By DOUG SCHMITZ

Iowa Correspondent

HARLAN, Iowa — If weather conditions in 2015 are anything like last year, the diseases and insect damage that ravaged Iowa fields in 2014 may return this spring, according to plant and insect experts.

“The incredibly wet weather we had in 2014 was the driver for those diseases,” said Clarke McGrath, Iowa State University extension field agronomist, who’s also partner program manager for ISU’s Iowa Corn & Soybean Initiative. “If we have a similar weather pattern, I’d expect these diseases will challenge us again in 2015. If the weather shifts, no doubt some other diseases will move front and center.”

Last year, northern corn leaf blight (NCLB) slashed Iowa corn yields nearly in half and sudden death syndrome (SDS) decimated some soybean fields, he said.

“In corn, NCLB ate us alive in areas. We had corn with yields cut in half or better by the disease and its side effects (i.e., light test weights, stalk rots, stalk lodging).”

Alison Robertson, ISU associate professor of plant pathology and microbiology and extension field crops pathologist, said if Iowa farmers have a cool, wet spring this year, as they did in 2009-13, seedling blights on corn and soybeans may be an issue. “In 2014, we saw widespread northern corn leaf blight,” she said. “We also saw Goss’ wilt on susceptible hybrids planted north of Highway 30. Both of these diseases survive very well in residue. Seedling blights result in stand loss and replanting may need to be considered.”

Erin Hodgson, ISU associate professor of entomology and extension entomologist, said the cold 2013-14 winter temperatures and a wet June significantly impacted field crop insects last summer. “Some overwintering pests, like corn rootworm and Japanese beetle, had individually succumbed to extreme cold temperatures or saturated soils,” she said.

In fact, the unfavorable weather conditions altered normal pest development, and pest activity throughout Iowa was dampened or delayed in corn and soybeans, she added.

“As a result of lower-than-expected insect pressure in 2014, I would anticipate reduced activity in the 2015 growing season for those insects that overwinter in Iowa.” But predicting pressure from migratory insects, Hodgson added, “is very difficult to do and we won’t likely know more until (this) spring. However, field conditions (last) year can influence seed and seedling pest abundance (this) year. Weedy fields or borders are attractive to migratory, egg-laying cutworms and armyworms in the spring.

“Pests can also bounce back quickly because of high reproductive rates,” she said. “For example, a single female corn rootworm can produce 400 eggs. Even though the 2014 numbers were down, there is still concern root injury could occur in continuous cornfields.”

Moreover, it’s important to protect field crops from insect injury – especially as farmers look to 2015 spring planting, Hodgson said. “Scouting on a regular basis will provide information for timely foliar applications, if applicable, to protect yield,” she said. “Reducing weeds and other egg-laying habitat will discourage spillover into field crops.”

Robertson said the best management practices for crops include rotation to a non-host crop like soybeans, and residue management.

“Continuous-corn fields or fields adjacent to the affected fields should be planted to a hybrid with good resistance to the prevalent disease,” she advised. “If we have above-normal soil moisture throughout the growing season, we may see SDS in soybeans.

“If you can tell me what the weather will be like (this spring), I’ll tell you what diseases to expect.”