Regional reports on Michigan fruit - July 19, 2011

MSU Extension educators’ pest and fruit updates for Michigan.

This week’s regional reports:

Southwest Michigan – Mark Longstroth, Bill Shane, Diane Brown-Rytlewski, Michigan State University Extension

Southwest Michigan
Southwest Michigan

July has been hot with highs generally in the 80s. There has been no significant rain since the storms on Monday, July 11. Soils are dry and soil temperatures are as warm as the air temperatures. Dry, hot conditions are forecast for the upcoming week. The hot, summer conditions in June and July have the region only about three days behind normal. Check for the closest weather station near you at Enviro-weather.

Southwest Michigan Growing Degree Day Totals from March 1 through July 17, 2011
Location GDD 42 GDD 45 GDD 50
Bainbridge 2066 1774 1335
Trevor Nichols 1915 1658 1219

Tree fruit

Cherry fruit flies and apple maggots have emerged. Japanese beetles are easy to find and are congregating in groups on favored feeding sites. The second generation of oriental fruit moth is flying and laying eggs. Potato leafhopper damage can be found in many crops. A spotted wing Drosophila was trapped in Allegan County on July 7. Stone fruit growers should be aware of this pest, which has the ability to lay its eggs in thin skinned fruit such as cherries.

In peaches, harvest of PF1 and Harbinger has begun with Early Star and PF5D Big in a few days. We have seen several instances of copper damage to foliage this year where trees were pruned after bloom. Copper was applied at low concentrations as part of a bacterial spot suppression program. The second oriental fruit moth began flying soon after July 4 and we set the regional biofix as July 7. We are 300 GDD base 45 past biofix and egglaying by the second generation is underway.

Sweet cherry harvest is ending. Birds feeding and brown rot were the major problems with harvest. Cherry fruit flies have been trapped and fruit should be protected. Pruning of mature cherry trees can be done until early September.

Tart cherry harvest is ending. Wind whip damage and brown rot of the fruit have been a problem. Cherry leaf spot symptoms are becoming common in many orchards. Cherry leaf spot has completely defoliated some neglected orchards.

Plums expected to harvest soon are Shiro and Vibrant. Plums should be protected from brown rot and apple maggots. White apple leafhoppers also attack plum leaves. Watersoaked spots can be seen on some fruit due to bacterial spot infections.

Apples are about 2 inches in diameter. There was some damage to apples from the July 11 storm – broken stakes and graft unions are the most common complaints. New fire blight symptoms from the July 11 storm should be appearing now. The dry conditions before and after the storm make further spread of fire blight unlikely, except in orchards that already had fire blight. The 2011 survey in southwest Michigan for streptomycin resistant strains of fire blight done by the lab of MSU researcher George Sundin did not find any expansion of resistance further westward into Berrien County from the immediate vicinity of the north south line of highway M-140.

Golden Delicious apples
Golden Delicious apples are almost 2 inches across.

Apple scab is defoliating unsprayed trees. The second generation of oriental fruit moth is laying eggs. Biofix was set as last Friday, July 8. Codling moth trap catches are rising in some orchards, indicating the start of the second flight. Codling moth biofix was June 1 or 3. We are almost 1,000 GDD base 50 after biofix when the second generation should emerge. You should reset your orchard biofix with the initial catch of the second generation. You should have new lures in your codling moth traps for the second generation.

Obliquebanded leafroller biofix in southwest Michigan was June 13. We are about 1,000 GDD base 42 past biofix and trap catches are low. Apple maggots have emerged and growers and scouts should have apple maggot traps out.

Pear fruit are 1.8 inches in diameter. Pear psylla adults, eggs and nymphs can be found. Second generation codling moth is a concern in pears and growers and scouts should have codling mothtraps out.

Small fruit

Japanese beetles are easy to find and are congregating in small fruit plantings.

Grapes are at cluster tightening. We are 1,350 GDD base 50 from April 1, and grape berries are over half their final size. We have a very heavy grape crop and growers should consider thinning their crop down to manageable levels. Grape berry moth second generation controls should be applied. We set biofix (bloom in wild grape) for grape berry moth May 30-31 in Berrien County and June 1-2 in Van Buren County. We are now about a week or more past beginning of egglaying. Check the grape berry moth model for timing based on the Enviro-weather station closest to your vineyard.

Trellis knocked over
The grape trellis was blown down by strong winds on Monday,
July 11.

No major damage from grape leafhoppers and potato leafhoppers has been reported. Japanese beetle feeding in vineyards has increased this week. The grape mildew diseases are the primary disease concern now. Powdery mildew symptoms have been found on Concord fruit. Downy mildew symptoms have been observed at generally low levels in commercial vineyards and at moderate levels in untreated research plots.

Blueberries are being harvested across the region. The harvest of Bluecrop continues as well as mid-season berries such as Jersey and Nelson. Shoot growth has stopped with the heat and hot weather. Growers who can irrigate should be replacing the 0.2 to 0.25 inches of water that is lost each day.

Spotted wing Drosophila was trapped in Allegan County on July 7. Growers should monitor for this pest. Cane collapse from phomopsis cane blight continues. Insects of concern include Japanese beetles and blueberry maggots. Anthracnose fruit rot can be found on ripening fruit

Most strawberry fields have been renovated. Growers should be prepared to control potato leafhoppers, which can stunt strawberry growth.

In brambles, harvest of summer bearing red raspberries and black raspberries continues. Blackberry harvest has begun. Two-spotted spider mites have been found in raspberries. Growers should protect against Japanese beetles.

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Southeast Michigan – Bob Tritten, Michigan State University Extension

Southeast Michigan
Southeast Michigan


A series of strong thunderstorms moved across the region on Monday afternoon (July 18), bringing high winds and quick downpours of rain. Rainfall totals ranged from 0.1 to 1 inch, however, there was a great deal of variability within short distances. With our dry spell continuing, any rain is beneficial, but the rain came so fast for most fruit growers that much of it was lost to runoff. No hail was reported in these storms.

Our soils remain very dry and both tree and small fruits are increasingly showing signs of drought-stress. Newly planted and younger blocks of tree fruit are blocks where I am seeing more severe signs of drought-stress, as well as newly planted strawberries. I think this problem is related to the abundance of soil moisture this spring when the newly developing root systems did not need to “reach” for moisture. Therefore, root systems were poorly developed. Then when the time came where quickly growing plants needed moisture, the root system did not have the capacity to respond. Fruit growers are devoting more and more time to irrigation with each passing week.

With continued warm weather, our season continues to move ahead of normal in terms of both degree day totals and the beginning of harvest for our fruit crops. We are now running between five to seven days ahead of normal.

Southeast Michigan Growing Degree Day Totals for March 1 to July 18, 2011
Location GDD42 GDD45 GDD50
Commerce (Oakland) 2039 1761 1337
Emmett (St Clair) 1967 1692 1277
Flint (Genesee) 2051 1764 1342
Lapeer (Lapeer) 2037 1759 1339
Petersburg (Monroe) 2180 1886 1438
Pigeon (Huron) 1832 1565 1166
Romeo (Macomb) 2026 1751 1334

Tree fruits

Apples continue to size well, despite dry soils at most farms. Apples are mostly at 2.25 inches in diameter. Lodi and other summer apple varieties are quickly approaching maturity. Summer pruning is just beginning in apples.

Apple maggot catches on both yellow sticky traps and red ball or sphere traps started late last week at a few farms. I have not seen or heard of extensive apple maggot trap catches across the entire region. I would expect to see more trap catches later this week as a result of the rain event yesterday (July 18). Woolly apple aphid numbers are steadily increasing in several apple blocks that I have seen in the last week. They are slowly progressing toward the terminal leaves; if this is the case, then control measures need to be applied in the next week.

Japanese beetle populations are present, however in low to modest numbers at most farms. Codling moth and oriental fruit moth trap catches remain low across the region. I am finding a low percentage of codling moth fruit-infested in a few blocks. The damage is mostly in smaller apples that will most likely drop prior to harvest or where fruit is clustered in twos and threes and fruit is touching each other. Most farms have seen predators finally controlling the remaining green apple aphid populations.

I am seeing a few large obliquebanded leafroller larvae. European red mite, two-spotted spider mite and apple rust mite numbers are steadily increasing, especially with this hot, dry weather. A few apple blocks are now at threshold for control of mites – now is a good time to be scouting for them in apple blocks. Predator numbers and diversity of the population is very good in most apple and tree fruit blocks at this time.

Powdery mildew is showing up in above average amounts in many apple blocks. With changes in apple scab control program at most farms this season, growers have not kept an eye on including the right fungicides to control powdery mildew. More and more apple scab continues to show up, especially fruit scab, and not so much, leaf scab.

Pears are 1.75 inches in diameter. Pear psylla populations continue to grow in a few pear blocks, most should have been controlled several weeks ago.

Peaches have started to swell, with pre-Red Haven varieties starting to color. Now is a critical time for soil moisture in peaches, and with most fruit farms having dry soils, final fruit size could be a problem this season.

Sweet and tart cherry harvest is now complete at almost all farms across the region. Cherry fruit fly trap catches have remained high at most farms. It has been suggested by our MSU Entomologists’ that a post-harvest insecticide application can help to reduce the population for next season. Leaf yellowing and drop from cherry leaf spot disease is occurring on both sweet and tart cherry, however the symptoms are more severe on tarts. A post-harvest fungicide is recommended on both that will help to retain as much of the foliage as possible for the remainder of the season.

Plums continue to size, with Methley plum coloring and nearing harvest soon.

Small fruit

Strawberries continue to rebound from renovation. On farms where soil moisture has been adequate, there is a good amount on new foliage growth taking place. Where soils have been dry, strawberry leaf growth have been standing still; this is not a good start for the 2012 strawberry crop.

Raspberry harvest continues for summer red and black raspberries, with supply pacing well ahead of demand at this time (mainly due to hot weather). Harvest from the fruiting lateral canes or bud berries on fall bearing raspberries is quite sizable at several farms this season, which is unusual. Potato leafhopper leaf curling is common in many fall red raspberry plantings over the last few weeks. There are lesser amounts of leaf curling from powdery mildew in far fewer numbers of plantings.

Blueberry harvest is underway at farms across the region, with Blueray and Bluecrop being harvested. Berry quality and picking is excellent. I have no reports of blueberry maggot trap catches, but I expect it soon. Japanese beetle populations are present, however in low to modest numbers at most farms. Bird feeding is a common concern at many farms.

Grapes are now at berry touch for Concord types and nearly so on French hybrid types. Japanese beetle populations are present, however in low to modest numbers at most farms. Their populations have been very high in wild grapes.

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Grand Rapids Area Small Fruit– Carlos García-Salazar, Michigan State University Extension

Grand Rapids Area
Grand Rapids Area

Major small fruit crops are in full harvest in the Grand Rapids area. Despite a slow start at the beginning of the season (that in some cases amounted to a two-week delay in growth and development), currently the harvest of most crops is, at most, four to five days behind in relation to the 2010 crop season. Hot and humid temperatures occurring over the past two weeks have sped up the degree-day accumulation and the maturation process.

The strawberry harvest has concluded and growers started the renovation in preparation for the next crop cycle. Because of the weather conditions that prevailed during the past weeks, the harvest ended rapidly and yields were not as good as was expected.

Regarding raspberries, the harvest of summer raspberries has continued with fruit of good quality. Raspberries were not affected by winter conditions and the size of the crop is good. There are some problems related to insects, mainly Japanese beetles and Lygus bugs, and in some fields, cane borers. But in general, there are no significant problems. For beetles and tarnished plant bugs, growers may apply Assail 30 SG, 4 to 5 oz. per acre. This insecticide has a small pre-harvest interval and it will allow continuing harvesting the next day after the application. Another good insecticide for controlling these insects is Sevin (Carbaryl), but it has a seven-day pre-harvest interval. For more options, please consult Extension Bulletin E-154, 2011 Michigan Fruit Management Guide.

Blueberries are in full harvest. Yields are lower than expected and because of the light crop, most fields are producing berries of excellent size and quality. In some cases, the sizing of the berries may compensate for yield reductions. The intense heat of the past few days may affect the fruit quality in those fields that are already ripe. Growers need to be alert to fruit roots. The combination of hot weather and ripe fruit are a perfect environment for the proliferation of anthracnose fruit root and Alternaria. To prevent fruit contamination with fungi and bacteria, avoid using overhead irrigation during the day hours of intense heat. Also, if the field has a history of fruit root problems, do not wait to see the first symptoms of fruit infection because when the symptoms are visible, the infection is already established in the entire field. At this time, the recommended fungicides are Pristine (18.5 to 23 oz. per acre) if the main problem is anthracnose, or Switch (11 to 14 oz. per acre) if the main problem is Alternaria fruit root. For more options, please consult Extension Bulletin E-154, 2011 Michigan Fruit Management Guide.

Problems observed at this time are related to insects, diseases and labor. Regarding insect pests, the Japanese beetle is present in most fields, but in low numbers. As always, the highest infestations are found in blueberry fields where weeds are a problem. If harvest is already in progress and beetles are creating a food safety problem, you may apply either Aqua Marathon 8 AC (2 to 2.5 pt. per acre) or Mustang Max 0.8EC (4 oz. per acre). These two insecticides can be applied one day before harvest. If the harvest is more than three days away, you may apply Imidan 70 WP (1.33 lb. per acre).

Other insects of concern are blueberry maggots and the spotted wing Drosophila. No problems are reported related to blueberry maggot. Regarding the spotted wing Drosophila, we are conducting an extensive survey with apple vinegar traps. So far, only one confirmed detection has been reported in Allegan County. In Kent, Ottawa and Muskegon counties, no spotted wing Drosophila flies have been found. However, we are continuing its monitoring in blueberries and raspberries.

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