It appears that 2014 is going to be the year of the armyworm in rice. I have had numerous calls, texts, and Tweets about armyworms in rice over the last week. If you have not had them in your rice to this point, consider yourself very lucky. The one thing that stands out is that no 2 situations are the same. I have had calls that range anywhere from a few small isolated spots, to only on the levees, to large isolated spots, to scattered all across the field. Some trends that I have noticed is that most of the situations are in rice that has not yet been flooded. That’s not to say that they are not in flooded rice, because they are. Just not to the same extent as rice that has not been flooded yet.
As far as management goes, armyworms are not likely to severely hurt yields at this time of year unless they are really heavy and widely distributed across a large percentage of the field. However, one thing to consider is that armyworms can hold the plants back and reduce the uniformity of the crop. Also, the smaller the plants are, the greater the impact will be. The important aspect of the non-uniformity is that it will make management of the crop much more difficult for the rest of the season.
In terms of control, the armyworms we see in rice are very easy to control with a mid-rate of a pyrethroid. If you are finding small worms (< 3/8 inch long), you have a few days until they are big enough to cause significant damage. In contrast, worms that are 1/2 inch or bigger will cause a lot more damage and will need to be controlled sooner.
Finally, as I said earlier, every situation has been different and each field will need to be considered independently when deciding whether or not to spray. You should consider the stage of the crop, the extent of the feeding, and what percentage of the field is being damaged. In many situations it may be difficult to decide. If you need help or have any questions, feel free to call at any time.