Regional reports on Michigan fruit – July 10, 2012

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

Weather

Last week was hot, with highs near or above 100 and lows near 80. Rainfall was light and variable across the region. Storms moved through the area on Sunday, July 7. Some areas received 2/10 to 3/10 of an inch, but most areas received no rain at all.

Weather for this week is forecast to stay dry, with no rain. Soils are very dry. Plant water use last week was over 0.25 inches of water per day. Evapotranspiration will be about an inch of water every five days during this cooler week. The dry conditions can suppress the emergence of insect pests from the soil. Our growing degree day accumulations continue about a week and a half ahead of the average of the last five years. Southern sites are only about a half a week ahead of northern sites in the region.

Southwest Michigan Growing Degree Day Totals from   January 1 through July 8, 2012

Location

GDD 42

GDD 45

GDD 50

Bainbridge

2344

2031

1556

Trevor Nichols

2228

1916

1225

Increase since 7/1/2012

282

261

214

Small fruit

Japanese beetles are spotty; in some areas they are causing significant injury. Spotted winged Drosophila (SWD) trap numbers are down because of the heat, but we expect them to increase when temperatures fall into the 80s. So far this pest has not been found in fruit that is being harvested.

Strawberry growers have finished renovation and plant regrowth is underway. It is very important under these dry conditions to irrigate to maintain good plant growth. Growers should treat for potato leafhopper as the new leaves emerge to prevent this pest from stunting their plants. Day neutral strawberries in tunnels at the Southwest Michigan Research and Extension Center (SWMREC) are producing good quantities of reasonably- sized berries despite the heat.

In brambles, summer raspberry harvest is winding down. Size and quality have suffered from the hot, dry weather. Summer bramble yields were also impacted by spring freeze injury to canes in the spring. Primocanes are about 3 feet tall. Growers should irrigate to maintain plant and fruit growth.

Growers should be on the lookout for spider mites, Japanese beetles and potato leafhoppers.Spotted wing Drosophila females were trapped in high tunnel blackberry plantings at SWMREC and are expected to spread to raspberries. With last week’s high temperatures, spider mite numbers are continued to increase in tunnel plantings at SWMREC.

Blueberry harvest is moving rapidly and most growers are machine-harvesting Bluecrop and other early varieties. Fruit is ripening quickly and growers continue to report fruit losses to birds and raccoons. Growers need to irrigate. Young plants and plants in unirrigated fields are collapsing. Even growers who are irrigating are having a hard time maintaining adequate moisture levels in the soil and report leaf burn and fruit shriveling even on plants growing in moist soil. Blueberry roots systems are very small and lack root hairs, so the absorptive surface of the roots is hard pressed to move enough water up to the leaves under these hot conditions.

Drought
Drought-stressed blueberry bushes.

Spotted winged Drosophila flies are being trapped and many growers are spraying for this pest as well as for blueberry maggots. See the Blueberry Insect Scouting Report for July 1-7, 2012 for more information. Controls for anthracnose and Alternaria fruit rots should be maintained.

Grapes in established vineyards still seem to be growing well and berries are putting on size. Young vines are beginning to show the effects of the abnormally dry conditions we are experiencing. Supplemental irrigation needs to be provided for these plants to ensure good establishment. Young grape vines do not have the deep, extensive root systems of mature vines, and their long-term health can be adversely impacted by drought stress. Fruit size on secondary clusters is catching up to fruit on primaries shoots and bunches are closing. Wine grape varieties are at berry touch and approaching bunch closure.

Japanese beetle feeding has increased over the last couple of weeks, but is still not extensive in most vineyards, probably due to the dry soils. For grape berry moth, the 810 GDD treatment window for materials such as Intrepid, Alticor or Belt for second generation egglaying was reached on June 27 and 29 in southern Berrien County and around June 30 or July 1 in northern Berrien and Van Buren counties. The 910 GDD window for conventional insecticides was reached on July 1-4. Grape berry moth trap catches decreased last week.

Disease pressure has been minimal. Traces of black rot have been found on berries and foliage in Niagara grapes at the Trevor Nichols Research Complex (TNRC) near Fennville, Mich. Powdery mildew was detected in trace amounts on foliage of Concord grapes in an unsprayed vineyard we scout. No downy mildew has been detected so far.

Tree fruit

Drought conditions continue to cause daily wilting and the yellowing and dropping of older leaves of many fruit trees on sandy sites. Growers are hauling water to new plantings. Surface-applied, soil-active herbicides are not suppressing weed growth because the herbicides require rain to move them into weed seed germinating zones. Grasshoppers are defoliating young tree plantings near grassy fields. The flight of the second generation of San Jose scale has started. Sprays for crawlers of this generation are generally targeted for 600 degree days base 50 F after this biofix.

Peaches are available at local fruit stands but supplies are very limited. Fruit flavor is very good; this is usually the case under dry conditions. Yellowing and drop of older leaves is common in sandy sites from a combination of stresses. Harvest of Brightstar, Risingstar, Garnet Beauty, Summer Serenade and PF 8 Ball is underway.

Peach fruit
There are a few local peaches in the best peach sites
in Berrien County.

Oriental fruit moth trap catches started to increase two weeks ago, marking the start of the second generation moth flight. Control for oriental fruit moth, if you have fruit, is recommended at approximately 100 to 150 GDD base 42 after the start of the second generation flight for selective products with ovicide activity or 170 to 195 GDD (10 to 15 percent of egg hatch) for organophosphates, carbamates and pyrethroids (check product) from the biofix date. Trunk sprays to control peach tree borer are usually applied in late June to early July, but these sprays may need to be done earlier or after harvest to avoid problems with days to harvest restrictions for Lorsban.

Cherry harvest has ended. Due to the dry conditions, cherry leaf spot is not a serious problem in either sweet or tart cherries. Birds did a good job of cleaning up the fruit. Growers believe that raccoon numbers are very high this year.

Japanese plums are over an inch in diameter. Leaf tattering and shot holes are common due to a wide variety of causes such as earlier frost damage, bacterial infection and physiological causes.

Apple fruits are generally 2.5 inches in diameter, with summer apple varieties, such as Zestar, at 2.75 inches or more. Redbanded leafroller trap catches declined last week. The tiny, white, fluff-like, winged stage of wooly apple aphid is common now in Berrien County. Codling moth biofix was set as May 7 and moth flight of this generation should be declining but may overlap with the start of the second generation flight which is estimated to begin by the end of June.

Obliquebanded leafroller biofix was May 19 and we are past peak egg hatch. Catches are generally low. Scout for larvae feeding in terminals – damage by this pest is relatively scarce. Oriental fruit moth second generation moth flight was estimated to begin the second week of June in Berrien County – fruit entries by the larvae are being reported now. European red mite populations are continuing to increase and have been found well over threshold in one orchard we scout (20 adults per leaf). Bronzing is very apparent at this level of infestation. The treatment threshold is five mites per leaf. Mature trees without fruit can probably withstand higher levels of mite infestation with little damage.

Apple maggot flies have been out for several weeks. Dry conditions tend to inhibit maggot emergence and we expect a well spike in numbers if or when we get rain. Powdery mildew symptoms are common and growers should control this disease until terminal bud set. Green apple aphids are out at some sites. Spotted tentiform leafminer numbers increased last week with over 400 per trap. Leaf symptoms due to the spotted tentiform leafminer sap-feeding stage should be showing up over the next week.

Pear fruit are about 2.25 inches or more in diameter on Harrow Sweet. Pear psylla is present in low numbers.

Meetings

The 23rd annual Viticulture Field Day will be held at SWMREC on July 25.

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Southeast Michigan – Bob Tritten, Michigan State University Extension

Southeast Michigan
Southeast Michigan

Weather

Dry soils are a major concern across the region. Many fruit growers report that they have not had significant rain for much of May and June. Fruit growers are seeing signs of drought stress in newly planted tree and small fruit plantings, and are now starting to see signs in established fruit plantings as well. I believe that drought stress has contributed to cane collapse in summer red and black raspberry plantings, causing many farms to end harvest just as it began. I am also starting to see signs of drought stress in blueberries as they are just beginning harvest. Growers need to be checking newly planted fruit blocks every few days for signs of drought stress. Growers are devoting a great deal of time to irrigation.

Most of the region has received some rainfall in the last week, in the form of fast moving thunderstorms. While these storms did bring some moisture, much of it was lost due to runoff. There was also a fair amount of hail and strong winds in these storms.

Our early, warm season is still running more than two weeks ahead of normal in terms of growth stages, and with all of the heat of last week, we are back to being three weeks ahead of normal in terms of degree day totals.

East Michigan Growing Degree Day Totals   for March 1 to July 9

Location

GDD42

GDD45

GDD50

Commerce (Oakland)

2218

1905

1431

Emmett (St Clair)

2193

1886

1420

Flint (Genesee)

2244

1929

1457

Lapeer (Lapeer)

2234

1926

1456

Petersburg (Monroe)

2359

2039

1550

Pigeon (Huron)

2083

1781

1328

Romeo (Macomb)

2272

1960

1481

Tree fruits

Apples are just over 2.25 inches in diameter where growers have a crop. Growers are continuing to bend limbs down in high density blocks to promote flower bud development for next year’s crop.

Where apple growers have a crop this year, I am finding that direct pests are seeking out fruit to feed or breed with a vengeance, resulting in far more fruit damage than growers are accustomed to finding. This has been the case for codling moth and plum curculio and most likely will for apple maggots as well.

Apple maggot trap catch on yellow sticky traps started to be seen on June 30 and high trap catches have continued since then. I find it interesting that growers are even finding high trap catches despite our soils being so dry. It seems that not much is normal this season. With last week’s heat and bright, sunny days, insecticides tend to break down more quickly. Thus, growers with an apple crop need to tighten up their spray programs for apple maggots.

Potato leafhopper leaf curling continues to be very common in unsprayed blocks. I recommend that this pest be controlled in young apple blocks and in valuable varieties, like Honeycrisp. Codling moth trap catch has remained steady the last few weeks. I believe that we are seeing an overlap in the end of the first generation adult flight and the beginning of the second generation. Overall, we have had very high numbers of codling moths caught on traps this season. Where growers have an apple crop this season, the second generation adult flight will need to be closely monitored and controlled.

Japanese beetles are being found in a few varieties, most commonly in Honeycrisp. European red mite numbers are being kept in check by predators at most farms where there is no crop, however, I am just starting to see some bronzing of leaves in a few trees where growers are controlling pests this season. Some terminal branch flagging from oriental fruit moth is being seen in a few apple blocks, especially in unsprayed blocks.

Powdery mildew-infected terminal branches continue to be prevalent in unsprayed apple blocks and some terminal limbs are starting to die from this disease. I am encouraging apple growers to keep a close eye on powdery mildew infections in valuable and susceptible varieties, even in blocks with no fruit. Sooty blotch and fly speck symptoms continue to be seen in light amounts. In unsprayed apple blocks, I am not seeing as much apple scab as I had expected to see.

Pear psylla populations seem to be finally leveling off in unsprayed blocks. Suckers need to be removed to help reduce pear psylla populations.

Peach harvest has begun on early varieties. I am starting to see some yellowing of older leaves in drought areas. I am getting a number of reports of raccoon, squirrel and bird damage to ripening fruit.

Sweet cherry leaf drop from cherry leaf spot disease is just starting to be seen. Japanese beetle feeding is beginning in sweet cherries.

Tart cherry harvest has wrapped up. Growers need to be on top of cherry leaf spot symptoms for the remainder of the season.

Plums are very hard to find this season, as most blocks have little to no viable fruit. Leaves in most of these unsprayed blocks are in tough shape due to insect feeding and disease.

Small fruits

Strawberry renovation is complete at most farms, with the exception of a Sinbar application where growers are waiting for rainfall. I am concerned about dry soils in renovated strawberries fields. Growers need to reset irrigation pipe and begin watering as soon as possible in dry areas. Potato leafhopper leaf cupping and leaf margin burning is common in many new plantings. Fields need to be scouted immediately for this insect and damage.

Raspberry harvest continues on summer fruiting varieties. However, at many farms harvest has come to a quick end due to extensive cane collapse caused by a combination of dry soils and freeze damage that has become evident only in the last few days. At these farms, harvest will be less than 10 percent of normal years. Canes of fall bearing types have 24 to 30 inches of new growth.

Spotted wing Drosophila trap catch began last week at farms that had trap catch last year. We are finding that trap catch declines a bit in hot weather, however it will increase again when cooler temperatures resume. Potato leafhopper feeding injury has caused extensive leaf cupping in many fall raspberry plantings over the last three weeks. Fields need to be scouted immediately for this insect and damage. Japanese beetles are being found, mostly in fall raspberry plantings. Growers need to be on the lookout for this pest.

Blueberry harvest began in the last few days on early maturing and even on mid-season varieties. There does not seem to be much spread in ripening dates of early and mid-season varieties this year. I am starting to see some berry size issues in blueberries growing in dry areas.

No blueberry maggots have been caught in traps in east Michigan this season, although they are being caught in traps in west Michigan. I usually find that blueberry maggots emerge the same time as apple maggots, and I started to find apple maggot trap catches on June 30. So, growers need to be on the lookout for it. Japanese beetles are being found, mostly in low to moderate numbers. Remember to check spotted wing Drosophila traps. Bird feeding is extensive at many farms.

Grapeberry size is extremely variable this season due to freeze damage that killed most of the primary flower buds. The largest berries from the primary shoots are at berry touch. Many of the fruit clusters are not filled out very well. Grape berry moth feeding injury is being found. Japanese beetles are being found, mostly in low to moderate numbers.

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

Grand Rapids Area
Grand Rapids Area

Crop update

For those with early peach cultivars, harvest is beginning. Early apple cultivars could be ready in the next seven to 14 days. Growing conditions are very dry and growers continue to irrigate tree fruits where they have trickle irrigation. Trees planted in 2012 and 2011 need to have regular supplemental irrigation to prevent water stress.

Fire blight update

Fire blight continues to run in blocks that have it. Watch out for stormy conditions that rip or tear foliage and that will make it even worse. Until we get terminal bud set in apples, fire blight will continue to spread.

Apple scab

Continue to monitor blocks where primary scab became established and apply fungicides as needed to prevent spread to leaves. With the light crop load, you might think that you can just let the scab go, but heavy infections could lead to early defoliation which will weaken trees and open them up to winter injury.

Powdery mildew

Mildew continues to spread, especially with the humid weather last week. Some apple orchards have 50 percent or more infected terminals. This much mildew is going to cause problems for next year if you don’t do something now to try to burn it out and slow it down or stop it.

Brown rot in peaches

As we are nearing harvest of peaches, growers need to start considering tightening up their fungicide program to protect fruit from brown rot. The dry weather conditions this week do not favor brown rot, but if the humidity moves back in, it will take off.

Summer diseases

We reached enough hours of leaf wetness about 15 days ago (as of July 10, 2012) to satisfy the models that indicate when summer diseases such as sooty blotch and flyspeck will start to sporulate. If you haven’t started to add summer disease fungicides into your spray programs, you need to do so in blocks you plan to harvest to prevent these diseases from showing up on fruit.

Tree fruit pests

Obliquebanded leafroller adult flight has ended. A regional biofix was set for May 26. We will have accumulated 1,208 degree days base 42, which our models indicate we are well past the end of egg hatch, so all first generation larvae should be hatched. Second generation adult flight should begin at any time if not already.

Codling moth. In general, adult males in traps are low, but some have reported a slight increase in adult trap numbers in the last few days. This most likely indicates the beginning of second generation adult flight. If you had trap numbers that went to zero for at least one week, you could set a new biofix for second generation when you start catching moths again. If your trap numbers have not gone to zero, you will have to stick with the initial biofix. We have accumulated 1,118 DD50 since the May 3 biofix on the Ridge, indicating that second generation adult flight should be starting. Many sites set a later biofix around May 18 – we have accumulated 998 DD50 since that date, which indicates that egg hatch should be just at an end and second generation flight might begin this coming weekend (July 14-15).

Oriental fruit moth. A regional biofix was set for oriental fruit moth on April 15 and we’ve accumulated 1,543 DD45 since then. Flight of second generation is probably lessening, but egg hatch is at a peak. Cover sprays to protect growing shoots and fruits of stone fruits are again necessary to maintain. I am also hearing a few reports of high numbers of flagged terminals in apples from oriental fruit moth this year, especially where codling moth cover sprays have been minimal or non-existent. Codling moth can infest new shoots as well, so it would be best to properly identify which pest is causing this flagging in apples.

Dogwood borer adult flight is well underway and most likely at a peak. If you have young apples blocks on M9 clonal rootstocks, especially trees in their fourth or fifth leaf, pay close attention to the graft unions and look for dogwood borer pupal cases sticking out of burr knots. This age of tree needs to be protected from dogwood borer infestation.

Japanese beetles and other scarab beetles. I’ve seen and heard of people thinking they are seeing Japanese beetles, but until about 10 days ago, they really hadn’t been present. The other scarab beetles were either rose chafer or European chafer – neither of which look like Japanese beetles, but could feed on tree fruits and leaves and cause some possible confusion. See the pictures below for help in proper identification.

Rose chafer

European chafer

Japanese beetle

rose chafersPhoto credit:   Tom Zabadal

European ChaferPhoto   credit: www.maine.gov

Japanese beetle
Photo:MSU IPM

Feeding damage is most obvious on   the leaves, though the greatest impact can be on young clusters when adult   beetles (about 12 mm) remove the developing berries.

European chafer adults are 0.5 inches long. Males and females are a uniform tan or light brown color.

Adults are bright metallic-green with coppery red wings and small, white tufts on the sides and tip of the   wing covers (about 12mm).

I would expect Japanese beetles are delayed in their emergence somewhat due to the dry conditions. When we get rain, there could be a big flush of emergence. I would expect this foliage feeder to move right to tree canopies since the orchard floor plants have mostly gone into a dormant stage with the hot, dry conditions of late.

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

Northwest Michigan
Northwest Michigan

Weather report

Daytime temperatures have returned to a more “normal” range in northwest Michigan; we have been in the high 70s and low 80s, and those temperatures are predicted to continue throughout the week into the weekend. Little rainfall is in the forecast. Thus far this season, we have accumulated 2,036 GDD base 42 and 1,301 GDD base 50. These accumulations are higher than our averages: 1,568 GDD base 42 and 949 GDD base 50.

We received some rainfall over the weekend (July 7-8), but overall accumulations were low – the Northwest Michigan Horticultural Research Center (NWMHRC) received less than 0.25 inches of rain. With little rainfall in the past two weeks, conditions are becoming drier and soil moisture is dropping. However, compared to other fruit growing regions in the state, our soil moisture levels are not as low.

Crop report

Sweet cherry harvest is already winding down this season. Because of the small crop, growers have moved through the blocks very quickly and most growers have completed sweet cherry harvest. Quality of fruit was variable as some growers have reported cracking and American brown rot. Growers also competed for cherry harvest with the birds; with the small crop, bird predation has been particularly problematic in area orchards and few orchards did not have flocks of seagulls, crows and cedar waxwings in them at some time during the harvest period. Tart cherry harvest has begun for those growers that will harvest – the overall number of blocks that will be shaken is very small. The apple crop continues to look good and are sizing well. We have had no reports of hail in the past two weeks and growers on good apple sites are optimistic about the crop. Red raspberry harvest has begun in early varieties.

Pest report

Cherries. Cherry leaf spot is not hard to find in any orchard, and some orchards have better cherry leaf spot control than others – we are in the process of trying to understand the different levels of control. We are seeing a second wave of cherry leaf spot on new growth in regional orchards and there are many questions about efficacy of our fungicides at this time. There are many inconsistencies with control and use of particular products and we will need to evaluate different orchard situations to determine the causes of reduced control this season.

Again, we encourage growers to continue to scout the orchard as a cherry leaf spot infection in early July can result in early defoliation, and set trees up for damage as we head into winter. We are recommending that growers use full covers if their cherry leaf spot infection is high or if they have already lost lots of leaves this season. Again, a reminder to growers that we still have a long season to go as it is only the second week of July and we need to keep the new foliage covered as we head into July and August.

Powdery mildew is evident in most tart cherry orchards, and once the white mycelium is on the leaf, control options will only further protect new foliage; we do not have any products that will eradicate powdery mildew.

As we are now harvesting sweet cherries across the region, American brown rot is the disease to watch. Growers should be cognizant of pre-harvest intervals (PHIs) at this time, but if American brown rot is detected, they should move to an every row spray regime for fungicide applications, particularly if the trees are large. The SIs remain the optimal choice for American brown rot control and Indar has routinely provided the best control of that class of chemistries.

Obliquebanded leafroller trap counts continue to remain relatively high in regional blocks with an average of 20 moths per trap. These insects are mating and females are laying eggs at this time. We anticipate larvae to be present in trees now; however, we have been scouting for larvae for the duration of the season and we still cannot find them in regional blocks. We will continue to look for larvae and will keep growers posted as the season progresses. Perhaps we will be fortunate this year, and no obliquebanded leafroller larvae will be found in area orchards. Depending on when certain blocks of tart cherries will be harvested, obliquebanded leafroller larvae could be present at the time of harvest.

In the past three years, this insect has become a contaminant pest in tanks of harvested fruit. To ensure these insects are not in the tank at harvest, growers will need to apply an effective material that specifically targets Lepidoptera. Additionally, growers will need to be aware of the pre-harvest intervals (PHIs) as they approach the harvest window. We have three new Lepidopteran materials that work well against obliquebanded leafroller: Delegate (seven-day PHI), Belt (seven-day PHI) and Altacor (10-day PHI), and all three materials provide excellent control of obliquebanded leafrollers. Bts, such as Entrust, will work against obliquebanded leafrollers, but should not be used at this time as they are slower acting than the other materials and we need a fast kill if the block will be harvested in the next week. Sevin and the pyrethroids have a three-day PHI, but older data tell us that these chemistries will not be effective due to cross resistance with the OPs.

We have also caught cherry fruit flies again this week. Growers should be applying an insecticide to control cherry fruit flies as we head into the harvest season to prevent larvae in the fruit at harvest. However, if a block does not have fruit, growers can eliminate a cherry fruit fly spray at this time. These insects lay eggs in fruit and if there is no fruit, no insecticides are needed. Growers should keep in mind that even if there are few fruits per tree, the females will seek out these fruits and lay eggs. With no cherry fruit fly-targeted insecticide sprays, the result of this situation could be an increase in cherry fruit fly populations in 2013.

Growers should also be aware that cherry fruit fly populations are unique to individual farms and growers should be monitoring for these insects with a yellow sticky trap baited with ammonium acetate. Neonicotinoid, such as Provado or the generics, are rated as good against cherry fruit flies, but only last for about seven days in the orchard.

In a few blocks, we have seen sap beetle numbers on the rise when neonicotinoids are used – growers should keep an eye out for sap beetles and make insecticide decisions for cherry fruit flies based on sap beetle infestation. If the harvest window is stretched, Provado or the generics will need to be reapplied to reduce the potential for fruit infestation. Organophosphates (Guthion and Imidan) last longer, but Guthion’s PHI is 15 days and Imidan’s PHI is seven days. Imidan cannot be used in sweet cherries.

Sap beetles have been found in ripening sweet cherries, but we have had no reports of these insects in tart cherries. However, these insects can infest tart cherries and can be found in fruit that is ripening or damaged as they are attracted to ripe or overly ripe fruit. As we are at or approaching harvest, growers will need to pay special attention to the PHIs of the materials. Pyrethroids have good knockdown and short PHIs, Sevin and malation also have three-day PHIs. Danitol has been reported to be effective against sap beetles by area scouts.

We caught an average of 17 lesser peach tree borers this week and an average of 15 peach tree borers.American plum borer second flight began last week, and we caught an average of 11 moths in the traps this week. Borers still need to be controlled even if there is no fruit in a block.

Apples. Apple scab has been reported as low throughout the state, and we have observed little scab in area orchards here in the northwest. The apple scab model on Enviro-weather predicted a light scab infection on July 8. The dry conditions will minimize the need for scab control in the coming week. Growers that were not able to control scab in this primary season need to keep fruit protected from this pathogen as we move through the season. Growers should also note that strobilurin resistance has been confirmed in all major apple growing regions of the state and the mutation confers complete resistance – fungicides containing strobilurin will not work against apple scab and increasing the rate of a strobilurin is not an effective option.

Powdery mildew is evident in area orchards, and other areas of the state are reporting severe powdery mildew infections. Once the white mycelium is on the leaf, control options will only further protect new foliage; we do not have any products that will eradicate powdery mildew.

Fire blight is showing up at a slower rate than last week, but we can still observe strikes in area orchards. We hypothesize that these infections were the result of tag bloom or the long lasting bloom in apples coupled with the right weather conditions. Growers should keep an eye on weather as trauma events can spread the bacteria in orchards where strikes are evident. However, at this time, the forecast is not predicting rainfall or thunderstorms.

Codling moth trap counts are still high throughout the region. Growers that have a crop of apples need to be monitoring this pest diligently as they are internal feeders and will infest marketable fruit. With fewer apples in area orchards, codling moths will be competing to lay eggs in the reduced number of fruit that is available; therefore, growers need to be sure that fruit is covered at all times to minimize the risk of codling moth infestation.

Again, we emphasize that growers monitor for this pest in their own orchards as there is variability in the pest population from block to block; the degree day accumulation is HIGHLY dependent on the biofix date (the first date of sustained codling moth trap catch) for each apple block. Growers should track the progress on their farms using the Enviro-weather codling moth model and on-farm trap catch data.

Obliquebanded leafroller numbers have declined in apples and we caught an average of six moths per trap this week. The summer generation larvae will begin showing up in regional orchards in the coming weeks, and fruit should remain protected from these hatching larvae. Unlike cherries, this pest in apples feeds on the fruit, which makes control paramount for the remainder of the season. There are materials that will control both codling moths and obliquebanded leafhoppers in apples, and the use of these combination sprays will minimize costs for control of both of these pests.

Oriental fruit moth catch is higher this week than we typically see here in northwest Michigan, where we caught 24 moths per trap. This insect has also been reported across the state in higher numbers and in blocks of apples where growers have eliminated insecticide sprays, oriental fruit moth has been observed causing flagging in terminals.

Wine grapes. Fruit set in northwest Michigan looks very good for most cultivars. Some sites are rapidly approaching berry touch.

In general, foliage condition looks great throughout the region. Rose chafer populations were very high this year, but new shoot and leaf growth has now hidden their damage. In some vineyards, the rose chafers reduced the crop to a small degree by direct feeding on clusters before bloom. Japanese beetles should appear very soon. In most northwest Michigan sites, Japanese beetles are not numerous enough to be much of a concern. Vineyard sites with a history of infestations should scout frequently for Japanese beetles until the general population levels for this pest this year are known. Potato leafhopper numbers appear to have moderated, and recent shoot and leaf growth do not show as much injury.

As usual, we have had very little success trapping grape berry moths in pheromone traps in northwest Michigan. Thus far, cluster infestation levels have been very low and hard to detect in most areas.

The adults of Pandora, Achemon and hog sphinx moths are still flying and larvae should be present in vineyards. These are insignificant in mature vineyards, but a very significant threat to young vines that can’t afford to give up a lot of foliage to the voracious appetites of the larvae.

Powdery mildew remains at very low levels in the area. Untreated vines of very susceptible cultivars are still free of infection at the Northwest Michigan Horticultural Research Station. Berries have reached the developmental period where they are temporarily not susceptible to infection.

Saskatoons. Harvest has been completed through most of the area. The biggest concern for the rest of the season is maintaining foliage health to assure maturation of wood and buds. Entomosporium leafspot and rust disease are the problems to watch for now.

Important meeting notice – change of location

The “Sprayer Rodeo” on July 13 has been changed to a different location. It is now going to be held at the vineyard managed by Jerry Stanek, 9120 South Center Highway, Traverse City, Mich. (view map), about 1.5 miles north of the intersection of Center Highway and Crain Hill Road.

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