Northwest Michigan fruit regional report – Aug. 27, 2013

Things are quiet across the north now that cherry harvest has finished; growers are waiting to start apple and grape harvest.

Tart cherry harvest is complete and we have come in just under the 125 million pound average. Numbers will be recalculated this week for changes and the totals will be complete for 2013. Growers across the region are taking a small and deserved breather before apple and winegrape harvest begins.

Although fall is in the air, current temperatures make it feel like the middle of summer. Daytime temperatures have been in the mid-80s and the nights have cooled down into the mid-60s. We received some rain early this morning (Aug. 27), less than 0.2 inches in most locations, and by mid-morning the skies cleared and the remainder of the day has been sunny. We could have really used the rain as the region is extremely dry. Sweet cherry trees at the Northwest Michigan Horticulture Research Center (NWMHRC) have really started to show drought symptoms and mite populations are exploding in this heat. So far this season, we have accumulated 2,858 GDD base 42 and 1,910 GDD base 50. Our 20-plus-year averages are 2,917 GDD base 42 and 1,909 GDD base 50.

Apples. Harvest is almost here and early varieties have started to come off the trees. Color on apples this year is terrific and growers are mostly pleased with size. Growers have done a nice job controlling apple scab this season and the dry and cool weather early gave us an extra boost in protecting fruit from this disease.

Codling moth numbers are the highest they have been all season here at the NWMHRC. Growers have also reported that numbers have been climbing in the past few weeks and some farms are reporting trap catches in the 40s and 50s. This second generation took slightly longer to start flying, likely due to cool temperatures earlier in the summer, which likely slowed them down. However, the moths that are flying now are mating and laying eggs – fruit needs to continue to be protected. In addition, the nighttime temperatures are conducive for codling moth flight.

Obliquebanded leafroller numbers are also higher this week than they were last week at the NWMHRC. Both obliquebanded leafrollers and codling moths are internally feeding pests, and both are in the family Lepidoptera; we have good insecticides that will control these pests. Growers need to use an insecticide with a different mode of action than they used with first generation obliquebanded leafrollers and codling moths.

Oriental fruit moth numbers are also at a season high: 8.5 moths per trap.

Cherries. Mite populations are increasing in many cherry blocks across the region, likely due to the hot and dry conditions. Some tart cherry orchards are also showing some firing at this time. Firing is typically the result of hot and dry weather coupled with two-spotted spider mite infestations, but firing can happen with no mites. Growers need to assess if they have high mite populations before applying a miticide. Please see last week’s FruitNet, “Firing Observed in Tart Cherry” for more information on firing.

Obliquebanded leafroller numbers have also jumped in cherries from eight moths per trap last week up to 24 moths per trap this week. Growers that have these high populations of obliquebanded leafrollers will need to be aware of these populations next season.

Now that insecticide sprays have stopped in cherry orchards, spotted wing Drosophila numbers are increasing. We are catching up to 75 flies per trap at this time.

Cherry leaf spot is showing up in the tops of trees in many blocks, but overall growers did a good job of controlling this disease this season. Most growers put on a post-harvest spray to keep leaves on through September.

Wine grapes. A number of cultivars have now reached veraison. A few very early selections at the NWMHRC have already softened and developed ripe flavors! We will start reporting brix and pH levels for interesting cultivars next week.

Powdery mildew continues to increase in intensity on susceptible cultivars. The use of eradicant materials at this time can halt the progression of berry infections if good penetration and coverage can be achieved. The Michigan State University Extension Michigan Fruit Management Guide lists JMS Stylet Oil, Armicarb, Kaligreen or MilStop (all potassium bicarbonate salts) and Sulforix and Oxidate as possible products for this purpose. JMS Stylet Oil can cause a temporary delay in brix accumulation and should not be used more than twice after veraison. Oil and sulfur products should not be used within 14 days of each other.

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