We have observed a large amount of rice billbug activity in row rice across the state this week. Fields that have been in continuous row rice are at greater risk of having billbug infestations.
Prior to the growing season, observations of larvae and adults were found overwintering in the field approximately 4 to 6 inches beneath the surface.
When billbugs emerge, the adults move to a viable food source, such as bermudagrass, on ditch banks and turn rows. They will remain there until the rice crop begins to tiller. Once the rice becomes desirable, the adults will move into the field and begin to feed on the crop.
The Key Time Period
During 2019 and 2020, our peak trap catches occurred during the first week of June, with a dramatic increase in trap catches the following weeks. The rice during this time period was between 3 to 5 tillers for both years. We believe this is the time period when rice billbug moves back into rice.
The adults will feed by inverting themselves on the rice and puncturing the tiller with their rostrum. Greenhouse observations show that billbug damage can be seen 5 to 7 days after the adult feeding has occurred. While scouting row rice, look for dead tillers.
The leaf blade will be brown until it reaches the joint of the tiller. Trace the damaged tiller to the base of the plant near the soil line and inspect for puncture wounds.
Where To Find The Eggs
Female feeding may result in oviposition, and eggs will be laid within the leaf sheath in the base of the tiller. Billbug eggs are cream colored and oblong in shape, and measure approximately 2 mm in length and 1 mm in width.
After the eggs hatch, billbug larvae will feed in rice tillers as well as on the roots and bases of tillers, causing seed heads to abort. If egg lay and adult activity are observed, a foliar insecticide application may be warranted.
These applications do not achieve 100% control but could help reduce damage. Use a high rate of a pyrethroid, such as Lambda-Cy or Mustang Maxx.
