West central Michigan tree fruit regional report – May 12, 2015

Wet conditions create disease pressure in tree fruits in west central Michigan.

Crop stage and growing degree days (GDD)

Apples are mostly in the full bloom stage. Pollination is of concern with all the rainy weather in the last several days, right during the full bloom period. GDD totals are near normal averages.

Apple scab

Beginning May 8, there was a long wetting event according to data from most west Michigan Enviro-weather stations. Apple scab primary spore numbers were caught in relatively high numbers. This is a major apple scab infection period; for most sites, this is only the second scab infection of the season. Lesions from the only other scab infection back on April 19 started to show up on minimally managed trees Saturday, May 9. Look on spur leaves or the first true leaf on early developing varieties.

Fire blight

Very warm temperatures and rainy conditions along with bloom opening created an infection risk for blossom blight for susceptible apple cultivars. Cooler conditions that moved in Sunday and Monday, May 9-10, greatly reduced the risk for blight. However, that risk goes back up next weekend with forecasted warmer weather and late, rag tag bloom could be at risk then.

Tree fruit insects

With apples in bloom and bees present in orchards, no insecticide covers are needed. There have been initial reports of rosy apple aphid egg hatch. A few, small, overwintering obliquebanded leafroller larvae can be found, but overall numbers appear to be very low. Oriental fruit moth began flying with the warmer weather 10 days ago and trap numbers were consistent up until this recent cooler weather. Most of the area will likely go with a May 1 or 2 biofix for oriental fruit moth. Mating disruption should be set for this pest and traps should be up with lures in them.

Codling moth flight has not been reported, which is as expected. Codling moth flight could begin with the warmer weather forecasted for the coming weekend, May16 – traps with lures need to be placed soon and mating disruption can go up anytime.

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