Vol. 19, No. 3, May 18, 2004

In this Issue
Tree fruit news
2004 Trevor Nichols Research Complex Trapline Data - redbanded leafroller
Managing internal feeding fruit pests of cherry
Current post-bloom fire blight control
Management of cherry powdery mildew
Quick strategies for peach crop thinning
MSU Organic Apple Field Day
Small fruit news
Early-season insect management in vineyards
Managing blueberry fruitworms
Timing is important in control of blueberry anthracnose
Other news
Regional reports
Clarksville Horticultural Experiment Station Organic Plot Report
Weather news

Managing internal feeding fruit pests of cherry

John Wise and Larry Gut
Entomology

There are two primary internal feeding insects that infest cherry fruit, plum curculio and cherry fruit fly (including eastern cherry fruit fly and black cherry fruit fly). The plum curculio (PC) is active earlier in the season than the cherry fruit fly (CFF), but there is often significant overlap in mid- to late June where both pests are a threat to the cherry crop. The PC overwinters as an adult and can be present in orchards as early as bloom time, but usually will not begin laying eggs into fruit until shuck-split or shuck-off period. The CFF emerges as an adult from the soil around mid-June. Females will begin seeking ripening fruit to lay eggs into 7 to 10 days later; this oviposition activity lasting through cherry harvest and after.

PC control options include insecticides in the organophosphate (OP) class, synthetic pyrethroids and more recently the neonicotinoids. One or more sprays are generally applied beginning at shuck fall, or earlier if PC adults are detected in the orchard or densities are suspected to be high. From second cover to a few weeks before harvest is a critical time for PC control. At this time, adults are continuing to lay eggs and the hatching larvae will be present in fruit at harvest. The OP's, like Guthion and Imidan, have generally been the standard for control because of their strong contact activity on PC and long stable residues. The synthetic pyrethroids, like Asana and Warrior, also have the strength of being contact poisons and are very fast acting, but their residual activity is generally shorter than the OPs.

The newest control option on the market is the neonicotinoid, Actara, which has performed very well in field efficacy trials at the MSU Trevor Nichols Research Complex and Northwest Michigan Horticultural Research Station. This compound is unique in that it is lethal to PC as a nerve poison when initially applied, but then as a translaminar (i.e., locally systemic) material provides long lasting fruit protection. Organic cherry growers may want to consider use of Surround WP (kaolin). Field trials have shown it to provide measurable fruit protection when used on large blocks when coverage is maintained.

Cherry fruit fly control options include insecticides in the organophosphate (OP) class, synthetic pyrethroids, and more recently the neonicotinoids, Fruit Fly Bait and Particle Film. The OP's, like Guthion and Imidan, have been the standard for control because of their contact activity on CFF and long stable residues. The synthetic pyrethroids, like Asana and Warrior, also have contact poisons activity on CFF adults, but generally provide only moderate control because of short residual activity.

Two new control options on the market are the neonicotinoids Provado and Actara, which have performed well in field efficacy trials. Provado has a 7-day pre-harvest interval, while the PHI for Actara is 14 days. Thus, Provado provides a good option for CFF control at that critical window of a week or so before harvest. Additionally, it is registered for use in both sweets and tarts. Since Actara is also active on PC, economical options for using this material would be a single application at 4.5 to 5.5 ounces/acre at second cover or a few weeks before harvest when control of both pests is often needed. Organic cherry growers may want to consider use of GF120 Fruit Fly Bait, Entrust (organic formulation of SpinTor) or Surround WP (kaolin). GF120 Fruit Fly Bait has been shown to provide effective control on various fruit fly species, but requires precise timing (CFF pre-oviposition period) and specialized application equipment. Entrust has shown to be active on fruit fly species but starting sprays during the pre-oviposition period on a 7-day interval is important for good performance. Field trials with Surround WP have shown good fruit protection from CFF when used on large blocks when coverage is maintained.

Current post-bloom fire blight control

George Sundin, Plant Pathology

We've seen conditions conducive for fire blight throughout Michigan in 2004. As we are at or beyond petal fall in most regions of the state, it is recommended that growers cease using streptomycin (Agrimycin) after a petal fall application for current season control. Overuse of streptomycin in apple orchards (greater than four applications) is the most important factor in the selection and maintenance of streptomycin-resistant strains of the fire blight pathogen, Erwinia amylovora. Our current survey results indicate that the range of streptomycin-resistant E. amylovora is limited to Southwest Michigan with scattered occurrences of resistant strains in the Fruit Ridge area. Streptomycin resistance has been present in Michigan for at least 11 years now, so it is surprising that the spread of resistant strains to other apple-growing regions has not yet happened. However, to continue limiting the spread of streptomycin resistance, growers must be vigilant using anti-resistance strategies, i.e. do not overuse streptomycin, and do not use streptomycin after bloom. The use of streptomycin after bloom is only recommended in conjunction with a severe weather event such as a hailstorm.

Unfortunately, there are few options for fire blight control at this time of the season. Remember that effective control with streptomycin and/or oxytetracycline (Mycoshield) during the blossom phase should strongly reduce the occurrence of shoot blight in orchards. Shoot blight may still occur on susceptible varieties, especially if active fire blight cankers are present in blocks. The amount of shoot blight observed will be mostly affected by varietal susceptibility, inoculum pressure, warm weather (high temperatures in the 70's-80's) with rain, and extreme weather (ex. hail, strong storms, high winds).

Two possibilities for late-season fire blight management are the growth regulator Apogee and the biological control Serenade. The biological control Serenade can partially control fire blight infections. Our current knowledge of Serenade indicates it is best used between streptomycin applications. We have little data concerning the ability of Serenade to suppress shoot blight and are currently studying this in experimental orchards.

The optimal timing for Apogee is petal fall of the king bloom. A maximum rate of Apogee (36 oz per 300 gallons per acre for full-size trees) can be applied at this time when infection risk is high. Apogee inhibits apple shoot growth, thus limiting the amount of susceptible tissue for infection. Apogee does not reduce fire blight bacterial populations in orchards. If the petal fall timing for Apogee has already been missed, growers should consider applying the maximum rate of Apogee in a single application immediately. Another option for growers is to split the seasonal rate into three applications put on at two-week intervals (ex. 12 oz, 12 oz, 12 oz). In a season such as this under high fire blight pressure, a single application at the maximum rate is probably the better choice. One more thing - if fire blight symptoms are already present, an application of Apogee will have no effect on further symptom reduction. In the time it takes for Apogee to influence tree growth (approximately two weeks), the fire blight pathogen will already have further spread within blocks, initiating new infections.

Management of cherry powdery mildew

George Sundin, Plant Pathology
Jim Nugent, Northwest Horticultural Research Station

Editor's note: We gratefully acknowledge Dr. Alan L. Jones, retired fruit tree pathologist at Michigan State University, for important contributions to this article.

Powdery mildew on tart cherry is a fungal disease of sporadic importance in Michigan. However, when favorable environmental conditions occur, such as in 2003, disease can be significant in affected blocks. Powdery mildew is most important during summers with hot, dry weather. The fungal pathogen requires little moisture for spore germination and growth on leaf surfaces. As little moisture as that present from high humidity from fog can stimulate spore germination and growth; intermittent rains can provide enough moisture to initiate epidemics. Powdery mildew typically is first seen on the underside of leaves and so orchard scouting is important for initial disease detection. The fungus grows as a white mat on leaf surfaces; continued fungal growth results in spread to upper leaf surfaces (Photo 1). Mildew can cause leaves to become brittle, and these leaves can then be subject to premature removal during harvest. The most significant economic aspect of mildew is fruit infection of sweet cherry, which is significant in the Pacific Northwest. Fortunately, fruit infection of tarts or sweets rarely occurs in Michigan. Continued buildup of powdery mildew late into the season could affect the overall photosynthetic capacity of trees, although data demonstrating this is not available.

As we also observed in 2003, conditions suitable for powdery mildew are less favorable for cherry leaf spot and brown rot. Thus, during hot, dry summers, growers are apt to spray fewer fungicides for disease control, resulting in less suppression of powdery mildew. In years favorable for leaf spot and brown rot, mildew is typically less of a problem in part because growers are spraying more frequently.

We rated the efficacy of several classes of fungicides for powdery mildew control on Montmorency tart cherry in 2003. The experiment was conducted at the Northwest Horticultural Research Station on 24-year-old trees. We utilized single-tree blocks with four replicates per fungicide treatment. Fungicide applications were initiated at late bloom and continued on a 10-day interval through a fourth cover spray. We did not apply any postharvest sprays. Powdery mildew occurrence was assessed in late August as the percentage of infected leaves on 20 terminals selected randomly from each tree.

The overall occurrence of powdery mildew was 45.6 percent on unsprayed control trees (Table 1). The best mildew control was achieved using the strobilurin fungicide Flint and the new combination stobilurin/boscalid fungicide Pristine. It should be noted that these fungicides were applied for the full season in the test plots for efficacy analyses; for resistance management, stobilurin and sterol-inhibitor (SI) fungicides should not be applied more than two times consecutively. As a group, the SI fungicides Elite, Indar, and Rubigan provided a middle level of mildew control, approximately 50 percent less mildew on SI-treated trees compared to that observed on untreated trees.

Timing of fungicide applications for powdery mildew control is very important. The fungus probably overwinters in buds, and the level of overwintering survival is governed by winter temperatures with reduced survival following severe winters. Control of primary disease inoculum appears to be of less importance for powdery mildew. Gary Grove at the Washington State University Center for Tree Fruit Research and Extension has reported in journal articles that secondary cycles drive powdery mildew epidemics. Thus, summer cover sprays targeting mildew control would be critical.

Tart cherry growers have to balance fungicide applications to target two major diseases (leaf spot and brown rot) and powdery mildew, a disease of sporadic importance. Mildew control can be initiated at petal fall; this timing would be especially important in orchards with previous significant mildew infection. This spray timing is more critical for leaf spot control, and this disease must take precedence because leaf spot is the most economically important tart cherry disease. Chlorothalonil is currently the most important early-season fungicide for leaf spot control both for its broad-spectrum activity and because it lessens the dependence on strobilurin and SI fungicides. Remember that chlorothalonil is not registered for use after shuck split. Since chlorothalonil does not control powdery mildew effectively, growers could consider including a mildew control during the early season, if necessary. One possibility is the use of low rates of sulfur for mildew suppression. Sulfur can be applied throughout the season, but the combination of low rates and long spray intervals may not suppress mildew under disease-conducive conditions. In seasons with reduced powdery mildew risk, low rates of sulfur could be tank-mixed with fungicides throughout the season yielding an overall suppression of fungal diseases.

As stated above, cover sprays applied after shuck split represent the critical timing for mildew control. Strobilurins are currently the fungicides most effective in mildew suppression; these fungicides are also excellent for controlling leaf spot and very good to excellent for controlling brown rot. One program which might be effective would utilize a strobilurin or the strobilurin/boscalid fungicide Pristine for the first and third cover spray using SI's or another alternative for the second and fourth cover sprays. Remember, the fourth cover spray timing is important for brown rot control as well. The combination of effectiveness of the fungicide and timing will drive the overall success of the program.

Table 1. Management of powdery mildew of tart cherry using fungicides. Full season applications involved six sprays that were initiated during late bloom and continued at approximately 10-day intervals. Treatments 1, 3, and 4 were SI fungicides; treatments 2 and 5 were strobilurin and strobilurin/boscalid fungicides, respectively.

^a Means within a column followed by the same letter are not significantly different according to Fisher's Protected LSD (P< 0.05).

Quick strategies for peach crop thinning

Bill Shane
SW Michigan Research and Extension Center

Peaches are thinned to prevent limb breakage, increase fruit size and quality. Thinning is a time-consuming, expensive job. Thinning techniques are used before, during and after bloom to reduce peach crop load. Early season thinning techniques can enhance fruit size by reducing competition. Early ripening varieties and varieties with less genetic potential for large fruit should be thinned first to provide the best opportunity for size enhancement.

A large mature tree of a mid- to late season variety can produce four or five bushels of 2.5-inch diameter fruit. A bushel of 2.5-inch diameter peaches contains approximately 150 fruit. So a target fruit load is 600 to 750 fruit per mature tree - nowdays the target fruit load should be less for larger fruit required by today's markets. For a typical 4-scaffold open center tree this works out to approximately 150 to 190 fruit per scaffold. For smaller, closer-spaced trees, or where the goal is slightly larger fruit, the number of fruit per scaffold could be as low as 60.

Thinning by pruning
An efficient way to reduce final numbers of fruit per tree is by aggressive pruning of excess or poor-quality fruiting wood in the dormant to pre-bloom pruning window. Aggressively eliminate limbs in the low center area of the tree where poor light and insufficient foliage will cause small fruit size. Prune to remove all fruiting shoots shorter than 8 inches long, as these limbs tend to produce smaller fruit. Crop load can be also be reduced by making heading cuts to shorten fruiting wood (limbs that grew last year), although do not cut shorter than 12 inches.

First assessments of crop load
An experienced orchard manager can look over a peach orchard shortly after bloom to estimate the fruit thinning job to come. For the novice, a quick approach to crop load assessment is to take a 12-inch ruler out to the orchard to quickly estimate average fruit density through a method we use at the Southwest Michigan Research and Extension Center (Table 1). After looking at 10 to 20 "typical" limbs in a peach block, a rough pre-thinning crop load estimate can be made. This is only a crude estimate - fruit size is greatly affected by weather following bloom. Mild conditions following bloom increases cell division numbers and the potential for fruit size. Higher rainfall, especially during the few weeks before harvest, can also increase final fruit size.

Table 1. Quick assessment for peach and nectarine crop load shortly before hand thinning time.

*Notes: A 12-inch ruler is placed in the middle of a fruiting limb and the number of viable fruit counted. These counts do not include "June drop" peaches that have stopped growing and are expected to fall.

Preliminary thinning
With very high fruit densities it is efficient to go through the orchard with loppers to adjust crop load by cutting out entire fruiting limbs and remove the ends of many fruiting limbs longer than 12 inches. In the two to three weeks after bloom, the very short fruiting limbs less than four inches are brittle and can be quickly snapped off completely by hand with little damage to the supporting limb. At this early stage, running a hand along the bottom of a fruiting limb can remove half or more of the fruit. These strategies are much faster than plucking off individual fruit by hand later when the fruit are larger and held tighter to the limb.

Target final fruit densities
A general rule of thumb is to leave an average of 6 to 8 inches between fruit. A 24-inch limb can support two to three peaches. To achieve proper size, an early ripening variety should be thinned harder than one ripening later. Hand thinning can start before various striking and shaking methods, which require fruit large enough to be dislodged by the vibration.

If the fruit thinning has not been completed earlier, rubber-tipped poles, padded bats, plastic "wiffle" bats can be used to strike limbs to remove excess peaches and is faster than hand thinning. In addition, portable hydraulic or pneumatic limb shakers are available and do a satisfactory job on limbs rigid enough to transmit vibrations to the fruit. If limb shakers are to be used, the trees should be pruned carefully to remove willowy growth that prevents good shaking action. Both striking and shaking strategies generally require follow-up hand thinning. Hand thinning provides greater control and causes less limb damage than limb shaking and striking.

The proper strategy for fruit thinning depends on many factors such as the variety characteristics, pruning style, the crew, fruit set and fruit growth rates. Each grower will develop the strategy that works for them. The key is to do what can be done earlier, quicker and more efficiently while there is time to benefit by improved fruit size growth.

MSU Organic Apple Field Day

The MSU Organic Apple Field Day will be held on Thursday, June 17 from 1:00 to 4:00 PM at the Clarksville Horticulture Experiment Station. Reserve your place today! Michigan State University invites you to visit its certified organic apple orchard to see the 2,500 trees on five acres and discuss some of the lessons researchers have learned over the past five years of orchard establishment and management. The planting includes three apple cultivars with different susceptibility to disease. It is certified organic by the Organic Crop Improvement Association (OCIA). The orchard project is funded primarily by Project GREEEN and a USDA Sustainable Agriculture grant through the Michigan Agricultural Experiment Station. More than 40 scientists, staff, Extension agents, farmers, advisors and students contribute to the organic orchard project. Results from this work benefit both organic and conventional apple growers.

The field day will feature presentations and discussion on three of the major areas being investigated in research at the orchard:

§      Building soil quality, fertility and biological diversity is essential in organic production systems. Alfalfa hay mulch, compost and clover are primary orchard nutrient sources. Routine soil sampling has documented changes in nutrient availability and in quantities of soil bacteria and fungi as the length of time in organic management increases.

§      Research on orchard floor and tree management in the organic orchard has results applicable to all orchards. Comparing three rootstocks and three vegetation management systems (mulch, flaming, Swiss sandwich) shows differences in tree growth and fertility.

§      Disease and insect management concerns in the orchard have focused on apple scab, fire blight, coddling moth and plum curculio. Management strategies including trapping, attractants, organic approved sprays and plant diversity are being tested in the orchard.

In addition to these three important aspects of organic apple production, research at the organic orchard also deals with orchard management education, certification, marketing and economics.

Plan to arrive at the Station no later than 1:00 PM, when wagons will transport field day visitors from the Clarksville station headquarters to the orchard plots. Separate tours visiting three educational stations in the orchard are planned for first time visitors and return visitors. Visitors will receive a printed copy of research results. There is no charge to participate in the field day but advance reservations - by Monday, June 14 - are requested to assure adequate transportation and materials. To reserve your place contact Sandy Allen by telephone (517-355-5191, extension 339) or email (allens@msu.edu). Let her know who and how many are coming and whether they are first time or return field day participants.

Directions to Clarksville Horticultural Experiment Station (CHES)
Take I-96 to Clarksville exit #59. Go south 1/2 mile to Portland Road, then west (right) 3/4 mile. The station is on the north (right) side of the road. For additional information, telephone CHES at 616-693-2193 or email CHES at stewar28@msu.edu

Early-season insect management in vineyards

Rufus Isaacs
Entomology

This article is the first of a series of three articles addressing vineyard insect management issues for the 2004 growing season. This article will cover the key insect pests during pre- and post-bloom period. The next will cover mid-season insect management, and the third will address issues to consider after veráison. Thanks to John Wise, Keith Mason, Natalia Botero-Garcés, Rodrigo Mercader, Paul Jenkins and our grower-collaborators for helping with our research projects which provide the basis for some of what follows.

Successful management of insect pests in vineyards depends on combining knowledge of many separate things. Growers need to scout their vineyards to know when pests are present, at what levels and in which parts of their vineyards. Scouting is the foundation of vineyard integrated pest management (IPM), because every vineyard is different and the best management will be that which is tailored to the site's particular needs. Biological and cultural controls can help to maintain pests below economic injury levels, but if pest levels get too high, there are many insecticides available that growers can apply. However, they all work a little differently. Knowledge of the pest spectrum and properties of different insecticides, and how to target them for maximum effect will also help achieve control.

Leafhoppers
Leafhoppers damage grapevines by killing the leaf cells they feed on. Damaged leaves have reduced ability to make sugars to ripen fruit, but regular monitoring and effective management can easily prevent their populations getting to levels that cause economic damage. In June, the native species of grape leafhoppers will start to move to the new growth from overwintering sites on the vineyard floor and in nearby wild areas. In addition, the spring weather patterns, with warm air moving into Michigan from the south, are ideal for bringing potato leafhoppers from the southern states. This insect re-invades our vineyards each spring, and gets washed out of the air column by thunderstorms over Michigan. Potato leafhoppers have already been spotted on yellow sticky traps this year and growers should be scouting for these, particularly in vineyards sensitive to their feeding, such as some of the labrusca and hybrid varieties. Regular checking of the undersides of leaves can help identify whether leafhoppers are present. Juice grape vines can withstand a high number of leafhoppers before the vine is damaged, and a postbloom insecticide (see following) will typically control these pests, so there is rarely a need for pre-bloom sprays for leafhopper. The main exception is on winegrape varieties sensitive to potato leafhopper. Although we have not tested all varieties, recent studies have shown that Chardonnay and Pinot Gris are particularly sensitive, showing the typical leaf yellowing, leaf cupping and stunted internode growth associated with sensitivity to potato leafhopper.

Growers have a range of insecticide options for leafhopper control that we have lots of experience with, and the most effective include the carbamates Sevin and Lannate, the pyrethroid Danitol, and the neonicotinoid Provado. All of these products provide control, though the length of activity varies, with Provado giving the longest control and the least disruption of biological controls. In some areas of southwest Michigan, resistance to Sevin has been documented in grape leafhopper, and in these areas different insecticide classes should be used. The availability of new insecticides Assail and Capture provide growers with some new alternatives that growers could try in 2004 to get experience with these products. In 2003, we tested Assail and Provado side-by-side in a demonstration trial at a highly infested Concord vineyard. There was slightly longer activity from the Assail, but both provided immediate and long-lasting leafhopper control. They will also both work well on rosechafer, but do not provide any control of grape berry moth.

To view information about leafhoppers from the A Pocket Guide for Grape IPM Scouting in the North Central and Eastern U.S., visit: http://grapes.msu.edu/aboutleafhoppers.htm

Rose chafer
The rose chafer is a scarab beetle that emerges a little before grapevines bloom and is present for two to three weeks. It is more of a pest on sandy soils, and overwinters as a grub feeding on grass roots. Vineyards next to hay fields or other grassy areas typically have higher pressure than fields next to woods or cultivated fields. Rose chafers feed on leaves and clusters, and if they are present in high numbers, they have the potential to cause significant injury if not controlled. Recent research by graduate student Rodrigo Mercader showed that high levels of defoliation by rose chafers made vines less able to tolerate injury from Japanese beetles later in the season. This, coupled with the risk of cluster feeding, makes the rose chafer a pest to watch out for before bloom.

Rose chafers rarely infest vineyards evenly, and more beetles are usually on the border rows than the interior. Because of this, a targeted application of insecticide can be made to save having to treat the whole acreage. Scouting in the middle of the day when beetles are most active can help determine where control is needed. This pest is sensitive to most of the broad-spectrum insecticides registered in vineyards, and if pest pressure is not very high, a single application is sufficient to achieve control. In 2003, we compared Sevin and Assail for control of rose chafers in a winegrape vineyard on the Leelanau Peninsula. Both products caused immediate control of the beetles, but Sevin provided only 7 to 10 days control while Assail provided at least 14 days of control.

To view information about rosechafer from the A Pocket Guide for Grape IPM Scouting in the North Central and Eastern U.S., visit: http://grapes.msu.edu/rosechafer.htm

Grape berry moth (GBM)
This pest continues to be a challenge for many growers in Southwest Michigan and in a few isolated spots in Northwest Michigan. Monitoring over the past three years in vineyards with high GBM pressure has shown consistent patterns of development of this pest, with the greatest egglaying activity occurring from just before veráison until harvest. In vineyards with low risk from GBM, growers can wait until later in the year to monitor and then decide whether a vineyard needs protection against this late season activity. However, in high-pressure vineyards, control of the first generation can help reduce GBM pressure later in the season.

The first flight of moths starts in early May, but egglaying does not start until around the time of bloom. Because of this, larvae of the first generation are well controlled by the typical ten-day postbloom spray. Some growers still apply a pre-bloom insecticide for grape berry moth, but there are some reasons this spray is best saved until after bloom: 1) egglaying usually starts when the clusters are close to bloom and the eggs will take time to hatch after that, 2) the small larvae eat very little, 3) a typical grape cluster sets only a fraction of the berries present before bloom so losing some to berry moth is unlikely to cause a large reduction in yield. By waiting until immediately after bloom, larvae are big enough to scout easily, most of the egg-hatch will have occurred, and an effective insecticide will be able to achieve very high levels of control of this generation. If leafhoppers are building in abundance at this time, an appropriate insecticide can get control of both pests.

For grape berry moth control at the immediate post-bloom timing, there are many insecticides with proven track records of control against this pest. Because the larvae are exposed, a spray with good coverage of the young clusters is needed to achieve control. A grower's choice of what insecticide to use at this time depends on the other pests present at the same time, what residual activity is needed and the price.

One new option for GBM control is Capture 2EC, labelled at 3.2 to 6.4 oz per acre. This pyrethroid was just labelled for grape leafhopper and two-spotted spider mite, but we also tested it against GBM in 2003 and it now has a 2EE label with GBM and Japanese beetle on the label. The low rate is expected to control leafhoppers, but if you are aiming for berry moth control in the same spray, use the highest rate. Only one 6.4 oz application will be allowed per season, and there is a 30-day PHI. Growers considering trying Capture in their insect control program this year should consider resistance management when using this product, because it is in the same class as Danitol. Rotate to a different chemical class through the growing season (e.g. carbamates Sevin/Lannate, organophosphates Guthion/Imidan, or growth regulator Intrepid), to help reduce the risk of resistance developing against this effective class of insecticides. It would also be a good idea to keep pyrethroid use to early in the season when natural enemy activity is lowest, and when a broad range of insects may need control.

To view information about grape berry moth from the A Pocket Guide for Grape IPM Scouting in the North Central and Eastern U.S., visit: http://grapes.msu.edu/grapeberrymoth.htm

Managing blueberry fruitworms

Rufus Isaacs and John Wise
Entomology

Cranberry and cherry fruitworm moths have been caught in pheromone traps in Southwest Michigan fields over the past week to 10 days. Egglaying is expected as petals fall and the fruit becomes suitable for the female moths to lay eggs. The larvae of two moth species can be found inside young blueberry fruit during and after bloom, but their presence is often not noticed until the premature ripening of infested berries, or the webbing of berries together by cranberry fruitworm are noticed. However, an integrated pest management approach using monitoring, scouting and appropriate application of effective controls can prevent fruit contamination by these pests.

The cranberry fruitworm and the cherry fruitworm have similar biology so they are usually controlled together. Adults of both species can be monitored using pheromone traps hung in the top third of bushes, preferably on edge bushes near to wooded borders. Traps are checked weekly to provide information on the start of moth flight and duration of adult emergence. No degree day model has been developed for this insect, and so once adults have been trapped, scouting for eggs on bushes near to woods where abundance is usually the highest can provide more accurate information on the best time to apply an insecticide. Eggs are laid in or around the calyx cup of young developing fruit, and so some petal fall has to start before eggs will start to be laid. A hand lens will be needed to see these eggs, and a fact sheet on identifying fruitworms in blueberry is available at the MSUE blueberry information page: http://web1.msue.msu.edu/fruit/bluberry.htm.

At many sites this year, fruit set started while other flowers are still in bloom. In this situation, bee-safe insecticides may need to be applied to get control of fruitworms in sites where fruit set occurs in fields where bees are still working and moths are trapped.

Once eggs hatch, the young larvae burrow directly into the fruit, so there is only a small window of time when insecticide residues can be picked up by the insect. Cherry fruitworm will spend all of their larval stage within one or two berries, whereas cranberry fruitworm larvae will move from berry to berry until the whole cluster is webbed and full of frass. Correct timing and coverage are critically important, so regular scouting of fields, use of sufficient spray volume to get good fruit coverage and selecting appropriate spreader-stickers can increase activity of most insecticides applied for fruitworm control.

During bloom, options for control are limited due to the need to protect bees. Two products registered for use during bloom have provided consistent control of fruitworms in trials at the Trevor Nichols Research Complex and at grower fields over the past four years. These are the B.t. products such as Dipel^® and the insect growth regulator Confirm^®. Both of these products must be actively eaten by the larva to be effective, so they should be applied when daily temperatures are likely to reach 70°F. B.t. has a short activity, providing up to five days active residue depending on the weather conditions. Confirm is more resistant to breakdown, giving between seven and 10 days activity, and it is quite rainfast, which can be a useful property in Michigan spring weather. Another option for control of cranberry fruitworm is the growth regulator Esteem^®. We have less experience with this product at Michigan farms since its registration last year. This product disrupts the adult moth's ability to make eggs and disrupts hatching of eggs and molting of larvae. Because of the way it works, it will be important to make an application closer to the beginning of egglaying.

After bloom, the range of options for fruitworm control increases, with Guthion^®, Imidan^®, Asana^® and Sevin^® being the most effective of the broad-spectrum insecticide options. With all these products, maintaining good coverage is still important to get residue to the parts of the berry where fruitworms are found. Recent research trials with Michigan blueberry growers have also demonstrated that SpinTor^® and Confirm^® applied after bloom can also achieve control of fruitworms. Because these products are more selective than the broad-spectrum materials, they have minimal negative impact on natural enemies such as parasitic wasps, ladybeetles and lacewings in the field.

Timing is important in control of blueberry anthracnose

Annemiek Schilder
Plant Pathology

Anthracnose fruit rot, caused by Colletotrichum acutatum, continues to plague blueberry production in most locations where blueberries are grown. The disease is characterized by orange spore masses on rotting berries. This fungus can also cause blossom and twig blight under certain conditions. Direct losses due to fruit rot can occur before as well as after harvest. Indirect losses result from increased costs of chemical control and sorting required for infected fruit lots. New evidence suggests that C. acutatum, while not known to be harmful to humans, may also contribute to high mold counts in stored blueberries.

The spores of C. acutatum are rain-splash dispersed. This means that irrigation water can also aid in spread of the pathogen. Monitoring of spore release of the fungus in Michigan with rainwater traps has shown that a peak in spore production usually occurs around bloom, followed by a second peak around fruit ripening (Figures 1 and 2). The first peak in spore production is thought to originate from infected fruiting twigs from the previous year. These spores cause the primary infections on young green berries. In years with cold springs, this peak may be somewhat delayed. These infections typically remain dormant until the fruit ripens. The second peak most likely results from sporulation of the fungus on ripe berries. At this time, healthy berries in proximity to infected berries can become infected and either rot in the field if harvest is delayed or they may start to rot after harvest. A timely harvest is therefore important to reduce the impact of fruit rots.

The spore release graphs also emphasize that timing of fungicide sprays is important in the prevention of primary infections as well as secondary infections. It is recommended to apply one or two fungicide sprays around bloom/early fruit development to prevent primary infections, and another spray at about 10 to 20 percent blue fruit to prevent secondary infections, which are more likely to lead to post-harvest rot. Most fungicides available for blueberries are protectants or only have limited curative action, so coverage and timing are important. The fungicides that are more effective for control of anthracnose are Captan + Topsin M (Captan does most of the work in this mixture), Abound, Cabrio and Pristine. The latter three fungicides belong to the strobilurins, which are surface-systemic and have about two weeks of activity. Switch is a fungicide with systemic properties that also has very good activity against anthracnose.

Of the above-mentioned fungicides, Pristine, Switch, and Topsin+Captan have the most broad-spectrum activity against other diseases, including other fruit rots and Phomopsis. All of these fungicides can be applied early as well as late in the season. However, Topsin M has a 7-day pre-harvest interval, so it would be more appropriate to use strobilurins later in the season. It is important to note that the strobilurins are prone to resistance development in target fungi, which means that they should not be sprayed more than two or three times per season and should be alternated with fungicides from a different chemical class.

Regional reports

1 - Southwest

Mark Longstroth
Bill Shane
Al Gaus

Weather
Last week was warm and wet. Highs were around 80 and lows in the mid-60s. Numerous thunderstorms moved across the area most days. The total rainfall varied from one to three inches. This means we had infection periods in all diseases. Soils are warm and moist with temperatures in the mid-60s. Plant growth was rapid. This week's forecast is similar with a chance of showers or thunderstorms almost daily but temperatures should average about 10°F cooler.

We are ahead of normal but not as much as we were in 1998 through 2001. For those four years we were several weeks ahead of normal. There has been a heavy fruit drop due to the weather conditions this spring. Bloom for most crops was during cool, windy weather and the May 3 frost was followed by warm, cloudy weather. Poor pollination, a frost and then stress by rapid growth and low light levels means that in many areas, the fruit set on the trees is light.

Tree fruit
Growers need to protect against plum curculio. Egg laying began this weekend and should continue this week. Plum curculio enjoys warm humid weather. Lesser peach tree borer and American plum borers are out.

Peach fruit set varies by variety and looks good for most varieties. Oriental fruit moth biofix was April 29 at 300 GDD45. We are now at 530 GDD and should be at peak egg laying now. Plum curculio sprays should control this pest in bearing orchards. Since the first generation attacks shoot tips and not fruit, this generation is seldom treated except in new orchards. Tarnished plant bugs are feeding on peach fruit. Last week we started catching lesser peach tree borer and flight continued this week.

In sweet cherries, plum curculio egg laying scars were easy to find Monday (May 17).

Tart cherry fruit is susceptible to plum curculio. Mature tart cherry leaves are susceptible to cherry leaf spot. Five mature leaves are out and now is the time to use Gibberellin sprays to control flowering next year. See the article by Jim Nugent in the May 11, 2004  CAT Alert and the Growth Regulator section of the 2004 Michigan Fruit Management Guide for more information.

European plums are 10 mm in diameter. Japanese plum fruit set is light. Growers should be applying plum curculio and black knot sprays.

In apples, there has been a heavy drop, and fruit set is light. Because of last week's warm, wet weather, thinning sprays should be very effective. The warm weather forecast also means that thinning sprays will be effective, so I would recommend only light thinning sprays of Sevin or BA6 in this thinning window. I would reduce rates if using combination sprays. See the Growth Regulator section of the 2004 Michigan Fruit Management Guide for more information.
While primary scab season is ending, apple scab lesions have been found in unsprayed orchards. This means that secondary spread from these lesions is possible and growers should be maintaining scab protection until they feel sure their orchards are clean. For apple scab secondary infections off the leaf lesions use the last column of the apple scab infection table on page 43 in the 2004 Michigan Fruit Management Guide. More scab symptoms should appear about May 19, 21 and 27. The May 27 symptoms are from last week's infection at the end of primary apple scab ascospore production. Powdery mildew symptoms are becoming common in apples.
Last week's warm, rainy weather included several fire blight infection periods. Blossom blight symptoms should appear late this week. A few oozing cankers and wilting shoots associated with old cankers can be found. There is still bloom in the orchards so growers may need to protect susceptible varieties during the warm stormy weather. Growers are applying petal fall sprays for plum curculio. Oriental fruit moth egg laying is peaking. Petal fall sprays control this generation. There are leafroller larvae feeding in terminals and fruit clusters. European red mites have been reported bronzing spur leaves and the interior of the trees in a couple orchards. Growers should be scouting for mites, aphids and spotted tentiform leafminer mines. We biofixed codling moth on May 7 at 235 GDD50. Last week we picked 20 GDD units base 50 per day. This week we should only be picking up about 10. Timing for codling moth control depends heavily on the mode of action of the material used. Traditional materials are used at 250 GDD50 after Biofix. Some very effective new materials are used earlier. See the article in last year's May 20, 2003 - Fruit CAT Alert.

Pear fruit set is light. In addition to those pests mentioned in apples, growers should also protect against pear scab. Pear psylla are scarce.

Small fruit
In blueberries mummyberry shoot strikes are easy to find. Growers should not use insecticides during bloom. There are leafroller larvae in some fields. We are catching cranberry fruitworm or cherry fruitworm but have not found any egg laying yet. We can expect these fruit pests to lay their eggs on the fruit as petal fall progresses. See the article in last year's May 20 2003 - Fruit CAT Alert. Tussock moth larvae have been found.

In grapes, two or three flower clusters per shoot are common. Vineyards in low areas damaged by frost show no (if any) green growth that can be seen from the roadside. A few secondary buds have come out in older Concord vineyards. Niagara secondaries show more movement. In vineyards that were heavily cropped last year and frosted this spring, many basal buds are beginning to grow. Accurate yield estimates cannot be made until the regrowth has begun, and the fruit buds are visible. Light to moderate hail damage is easy to find in Van Buren County. Warm, windy, rainy weather has growers struggling to maintain protective fungicide sprays against powdery mildew, black rot and phomopsis early fungicide applications as the flower cluster emerge will prevent infection of the cluster rachis during spring rains. There are few insects to worry about in grapes at this time.

Strawberry bloom is ending. There is tarnished plant bug damage to green fruit.

Raspberry flower buds are visible and early varieties have begun to bloom. Fall raspberry shoots are 10 to 12 inches long. There are leafrollers working in raspberries.

Miscellaneous
Roundup symptoms are easy to find now. We found them on apples, blueberries and brambles. Look for small strap-like leaves and stunted growth.

The next Monday Spray Meetings will be on May 24 at Fruit Acres Farms in Berrien County. Check the Fruit Code-A-Phones in Van Buren (269) 657-6380 and Berrien (269) 944-4126 ext. 1 for more information.

2 - Southeast

Bob Tritten

Weather
The wild weather roller coaster ride has continued for many fruit growers this past week. This time, however, the challenges of excessive rainfall and hail have been added to the mix for many. With all of the heat over the last two weeks, our season has jumped ahead of "normal." We are currently around five to seven days ahead of normal. There is also a lot of variability across the southeast region. In this brief weather summary I also want to update you on more details of the three frost and freeze events that occurred this spring. Most tree fruit growers have been very busy spraying for fireblight and stone fruit diseases.

With afternoon thundershowers many days at farms across the region, growers have received between two and three additional inches of rainfall on top of that same amount the week before. Several growers have reported hail along with these thundershowers. Most of the hail was in the pea- to dime-size, however a few have reported one-inch hailstones. Water ponding continues to be a problem at many fruit farms in low lying areas, making it difficult for spraying operations and other field work.

We continue to assess the damage from the three frost and freeze events that occurred on April 28, May 3 and 4. At this time, many farms have reported excessive flower and fruit damage in low lying areas and more than a "thinning frost" on the rest of the farm. Most of these growers with heavy fruit loss are south of a line from Mt. Clemens to Ann Arbor. Many growers in this area have reported back to me that they are still making a determination as to the possibility of discontinuing spraying operations in certain blocks of peaches, sweet cherries and apples due to lack of a crop. It will take another week or so to determine the full extent of the damage to make this spraying decision.

To contrast this, many other growers in different parts of the region are aggressively thinning apples and other tree fruits because of the abundant fruit set. Early thinning operations began mid- to late last week at several farms across the region and will continue throughout this week. It seems as if we have a season in terms of the fruit load of the "haves and haves-not." Many growers who have had frost and freeze damage have been severely hit, while others have had relatively no damage at all.

GDD totals for March 1 to May 18

Tree fruit
Apples are currently at 9 to 10 mm in size in the Romeo and Flint areas. In areas to the south, they are around 10 to 13 mm. In areas closer to Lake Huron, I had one report yesterday that they were nearing bloom. New insects to report this week on apples and other tree fruits include pretty good numbers of plum curculio, emergence of codling moth across the region, first sighting of tarnished plant bug and high trap catches of Oriental fruit moth. In more detail, plum curculio are now being found in good numbers on apples, plums and sweet cherries. Interestingly, a few apple curculio have been spotted at a few farms, feeding on apples. So petal fall or first cover sprays, depending on where folks are at, are being applied now to control plum curculio. Codling moth have generally emerged across the entire region now. One fruit farm has biofixed for codling moth on May 12, and many others will be biofixing this week. There are extremely high numbers of Oriental fruit moth flying throughout the region. Some trap counts are in the high 80's for a one-week count. Tarnished plant bug is another new pest that was seen last week for the first time, however numbers are very low. European red mite continues to be seen in good numbers at several farms across the region. Many growers are now accessing their mite numbers for possible treatment. Rust mites have also been seen at a few farms, as are twospotted spider mites. Rosy apple aphid leaf curling continues at a few farms. There are some predators beginning to take the numbers down a bit. Spotted tentiform leafminer first generation adult flight has peaked in the southern part of the region and are near peak in the Flint and Romeo areas. Larvae from a variety of fruitworms continue to be seen; these include green fruitworm, redbanded leafroller, fruit tree leafroller and obliquebanded leafroller. Generally, the larvae are fairly small and in low numbers. I've also seen a couple of white apple leafhopper adults, and also had some reports from a scout that white apple leafhopper nymphs had been seen in apples. More details on this next week. Many predators are building in apples, including ladybird beetles, Stethorus punctum, Amblyseius fallacies, Nabids and brown lacewings.

Apple scab spore discharge continues with each rain event. Last Thursday and Friday (May 13-14) I saw my first apple scab lesions. Powdery mildew also continues to be found at many farms. Fire blight spraying has been a common occurrence in many orchards across the region. The first fire blight shoot strike symptoms should start to show up this weekend. Several growers have reported putting on three to four streptomycin sprays. A few growers are moving on to use Mycoshield as they are needing to cycle off of streptomycin for resistance management reasons.

Pears are currently are at 9 to 10 mm in size with a fairly good fruit set. Pear psylla are very common across the region. Many growers are applying control measures for pear psylla, as well as fire blight.

Peaches are now out of shuck split to 9 mm in size. For growers that have a peach crop they appear to be growing quite nicely at this point in time. Keep an eye on Oriental fruit moth and fungicide cover sprays on peaches.

Sweet cherries are sizing quite nicely. Most are in the 12 to 14 mm in size. Scout now for plum curculio stings.

Small fruit
Strawberries are now in full bloom across the region. Many growers are reporting a few berries slightly smaller than thimble size at this time. A few twospotted spider mites continue to be seen, as do strawberry clipper. No tarnished plant bugs have been seen, but I expect them later this week.

Fall red raspberries continue to push new growth with most being around six inches in length. Watch for leafrollers on fall raspberries.

Summer raspberries continue to push out new growth, particularly from the base of the plant where canes were damaged from winter injury. Flower buds are present on summer raspberries.

Blueberries are at full bloom across the region. We have an excellent crop of blueberries coming along this year. Mummyberry disease control has been critical over the last week. Look for shoot strikes from mummyberry at any time. Growers are going through and removing Phomopsis twig blight and canker infested canes for the last time. Scouting for cranberry fruitworm and cherry fruitworm needs to be done now.

3 - Grand Rapids Area

Phil Schwallier
Amy Irish Brown
Carlos Garcia-Salazar

Weather
Degree days and precipitation are accumulated beginning January 1