Regional reports on Michigan fruit – August 2, 2011

MSU Extension educators’ pest and fruit updates for Michigan

This week’s regional reports:

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

Southwest Michigan
Southwest Michigan

July was generally hot with highs reaching 90°F several days. Storms on Wednesday and Thursday last week (July 27-28) dropped varying amounts of rain. Weekly precipitation totals varied from 1 to 3 inches. The heaviest rains were in the tier of counties along I-94 and close to Lake Michigan. Soils are moist for most of the southwest region, but some areas are dry. Soil temperatures are as warm as the average air temperatures. The hot summer has the region at or ahead of normal for heat accumulation. Find the closest Enviro-weather station near you.

Southwest Michigan Growing Degree Day Totals from March 1 through July 31
Location GDD 42 GDD 45 GDD 50
Bainbridge 2556 2222 1713
Trevor Nichols 2380 2061 1571

Tree fruit

Now is time to take leaf samples for tissue analysis. Various nutritional deficiency and soil-active herbicide related symptoms have been showing on tree fruit foliage, particularly on sandy sites. Horsenettle is particularly common this year. Apple maggots and Japanese beetles are out. We are at the end of the second generation of oriental fruit moth. Potato leafhopper damage can be found in many crops. San Jose scale moth biofix was on about July 11. We are about 550 degree days base 51°F from biofix and crawlers should be out. This is the generation that generally causes the most damage to fruit and trees.

In peaches, harvest of Garnet Beauty, Rising Star and Summer Serenade is underway. Redhaven harvest will start next week for some farms. This is later than the predicted date of August 4 for Berrien County. Hot weather has increased two-spotted spider mite populations and damage to leaves. Split pits are reported and are a common problem in early peaches. Bird pecks of the fruit have helped to initiate brown rot problems in immature fruit in some orchards.

The second oriental fruit moth began flying soon after July 4 and we set the regional biofix as July 7. We are 800 GDD base 45 past biofix and egglaying by the second generation is ending. Constriction canker disease is causing gumming and wilting of current season terminal growth. Cross-disease symptoms are becoming easy to find.

Cherry harvest has ended. Cherry leaf spot symptoms are common and it has defoliated some trees. Pruning of mature cherry trees can be done until early September.

Vanette, Voyaguer and Ozark Premier plum harvest is underway at some area farms. 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 2 to 2.5 inches in diameter. Apple scab is defoliating unsprayed trees. Sooty blotch and fly speck diseases are favored by rains and dewy nights. The number of wet hours at the Bainbridge Enviro-weather station for the sooty blotch and fly speck model has totaled 550 as of August 2, 2011. This compares to a sum of 727 hours for 2010, and 591 for 2011.

The second generation of oriental fruit moth is ending and the third generation should begin soon. Codling moth biofix was July 15 in Berrien County and July 18 in Van Buren County. We are about 433 to 415 GGD base 50 from the respective biofixes. Last week, we were picking up about 25 GGD every day. The second generation of obliquebanded leafrollers should emerge soon.

Apple maggot flies are out. European red mite numbers are building. From mid-July to mid-August, the treatment threshold for European red mite is seven mites per leaf. Heavy populations of green apple aphids on suckers and shoots were observed in Red Delicious.

Pear fruit are 2 inches in diameter. A few pear psylla eggs were observed in the orchards we scout, but populations were generally light. Second generation codling mothis a concern in pears and growers should be treating for this generation.

Small fruit

Japanese beetles populations vary widely. They are congregating in preferred feeding areas.

Grapes are at cluster tightening. Veraison is beginning in early varieties. Grape berry moth larvae are feeding in the fruit. Japanese beetle feeding in vineyards continues this week. Recent hot weather would have inhibited powdery mildew development. No powdery mildew was observed in the vineyards we scout. Daily heavy dews are ideal for downy mildew development. Downy mildew has been found primarily on foliage, with only a little so far on berries. No major damage from grape leafhoppers and potato leafhoppers has been reported.

Blueberry harvest continues across the region. The harvest of Bluecrop is ending. Rubel and other varieties are being machine harvested. Generally, the crop is light in Jersey. Now is time to take leaf samples for tissue analysis. Growers who can irrigate should be replacing the 0.2 to 0.25 inches of water lost every day. You can stop irrigating after rains, but do not stop and wait for rain.

Another spotted wing Drosophila was trapped in Allegan County on July 22. Growers should monitor for this pest. Cane collapse from phomopsis cane blight continues. Insects of concern include Japanese beetles and blueberry maggots. Anthracnose remains the most common fruit rot in ripening fruit. Many of these infections probably took place in the wet conditions soon after bloom.

Most strawberry fields are recovering from renovation. Irrigation is very important after renovation to get the strawberries off to a good start. Growers should control potato leafhoppers, which can stunt strawberry growth.

In brambles, harvest of summer-bearing red raspberries, black raspberries and blackberries continues. A spotted wing Drosophila was trapped in black raspberries in Allegan County on July 22. This new pest has the ability to lay its eggs inside thin-skinned fruit such as raspberries. Raspberry leaf miners and 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


We finally have had some moisture over the last week. Most of that came in thundershowers on Wednesday and Thursday, July 27-28. The rainfall totals from that storm varied greatly across the region. Most fruit farms report that they received close to 4 inches of rain from those two rain events. However, I am hearing totals as low as 1 inch and totals as high as 8 inches from those events. While 1 inch of rainfall is not nearly enough, it did help to alleviate some of the drought stress problems. Growers who are lucky enough to receive 3 to 4 inches of rain have seen a tremendous turnaround in drought stress symptoms and are also seeing a variety of positive effects on their fruit crops. While we are not through the drought at many farms, it is at least a temporary reprieve from the pressure of constant maintenance of irrigating tree and small fruit crops.

The heat of last week has also continued to push our growing season ahead of normal. We are currently just over a week ahead of normal in terms of degree day totals and just under a week in the beginning of harvest of our fruit crops. For some reporting stations in east Michigan, July was a record for heat. For other reporting stations, July was also the wettest July ever on record. Most of the moisture from Enviro-weather stations that broke a record for July came in the last few days from the thunderstorms of last week. Needless to say, the strange weather year seems as if it is continuing.

Southeast Michigan Growing Degree Day Totals for March 1 to August 1
Location GDD42 GDD45 GDD50
Commerce (Oakland) 2528 2208 1714
Emmett (St Clair) 2454 2137 1652
Flint (Genesee) 2531 2204 1710
Lapeer (Lapeer) 2517 2197 1707
Petersburg (Monroe) 2686 2350 1832
Pigeon (Huron) 2297 1988 1519
Romeo (Macomb) 2529 2211 1724

Tree fruits

Apple size has jumped ahead at farms that received good amounts of moisture in the last week. I am seeing many apple varieties that are 2.5 inches in diameter. Lodi and Bella Vista have both been harvested at most farms. Summer pruning is now underway at most farms. This is a good time to remove unneeded growth and to improve the quality of the fruit crop this season as well as the quantity of flower buds forming for next season.

Apple maggot trap catches have been on the rise across the region at most farms, with most of that trap catch on yellow sticky boards. I think that the emergence of apple maggot has been the result of more widespread soil moisture supply across the region. Codling moth trap catches are on the rise for the start of the second generation adult flight. I have a few farms that have biofixed for second generation adult flight mid- to late last week, and I expect that over the next few days that just about all farms will be biofixing. I continue to see some first generation codling moth fruit damage in several blocks.

Oriental fruit moth trap catches are all over the board this week. I am seeing trap catches range from a low of zero to as many as 25 per trap. A few San Jose scale crawlers are still being seen at a few farms. I have had a good amount of adult male flight being caught in traps this past week as well. The window for San Jose scale crawler control is closing very quickly. Green apple aphids are pretty much under control. Japanese beetles have been seen feeding more strongly in a few varieties, like Honeycrisp. However, I am not seeing anywhere near the numbers of Japanese beetles as in most years.

Potato leafhopper nymphs are present in apples; however, their numbers are fairly low. European red mite numbers have jumped up in hot spots at many farms across the region, quickly approaching threshold levels. I am starting to see some mite eggs in the calyx ends of apples, which concerns me. I am also seeing tremendous numbers of predators feeding on European red mites. Apple rust mites are common across the region. Two-spotted spider mites are being seen in apples; however, their numbers are fairly low.

I am starting to see a few apples around with black rot fruit rot symptoms. I am also seeing some rot from hail damage that is fairly wide spread across the region this year. I have been on the lookout for sooty blotch and fly speck, and have not seen any. More powdery mildew symptoms continue to show up in susceptible varieties of apples.

Pears are mostly 1.75 to 2 inches in diameter. Two-spotted spider mite populations have been high at some farms, causing leaf burning or scorch. Pears need to be scouting for two-spotted spider mites fairly quickly. Pear psylla populations are out of control at a few farms; however, most fruit growers have them pretty well in check.

Peach harvest has begun for several of the early varieties. Where soil moisture has been an issue, peach size is lacking. However, where soil moisture has been adequate, peach size is normal to above average this year. I continue to see some low level populations of two-spotted spider mites in peaches. I also continue to see fruit that was infected earlier in the season with bacterial spot

Sweet and tart cherry leaf drop continues across the region from cherry leaf spot disease. In severely infected blocks, I encourage growers to make a second fungicide application to try to retain as much of the foliage as possible throughout the rest of the season. I am concerned with the extensive leaf drop that we have seen, particularly in tart cherries; these trees will be more prone to winter injury.

Plums continue to size quite nicely, with most European types being around 1 inch in diameter. Stanley’s have not begun to color. Black knot is being seen more this year than in the previous five years or so. The cankers are hidden by leaves at this time of year; however, I think that when leaf drop occurs this fall, many growers will be surprised at the extensive amount of black knot that is in their plums.

Small fruits

Strawberries have responded very well to rainfall over the last week. Newly planted strawberries have continued runnering well and are filling in the rows quite nicely. Renovated strawberry plantings also have responded well to precipitation. The only pest problem to report that I reported previously and continues to be seen at a few farms are some fairly good populations of potato leafhoppers, causing leaf cupping or curling.

Raspberry harvest has now wrapped up across the region for summer red and black raspberries. Some growers have been able to pick fall red raspberries. The berries that are being picked are from the lateral fruiting canes, or what some growers refer to as “bud berries.” However, the yield from bud berries is very low and patches are picked out very quickly.

Japanese beetles have been a problem in several fall raspberry plantings. Their numbers have been such that I have made the recommendation to control them with an insecticide application. Now is the time to begin removing fruited canes from summer red and black raspberries, and tipping black raspberries.

Blueberry harvest continues across the region. I caught my first blueberry maggot of the season on a yellow sticky board late last week. Birds have been a serious problem at several farms since harvest started. Earlier in the season, we were having difficulty with robins and cedar waxwings. I am seeing flocks of starlings coming into blueberry plantings.

Grapes continue to fill out the clusters quite nicely. French hybrids are now at berry touch. In the last week, I have had a high catch of grape berry moth adults in traps. This is an indication of the second generation flight that is now underway.

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Northwest Michigan - Nikki Rothwell, Erin Lizotte, Duke Elsner, Michigan State University Extension

Northwest Michigan
Northwest Michigan

Weather report

We continue to be dry and hot in the north, but the forecast is for rain today (August 2), potentially with some severe stormy conditions. For the past week, our daytime temperatures have stayed consistent in the mid-80s. With these warm temperatures, our degree day accumulations have slightly exceeded our 21-year average accumulations: 2221 GDD base 42 in 2011 and 2217 base 42 for the 21-year average. The accumulations base 50 are similar, and this season’s total, thus far, is 1452 and the average is 1413. The degree day totals are a bit of a surprise, considering the cold and wet start to this season. We have had no significant rainfall since June 24, but as mentioned above, forecasts are predicting ample rainfall for today. Soils are extremely dry at this time.

Crop report

Sweet cherry harvest is finished around the region while tart cherries harvest is still underway. Growers in the southern part of the region have wrapped up their tart cherry harvest, and many are applying post-harvest applications. However, to the north, growers are still harvesting. Tart cherry quality continues to be good; fruit are firm, but small in size. Yellow leaves in both tart and sweet cherry trees are common across the region. Balaton harvest has started, and the crop loads are variable between orchards.

Most apricots have also been harvested. Strawberry growers are renovating their fields now, and raspberry harvest is still underway. In wine grapes, growers are still doing a lot of canopy management, and they will start crop load management in the coming week. Grapevine vigor has been excellent with the early rainfall followed by ample heat. Powdery mildew is just showing up in the region, and growers are concerned with spray coverage as the berry size has increased rapidly, particularly in tight clustering varieties.

Pest report

Apples. Minimal apple scab lesions have been reported around the region, particularly on highly susceptible varieties. In abandoned blocks scab, lesions are prevalent on the fruit. Still no signs of powdery mildew in apples.

Two apple maggots were caught in the trapline at the Northwest Michigan Horticultural Research Center this week; however, area scouts began reporting trap catches 7 to 10 days earlier than our catch. Apple maggot management should be targeted 7 to 10 days after detection for most insecticides. For more information on apple maggot management, refer to the article Managing apple maggots with insecticides.

Codling moth emergence continues at a slow pace. Green apple aphidnumbers remain high on foliage and fruit. Obliquebanded leafrollers continue to emerge as adults, though in lower numbers this week. Spotted tentiform leafminer numbers rebounded this week, with traps averaging over 100 moths.

Cherries. Obliquebanded leafroller activity slowed in cherries, with fewer adult moths trapped this week than the past six weeks. The ending of adult emergence is an indicator that we are past the ideal time for summer generation larvicide applications. Plum curculio activity continues; we are catching adults in pyramid traps this week and have observed feeding on fruit in the orchards. Second generation American plum borer emergence continues – delineating between generations can be difficult as trap catches often never reach zero. However, this week marked the highest trap catch since the end of May and was the highest catch of the year, which is a good sign that we are at peak flight of second generation American plum borer. Lesser peach tree borer emergence is slowing with an average of three per trap. Peach tree borer numbers continued to rise this week with an average of nine per trap.

Emergence of cherry fruit fly continues at high numbers, with the highest trap catches to date this week (330 in six traps). With high populations present, many growers will be applying post-harvest sprays in the coming weeks. Recent work has shown that a great deal of cherry fruit fly activity occurs after harvest, and this pest behavior provides an opportunity for management in sites with high populations after harvest. Preliminary research has shown that imidacloprid products, such as Prey and Provado, work well at the post-harvest application timing seven days after harvest. This spray could be tank-mixed with the post-harvest chlorothalonil application for cherry leaf spot. Refer to MSU Extension Bulletin E-154 Fruit Management Guide for more information, and always carefully read and follow pesticide labels.

Black cherry aphid activity has still been observed on the terminals of sweet cherry branches. Black cherry aphid feeding curls and stunts leaves and deforms shoot growth. There are a number of effective insecticides for the management of black cherry aphids in sweet and tart cherry, including Provado, Actara, Assail, Beleaf, Voliam flexi, Movento and Leverage (management may be delayed until post-harvest). As we approach harvest in some sites, growers should be aware of the pre-harvest intervals of various materials and always read and follow pesticide labels carefully.

The potential for early defoliation from high levels of cherry leaf spot early in the season remains a concern. We began seeing significant cherry leaf spot infections early this season and defoliation is already significant in many blocks, particularly those with foliar bacterial canker infections from the spring that caused leaves to drop last month. Keep in mind that cherry leaf spot is resistant to sterol inhibitor fungicides (Indar, Elite, Orbit) in all the major fruit producing areas of Michigan. This season, growers should consider one or two post-harvest chlorothalonil applications to retain as many leaves as possible going into fall. Refer to the article Post-harvest sprays for cherry leaf spot for more information.

Early bacterial canker symptoms allowed American brown rot infections to become established on green fruit early; hail damage and sites with a history of American brown rot also saw higher than usual American brown rot infections. Indar should be applied at a 6 fl oz/A rate on most sites; an 8 fl oz/A application rate should only be used if a shift in fungal sensitivity is suspected (only Indar 2F is labeled for increased rates). Surfactants, high water application volumes, full covers and slow speeds are important strategies for American brown rot management. Growers looking to treat for cherry leaf spot and hedge their bets against low American brown rot pressure could utilize Pristine.

Grape report

Recent hot and dry weather produced rapid growth of mature vines with deep root systems, but young vines without irrigation have started to show signs of drought stress. Hopefully the rains, which began today, will provide some relief.

Powdery mildew has now appeared in a number of vineyards in the area, mostly as foliar infections. Fruit should become resistant to new infections in the next week or so.

The big sphinx moth caterpillars are out now. Watch out for them on one- to three-year-old vines that can’t tolerate the foliage loss that these beasts can cause. Older vines can normally withstand the defoliation without much impact on the vine.

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