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Scouting for billbug damage can be challenging

Yellowish looking stems are a symptom of billbug feeding in row rice.

Forrest Laws

November 24, 2021

Chase Floyd walks into a rice field on the Haigwood Farm near Newport, Ark., reaches down and plucks a yellowish looking rice stem from a group of plants in a furrow-irrigated or row rice field.

It looks easy, but you have to wonder how long Floyd, a Ph. D. candidate at the University of Arkansas System Division of Agriculture, had to search to find the yellowish stem, a symptom of billbug feeding in row rice.

“As you move down here, you’re going to see that this plant tissue is yellow,” said Floyd, who discussed billbug damage with Dr. Nick Bateman, Extension entomologist with the University, in a presentation for its virtual Rice and Soybean Field Day. “And that’s going to let you know there’s some sort of feeding going on.

“Another sign for billbugs is if you take that tiller and pull it, it will break directly at the soil line. The larvae stay very close to the soil line, and, as they feed, they weaken that plant. So when you pull it, and it breaks at the soil line, that’s a sign of billbug damage.”

Tracing billbugs

Floyd moved to the turn row and showed viewers a clump of rice tillers from that location in the field. “I’ll take the dead tiller we found and pull it away,” he noted. “I’ll trace it to the base of the plant near the soil line you’ll see where the adult has fed and possibly deposited an egg.”

In the adult stage, rice billbugs are large black weevils with a long snout they can insert into the soft tissue of the rice tiller. If you see adult rice billbugs, it can be helpful to determine the sex of the insect by flipping them upside down.

“In between its second and third pair of legs, if it is indented, like in this picture, and there’s a small hair on the first abdominal segment, that let’s you know it’s a male,” he said. “The way we explain it is that, if it has the mustache, it is a male. In the other picture, there is no hair and the thorax tends to be smooth and not indented. That let’s us know it is a female.”

Floyd counted nine tillers in the clump he pulled. “One of them was damaged so that let’s us know we’re at about 11%  tiller damage in this field, which is pretty common for the row rice fields we’re surveying across the state.

From there, I look to break the root ball open,” he noted. “Typically, we’ll find a larva down at the base of the plants. Once the larva hatches, he’ll get in the root ball, and he’ll feed up and down the tillers. This is the later season damage we’ll see. The blank heads are from larva feeding.”

About the Author(s)

Forrest Laws

Forrest Laws spent 10 years with The Memphis Press-Scimitar before joining Delta Farm Press in 1980. He has written extensively on farm production practices, crop marketing, farm legislation, environmental regulations and alternative energy. He resides in Memphis, Tenn. He served as a missile launch officer in the U.S. Air Force before resuming his career in journalism with The Press-Scimitar.

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