| COMMENT |
The worms appear suddenly in masses and move like an army from field to field so that seedbeds or the direct seeded fields look as if grazed by cattles. Generally, a transplanted crop is not severely affected. Damage by armyworms is most serious during periods of stem elongation and grain formation. Larvae defoliate plants, typically by chewing angular pieces off leaves. They may also feed on the panicle near the developing kernels causing these kernels to dry before filling. This feeding causes all or parts of the panicle to turn white. If the entire panicle is white, the damage may also be due to stem rot or feeding by rats. The seriousness of armyworm injury depends on the maturity of the plant and the amount of tissue consumed. Significant yield reduction can occur if defoliation is greater than 25% at 2 to 3 weeks before heading. They migrate from field to field and extensive losses are often caused within a week. Their migration is facilitated by the absence of standing water in the field. |