Harvest time activity of codling moth and Oriental fruit moth in 2010

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

The prolonged high temperatures experienced in fruit orchards across Michigan this summer have resulted in third generation activity by codling moth and a fourth generation flight by Oriental fruit moth. Captures of codling moth are just beginning to climb, and whether or not growers will need to treat to protect against codling moth damage to fruit will depend on continued monitoring of traps and visual inspections for larval entries into fruit. Several environmental factors need to be considered as well.

Once flight over thresholds is determined, it will require 100 GDD, base 50, before codling moth eggs will be laid, and another 150 GDD (250 GDD total) before eggs will begin to hatch. The weather and temperatures between now and expected egg hatch will play a major role in determining the need to treat. Moths will fly during evening twilight hours only when temperatures are above 60ºF, there is no rain, and winds are below about 5 MPH. Weather impacts Oriental fruit moth activity in a similar manner, although the GDD numbers differ. From the time of detection of flight over threshold, there must be an accumulation of 150 GDD, base 45, before egg hatch occurs.

The bottom line is that even if daytime temperatures rise into the 70’s, if evening temperatures remain low, GDD’s will accumulate slowly and moth activity will be subdued. Fruit that will be harvested in the next couple of weeks should escape late season injury. For fruit that remains beyond that time, growers will need to keep a close eye on their trap catches, visually scout for larval entries and monitor weather conditions to determine the need to treat to protect fruit at harvest.

Dr. Gut's work is funded in part by MSU's AgBioResearch.

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