Regional reports on Michigan fruit – August 9, 2011

MSU Extension educators’ pest and fruit updates for Michigan

This week’s regional reports:

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

Southwest Michigan
Southwest Michigan

Weather: Cooler in Southwest Michigan

Weather the last two weeks has been cooler with highs generally in the 80s and lows in the 60s. Sporadic storms have dropped varying amounts of rain. This is a welcome change from the dry June, but has been too much of a good thing for some growers. Soils are moist for most of the Southwest region but some areas remain dry.

The rainy growing season has many growers complaining that weed control is failing. Crabgrass seems particularly troublesome this year. Heavy rains have leached herbicide residues out of sandy sites and summer weeds are off to a good start. Soil temperatures are similar to the average air temperature. The hot summer has the region at or ahead of normal for heat accumulation (GDD), but fruit harvest appears to be about four to five days later than predicted for apples and peaches. Check for the closest weather station at

Southwest Michigan Growing Degree Day Totals from March 1 through August 7, 2011


GDD 42

GDD 45

GDD 50









Tree fruit

We are nearing the end of the time to take leaf samples for tissue analysis. With the sporadic heavy rains some nutritional deficiency and soil-active herbicide related symptoms have appeared on tree fruit foliage especially on sandy sites. Apple maggot and Japanese beetles are out and a problem in some hot spots. We are between generations of Oriental fruit moth, but trap catches remain high in some sites. Potato leafhopper damage is common in many crops. San Jose scale moth biofix was on about July 11. We are about 670 degree days base 51 F from biofix and crawlers are out. Growers who have had a problem with scales should have treated for crawlers.

In peaches, Redhaven harvest is underway. Other varieties being harvested include Rising Star, PF 8 Ball and PF 11 Nectarine in the Flaming’ Fury Series. Harvest is delayed from our predicted dates and growers should be monitoring peach fruit for the desired ripeness. Hightwo-spotted spider mite populations are damaging leaves. Bird pecks have started brown rot infections on 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 egg laying by the second generation should be ending. Trap catches for oriental fruit moth have remained high in some orchards and some growers have complained that a control with Imidan has been poor and that newer materials are working much better. X-disease symptoms are becoming easy to find.

In cherries, cherry leaf spot symptoms are common and continue to defoliate trees. Pruning of mature cherry trees can be done until early September.

Plum harvest continues. ‘Vibrant’ plums are being harvested and Stanley plums are beginning to color. Plums should be protected from brown rot and apple maggot. White apple leafhoppers will also attack plum leaves, causing white speckling on the leaves.

Apples are about 2.5 inches in diameter. Pristine is being harvested. It appears we are about 4 to 5 days later than the predicted apple harvest dates. This may be due to poor conditions during pollination and setting fruit on later bloom. Apple scab continues to spread to new leaves. Sooty blotch and fly speck diseases are favored by rains and dewy nights, so fungicides should be included in late season cover sprays. The number of wet hours at the Bainbridge Enviro-weather station for the sooty blotch and fly speck model totaled 609 on August 7, 2011. The second generation of Oriental fruit moth has ended and the third generation should begin soon. Codling moth biofix was July 15 in Berrien County and July 18 in Van Buren. We are about 660 to 550 GGD base 50 from the respective biofixes and just past peak egg laying for the second generation. Last week we were picking up about 25 GGD every day, and next week we expect about 20. The second generation of obliquebanded leafroller should emerge soon. Apple maggot flies are out. European red mite numbers are building, and we have observed orchards over the threshold of 7 mites per leaf. Heavy populations of green apple aphids are on suckers and shoots tips.

Apple fruit starting to color
Apple fruit are starting to color.

Pear fruit are 2.5 inches in diameter. A few pear psylla eggs were observed in the orchards we scout, but populations were generally light. Second generation codling moth is a concern in pears and growers should be treating for this generation.

Small fruit

With the recent heavy rains some nutritional deficiency and soil-active, herbicide-related symptoms have appeared on sandy sites. Japanese beetle populations vary widely. They are congregating in preferred feeding areas. Although spotted wing drosophila traps are out in Berrien and Van Buren counties, so far no adults have been trapped. There have been additional catches in Allegan County.

Grapes are nearing veraison and color is visible in early varieties, but is not visible in Concord. Grape berry moth larvae are feeding in the fruit and Japanese beetles on the leaves. We are expecting emergence of third generation grape berry moth this week. Powdery mildew has been reported in a few locations on wine grape varieties. Daily, heavy dews are ideal for downy mildew development and growers should plan their fungicide applications accordingly. Downy mildew is defoliating unsprayed research plots, but in commercial vineyards, downy mildew seems to be under control. In the unsprayed grape sentinel plot at SWMREC, berries of the variety ‘Chancellor’ are heavily infected (near 100%), and infection in ‘Vignole’ berries is increasing. No major damage from grape leafhopper and potato leafhopper has been reported. There is still time to do tissue testing for grapes as the window for collecting petioles for sampling is from about July 15 through August 15.

Blueberry harvest continues across the region. Fruit cracking due to rain has been a problem when rains fall on fields during harvest. Machine harvest of Bluecrop is ending. Jersey, Rubel and other varieties are being machine harvested. Elliot is coloring and hand-harvest of the leaders has begun. Soft fruit due to the heat and rain delays has been a problem. Hand-harvest crews are scarce and smaller growers report that labor is hard to find. Now is the time to take leaf samples for tissue analysis.

Cane collapse from phomopsis cane blight continues but has not been as severe as in recent years, or as severe as I would have expected from the cane dieback visible this spring. Insects of concern include Japanese beetle and blueberry maggot. Abandoned and poorly sprayed fields are infested with blueberry maggots and this fruit is unsalable. Anthracnose remains the most common fruit rot in ripening fruit. Harvest sprays should protect fruit from maggots, anthracnose and alternaria.

Strawberry fields are generally growing well except where potato leafhoppers have stunted growth.

Potato leafhopper injury
Potato leafhopper injury to strawberry leaves. Note the yellow streaking of the leaves
and yellowing of the leaf margin.

In brambles, blackberry harvest continues and growers will be harvesting fall-bearing raspberries soon. Growers should protect against Japanese beetles.

Back to top

Southeast Michigan – Bob Tritten, Michigan State University Extension

Southeast Michigan
Southeast Michigan


Over the last two weeks the region has received between 3 and 9 inches of rainfall. Most fruit farms have received 4 to 5 inches of rain in four to five events, mostly thundershowers. This much needed moisture has helped all of our fruit crops move forward very quickly and, at most farms, our fruit crops have recovered from the drought of earlier this season. At some farms the rain events of July 27-29 occurred so quickly that there was flooding and washing out of some tree and small fruit plants in low-lying areas.

With all the heat of the last two weeks our season continues to push ahead of normal. We are currently just over a week ahead of normal in terms of degree day totals. However we are not that far ahead if I look at the beginning of harvest at some of our fruit crops. Most notably is peaches which appear to be running about five days behind their predicted harvest dates for the year. Look for more details in both the apple and peach sections of this report.

Southeast Michigan Growing Degree Day Totals for March 1 to August 8 , 2011





Commerce (Oakland)




Emmett (St Clair)




Flint (Genesee)




Lapeer (Lapeer)




Petersburg (Monroe)




Pigeon (Huron)




Romeo (Macomb)




Tree fruits

Apples size continues to march along quite nicely, with most fruit around 2.75 inches in diameter. With all the heat and sunshine that we have had the last several weeks, I am seeing more and more sunburned spots on apples. Summer pruning continues across the region at a rapid pace at many farms.

I have been looking at the predicted harvest dates that were published earlier this year for each region of the state. I am now beginning to believe that the published dates are not quite accurate for east Michigan this year. It appears at this time that the actual maturity dates for most of the apples will be 5 to 7 days later than what was published earlier. The table with those dates follows as well as the adjusted harvest dates. Please stay tuned for details as these harvest dates seem to be a moving target this year.

Full bloom date

Original predicted harvest dates

Revised predicted harvest dates































Apple maggot trap catch continues across the region although trap catch numbers have dropped off. Most of the apple maggots being caught have been on yellow sticky board traps. Over the last week, I’ve had an average trap catch of 2 per trap. I find it odd that I have not had any trap catch on red sphere traps in the last week. Codling moth trap catches continue to be high for the second straight week, so this confirms that they are indeed at the start of second generation adult flight. In most mating disruption blocks the trap catch numbers have been just a few moths. However, in conventional blocks the trap catch numbers have been in the range of 10 to 15 per trap. Most growers biofixed for the second generation flight on July 30, and control measures for this seasonal generation larvae will be going on later this week.

Oriental fruit moth trap catches remain high across the region. This is a bit puzzling to me as to why we continue to have such high trap catch of oriental fruit moth, but it is what it is! Woolly apple aphid populations are very heavy at just a few farms. At most farms, they are under control. Japanese beetle populations are starting to decline. I have not seen any mass aggregating of Japanese beetles this season. Most of the damage has been found where there are wild host plants (i.e. wild grape vines) in the orchard that have attracted the beetles into the block. The only exception to this has been on Honeycrisp which seem to attract more Japanese beetles.

European red mite numbers continue to be high in hot spots at most orchards. However there are generous numbers of predators this year that seem to be keeping them under control. Many growers have been on the fence as to their need for a miticide, and several have decided to wait to see if predators can keep them in check. Two spotted spider mite populations have also been on the rise, but here again predators are keeping their numbers at bay. Apple rust mite numbers continue to be high, but predators are also keeping them in check as well. Speaking of predators, I have seen very good numbers of lacewings and lady bird beetles in the last two weeks. Many of these predators have now moved on to other plants due to a lack of food.

The only disease that I have been on the lookout for this week has been sooty blotch and fly speck, and I have not seen any.

Pears are mostly at 2 inches in diameter. Pear psylla are still a problem at some farms as are two spotted spider mites, which have caused some leaf burning or scorch in some pear blocks.

Peach harvest continues, however at a slow pace. As with the predicted harvest dates for apples, I believe that peaches are maturing about 5 days later than dates published earlier this season. This is most notably true for Red Haven which were predicted to begin harvest on August 8, and now appear to be ready late this week or over this coming weekend. The only pest to report in peaches is the possibility of two spotted spider mite populations being a bit high. Predator numbers are keeping the population in check at most farms.

Sweet and tart cherry leaf drop continues from earlier infections of cherry leaf spot. I believe that where fungicide applications have been made that leaf drop has been slowed.

Plums continue to size fairly well with most European plums beginning to color in preparation for harvest.

Small fruit

Strawberries continue to rebound from the renovation process. I have seen a great deal of new runner development in new plantings in the last week. The only pest to report is very high populations of potato leaf hoppers in some new plantings. Weed control has not been satisfactory in many renovated strawberry plantings; it appears that problem weeds are already breaking through. Some growers are considering other herbicide options.

Raspberry harvest is now wrapped up for summer red and black raspberries, and harvest has now begun on some of the earlier varieties of fall red raspberries. Fall blackberry harvest has not begun as of yet. The only pests to report in fall red raspberries is high populations of two spotted spider mites at some farms, and potato leafhoppers at others. We had our first trap catch of spotted wing Drosophila in a black raspberry planting in late July in west Michigan. Growers need to continue to scout for this pest.

Blueberry harvest continues across the region. I am starting to see that blueberry fruit size is starting to decline as some farms are past the peak of production for the season. Japanese beetle feeding has been a problem at a few farms this season. Blueberry maggot trap catch continues at most farms. Birds continue to be a serious issue; starlings have been feeding in high numbers.

Grapes continue to put on a great deal of new growth and berry size continues to march along. Grape berry moth adult flight continues for the second generation flight. Growers need to be on the lookout for grape berry moth larva at this time.

Back to top

Grand Rapids Area Tree Fruit Amy Irish-Brown and Phil Schwallier, Michigan State University Extension

Grand Rapids Area
Grand Rapids Area


The hot and humid weather continued over the past two weeks. Degree day accumulations continue to move ahead of normal averages in the region. Rainfall has been higher than normal for late July and early August with totals reported between 1 and nearly 7 inches in the last two week (July 26 through August 8, 2011).

Weather Station

Rainfall Total since July 26, 2011





Fennville (TNRC)




Kent City




Peach harvest is slowly moving forward. Redhaven harvest is just beginning. Early apple harvest of Pristine is ongoing and Gingergolds, Zestar and Paula Reds should begin soon. It is thought that the predicted harvest dates are slightly ahead of what is actually taking place in orchards. Growers should adjust Retain and other stop drop applications accordingly.

Tree fruit pests

With all the rain of late, and the dewy nights, be sure not to stretch your summer disease fungicides too far at this time.

A new codling moth biofix is being set for second generation flight that just got started over the past weekend (August 5-7). We have accumulated 378 degree days base 50 since that date of July 23, 2011. This indicates that about 25% of second generation eggs are hatched. Looking forward, peak egg hatch is predicted to happen around the middle of next week (August 15-19). In blocks over threshold for adult moths, management sprays are necessary.

Obliquebanded Leafroller adult flight of the summer generation is most likely past peak flight. Trap numbers reported are all over the board. Newly hatching larvae could start to be found at any time, but will be easier to find by the end of next week.

Japanese beetles continue to be found, but seem to be decreasing overall. Continue to monitor for their presence, especially in high value varieties such as Honeycrisp.

European red mites can be found in all life stages. As we are within a month of harvest of some major apple varieties, growers will need to be mindful of Pre-Harvest Intevals (PHIs) for miticides. The threshold for European red mites can be increased to 5 to 10 mites per leaf for August.

Woolly apple aphids are still present and building in some blocks. Continue to monitor and apply controls as needed. At this late date, it might be best to let them go and build some predators to help control them for 2012.

Oriental fruit moths are in between their second and third generation. Third generation egg hatch is expected to begin in a week or so.

Some sporadic adult flightof apple maggots is being reported from known hot spots. Most scouts are not catching maggots on yellow boards or red sphere traps, which is a little surprising given that it’s time to be catching them and all the rain we’ve had of late. Apple maggots should be flying at any time.

Back to top

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

Grand Rapids Area
Grand Rapids Area

At this time, small fruit crops in the area are mainly blueberries and raspberries. Hot weather from the past days continues to be a problem for both crops. High temperatures in blueberries are creating problems because the fruit becomes soft and increases the risk of fruit rots. Soft fruit can’t be packed for the fresh market and has to be diverted for processing. For raspberries, these conditions reduce the quality of the fruit and accelerate its decay. So far, late summer raspberries are ripening and harvest of early varieties has finished.

On the other hand, harvest of blueberries has continued with some problems related to weather conditions and labor availability. Fields planted with the variety Bluecrop are in the second harvest. And Elliott fields are initiating the first harvest in Allegan and Van Buren counties. The fruit from the first harvest of Elliott is of very good quality. North of Allegan, this variety is approximately two weeks behind with respect to the Bluecrop harvest. In addition to hot weather, intermittent rains have caused problems for harvesting. In some places both hand and mechanical harvest have been interrupted or conducted under difficult conditions due to excessive moisture in the ground. Another problem affecting blueberry harvest is a deficit of pickers. There aren’t enough workers for hand harvesting. Small growers in particular can’t find people to help them with harvest, so a large number of fields are being machine harvested. The shortage of laborers is a consequence of immigration problems and the past years’ troubles with the Labor Department.

One problem in particular requires growers’ attention; stealing of blueberries. Growers in Allegan County are suffering subtractions of large quantities of fruit by thieves that enter blueberry fields at night. In several instance growers ready to harvest are finding they have no ripe fruit left in their fields only green berries. So, growers need to be alert and report any suspicious activity in their fields.

Apart from these problems, Japanese beetles have been the major problem for both raspberries and blueberries in the entire region. Growers have been forced to spray insecticides before harvest to keep beetles away from the crop. Applications of insecticides against the Japanese beetles are mainly Aqua Malathion, Imidan, Mustang Max and Danitol. These insecticides are giving good protection when applications are well-timed. Under the current market demands regarding food safety, Jananese beetles are not only a food contaminant but also a food safety biological hazard that requires attention. When applying insecticides near harvest, pay particular attention to the pre-harvest interval on the product’s label. If the pre-harvest interval is 1 day, it means 24 hours. This is very important from the stand point of food safety. If fruit is harvested before the 24-hour period, pesticide residues may become a health risk for consumers that may have hypersensitivity to some chemical products (environmental allergies).

Other insects of concern in blueberries are blueberry maggots and spotted wing Drosophila. No problems are reported with blueberry maggots. Scouting for spotted wing Drosophila has continued, and so far, only in Allegan County. In Kent, Ottawa and Muskegon Counties no spotted wing Drosophila flies have been found, yet, however, we are continuing monitoring in blueberries and raspberries. Due to insecticide applications against Japanese beetles, it is possible that this season we will see spotted wing Drosophila only at the end of harvest when no more insecticide applications are occurring. Growers that installed traps in their fields require assistance to identify trapped flies, please call your Extension office for assistance, or Carlos Garcia at 616-260-0671. You may also bring samples to Ottawa County Extension (Fillmore Complex) in West Olive, MI or to the Trevor Nichols Research Complex (TNRC) in Fennville, MI (phone: 269-561-5040).

West Central Michigan – Mirjana Bulatovic-Danilovich, Michigan State University Extension

West Central Michigan
West Central Michigan

Weather:The Hot and Humid Summer Continues

This has been one of the hottest and certainly the muggiest Julys here in recent history. We had only nine days when humidity was below 70 percent. The rest of the month was extremely humid and very uncomfortable. Contrary to the rest of the state, we did not have extreme precipitation totals for the month of July. Our Enviro-weather weather stations in Hart and Ludington recorded 2.52 and 2.47 inches as total rainfall for the month. Compared to the normal precipitation for the month, Hart is coming about 0.4 inch behind and Ludington 0.3 inch ahead of normal. Overall seasonal balance is above normal. The Hart area is showing 1.1 inches and Ludington 4.29 inches above normal for the period April 1 until present.

Tree fruit

Tart cherry harvest is done. Final numbers have not been posted yet for Week 5, but the report for Week 4 is showing 47.2 million pounds for the West Central area. Our projected value is 55 million and it looks like we will fall a bit short of that. Quality has been very good to excellent.

There is a full crop of apples. They continue to size and develop well though the crop load will delay maturity somewhat. The weather conditions and the crop load will require some harvest date adjustment.

Peach harvest is underway. Redhaven harvest is expected to be in a full swing in about 7 to 10 days. Early plum harvest is underway. Pears will have just about a full crop.

West Central Michigan Growing Degree Day Totals Since March 1, 2011

As of Monday, August 8






Last 2-Week2

Since 4/1














Insects are starting to slow down. Codling moth numbers are dropping for the second week. The average number has dropped from 3.7 to 3.3 moths per trap. Greater peachtree borer numbers were up last week but have since dropped significantly. Lesser peachtree borer trap catch peaked last week with the average count of 58 per trap. This week the average trap catch has gone down to 7 per trap.

Oriental fruit moth numbers have gone down from 19 to 12 since the previous report with no change in the last week. Apple maggot numbers are low despite the few rains and high soil temperatures in the last two weeks. Leafroller complex numbers are still relatively high. There are reports of some larval activity as well. Spider mite activity has been on the rise. Red Delicious is showing some leaf bronzing. After a slow start leafhopper activity has picked up. Japanese beetles are commonly seen throughout the area. Aphid colonies are still quite active.


Humid and hot weather has been conducive to fire blight development. There are new shoot strikes throughout the area. Powdery mildew is still active. Scouts are reporting secondary apple scab infection lesions throughout the area. Some blocks have had apparent failure of the scab control program. Cherry leaf spot has not been a major problem. There is some leaf drop but overall, trees are looking green and in very good shape.

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

Northwest Michigan
Northwest Michigan


The weather continues to be warm in the north. We are now used to 80-degree days, although somewhat cooler temperatures are predicted for this week, at least for a few days. In terms of degree days, we have moved ahead of our 21-year average, but by very few degree days. In 2011, we have accumulated 2449 base 42 and 1624 base 50. Rainfall across the region was variable, which seems to be a theme this season. At the NWMHRS, we received 0.43” inches of rain on Saturday, August 6. However, other weather stations in the area did not record any significant rainfall.

Crop report

Tart cherry harvest is winding down, and most growers anticipate finishing by the end of this week. Fruit quality is still holding up, but we are picking out lighter than our estimated 135 million pounds in northwest Michigan. The majority of our harvest has been reported, and we are still under our estimate for the season. Sweet cherry harvest is completed. Raspberry harvest is also winding up for the year. Apricot harvest is underway, and peaches are anticipated to be picked around the third week of August. Wine grapes are looking good at this time if growers had good timing and coverage for powdery mildew. Growers that missed the window or had too much foliage for good coverage are fighting this disease at this time. Most canopy management has been completed, and vine growth has been incredible with the early water followed by the heat.

Pest report

In cherries, trap counts for most insects have decreased this week as all blocks where we hang our traps have been harvested. Obliquebanded leafroller numbers are down, and we averaged just over one moth per trap this week. In the lesser peachtree borer traps, we caught an average of 3 moths per trap. Peachtree borer trap counts were highly variable this week: 20 in one trap while the remaining five traps had only 1 to 5 moths. We are still catching American plum borers, and our average number of moths per trap was almost five. The big decrease this week was in our cherry fruit fly traps, where we caught eight flies on two traps, which is down considerably from the high of last week. Two-spotted spider mites are present on inner cherry leaves, but are far fewer in orchards that did not have good weed control this season. Cherry leaf spot is ubiquitous in regional orchards, and growers need to be applying a post-harvest control spray to keep leaves on the trees for as long as possible heading into the fall.

In apples, we caught very few insects in the one abandoned block of apples this week. Due to restricted entry intervals (REI), we will be checking the grower-standard block later this week. Codling moth numbers were low in the untreated block, and we only caught one moth in two traps. We caught no obliquebanded leafrollers or apple maggots in this block. Very few Oriental fruit moths were caught, and spotted tentiform leafminer numbers were down this week.

For grapes, recent hot weather produced rapid growth of mature vines with deep root systems, but young vines without irrigation have started to show signs of drought stress. Recent rains have helped a bit, but our long-term rainfall totals remain below normal thanks to a very dry July.

Powdery mildew has now appeared in a number of vineyards in the area, mostly as foliar infections. I’ve had reports of heavy infections, but not many vineyards fall into this category. Fruit should become resistant to new infections in the next week or so.

Grape berry moth flight is continuing, and berry injury from larval feeding is getting easier to find in many vineyards.

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. Two species are common, the Pandora sphinx and hog sphinx.

Pandora sphinx
Pandora sphinx.

Numerous aphid colonies were found on the terminal growth of Riesling vines at one vineyard in Leelanau County. These are very infrequently found in northwest Michigan. Some colonies were being tended by ants. Predatory syrphid fly larvae were on duty as well.

Larvae and aphids
Syrphid fly larvae and aphids.

Some stippling from leafhoppers has been seen, but very few potato leafhoppers are present in managed vineyards at the moment.

Leafhopper stipple
Leafhopper stipple.

A number of relatively insignificant lepidopteran leafrollers and leafminers are now present in vineyards.

Serpentine leafminer
Serpentine leafminer.

Back to top

Related Events

Related Articles

Related Resources