MSU Extension

Weather

Last week began with warmer weather over the holiday weekend and highs into the upper 80s. Tuesday, July 7, rain showers crossed the region ahead of a cold front bringing cooler air. Mid-week was cool with high temperatures in the low 70s and lows in the 50s. Showers Thursday, July 9, brought scattered rain. Thunderstorms Monday, July 13, morning and evening, brought high winds and heavy rain to some areas. Rainfall totals for the week ranged from 1.5 to 2.5 inches. With the cooler weather this month, evapotranspiration values have been relatively low near 0.15 inches per day, with a weekly total near 1 inch. Many soils are wet, but there are also some dry areas and some growers are irrigating sandy soils.

Weather for the upcoming week will be similar to the last two weeks. It will be cooler mid-week (70s) and warmer over the weekend. With the recent cooler weather, we are about a week behind normal. With the pleasant weather last week, we picked up about 24.7 growing degree days (GDD) base 42, 21.4 GDD base 45 and 16.4 GDD base 50 per day. With a warmer week, we expect increased heat accumulations this week.

Tree fruit

Soil moisture is adequate with good growth. Foliar diseases are common in some orchards. Oriental fruit moth second generation is flying. Obliquebanded leafroller egg hatch is underway and adult trap catch is declining across the region.

Apricot harvest is ending. Bacterial spot problems have been minor.

Peaches are growing rapidly. Split pits are common on some early season peach varieties with light crops. Early season peach varieties being harvested include PF-1, Earlystar, Desiree and PF5D Big. Bacterial spot is continuing to cause leaf and fruit spots, especially on susceptible varieties grown on sandy sites with low vigor. Mycoshield (210-day pre-harvest interval) can be used to help keep bacterial spot on foliage from spreading to fruit. Oriental fruit moth trap catch peaked in early July, but still in significant numbers to be concerned. Other direct fruit pests include tarnished plant bugs and common stink bugs, which cause pinhole punctures on fruit. Peachtree borer moths are still flying in area orchards and have the potential for egglaying in limb and trunk wounds.

 
Lesser peach tree borer adult on a peach trunk. Photo by Bill Shane, MSU Extension

Sweet cherry harvest is winding down. There has been some fruit cracking from rain and associated brown rot. Cherry leaf spot symptoms are easy to find in some orchards and growers need to maintain protectant fungicide coverage before rain events. Warm rains are good infection periods for brown rot and sweet cherries are very susceptible to brown rot as the fruit ripens. Eastern cherry fruit flies are being trapped in the region. Late-harvested cherries that are soft-ripe on the tree may be prone to infestations by cherry fruit flies and spotted winged Drosophila (SWD) vinegar flies.

Tart cherry harvest is ending in southwest Michigan. Many growers have finished and the rest will finish early this week. Crop yields and quality were very good. Cherry leaf spot is a significant problem in many orchards and growers are applying chlorothalonil after harvest to protect their remaining leaves. See “ Controlling cherry leaf spot in orchards with existing symptoms” from Michigan State University Extension for more information. Growers using copper need to avoid copper building up on leaves to phytotoxic levels. Discontinue copper use when there is little or no rain between sprays. Powdery mildew is becoming common in many orchards. There was a strong flight of greater peachtree borers and lesser peachtree borers. Treat with trunk sprays after harvest to prevent these pests.

Japanese plum harvest will start with Methly this week. Plum fruit and leaves are susceptible to bacterial leaf spot, but Mycoshield is not labeled for use on plums. Ripening plums are very susceptible to brown rot. Oriental fruit moths, codling moths and obliquebanded leafrollers can infest fruit if not protected

Apples are showing good sizing and shape development. Estimated harvest dates are available from MSU Enviro-weather. Some of these dates include Sept. 8 for McIntosh and Sept. 30 for Red Delicious for central Berrien County. Apple maggots emerge after rain. Generally, 0.25 inches is enough for these flies to emerge. Growers need to include fungicides in some of their cover sprays to control sooty blotch and flyspeck. Growers should also reapply fungicides for these two diseases whenever the hours of leaf wetness exceed 250 since the last fungicide application. Growers with a light crop or with bitter pit-susceptible varieties should include calcium in their cover sprays to reduce bitter pit.

We are still catching codling moths and according to the Enviro-weather codling moth model, we are seeing the initial emergence of second generation. Growers should be scouting for obliquebanded leafroller larvae. The Enviro-weather obliquebanded leafroller model indicates we are past peak egg hatch in the region. Green aphids are increasing on active shoot growth.

Pear crop potential is good. Growers are removing watersprouts from trees to discourage pear psylla populations, which is increasing.

Small fruit

Japanese beetles are becoming more common. We are catching spotted wing Drosophila (SWD) in southwest Michigan. Many traps have not caught any flies, but more traps are beginning to catch flies. Yeast-sugar traps appear to be catching more flies than some of the artificial lures. SWD is a pest of ripening fruit and numbers increase as wild berries ripen. Honeysuckle bushes (Lonicera) and black raspberries are ripe at the wood’s edge now and serve as wild hosts for SWD.

Grape berries are at berry touch in Concord, Niagara and some hybrids. Clusters are still open in vinifera and other hybrid wine grapes. Juice grapes have grown out of their susceptibility to fruit infections of powdery mildew, downy mildew, black rot and phomopsis. Vinifera grapes remain vulnerable to infection from all these fungi, and frequent rains are expected to worsen these infections. Wine grape growers should apply a Botrytis fungicide before bunch closure to reduce late-season fruit rots. This spray is especially important with these wet conditions. See “Don’t let bunch rots ruin your grapes” for more information.

Black rot fruit infections are developing in some vineyards. Second generation grape berry moth egglaying continues. Growers using broad-spectrum contact insecticides should apply a second insecticide about two weeks after the first to control the current generation of this pest. In wine grapes, continue scouting for potato leafhoppers, which are becoming common in the area. Look for grape leafhoppers in juice grapes. Japanese beetles are feeding on leaves in some vineyards. Usually, only severe outbreaks of these insects require treatment.

Blueberry hand-harvest and machine harvest are underway. Bluecrop harvest began late last week. Fruit size for these first pickings was very large and harvest volumes are up. Scouts are catching blueberry maggot flies and SWD. Ripening fruit needs to be protected from these pests. Growers should apply fungicides to protect fruit from anthracnose and alternaria fruit rots and new shoots from stem blights such as phomopsis. Some growers report fields that were pruned last fall to remove weaker wood now show more phomopsis or winter injury.

Collapse of blueberry canes caused by phomopsis or winter injury appears to be worse in fields that were pruned hard last fall. Photo by Mark Longstroth, MSU Extension

Strawberry fields should start to put out new leaves after renovation. Protect newly emerging leaves against potato leafhoppers and strawberry foliar diseases. For a discussion of strawberry diseases and controls, see “What fungicide do I choose for disease control in strawberries?”

Leaf feeding by potato leafhoppers causes a distinct yellowing and stunting of strawberry leaves. Photo by Brad Baughman, MSU Extension

Raspberry harvest is underway with red and black raspberries. SWD and Japanese beetles are out and can be a problem in raspberries. Growers need to time their controls with harvest and pay close attention to the pre-harvest intervals (PHI) on the pesticide label. Raspberries are also very attractive to SWD and growers should pay close attention to protecting against this pest.

Upcoming meetings

Be sure and register for the annual Viticulture Field Day July 29 from 9 a.m. to 6 p.m. at the Southwest Michigan Research and Extension Center, 1791 Hillandale Rd., Benton Harbor, MI 49022. Grape, winemakers and others interested in viticulture are invited to attend. This is a full day of viticulture. The event includes an outdoor trade show, equipment demonstrations and tours of the research farm. Follow the link above to learn more about the event and register for this annual open house focused on grape production in southwest Michigan. For more information, contact Diane Miner at minerd@anr.msu.edu

See also

• Rainfast characteristics of insecticides on fruit
• The challenges of disease control during rainy spells
• Controlling cherry leaf spot in orchards with existing symptoms
• Peach harvest dates available on MSU Enviro-weather
• Sooty blotch and flyspeck disease of apple and pear
• Bitterpit control in apples
• Managing Japanese beetles in fruit crops.
• Where else does spotted wing Drosophila like to feed?
• Time to renovate strawberries
• Assistance in raspberry virus diagnosis offered