Cereal leaf beetle population on the rise

WOOSTER, Ohio — Some wheat growers in Ohio are reporting outbreaks of cereal leaf beetle in numbers that could cause economic losses in grain, according to an entomologist from Ohio State University’s College of Food, Agricultural, and Environmental Sciences. Some growers have reported adult cereal leaf beetles in their fields along with larvae in large enough populations to potentially cause losses of up to 40 percent in both wheat and oats, said Ohio State University Extension entomologist Ron Hammond.

With wheat nearing or reaching the flag leaf emergence and the boot stage, the crop is coming into the susceptible period where significant feeding on the flag leaf can cause a major reduction in yield, said Hammond, who also holds an appointment with the Ohio Agricultural Research and Development Center. OSU Extension and OARDC are the outreach and research arms, respectively, of the college.

“This is something that may be going on across the state and is something that we need to pay attention to now,” Hammond said. “We don’t yet know how widespread it is, but in past years it has shown up in several areas of the state.

“Growers need to be out in their fields scouting and, in some cases, may need to treat their grains with insecticides to stem the problem.”

Measuring loss

While in previous years the threshold for economic loss was two larvae per stem or flag leaf, that number is now down to one larva per stem or flag leaf, he said.

This is because the larvae feed heavily on the flag leaf at a time when it is critical to the growth of the wheat head and can cause losses.

“And with the value and pricing of wheat as high as it is now, we want to make sure that we’re not letting the cereal leaf beetle problem go above one larva per stem or leaf,” Hammond said. “We need to get farmers out there scouting in at least 10 locations in their fields and counting larvae per stem to ensure that one-per-stem threshold hasn’t been met.”

Native to Europe and Asia, cereal leaf beetle is a grain pest that was first identified in Michigan in the 1960s, and was effectively controlled by parasitoids such as parasitic wasps for over three decades, he said.

But in recent years, entomologists have noticed that the beetle is re-establishing itself, with some speculation that overall warming may be a cause.

“The most destructive life stage of the cereal leaf beetle is the larva, which causes the most damage to the wheat crop, attacking the plant’s flag leaf soon after emerging in the spring,” Hammond said. “Just one larva per flag leaf stem can be devastating, since the flag leaf is the center of grain fill and ultimately controls yield.”

The problem is significant for Ohio, considering that the state is the No. 1 producer of soft red winter wheat in the United States., having produced more than 49 million bushels in 2011, according to the Columbus-based Ohio Corn and Wheat Growers Association.

The total value of wheat production in the state is $353 million, according to the industry trade group. Adult cereal leaf beetles lay eggs in the spring on grasses, such as wheat and oats. The emerging larvae, one-quarter to three-quarters of an inch in size, appear as small black slugs, due to their feces adhering to their bodies.

Spotting infestation

An infested field can take on a frosted appearance if injury is severe, Hammond said. Growers who spot an average of one larva per stem should treat their fields with insecticides, he said. More information on cereal leaf beetle and a list of labeled insecticides can be found at http://entomology.osu.edu/ag/images/Small_Grains_2013_CLB.pdf.

Organic cereal grain fields are also at risk from cereal leaf beetle damage, Hammond said.

“Organic growers with cereal leaf beetle on wheat and other cereal grain crops can use Entrust, which is an organically approved product,” he said. “Entrust contains spinosad, which is produced through the fermentation of living organisms.”