Grand Rapids, Mich., area tree fruit regional report – July 23, 2013

Several tree fruit pests have not taken a summer vacation in the west central region.

While a few apple pests are in between generations right now, there is still plenty of activity in the insect and disease pests of tree fruits in the Grand Rapids, Mich., region.

First generation codling moth activity has ended. Second generation adult flight should begin any day. A regional biofix was set for:

  • May 18 (260 GDD50) – GDD since biofix = 1,144
  • May 28 (367 GDD50) – GDD since biofix = 1,037

Michigan State University Extension advises this is a good time to change lures for second generation if you haven’t yet. Most blocks have had zeros for a week or two and will be able to set a new biofix for second generation.

Obliquebanded leafroller adult flight for the overwintering generation could begin at any time. Larvae are present from the summer generation in low numbers with hot spots here and there. A regional biofix was set for June 16 (1,074 GDD42) – GDD since biofix = 1,055. Larvae should be very easy to find now, and pupation is underway. Having fresh lures in traps is a good idea this week. Early egg hatch for the overwintering generation won’t show up for 10 to 14 days (estimated to be Aug. 6) with larvae much easier to find a week later (estimated near Aug. 13).

Apple maggot spotty trap numbers are being reported around the state and in west Michigan with higher numbers in areas with significant rainfall and sandier soils. Continue to monitor with sticky traps. Upon emergence, there is an eight- to 10-day period before female flies begin to lay eggs and fruit needs to be protected.

All stages of European red mites are present. Beneficials are present. Threshold for July is five mites per leaf. Continue to monitor for European red mites and their predators. In early August, the threshold for European red mite goes to 7.5 mites per leaf. Once you get to Aug. 15, controls are not needed.

Green apple aphids continue to be present with beneficials helping curb numbers in some blocks. Wooly apple aphids are also present in some blocks in rather high numbers.

All stages of white apple leafhoppers and potato leafhoppers are being found. Management in apples is typically not needed with the exception of non-bearing trees where you are trying to fill the growing space.

Spotted tentiform leafminer second generation flight is declining and new sap feeders are easier to find, but numbers are low overall. Continue to monitor. This insect is not a major pest of apples.

There are reports from southeast and southwest Michigan of San Jose scale present on apple fruit already – this is highly unusual to see from first generation San Jose scale, so be on the lookout for it in this area as well. First generation crawlers have settled in to their permanent spots and are now difficult to manage. New crawlers are expected 500 GDD51 from the start of the second generation flight (estimated first week of August).

Oriental fruit moth second generation flight should be at or near peak. Cover sprays are crucial for stone fruits now. A regional biofix was set for May 15 (337 GDD45) – GDD since biofix = 1,504. Cover sprays for second generation will need to be maintained for the next several weeks in stone fruits to prevent fruit and shoot injury to stone fruits. Be sure to check PHIs as early harvest gets started. This generation is not an issue in apples in general, but can sometimes bore into shoot tips in young trees, which is easily mistaken for fire blight infections.

In invasive species, the number of spotted wing Drosophila trapped across Michigan is increasing. No brown marmorated stink bugs in black light traps yet.

Japanese beetles continue to be active and increasing in some areas. Continue to monitor and apply cover sprays as needed.

Continue with apple scab covers in blocks with primary scab. If we continue to get extended dry weather, you can stretch out fungicides, but be sure you have enough on when it does rain.

As harvest nears for many stone fruits, you will want to step up your fungicide program to prevent brown rot from blooming on ripening fruits. Brown rot can really take off quickly in blocks with any fruit damage from earlier frosts or bacterial infections.

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