Northwest Michigan fruit regional report – July 14, 2015
Higher numbers of cherry fruit flies and obliquebanded leafrollers have been reported in traps throughout the region this week.
We had another beautiful summer week in northern Michigan. Last week, daytime temperatures were in the mid-70s and temperatures hit the 80s over the weekend. We have accumulated 1,618 growing degree days (GDD) base 42 and 974 GDD base 50, and we are a few days behind our 25-year average. Rain was predicted for yesterday, July 13, and we received a few sprinkles, but no substantial rain was observed in the area. Conditions are very dry, but as sweet cherry harvest is underway, growers are hoping the rain holds off. There is a 93 percent chance of rain again today. Overnight, we did end up receiving some rain. We recorded 0.23 inches at the Northwest Michigan Horticulture Research Center (NWMHRC).
As mentioned above, sweet cherry harvest has begun in earnest. Although the crop is variable across the region, fruit quality is good. There is some detectable bird damage, particularly in early ripening varieties. However, very little brown rot has been reported so far. There was some cracking from the light rain a week ago, and growers want to get the crop off before a potential big rain event. Trees with a light crop are more at risk from cracking, and orchards with a lighter crop are ripening fast. A lot of ethephon is going on cherries this week.
Tart cherries are coloring up. We have some blocks at the NWMHRC that look like we could harvest next week. Some orchard blocks in the area have a big crop, and growers are trying to keep leaves on as long as possible to ensure the crop ripens. Leaf spot and virus have taken a toll on many trees throughout the region.
Apples are sizing and growers are assessing their thinning efforts from spring. Some growers are hand-thinning fruit at this time.
We are continuing to see cherry leaf spot-infected leaves and virus-infected leaves falling from trees in the area. Fortunately, we have had only a few days with rain and very few infection periods reported on Michigan State University Enviro-weather since the beginning of July. Cracked fruit as a result of rain early last week is showing up and growers are concerned with the potential for brown rot development. We have seen very little brown rot infection and have only received a few isolated reports of brown rot in orchards. However, Michigan State University Extension advises growers to be on the lookout for brown rot in cracked fruit, in particular if fruit are still on trees after more significant rainfall. Overall, recent dry conditions have been in our favor and have posed fewer challenges with cherry diseases, especially compared to our wet start to the season.
Rain last week stimulated cherry fruit fly emergence, and we are finding higher numbers of cherry fruit flies in the region (10 cherry fruit flies per trap have been reported) and at the NWMHRC (a high of four cherry fruit flies on a trap) this week. Some growers harvested sweet cherry blocks before cherry fruit flies were detected in more significant numbers. Many growers will be protecting against cherry fruit flies this week in blocks that will not be harvested for another couple of weeks.
Fortunately, spotted wing Drosophila (SWD) numbers continue to be low, and many growers have decided to focus on managing cherry fruit flies at this time. We found one female SWD adult in a trap that was placed in mulberry, a non-crop SWD host, in Antrim County late last week.
Obliquebanded leafroller trap numbers are on the rise this week, and most traps are catching well above the 20-moth threshold throughout the region (about 50 moths per trap in some blocks). Growers should remember most materials effective against cherry fruit flies are not as effective for obliquebanded leafrollers and vice versa. Therefore, growers with high obliquebanded leafroller trap numbers should put a Lepidopteran material for obliquebanded leafrollers in the tank as we approach harvest. We have not found obliquebanded leafroller larvae, but these larvae typically become active at approximately 1,405 GDD base 42 F, and thus far we have accumulated 1,618 GDD.
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