Dry conditions are likely to continue through the early part of winter and one Purdue University entomologist says crop insect pests will probably survive the mild season.
Most of the crop pests in Indiana have been around for a long time," said Christian Krupke. "They are well-equipped to cope with weather changes and they can withstand a wide range."
Indiana is located in a region where both temperature and precipitation can swing widely above and below average, said associate state climatologist Ken Scheeringa. But, with the current weather pattern and little precipitation expected until late winter, insect pests might not have to cope with too many extreme conditions.
"Indiana is currently in a La Nina weather pattern, in which we can expect drier-than-normal conditions to continue in the state through early winter," he said. "As we get into late winter, however, the chances for more frequent precipitation and replenishing of soil moisture will improve."
If La Nina were to occur for a whole calendar year, Scheeringa said that historical observations suggest January and February will be warm and wet. Moist conditions would continue in March and April and a long cool spell would begin.
On average Indiana receives 41.3 inches of precipitation annually. During La Nina the average increases slightly to 41.6 inches, Scheeringa said. But the effects of La Nina are better seen per month. January, February, March, June and December tend to receive more precipitation, while April, May, July, August, September and November are abnormally dry. October tends to be normal, he said.
If La Nina does bring a lot of precipitation in the spring, it could potentially affect crop pests, Krupke said. That is because some pests come to the surface of the soil at the end of winter and beginning of spring and could drown.
Pests that usually cannot overwinter in harsh and severely cold conditions are corn earworm and armyworm, Krupke said. They must be transported north on storm fronts in the springtime of each year. In a relatively mild winter like the one expected for this year, however, they are expected to survive further north, meaning that they have less distance to fly to infest crops in the springtime.
"There is not much growers can do now," Krupke said. "The best thing to do is wait until spring when pheromone tap catches are reported, which will give an indication of early season pressure on crops."