Southwest Michigan fruit regional report – August 6, 2013

Harvest of peaches and blueberries is moving along. Spotted wing Drosophila numbers continue to rise.

August 6, 2013 - Author: , Bill Shane, and Mark Longstroth,

Jersey fruitWeather

Last week was cool. Highs were generally in the upper 70s with lows in the lower 50s. Wednesday and Friday had scattered showers. Rainfall totals for the past week varied from 0.5 to 1.3 inches with an average of 0.7 inches across the region. Evapotranspiration varies a lot due to the weather – almost 0.2 inches per day on sunny days, to less than 0.1 inches on cloudy days. Potential evapotranspiration for the week was about 0.9 inches. Many areas have adequate soil moisture, but because of the scattered showers, many sandy sites in southern Berrien County are short. This week will begin slightly warmer with highs in the upper 70 and 80s and lows near 60, and then cool back down. We are about a week behind the five year average in growing degree days. Check your local weather station and conditions at Enviro-weather.

Southwest Michigan GDD Summary from March 1 to August 6, 2013


GDD 42°F

GDD 45°F

GDD 50°F

Benton Harbor (SWMREC)




Fennville (TNRC)




Average for the region




GDD increase last week




Five year average




General comments

These cooler temperatures are ideal for spotted winged drosophila (SWD) and growers should expect increasing pressure from this pest. We are catching SWD in almost all our Michigan State University Extension monitoring traps. Some traps are catching only a few males and females and others are catching dozens to hundreds of males and females. In general, trap catch of SWD continues to increase. Growers should assume that SWD is available to attack their fruit. Japanese beetles numbers seem to be in decline.

No reports yet of brown marmorated stink bugs. San Jose scale has been found on the fruit. We expected the flight of the second generation to start last week with new crawlers expected 500 DD51 from the start of the second generation flight. Oblique-banded leafroller trap catches have been generally low. Fruit brown rot has become much more obvious in area peach and plum orchards as damaged and over mature fruit become infested.

Peach harvest of Redhaven, PF9A-007, PF11 Peach, Saturn, and Virgil has begun, with Redstar and Starfire to start soon. Brown rot, Rhizopus rot, and peach scab are easy to find. X-disease is relatively common this year in peaches and in cherries grown on mazzard rootstock. Brown rot control programs and possibly insect control of spotted wing drosophila will need to be ramped up as we approach harvest. Oriental fruit moth trap catches have been steady at a relatively low level.

In sweet cherry, sprays to control cherry leaf spot are still needed. Now growers can use post-harvest materials to protect the leaves.

Tart cherry growers should continue to protect against cherry leafspot. Many tree tops have defoliated. Pruning can be done on mature trees, but should not be severe to avoid devigorating the trees. Post-harvest pruning from now to early September will reduce bacterial canker infections that are favored by spring pruning under cool, wet conditions.

In plums, harvest of Shiro, Santa Rosa, and Vibrant is underway. Preharvest drop of plums has been significant in some area orchards. Low boron levels, particularly in sandy sites, can contribute to fruit drop. Brown rot controls should increase as fruit begins to color and ripen. Information on plums, including where to buy Michigan plums can be found at the Michigan Plum Advisory Board web site.

Apple harvest of Earligold, Pristine and PaulaRed has begun in some sites. We are a month away from Gala harvest and growers should check the dates for applying Retain for stop drop control for the apple varieties they grow. Make sure you do not miss the application window (30 days or less). Sooty blotch and fly speck symptoms are now being reported on apple fruit. Trap catches for oriental fruit moth and codling moth are generally low; however, a few sites are in their second week of high codling moth trap catch, indicating a strong flight at these sites. Apple maggot fly catch has been reported for two weeks in some area orchards. Growers who are participating in the Brazilian apple export program are reminded that the insecticides approved by this program as effective against maggot do not include many of the newer compounds. White apple leafhopper, European red mites, green apple aphids, and wooly apple aphids have built to noticeable levels in a few orchards.

 Table 1. Normal and predicted 2013 peak harvest dates for apple varieties for the Benton Harbor area.


Normal date SW

2013 predicted date SW

























Golden Delicious



Red Delicious


















This information is based on the weather data from the MSU Enviroweather weather station at the Southwest Michigan Research and Extension Center in Berrien County.

In pears, Clapp’s Favorite pear is being harvested in some area orchards. Growers should monitor for pear scab, Fabraea leaf and fruit spot, and pear psylla activity. Pear psylla numbers are starting to increase in some sites. Pear fruit should be protected against second generation codling moth.

Small fruit

In grapes, clusters are tight and veraison has begun in early varieties such as Fredonia and Marquette. Crop loads in vineyards are very high this year. A workshop at the Viticulture field day last week demonstrated this high crop load. Terry Holloway and Steve Tomac of National Grape removed grapes from 1/100th of an acre of Concord grapes at SWMREC. The hanging crop load was a whopping 10.5 tons per acre. Since, Concord grape berries were at 65 percent of their final size, the potential harvest works out to 14 to 16 tons at harvest. This is over twice the normal harvest tonnage of Concords in Michigan. This tonnage of grapes will not make minimum sugars in a cool year like this. We are behind the five year average for growing degree days, about in line with 2008 and 2009. Growers should look over their records and see what tonnage they have been able to ripen in the past, sample a few blocks and adjust crop loads accordingly. Crop adjustments should take place soon, before veraison, to have a favorable impact on Brix at harvest.

Trap catches for adult grape berry moth (GBM) were low in the vineyards we monitor, but larval feeding was higher. In several vineyards we monitor, percent GBM-infested berries was 10-11 percent, which is above the treatment threshold of 6 percent. The grape berry moth model on Enviroweather is predicting that 1620 GDD base 47, the start of third generation GBM egglaying, will occur Wednesday or Thursday of this week for Berrien and much of Van Buren Counties. Growers should be checking bunches for feeding by larvae. Keep track of GBM pressure in the vineyard. Check 100 clusters on vineyard edges and areas bordering woods and 100 clusters in the vineyard interior to determine percent infestation and to monitor whether or not GBM is moving into the vineyard interior or remaining along the edges. Berries of red grape varieties infested by GBM turn red prematurely, so finding them is easy, but is still not difficult on white varieties. Look for webbing on berry clusters and hollowed-out berries. At this stage, single GBM larva can infest multiple berries.

Japanese beetle feeding is declining. Watch for damage to young vines and wine grapes. We are seeing SWD in traps along vineyard borders, but there is no risk to grapes now because the berries are too hard for the flies to penetrate. Grape and potato leafhopper numbers in the vineyards we monitor have been low.

Black rot infected berries are quite noticeable now. Certain vinifera cultivars remain susceptible to black rot through veraison. According to the grape black rot model on Enviroweather, the most recent black rot infection periods were July 27-28 for Lawton and July 28-29 for Fennville and SWMREC. We have seen little in the way of powdery mildew so far. Downy mildew can easily become more serious in August, when there can be many mornings with heavy dew on the vine. There is considerable downy mildew in the unsprayed sentinel plots we monitor.

In blueberries, mechanical harvest of Jersey and other varieties is continuing. The crop load is very heavy in many fields and some fields apparently are not being harvested. This can lead to high numbers of SWD migrating in from these unsprayed fields as well as high numbers from wild brambles on the field edges. Growers with ripening fruit need to scout for blueberry maggot and spotted winged drosophila (SWD). Blueberry maggot is being trapped across the region and most SWD traps are catching flies. Larvae of both flies have been found in fruit in the field and also harvested fruit. Growers who are not monitoring for these pests should be applying controls. Recommendations for SWD control in blueberries are posted at the Michigan State University Extension's spotted wing Drosophila website as well as weekly reports on SWD trapping across the state. Many growers have shortened their harvest interval to reduce the amount of ripe fruit in the field. Under these wet conditions growers should also apply controls to suppress anthracnose and alternaria fruit rots.

In strawberries, renovated fields are putting out new leaves and irrigation is needed where soils are dry to maintain good plant growth. Protect the new leaves against potato leafhoppers to prevent this insect from stunting the new growth. Everbearing strawberries are producing berries. Watch berries for signs of SWD. Infested fruit tends to have a soft spot on one side and very small, white maggots may be present.

In brambles, harvest of summer red raspberries is finished. We are beginning to pick fall red raspberries in the high tunnels. Growers should be monitoring their raspberry and blackberry plantings for SWD and applying insecticides. Sanitation is very important for managing SWD. We had SWD trap catch last week in brambles with hundreds of flies. Frequent picking of ripe fruit and removal of overripe fruit is important to keep SWD populations in check. One sign of infestation in raspberry is a red staining on the receptacle when the raspberry is picked. Another pest to watch for now is two-spotted spider mite. Two-spotted spider mite activity generally picks up when plants are stressed by heat and drought. Multiple applications of insecticides to control SWD can lead to mite population explosions. Insecticides to control SWD in brambles and other insect problems should not be applied while bees are actively foraging. The Spotted Wing Drosophila Management Recommendations for Michigan Raspberry and Blackberry Growers has been updated. For detailed fact sheets, identification guides, and weekly reports on this pest during the growing season, see the online resources at the MSU Integrated Pest Management website.

Miscellaneous upcoming meetings

  • IPM workshop for raspberry growers on Friday, Aug. 9 from 6 to 8 p.m. at the De Lange’s Red Berry Farm in Hudsonville, Mich. See the flyer invitation for information on the location and the agenda. Growers attending the meeting will receive 2 RUP. There is no fee to attend this workshop, but we need pre-registration for handouts and other materials needed for this event. To pre-register, please call or email Judy Hanson at 616-994-4548 or
  • The next in-season grape IPM meeting will be at Lemon Creek Winery on August 27th from 6-8 pm. Contact the Berrien County Extension Office 269-944-4126 to register or for more information about the program. Registration is $15 and includes supper. Speakers will be Stan Howell, Rufus Isaacs and Annemiek Schilder.
  • A peach and plum variety showcase will be held at SWMREC August 27 from 4-7 pm. The meeting will include a picnic dinner hosted by Summit Sales. There is no charge for the meeting. For further information, contact Bill Shane,, 269-208-1652.

Tags: agriculture, blueberries, fruit & nuts, grapes, msu extension

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