Warmer temperatures have impact on field crop insects

We had a great meeting last Wednesday evening on the oil and gas leasing briefing. There were more than 130 people in attendance to hear Chris Penrose and Dale Arnold speak. We plan to have some follow-up meetings, so watch the newspaper and website for dates and times.

This weekend looks to be sunny and in the 60s. What a winter we have had with above normal temperatures and rainfall.

According to the National Weather Service, our 2012 spring will be quite different than last year — not as cool. They are calling for a wet spring, but not as wet as last year, with that wet cycle ending earlier than in 2011. Along with that comes the threat for severe storms due to the warm temperatures and active pattern. I hope we will avoid those severe storms.

Because of the warm winter that we have experienced, we have been getting the question of “what impact this warm winter will have on field crop insects.” OSU Extension Specialist Ron Hammond says it depends on the insect and crop in question. There are other factors that may impact crops more because it depends on when crops get planted. Hammond says that the warmer temperatures will allow for soil to warm up earlier and higher than expected spring rains might not allow for earlier crop planting if soil remains as wet as it is.

While survival might be greater, it remains to be seen if we will see hugely greater densities of many of our crop pests. This will require scouting and the first good example is with alfalfa weevil on alfalfa. Hammond say that the time to begin sampling for weevils and larval feeding is dependent on weather, with heat unit accumulations beginning on Jan. 1. At 300 heat units, he recommends sampling. Because of that, scouting should come earlier in the season.

“Because alfalfa is already planted and in the field, we would expect alfalfa growth to also begin its green-up earlier, probably at the same relative rate as we see with weevil growth” Hammond said.

Sampling to determine the actual need for treatment is recommended. Then, there are the many insects that migrate from southern areas, such as black cutworm, true armyworm and potato leafhopper — their development is affected by weather conditions further south.

We would expect to see insects that do overwinter in Ohio emerge from their overwintering sites earlier than normal because temperature often drive this event. Depending on the stage of crop development and growth will determine whether they become economic issues. According to Hammond, if insects arrive in fields early but no crop is even planted, this could lead to greater mortality if they cannot find alternative hosts. However, if the insect arrives or begins feeding earlier when crops are smaller in size, a greater potential for injury exists, such as with slugs on corn and soybeans.

The warmer temperatures that we have experienced the past three months will impact insect pests to some degree. However, according to Hammond, whether economic problems will increase — or perhaps decrease — depends on the specific pest–crop relationship, and then the weather conditions over the next two to three months. Depending on the crop and when they get planted will tell if we will have earlier economic problems.

Rob Leeds is the OSU Extension Educator Ag/NRD for Delaware County.