Grand Rapids, Mich., area tree fruit regional report – September 3, 2013

The 2013 pest management program is winding down.

Early harvested apple varieties are in bins and on the shelves ready for customers. These include Paula Reds, Ginger Gold, Zestar and SweeTango. So far for these early varieties, Michigan State University Extension’s predicted harvest dates seem to be right on target for 2013 and are very close to the normal average harvest dates or just slightly ahead of average for some sites. Fruit condition has been excellent so far and fruit finish is outstanding even for yellow and known rough cultivars.

Codling moth second generation adult flight is still ongoing and should be declining over the next week or two. Egg hatch should be occurring and is most likely past its peak. A second generation regional biofix date of July 25 was set and there have been 651 GDD base50 accumulated since then. This indicates we are on the downside of second generation codling moth egg hatch, but it is not over yet and cover sprays are still important to maintain in apples and pears.

It’s important to note that even if your trap catches are down now, you need to take a look backwards 250 GDD50 to know where you might be with potential newly hatching larvae. Adults that were flying 10 to 14 days ago, mated and laid eggs and now, 250 GDD50 later, those eggs are hatching. If your trap numbers were over threshold 10 days ago, there is the potential that significant egg hatch is occurring now that could lead to stings in unprotected apples.

Obliquebanded leafroller adult flight for the overwintering generation is done and all eggs that were laid should now be hatched. Small larvae are present now, but they are very low in number and controls this time of year are typically not needed or warranted.

Some apple maggots are still being trapped in apple blocks with known populations. Continue to monitor.

Oriental fruit moth third generation flight continues and egg hatch should be near 30 percent now and is expected to be at a peak by the weekend (Sept. 7-8). A regional biofix was set for May 15 (337 GDD45) – GDD since biofix = 2,400. Be sure to check preharvest intervals (PHI) for late harvested peaches and plums.

Third generation oriental fruit moth larvae have been known to feed on apples if blocks are near stone fruits or possibly in apple blocks that have been under mating disruption for many years. The only way to know for sure is to have a trap or two up in these scenarios and closely monitor for injury to fruit.

Each week, a few brown marmorated stink bugs have been trapped from known hotspots in more southern areas of the state. None have been trapped from any commercial production systems in Michigan at this time, but numbers overall seem to be increasing and both adults and nymphs are being found.

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