MSU Extension

The big push to move through tart cherry harvest is over, and most farms have finished or will soon finish harvest for 2013. Overall quality has been good, but there are reports of softer fruit this week compared to last week. The cool weather helped preserve quality, particularly compared to the hot and windy conditions we had just prior to harvest. Balaton harvest is also underway at this time. Apples are sizing, and many varieties are already showing nice color with our cool nights. Early varieties will start to be picked in the coming two weeks. As mentioned last week, many growers were pleased with their thinning efforts, but some hand-thinning was still needed in some blocks. Growers are also starting to harvest peaches here in northwest Michigan.

Weather has been pleasant for the past week although cooler than typical August temperatures. Daytime temperatures are in the 70s and dropping back into the mid-50s at night. We had 0.34 inch of rainfall last Wednesday, Aug. 7. Overall conditions are still dry across the region. We have accumulated 2466 GDD base42 and 1630 GDD base50 so far this season.

Apples. As mentioned above, apples are looking good across the region. With the cool temperatures and lack of moisture, disease pressure has been low. Insect counts have also been on the low side, potentially from the cooler nights and mornings that are slow to warm. We trapped an average of 1 codling moth per trap here at the Northwest Michigan Horticultural Research Center (NWMHRC), but growers have been catching higher numbers in their own orchards this week: 15 to more than 50 moths per trap. Growers should be trapping in their own blocks to ensure a more accurate population size, and to be sure insecticide applications are properly timed. Last week, codling moth trap counts jumped up compared to the prior two weeks when trap counts were particularly low and many orchards trapped no codling moth. This week, trap counts are even higher, and these second generation moths are now mating and females are laying eggs. The codling moth model on Enviro-weather will help growers make well timed insecticide applications targeting second generation larvae as we approach harvest. Michigan State University Extension advises that fruit needs to be protected from internally feeding pests through harvest (codling moth and obliquebanded leafroller). Apple maggot catch is also higher in our traps here at the NWMHRC where we caught five flies on one trap and three flies on another trap.

Cherries. With harvest wrapping up, some growers are making a post-harvest application for cherry fruit fly and cherry leaf spot. However, with the cool temperatures, many growers are waiting to make their cherry leaf spot application as the growth of this pathogen has been slow under these conditions. Many of our test trees in our efficacy trial look good for this late into the season. Growers should try and keep their leaves on through September to make sure trees go into winter with good carbohydrate reserves.

For insects, American plum borer moth catch is up again this week, and we trapped an average of 19 moths per trap. Peachtree borer catch is also up this week: we caught an average of 13 moths per trap. Spotted wing drosophila (SWD) continues to be caught in cherry orchards, and fruit needs to be protected through harvest. We caught more flies this week at the NWMHRC than in weeks past. We captured the following number of flies in five traps this week: 0, 0, 1, 7 and 15. We will check all of our 60+ traps in northwest Michigan and, we suspect that trap counts will be higher at these other sites as well. We are running efficacy tests on materials with three-day pre-harvest intervals (PHIs) at this time, but the data will not be available in time for this season. Peach growers need to remember that SWD can infest peaches, at a much lower risk than raspberries or cherries, but peaches will need to be protected against SWD.

Lastly, brown marmorated stink bugs (BMSB) have been trapped in Michigan in riparian areas but NOT in commercial fruit fields, orchards, or vineyards. Overall, we have identified two locations with BMSB capture in low numbers in the southern part of the state. We are surveying all of the state tree fruit growing regions, 100+ traps, and no other catch has been reported at this time. These are very low catches, and this information is not meant to alarm growers but to let them know that BSMB catch has occurred in the state. Our extensive monitoring system will inform growers if catches increase or if further precautions to protect fruit are needed.

Wine grapes. Some cultivars in the research vineyards are just at the beginning of verasion. We have seen what appears to be hail damage to leaves and berries in a few vineyards. Injured berries show a bruised or sunken area, splits in the skin and in some cases developing seeds are protruding from the splits. These injured fruits will be susceptible to botrytis rot. Growers should check carefully for areas of vineyards which may have been hit by hail and apply treatments for botrytis. Vangard, Endura, Scala SC, Luna Experience, Elevate, and Inspire Super have the highest efficacy ratings for botrytis bunch rots according to the E-154 Michigan Fruit Management Guide.

Powdery mildew has increased in incidence and severity during the past week, but there are still many vineyards with very little of this disease.

Cool weather conditions have greatly limited the adult feeding activity of Japanese beetles. Most of the large hornworm caterpillars are nearing the end of their leaf-feeding period of this year and their defoliation of vines will soon be over.