If you experience this situation where true armyworms are entering a rice field with Dermacor seed treatment, please contact me. We would like to determine if we are getting control with Dermacor, as it may provide some true armyworm control.

Dr. Gus Lorenz is an Extension entomologist with the University of Arkansas. Contact Lorenz at (501) 676-3124 or glorenz@uaex.edu.