Northwest Michigan fruit regional report – July 16, 2013
Hot weather moves into the northwest region just in time for cherry harvest.
Daytime temperatures have been hovering in the high 70s and into the 80s for the past week and a half, just as most growers are starting to harvest sweet cherries across the region. Temperatures are even predicted to reach into the 90s this week. Harvesting in this very hot weather is not ideal, but growers have little choice other than to keep the shaker moving. Ethephon sprays will be going on tart cherries, but most growers will wait for temperatures to cool or reduce the rates to prevent heat-related phytotoxicity.
Despite the rainfall last Sunday night (July 14), the region is extremely dry. However, this dry weather is welcomed as we move through sweet cherry harvest. Fungal diseases have also been held at bay with the warm and dry weather. So far this season, we have accumulated 1,741 GDD base 42 and 1,129 GDD base 50.
Apples. There is a little scab out in the orchards, but the warm and dry weather has helped minimize this disease’s spread. Some growers that had some leaf scab are spraying to keep the fruit clean until harvest. Apple pest trap catches are low this week except for spotted tentiform leafminers, which have jumped up since last week. Mite numbers are also increasing with this hot and dry weather. Thinning sprays were effective and many blocks have a good amount of fruit. Fruit is sizing, but rain is needed.
Cherries. Cherry leaf spot development has been slowed with the recent dry conditions. Even the untreated control trees in our efficacy trial look better than in most years. Powdery mildew is not hard to find in many blocks, especially on new growth. Cherry pest numbers are also low. American plum borer moth catch was up from last week, likely the start of the summer generation flight. Lesser and greater peach tree borer counts are both relatively low with an average of about four moths per trap.
Obliquebanded leafroller numbers also dropped off this week, and likely those eggs that were laid at peak flight have hatched and larvae are present in the orchard. Michigan State University Extension advises growers to be sure to control these pests as we move into harvest; obliquebanded leafrollers are a contaminant pest of cherries and drop into tanks during the shaking process. Obliquebanded leafrollers have developed resistance to the organophosphates, so an insecticide that specifically targets Lepidopteran pests is needed in the spray tank. Growers need to be sure to check the pre-harvest intervals on these insecticides as we near harvest.
Cherry fruit fly numbers are down here at the Northwest Michigan Horticultural Research Center, but regional consultants have caught cherry fruit flies in numbers similar to last week. Fruit needs to be protected against this pest through harvest. Post-harvest sprays will also reduce populations for 2014.
Mite populations are building in cherries, and again this dry weather is contributing to the increase in mite numbers. We have not seen any firing in tart cherries with these hot and dry conditions. No spotted wing Drosophila have been trapped in northwest Michigan in the 60-plus traps.
Wine grapes. Shoot growth and leaf area have increased rapidly in area vineyards. Canopy density is going to be an issue from here on out, requiring attention to hedging and removal of laterals in the fruiting zone to provide for air and light penetration to the clusters.
Despite high humidity that favors powdery mildew development, this disease is still a relatively minor problem at most sites I visited in the last week. It is very important to scout known powdery mildew hot spots frequently now to keep on top of this disease.