As row-rice acres grow, so too may billbug woes

rice levee billbugs
Rice levee billbugs are weevils and, as such, are related to rice water weevils — photo by Johnny Saichuk

Billbugs, once an occasional pest of rice that cannot survive in standing water, are increasing pressure as row-rice acreage grows.

Billbugs are weevils whose larvae bore into the side of rice tillers, or stems, and deprive developing grain heads of nutrients. This leads to “blank heads,” or heads that never develop kernels.

Billbugs cannot survive aquatic conditions, making row rice, which does not hold a continuous flood, an ideal environment.

“We’ve been saying for the last few years as row rice becomes more popular, we’re going to have a billbug problem,” says Nick Bateman, University of Arkansas Extension rice entomologist. “And there have been some reports over the past couple of years, but this is one of the first years we’ve seen, at least in pockets, a substantial number of billbugs.”

Because billbug larvae bore into rice tillers, most damage isn’t seen until it’s too late.

“The damage doesn’t stop the head from forming, but it kills the tiller, so in turn it’s killing that head as it’s trying to push out of the boot,” Bateman says. “Now that rice is mostly headed out, we’re starting to see a lot of blank heads.”

rice levee billbugs in a rice root
Billbug larvae bore into rice tillers,
causing kernel blanking — photo by
Nick Bateman, University of Arkansas

Billbugs tend to stay near the bottom of the plant, making scouting difficult, but there are clues.

“They’re most likely not moving up and down the plant a lot, so we could maybe get down on our hands and knees and scout for them, but that’s just not feasible,” Bateman says. “Similar to rice water weevils, billbugs come out of a tree line. So it’s going to be the high end of the field in row rice or on levees and it’s going to be near a tree line.”

It is still unclear what form of control will be effective, but the university is conducting trials this year and more are planned for the future. Because there is a period of time between when adults migrate into the field and when damage appears, Bateman says he hopes to test timed foliar applications as well as seed treatments.

“We’re exploring seed treatment combinations and we’re hoping there’s some combination that will give us some control,” he says. “We’re also trying to look at whether it’s based on the growth stage of the rice or maybe a calendar event so that we could maybe time a foliar application.”

This article was contributed by the University of Arkansas

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