Late Planting Increases Need to Scout for Pests

WOOSTER, Ohio – Crop growers should take extra care to scout their fields this spring for insects and invasive pests, including a relatively new pest that has shown up in unexpected areas across Ohio that has the potential to cause significant economic losses for growers, according to an entomologist with Ohio State University’s College of Food, Agricultural, and Environmental Sciences.

In addition to cereal leaf beetle, alfalfa weevil and black cutworm, crop growers need to be on the lookout for Asiatic garden beetle grubs, which are especially aggressive in their feeding habit, said Ohio State University Extension entomologist Ron Hammond.

Thanks to rains that kept many growers out of their fields later than in a typical year, many corn crops are smaller at this stage, which increases the chance for insect and pest damage, 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.

“We’ve had more calls about alfalfa weevil than in previous years, with quite a few people cutting early to help stem the pests,” Hammond said. “And we’ve had reports of Asiatic garden beetle grubs that have caused stand losses in corn fields in Tuscarawas County, which is much further south than we expect to find them.

“We always assumed Asiatic garden beetle grubs were in north and northwest Ohio, parts of Indiana and Michigan, but we’ve now found them in much wider area. We recommend growers throughout the state check corn in sandy soils, particularly paying attention to fields in river bottom areas where sandy soils are often found.”

Some of the invasive and damaging pests that growers can expect this year include:

• Asiatic garden beetle grubs: Last year was the first known instance of Asiatic garden beetle grubs causing significant stand losses in corn in northern Ohio just below Lake Erie. Growers who planted corn following soybeans in sandier soils reported last year finding Asiatic garden beetle grubs that caused some stand losses. What’s surprising about this is that the grub, which is a species that is more associated with being a minor pest in turf, now appears to be much more damaging to crops than most other grubs. At the present time, similar to other grub problems, there is not a rescue treatment available, and the only action would be replanting if necessary. Most of the grubs should be pupating shortly.

• Alfalfa Weevil: Many growers made their first cutting of alfalfa early this year, which is recommended over insecticide applications when large numbers of alfalfa weevil have infested taller alfalfa. If larvae survive the cutting and lack of food for a few days, they may still be alive when regrowth begins and possibly start feeding on the new growth. Thus, those growers should scout their fields for possible feeding on the new growth and apply an insecticide if feeding is occurring.

• Black Cutworm: This pest is a more common problem this spring throughout the Midwest including Ohio. Because of late planting, cutworms might already be at damaging stages when corn starts to emerge. Growers need to pay extra attention in those fields conducive to cutworm problems, such as no-till and or weedy fields.

• Cereal Leaf Beetle on Wheat: Some wheat growers in Ohio 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. 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.

Growers statewide should check their fields and those who spot an average of one larva per stem should treat their fields with insecticides, Hammond said.

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.

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. Entrust, which is an organically approved product, can be used to treat the insects.