Regional reports on Michigan fruit – June 12, 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


Last week was warm with highs around 80 degrees Fahrenheit and lows in the 40s. Temperature on the weekend rose to near 90 degrees Fahrenheit. A cold front Monday (June 11) dropped temperatures into the 70s and brought only scattered rain Monday night.

Weather for this week is forecast to become warmer with highs rising back to the upper 80s. There is little chance of rain in the upcoming week. With no rain last week, soils are really beginning to dry. The potential evapotranspiration last week was about 0.22 inches of water a day and this rate will continue this week. We have used almost 2 inches of water since the last significant rains on June 1. By next Monday (June 18), we are projected to have used almost 3.5 inches. This means that established crops are using about an inch of water every 4.5 days. Our growing degree day accumulations continue about two weeks ahead of an average year. Southern sites are only about five days ahead of northern sites in the region.

Southwest Michigan Growing Degree Day Totals from January 1 through June 10


GDD 42

GDD 45

GDD 50





Trevor Nichols




Small fruit

The season continues about two weeks early. Insects are early, too. Japanese beetles should emerge soon. Full bloom in elderberry bushes or linden trees (basswood) blooming are good indicator plants for the appearance of Japanese beetle adults. Lindens are blooming and elderberries are at early bloom now. Japanese beetles may emerge in good numbers following a rain (about 0.25 inches). We have not seen many rose chafers this spring. No spotted wing Drosophila have been detected in yeast-baited traps placed in the raspberry or strawberry plantings in the high tunnels at Southwest Michigan Research and Education Center (SWMREC).

Strawberry harvest is winding down. Fruit size is declining and after final pickings this week, many growers will begin renovation.

Brambles are coloring and harvest is underway for early varieties such as Prelude. Growers who can should be irrigating to maintain fruit growth as harvest nears. Insect pests to scout for include raspberry sawflies, leafrollers and raspberry cane girdlers. Japanese beetles usually appear at harvest time in raspberries. Potato leafhoppers are increasing in the fall raspberry plantings. Hopper burn seems more severe in the varieties ‘Polka’ and ‘Anne.’

In grapes, ‘Concord’ and ‘Niagara’ bloom continues. Fruit on the primary shoots are at buckshot berry size, while secondary shoots are blooming. Early bloom on the secondary shoots is at berry shatter.

Wine grape bloom continues and many varieties show the same range of developmental differences between primary and secondary shoots. Phomopsis and black rot leaf symptoms are common in unsprayed vineyards. We have not detected powdery mildew in vineyards we scout, but growers with susceptible varieties should be watching for this disease.

Grape berry moth trap catches decreased last week. We have not found larval feeding in the clusters. The grape berry moth model on Enviro-weather has been fixed so that the right dates appear for biofix. We set biofix for grape berry moth in southern Berrien County on May 18 and northern Berrien and Van Buren counties on May 21. The first Japanese beetle adult was found on a grape vine in Van Buren County yesterday (June 11).

Blueberry fruit is beginning to color. Harvest will begin soon. Fruit set is light in some fields and yields are very variable across the region. With the current, warm, dry conditions, many growers are irrigating. Growers should be irrigating as they would in early July. Shoot growth has stopped in many fields so fruit growth is the main demand on the plants. The plants are fully leafed out and will use all the water they can get. Reduced water will reduce fruit growth. Most fruit growth at this time is by cell expansion, so the plant needs water to maintain the late swell of berries.

Cane collapse from phomopsis is appearing. We expect to see a lot of phomopsis cane blight due to damage from all the spring freezes. Controls for anthracnose should be applied as the fruit reach 10 percent blue in fields. Blueberry maggot flies are being caught in commercial blueberry fields and spotted winged Drosophila flies are also being trapped in Allegan and Ottawa counties. Growers should be monitoring for these pests. For more insect scouting information, see the Blueberry Insect Scouting Report for June 4-10, 2012.

Early blueberry varieties such as these ‘Bluettas’ are beginning
to color and ripen. Harvest should begin next week.
Photo credit: Mark Longstroth, MSUE

Tree fruit

San Jose scale crawlers are still active, but some are beginning to settle. Growers should target this pest now before the young crawlers are covered by a protective scale. Trap catches for most moth pests declined last week. Redbanded leafroller trap catches are up marking the start of the second generation.

Dry soils are a problem in many sandy sites. Growers should examine plant material planted this spring to see if supplemental watering is needed. Growers with well-established planting and no fruit can reduce irrigation in tree fruits to reduce growth; irrigation should only be reduced by a quarter or a third, not cut off completely.

Apricot harvest has ended.

Peach fruit are 1.5 to 2 inches in diameter and the pits are beginning to harden. Growth is abundant in sites with little or no crop, adequate water and fertilizer. Oriental fruit moth catches dropped off with the end of the first generation. Rusty spot infections are not a problem after pit hardening. Bacterial spot susceptibility of fruit also declines with pit hardening.

Sweet cherry harvest is ending. Growers complained that the birds got most of the fruit.

Tart cherry fruit are red. Some growers have applied Ethrel and will be harvesting fruit next week. Growers with roadside stands will be harvesting this weekend. Birds are perching on the power lines near tart cherry orchards for easy access to the fruit. Cherry leaf spot is not yet a serious problem.

Bird Montmorency
There is so little fruit that the birds are eating tart cherries.
Photo credit: Mark Longstroth

Plum growers should protect against black knot as long as shoot growth continues. Japanese plums are about 1 inch in diameter.

Apple fruits are 1.25 to 1.5 inches in diameter and June drop is ending. Russeting and distorted fruit are common and the few fruit in unsprayed orchards are beginning to show a lot of injury from direct pests. Codling moth biofix was set as May 7 and moth flight of this generation is declining. Obliquebanded leafroller biofix was set as May 19 with egg hatch predicted for late this week or early next week.

Fire blight symptoms have become more common in some sites. Most appear to be associated with overwintering cankers. Fire blight has also been reported in young trees near older trees with symptoms. Powdery mildew symptoms are common and growers should control this disease to prevent loss of fruit buds in the winter.

Pear fruit are about an inch in diameter on Harrow Sweet. Pear psylla is present in low numbers.

Upcoming meetings

Our next Monday night Fruit IPM Meeting will be June 18 at Fruit Acres Farms at 5 p.m. Fruit Acres is located on the northeast corner of Friday and Carmody Roads about 1.5 miles south of the Coloma Exit on I-94. One RUP credit is available at the meeting.

See Upcoming fruit meetings in southwest Michigan for more information on the June 13 Blueberry Pre-harvest Twilight Meeting and the June 27 Sprayer Rodeo.

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Southeast Michigan – Bob Tritten, Michigan State University Extension

Southeast Michigan
Southeast Michigan


Dry soils are common across almost all of southeast Michigan. While most fruit farms received two rain events in the past week, the total rainfall was negligible. Most growers continue to irrigate all fruit crops, especially newly planted fruit crops.

Our early, warm season is still running two weeks ahead of normal in terms of growth stages, and even more than that in terms of degree day totals.

East Michigan Growing Degree Day Totals for March 1 to June 12





Commerce (Oakland)




Emmett (St Clair)




Flint (Genesee)




Lapeer (Lapeer)




Petersburg (Monroe)




Pigeon (Huron)




Romeo (Macomb)




Tree fruits

Apples continue to size where growers have a crop, with most being around 1.25 inches in diameter. Where growers have a crop (mostly in the very southern tier of Michigan counties), hand thinning is underway. More apples are beginning to show their presence in these areas. The crop is so inconsistent from variety to variety, tree to tree and even limb to limb, that hand thinning will be a time consuming and expensive process this year. Most apple trees have between 12 and 18 inches of new growth, with some terminals reaching 22 inches of new growth. Growers who have used Apogee this season are seeing that it is having an impact on reducing terminal limb growth. Growers using Apogee are encouraged to leave some check or untreated trees in order to tell if it is helping to reduce terminal growth.

Overall, insect pressure remains low. Codling moth trap catch numbers are on the decline after four weeks of record breaking numbers. Even mating disruption blocks have had high trap catches. San Jose scale crawlers are being seen for the second week. The window for crawler control is closing soon. Aphid populations have been reduced by predator’s in the last week. Mite numbers are being kept in check at most farms.

I did not catch any apple scab spores in yesterday’s (June 11) rain and none in the rainfall that occurred overnight. So, I am calling an end to primary apple scab season as of today (June 12). I am seeing more apple blocks with sheet scab.

Powdery mildew-infected terminal branches and individual leaves have become much more evident in the past two weeks; some varieties are heavily infected 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. Some growers without a crop are considering sulfur applications to help control it. It is hard on foliage, however.

Cedar apple rust spots continue to be seen in apples. Most growers are seeing frog eye or black rot leaf symptoms in several apple blocks, and some black rot-infected limbs are now starting to flag or dieback. Sooty blotch and flyspeck symptoms are just starting to be seen in a few apple blocks where the threshold of 240 hours of wetting has now been reached.

Pear suckers have put on a tremendous amount of growth in the past four weeks, some reaching 4 feet in length. Pear psylla populations continue to grow quickly in unsprayed blocks. Suckers need to be removed to help reduce pear psylla populations.

Peach leaves where there is no crop are looking more normal in appearance. Harvest is expected to begin for the earliest of peach varieties in a bit over two weeks – very early! Hand thinning continues in peaches. For trees with no crop, this year this is a good opportunity to do some major pruning to reduce tree height. Be careful not to remove more than a quarter of the leaf surface.

Sweet cherry harvest is underway for growers with a crop. This is a record start of harvest at most farms. Leaf curling from black cherry aphids is being reduced by predators. Cherry leaf spot disease needs to be controlled in blocks that have no crop and maybe cherry fruit fly in problem blocks.

Tart cherry harvest will begin this week at most farms where there is a crop.

Plums were severely damaged by the last freeze event. Most blocks have little to no viable fruit remaining.

Small fruits

Strawberry harvest continues across the region, with farms in the south at peak or just beyond peak of the season. Growers in the south hope to have fruit to harvest for 10 more days. Berry size in these areas is starting to diminish. Thrip fruit feeding damage has been seen at one farm in the southern part of the region and I have had reports of the same damage at another farm. Thrip damage is rare in Michigan strawberry culture.

Consumer demand for strawberries has been excellent this season. Where slug feeding was a problem, bait treatments seem to be working well over the past week. Plants are runnering well where growers removed flower trusses in new plantings early this season. Growers are finding more fruit damage from earlier tarnished plant bug feeding than in most years. Black caps from angular leaf spot disease have been seen over the past 10 days.

Raspberry harvest is underway on early maturing, summer fruiting varieties. Canes of fall bearing types have 18 to 24 inches of new growth. At most farms, summer bearing raspberries had a great deal of tip burn or dieback from the April freeze events. Raspberry cane borer flagging damage is now being seen. Raspberry sawfly leaf feeding damage continues to be seen at a few farms. Now is the time to set spotted wing Drosophila traps.

Blueberries are at 12 to 14 mm in size for most varieties. Fruit coloring continues on early varieties with harvest expected to begin in two weeks or so. Leaf growth has been very slow to recover from freeze damage mostly on early varieties; it is odd to see all of the fruit exposed as it has been so far this season. Some of the fruit on the effected varieties will most likely not mature correctly. Fruit drop continues on freeze damaged varieties. Now is the time to set spotted wing drosophila traps.

Grape bloom continues on most varieties from secondary buds. Canes that were damaged in the many freezes appear to have been killed. Now is the time to prune these damaged canes.

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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

While there are a few more apples now being found, the overall crop in the Grand Rapids, Mich., area appears to be about 10 percent of the normal expected average. Occasionally, in very high and protected sites, the crop load is 50 percent or better, but these are the exception, not the rule. Tart cherry harvest will start later this week where there is viable fruit. Sweet cherry harvest should begin shortly as well. Strawberry harvest is in full swing and the quality and flavor has been outstanding.

Predicted harvest dates for apples are now available on the MSU Enviro-weather website. Dates are about two to three weeks ahead of normal averages for the general Grand Rapids, Mich., area. We will have more data soon to publish on harvest dates for varieties other that Mac, Jonathan and Red Delicious. In the table below, you can see just how far ahead of normal the predicted harvest dates are – even when compared to the most recent early harvest in 2010.

Grand Rapids area historical predicted harvest dates


“Normal” date





Sep. 15

Aug. 20

Sep. 16

Sep. 2


Sep. 28

Sep. 11

Sep. 29

Sep. 16

Red Delicious

Oc.t 5

Sep. 20

Oct. 6

Sep. 22

Find more information for your local MSU Enviro-weather station at

Horticultural tasks to consider

No rain has fallen for the last 10 days. Soils were dry at the time of that last rain and they are even dryer now. Irrigation continues to be recommended in newly planted trees. Newly planted trees need 10 gallons of water per tree per week. It is best if you can break that up into two applications over a week’s time, but more important that you get it applied, even if it is only once per week.

Fire blight update

My message is the same as last week – we’ve moved past all risk for blossom blight for the year, however, trauma blight is something you should keep in the back of your mind. If we get weather with hail or high winds that tear foliage, preventative fire blight sprays will be needed. The risk for trauma blight remains until terminal bud set, which is normally in mid-July, but could be delayed this year with little fruit to hold back vegetative growth. If you see fire blight strikes, try to remove them as quickly as possible. You can just throw them on the ground as they will dry up very quickly.

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, although it has slowed a bit with the dryer air we’ve been under. Mildew does not need free moisture to grow – this disease prefers high humidity and high temperatures, but not free moisture. Heavy mildew infestations lead to higher inoculum for 2013 and can reduce bud health and lead to severe winter injury and death of flower buds for 2013.

Tree fruit insects

Obliquebanded leafroller adult flight continues and is most likely at or just past its peak. A regional biofix was set for May 26. We have accumulated 348 degree-days base 42 since then. Early start of egg hatch predicted for June 15 based on the degree-day model. In blocks with viable fruits, cover sprays will be necessary by June 15 where pressure was high in 2011 or trap numbers are over 25 moths per week this year. In low pressure blocks, you could scout for larvae and then manage them – this usually falls about a week after the early egg hatch prediction based on the degree-day model or around June 22.

Codling moth. We have accumulated 479 DD50 since the May 3 biofix on the Ridge, indicating that egg hatch should be nearing a peak. Adult males in traps are declining a bit, but are still fairly high in numbers in some areas. Some sites set a later biofix around May 18 – we have accumulated 360 DD50 since that date, which indicates about 25 percent of the eggs are hatched for that timing and cover sprays are essential at this time for those blocks that are over threshold and have viable fruit planned to be harvested.

Oriental fruit moth. A regional biofix was set for oriental fruit moth on April 15 and we’ve accumulated 767 DD45 since then. Egg hatch is over for first generation oriental fruit moth. Flight of second generation is getting started and lures should be replaced in traps if not done already. We are right in between first and second generation and cover sprays will not be needed again in stone fruits until early next week, around June 23.

Borers. American plum borer and lesser peach tree borer flight is lessening. It’s past the peak timing to get the most out of trunk sprays, but get it done if you haven’t. Adult flight is just beginning in very light numbers – it is only a week earlier than normal. Timing for dogwood borer trunk sprays is at peak adult flight, usually around July 4. It could be a week earlier this year.

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

Northwest Michigan
Northwest Michigan

Weather report

Summer weather has officially arrived in northwest Michigan this past week. Daytime temperatures were in the 70s and 80s, and over the weekend we almost hit 90 degrees Fahrenheit on Sunday (June 10). Nighttime temperatures over the past few nights never went below the mid-60s, which contributed to the summery-feel. As of this week, we have accumulated 1202 GDD base 42 and 689 GDD base 50. These are significantly higher than our 20-plus-year averages: 850 GDD base 42 and 453 GDD base 50. There were scattered showers on June 8-9 and rainfall amounts varied by the different Enviro-weather stations. At the Northwest Michigan Horticultural Research Station (NWMHRS), we received no rain while the East Leland station recorded 0.29 inches and Kewadin recorded 0.67 inches of rain on those two days.

Crop report

Fruit is sizing in all crops. Unfortunately, a few cracks are starting to show up in certain varieties of sweet cherries. Sweet cherries are also coloring up, and a few varieties in our variety trial are almost ripe here at the NWMHRS. There will be no doubt that we will have Michigan cherries for the National Cherry Festival. Some growers are starting to hand thin apples in blocks where they did not use chemical thinners. Sweet and tart cherry trees are starting to look a bit healthier over the past week – a lot of slow growth and light green leaves. Strawberry harvest began in the region on Friday (June 8) and growers are pleased with the size and quality.

Pest report

Cherries. Despite the varied rainfall levels around the region, the cherry leaf spot model did not indicate that any primary infection took place, though the symptoms from earlier infections continue to become visible around the region and produce secondary spores that are not accounted for in the cherry leaf spot infection model. Some of these early infections have not yet caused the leaves to yellow, but pose a significant obstacle to retaining leaves going into this fall. As temperatures warm, the infection will become more obvious as leaves yellow and drop from the canopy.

Leaf spot currently appears as red-purple lesions on the upper leaf surface. If you flip the leaf over, there is often a white dot in the middle of the lesion; these are the secondary spores. Some older cherry leaf spot lesions have also begun to drop out of some leaves, giving a shot hole appearance. If leaf spot is present, growers must be diligent about keeping the remainder of the leaves protected as we still have a long season ahead. Regardless of the crop load, growers should plan to continue to manage for cherry leaf spot.

Powdery mildew symptoms are also being reported in tart cherries. Light crop loads this year will likely lead to increased shoot growth and succulent leaf area that is highly susceptible to powdery mildew. Growers who have not yet applied a strobilurin fungicide (Pristine, Gem or Adament) for powdery mildew should consider it as they are effective against both cherry leaf spot and powdery mildew. The sterol inhibitor fungicides (Indar, Elite, Orbit) are also good powdery mildew materials, but must be tank-mixed with a leaf spot material as the sterol inhibitor fungicides are not effective against leaf spot due to widespread resistance in Michigan. Fungicides for powdery mildew must be applied on a protectant basis as there are no effective burn-out materials.

The Cherry Industry, Michigan State University,EPA, MDARD and Syngenta have worked together to obtain a 24 (c) special local need registration (SLN) for use of Bravo Weather Stick (chlorothalonil) beyond shuck split. Traditional timing of chlorothalonil for cherry leaf spot has been prohibited past the shuck split timing prior to this newly registered use. With the 24 (c), growers must follow a series of restrictions in order to use this product legally throughout the growing season to ensure that post-shuck split applications do not result in illegal residues. For more information, see the May 29, 2012, Northwest Michigan Regional Report.

Insect activity rebounded this week with the first catch of cherry fruit fly on Friday (June 8) at the station. Cherry fruit fly treatments target the adult to prevent egglaying with most requiring application seven to 10 days after the first fly is captured in the region. Growers should carefully consider the risk of not treating for this pest in low crop load situations, particularly in moderate-high pressure sites.

An average of 20 lesser peach tree borers were captured in each trap this week and the first greater peach tree borer was captured; significant first generation American plum borer flight appears to have come to an end. Obliquebanded leafroller adult flight was way up this week with an average of 21 moths per trap, indicating that we are well through the early treatment timing to target young larvae. Growers who haven’t had luck finding the larvae can hang delta traps with sticky liners and lures to determine if obliquebanded leafroller adult moths are present in their orchards at this time. During this growing season, growers may end up targeting the second larval generation of obliquebanded leafrollers, expected around harvest.

Plum curculio activity continues this week. Growers who have no harvestable crop may have decided to delay plum curculio insecticide applications and should also consider reducing their plum curculio management programs as the issue of internal larvae in the fruit at harvest is not of concern. Refer to the E-154 2012 Michigan Fruit Management Guide for more information on plum curculio management materials.

Rose chafers are out in high numbers and may be of particular concern in young orchards with limited leaf area. Established trees with light crops loads will be able to tolerate a substantial amount of foliar feeding. These insects are related to Japanese beetles, and both insects feed on many crops including apples, cherries and winegrapes, among a long list of other plants. Rose chafers are often more problematic in crops that are adjacent to grassy areas, particularly those with sandy soils where grubs overwinter and feed on grass roots. Rose chafer adults are tan, long-legged beetles and feed on tree fruit and grape vine foliage. The feeding damage is also similar to that of Japanese beetles where adult beetles feed on the leaf tissue between the large veins, a type of injury known as skeletonizing. However, if populations reach high enough levels, rose chafers can feed on developing fruits. The good news is that mating and egglaying only lasts for around two weeks, and the average life span of the adult is three weeks.

Rose chafer management can be questionable in orchard or vineyard systems, both because the insects are only present for a short time and they can re-infest an area quickly after an insecticide application. The feeding damage and population size of this pest may not warrant an insecticide, particularly on older trees or vines with ample leaves present at this time of the year. Many insecticides will knock down the beetle population effectively, but most are only rated as fair or good because of the beetle’s mobility and potential to re-infest an orchard or vineyard. There are many options for control and growers should consult the E-154 2012 Michigan Fruit Management Guide for specific insecticides. Growers should also consider using a control option that would be effective against other insect pests that are also present in orchards or vineyards at this time.

Apples. With the additional rainfall and warm temperatures, most growers in the region have likely moved out of the risk for primary apple scab, though growers with highly susceptible varieties or high pressure sites should consider a conservative approach to primary scab management, regardless of crop load. Inoculum can build quickly over a season and make control difficult in subsequent seasons. Refer to the E-154 2012 Michigan Fruit Management Guide for management options. Growers should also carefully consider their powdery mildew management as high infection levels are being reported from other regions of the state. Strobilurin or sterol inhibitor fungicides are the recommended materials for mildew and should be applied on a protectant basis. Once mildew is established, there are no adequate burn-out materials.

Codling moth flight picked up this week with an average of eight moths per trap. We continue to quickly accumulate degree-days with the hot weather this weekend, but 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. Treatments for first generation codling moth should only be applied when a single trap location reaches a cumulative catch of five moths or more. Based on the unusual patterns of emergence we have observed in other pests this season, growers should be carefully monitoring for codling moth and weighing the pros and cons of treatment in no crop situations. There are a number of effective codling moth materials. Refer to the E-154 2012 Michigan Fruit Management Guidefor more information.

Obliquebanded leafroller adult flight picked up this week in apple sites with an average of 11 moths per trap, indicating that we are passed the larvicide treatment window for the first generation. We expect a second larval generation in July. Growers can hang delta traps with sticky liners and lures to determine if obliquebanded leafroller adult moths are present in their orchards and to help determine the optimal treatment timing in July. The second generation flight of oriental fruit moth has begun. Rose chafers have been observed across northwest Michigan and some areas seem to have higher populations than usual.

Grapes. Early cultivars are into bloom; Chardonnay, Riesling and others are not far behind. Potato leafhopper adult numbers are still climbing in vineyards and nymphs are now more numerous. Rose chafer populations are extremely high at some sites, resulting in skeletonization of tender leaves and some injury to flower buds. Vineyards should be scouted closely for this pest so population hot spots can be found and treated where needed. The adults of sphinx moths are now in flight, so the first larvae of these will likely appear in the next couple of weeks.

No symptoms of powdery mildew have been seen in the vineyards we scout, but there have been some reports of this disease in the region. Scouting for this disease will become more difficult as the vine canopy becomes denser with leaves. We are now in the most critical period for preventing powdery mildew infections of fruit clusters, which will last until three to four weeks after bloom.

Saskatoons. Rose chafers are causing significant skeletonization of leaves at many sites, but the distribution of this pest is spotty – some areas have very few of them. Potato leafhopper adults are in high numbers at some sites. Infections of rust disease have been seen on leaves and berries; this is a particularly destructive and fast spreading disease that requires a tight fungicide schedule to manage it.

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