Corn Earworm – Vegetable Crops Hotline

Corn Earworm

Pheromone trap catches of corn earworms have been relatively low in most areas of the state, with northern Indiana having the highest counts. Counts from the Purdue research farms can be seen at Remember that as the field corn surrounding your sweet corn begins to silk and be attractive to the earworm moths for egg laying, the threshold for treatment in your sweet corn rises from 1 moth per night to 10 moths per night. I would like to express one note of caution about using thresholds. We recently had one trap that on seven consecutive nights caught 9, 7, 5, 9, 6, 7, and 7 moths. On none of these nights was the threshold of 10 moths reached. However, on two night 9 moths were caught and at least 5 were caught on every night. I think it is reasonable to assume that the accumulation of eggs laid during this period would be sufficient to justify spraying insecticides. My point is that a threshold is not a magic number. It is an estimation of when sufficient eggs would be laid to economically justify a spray or sprays. In a scenario like I described here, the common sense and prudent response would be to apply insecticides.

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