West Michigan tree fruit update – Aug. 1, 2017
The end of summer is no break for pest management in tree fruits.
Crop and weather update
Harvest of early peach cultivars continues. Peaches have been sizing very well despite drier conditions of late. Apples are sizing well and are between 2 and 2.5 inches in size.
Rainfall has been minimal in the last two weeks with irrigation systems running to make up for moisture. Let’s hope the high predictions for rain later this week come true.
Codling moth adults in traps have been increasing and I set a new regional biofix for second generation for July 19 (1,307 GDD 50) and 249 GDD base 50 have been accumulated. Many blocks have had very little in the way of second generation flight. In higher pressure blocks or blocks you are not trapping in, consider cover sprays now to protect fruit from newly emerging codling moth larvae. Low pressure and disrupted blocks might still be a week or two away from codling moth cover sprays. You have to be trapping in your own blocks to know what’s going on.
Apple maggot adults started flying in sandy sites and higher pressure blocks well over a month ago in light numbers. There has been some suspect apple injury that could be apple maggot. It could also be brown marmorated stink bug exploratory feeding from overwintering adults—we see the damage, but neither apple maggot nor brown marmorated stink bug have been trapped in these blocks. It’s a bit confusing.
With the dry weather, flight has been reduced. If we get significant rain of more than 0.5 inch, there could be a flush of apple maggot. We typically see a definite increase in apple maggot traps the last week of July, so it’s time. There has been a marked increase in apple maggot in the general Grand Rapids area over the last two or three years, and all blocks should be trapping for it.
Traps should be in place in known hot spots and along orchard edges near wooded areas with alternate hosts present. You only know what’s happening with apple maggot if you are trapping for it correctly. Red spheres with essence lures are the best for apple maggot. Adding more tanglefoot to traps is recommended if they have been hanging for more than four weeks—they get dried out, covered with dust and other insects, and don’t trap effectively over time.
Obliquebanded leafroller adult flight for the next generation should be at or past peak, but numbers have been very low. Large larvae are being reported, which would indicate they are delayed in development; the large larvae still have to pupate and be adults yet this summer. We should be nearing egg hatch for the late summer generation of larvae—these are the tiny obliquebanded leafroller larvae that are often found crawling on Paula Reds and other early varieties. A regional biofix was set for June 8 (1,017 GDD42) with 1,450 GDD accumulated since then.
We should be nearing the end of second generation oriental fruit moth activity with maybe a week left for the last eggs to hatch. Oriental fruit moth trap numbers have been odd this year, as there was a nice peak of flight with the first generation, but just a steady flight in the last several weeks with no peak except in the highest pressure peach blocks. Third generation flight could begin in the next week or two. This is a good time to change out lures for that final generation if needed.
The third generation of oriental fruit moth larvae need to be managed in high pressure blocks where peaches are still present—likely two or three weeks away. A regional biofix was set for April 28 (307 GDD45) with 1,800 GDD accumulated since then. Michigan State University Extension advises monitoring traps for adult activity and relative oriental fruit moth pressure. Scout for terminal collapse and fruit feeding in stone fruit.
Japanese beetle adults continue to feed on various fruit crops. They seem to be declining a bit, but we could see another flush of adults if we get rain this week. Continue to monitor and manage as needed.
All stages of European red mite continue to be found. Overall, red mites are very low in pressure this season. Predator mites are also present. The threshold for August is 7.5 mites per leaf for blocks with an average fruit load. If your crop load is light, you can use a higher threshold or let mites go altogether as they won’t compromise fruit size in a light crop situation.
For summer diseases, second applications of fungicides should be considered again soon. Reapplication would be necessary probably after the rains predicted for this week move through. The pressure from summer diseases is about the same as last year for early August. In 2016, late-season rains gave us tremendous pressure for sooty blotch and flyspeck at a time when fungicides had definitely run out.