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Warm Winter Doesn't Guarantee Pest Outbreak

Warm Winter Doesn't Guarantee Pest Outbreak
Too many factors affect insect survival to be able to say that just because it was a mild winter, there will be lots of insect problems this spring and summer.

The logical conclusion would be that because it was a mild winter, there would be hordes of insects to deal with this spring and summer, both in crops and around the house and barn. Purdue University entomologists John Obemeyer and Christian Krupke say that's not necessarily the case. Instead, they conclude that the most accurate prediction about insect numbers and the outbreaks of any particular insect pests in any one season is that they are unpredictable.

Warm Winter Doesn't Guarantee Pest Outbreak

For starters, it's not freezing that often damages pests that overwinter in Indiana anyway, they note. Instead, it's freeze-thaw cycles, when it freezes and then thaws out, then repeats itself, that many insects have trouble adapting to in their development.

Second, insect mortality is much higher than you might expect. The entomologists estimate that under normal conditions, it's about 70% mortality. Many insects are constantly struggling to survive. They survive if they have large number in the beginning. Even in controlled, greenhouse situations where entomologists are trying to raise insects for experiments, mortality is about 50%.

Weather plays a big role in that. If it's too wet or too cold or too dry at a critical stage in the insect's life cycle, it may greatly increase mortality. The exact effect depends upon the insect, and it varies, depending upon its life cycle.

The other factor people often underestimate is that insects have many natural predators. It may be another insect or a bird, or it may be a fungal pathogen or a disease that takes up residence on or inside the insect.

The bottom line is that while it always pays to scout fields, this season may not have more insects than any other season. Just because it was a warm winter doesn't mean that insects will control the growing season. 

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