What will 2016 be remembered for? If you ask me it might be known as the year of very high insect pressure. The South American rice miner (SARM) has been found just about everywhere in the southwestern part of the state this year. To put it in a different way, it was hard to find a field that did not have the SARM. This type of pressure is really unprecedented.
Little research exists to answer common producer questions such as, “How much yield am I going to lose from this insect?”
Although the rice really looks “ragged” from the SARM, we do not believe the yield loss will be that great. Currently, we do not have a management practice to control SARM since any foliar insecticide treatment for the insect would be uneffective because the SARM, also known as the “whirl maggot,” is protected in the whirl of the plant.
The SARM is typically an early-season to mid-season pest, and the rice typically outgrows the damage, so we really don’t see it during the reproductive stages of rice development. However, the SARM can still be found in the later-planted rice.
Now that a lot of rice has headed, or is beginning to head, across the southwest part of the state, we are beginning to see other insect pests become more prolific.
Grasshoppers: I have received several calls about grasshoppers in rice.
We are all familiar with grasshoppers, and their presence in rice is typically isolated to field edges. Rarely do we need to treat for them. However, I have had discussions with multiple crop consultants about the presence of very high grasshopper numbers in rice fields and not just the edges of the field.
One consultant mentioned that scores of grasshoppers would just keep jumping ahead of him as we walked through the rice field. In addition to feeding on leaf tissue, these grasshoppers also seem to be feeding quite a bit on newly emerged panicles.
Currently, we do not have management guidelines or thresholds for grasshoppers in rice. However, we do know that an application of a pyrethroid insecticide will take care of the grasshoppers. A judgement call on whether the pressure is high enough to justify an insecticide application will have to be made based on the judgment of the crop manager. If the rice stink bug is also present in high numbers, and both pests could be controlled with one application, the determination to apply would be much easier.
Stink bugs: Early reports are that the rice stink bugs are present in many fields. Fortunately, we do have gridelines for management of the rice stink bug. Rice stink bugs should be scouted for during the morning.
During the heat of the day, the stink bugs move downward in the canopy seeking shelter from the heat. During the first two weeks of heading, the threshold for applying an insecticide treatment is 30 stink bugs per 30 sweeps of a 15-inch diameter sweep net. After that the threshold is 100 stink bugs per 100 sweeps with a sweep net.
Pyrethroid insecticides do a good job controlling the pest. Karate Z and Prolex have 21-day pre-harvest intervals. Tenchu, a neonicotinoid, can also be used but cannot be used when the rice is flowering. Orthene (Acephate) should not be used in rice to control stink bugs.