We have observed several fields and had reports across the state indicating that armyworms are moving into rice from adjoining wheat fields and fields being burned down with herbicide in preparation for planting. In the latter case, these are fields that had considerable winter grass, Poa annua, in them.
After armyworms are discovered in a field, it’s a common misconception to think that because no worms are seen during scouting that the armyworms are gone. This is NOT necessarily the case. During the day, armyworms go into hiding. If you will flip some clods, you may be surprised at how many armyworms can hide under a 50 cent piece-sized clod of dirt, so don’t be caught thinking the armyworms are gone and the damage is done. Remember, armyworms are active at night and unless it’s a cloudy day, will stay hidden until evening.
In most cases, the rice will grow back with little or no damage, but in severe cases, if the rice is eaten below the growing point it will not survive. If treatment is warranted try to wait as late in the day as possible to spray. Pyrethroids are photo labile, meaning they break down in sunlight, so spraying late in the day will help maintain efficacy for when the armyworms come out at night. Pyrethroids are the product of choice so consult the MP-144 for selection and rates or contact your local county agent.
The most important thing is to get out there and check your rice and corn fields, particularly the ones with wheat fields or fields burned down with herbicide near by, for armyworms moving in on you.