Northwest Michigan fruit regional report – July 30, 2013

Tart cherry harvest continues across northwest Michigan, and the quality is still looking good.

Tart cherry harvest continues this week across all of northwest Michigan. Tart cherry quality is good, and the very cool temperatures will maintain fruit quality as harvest is expected to last for at least another one to two weeks. Temperatures have cooled off dramatically, and it seems more like fall than the end of July. Daytime temperatures over the weekend peaked out in the low 60s and following the 90 degree days a week ago, it feels downright cold. The cool temperatures have been coupled with rain, and the Northwest Michigan Horticultural Research Center (NWMHRC) received 0.43 inches of rain over the weekend. We have accumulated 2,136 GDD base 42 and 1,413 GDD base 50 so far this season.

Apples. Insect catch in apples is low again this week, and codling moth numbers have been low across the region. Some growers have commented that these codling moth numbers are the lowest they have seen in many years. Spotted tentiform leafminer numbers are still in the hundreds, and we still have not caught apple maggots at the NWMHRC. Obliquebanded leafroller adult numbers are also down again this week, and some small larvae are visible in terminals.

Cherries. With the cool temperatures, both leaf spot and powdery mildew have slowed down. Growers are busy harvesting and will likely be putting on post-harvest leaf spot sprays after they move out of a block. Obliquebanded leafroller larvae have been difficult to find in tart cherries, and we caught no adults in pheromone traps this week. We have identified obliquebanded leafroller larvae in tanks of tart cherries. As we expected, the larvae would be showing up at the same time as tart cherry harvest. Michigan State University Extension advises growers to keep an eye out for these caterpillars as they harvest.

American plum borer moth second generation flight began last week, and we trapped an average of 19 moths this week. Cherry fruit fly numbers are up from last week, and we trapped a total of 22 flies at the NWMHRC this week. Consultants have also reported high cherry fruit fly catches at many farms in the region.

We continue to catch spotted wing Drosophila (SWD) at multiple sites across northwest Michigan. Our first catch was last week here at the NWMHRC, and a second fly was trapped on Old Mission Peninsula. At the end of last week, we also trapped SWD flies in Antrim County and Grand Traverse County near the Williamsburg area. A SWD was caught in Benzie County late last week as well. We have also found tart cherries infested with SWD eggs and larvae in a block that has received minimal sprays this season.

This insect will be challenging to control as it shows up so close to harvest. Delegate and Entrust are both rated excellent on SWD in cherry, and both have a seven-day pre-harvest interval (PHI). Imidan and Mustang Max are also rated excellent, but have a 14-day PHI. Danitol (three-day PHI) and Baythroid (seven-day PHI) are rated good against SWD.

Wine grapes. Many cultivars have reached the point of berry touch, and some tight-clustered cultivars like Vignoles and Pinot Noir now have completely closed clusters. Some Vignoles berries at the research center have seeds pushing through the flesh of the berry, which is not uncommon for this cultivar. Topping or side-hedging will soon be needed in many vineyards.

Powdery mildew berry infections are starting to show up in many sites, although foliar infections are still very light. Good canopy management, including leaf removal in the fruiting zone, is going to be important from here on out to limit the progress of mildew diseases.

No Japanese beetles have been reported in Grand Traverse area vineyards. Shoot defoliation by the larger sphinx moth larvae has started to become noticeable.

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