Vol. 18, No. 3, April 29, 2003

In this Issue
Tree fruit news
Section 18 Crisis Exemption granted for Mycoshield use
Apple thinning for 2003
2003 TNRC Trapline data: green fruitworm
Apogee on apples
Pheromone-based management programs for codling moth and oriental fruit moth
Pest monitoring in apple from bloom to petal fall
Small fruit news
Uses of Dacthal herbicide canceled
Protecting blueberries from frost
Focus on early sprays for Phomopsis control in grapes
Using bees for pollination of small fruit crops
Indar Section 18 granted for blueberries in 2003
Other news
Michigan fruit Section 18 pesticide labels posted on the Internet
New job responsibilities for Amy Irish-Brown
Regional reports
Weather news

Section 18 Crisis Exemption granted for Mycoshield use

George Sundin, Plant Pathology, Bill Shane, SW District Agent and Horticulture Specialist, Mark Longstroth, District Horticultural Agent

EPA has granted a Section 18 Crisis Exemption effective April 29 to June 30, 2003 for the use of Mycoshield on apple for fire blight control in orchards where streptomycin resistance has been documented. Mycoshield (oxytetracycline) is an alternative antibiotic for fire blight management. Mycoshield will work equally on streptomycin-resistant and streptomycin-sensitive strains, however, the overall level of control is not as effective as with streptomycin in orchards without resistance problems. A maximum of five applications of Mycoshield can be made at a recommended rate of 1.0 to 1.5 lbs/acre. Only one post-bloom application can be made.

The Section 18 Crisis Exemption label for Mycoshield is posted on the MSU Fruit Area of Expertise webpage at http://web1.msue.msu.edu/fruit/MIfrt_s18.htm

The US Department of Agriculture reported on April 25 that tart cherry producers and processors voting in a March referendum have decided to continue their federal marketing order (FMO) program. USDA's Agricultural Marketing Service reported that among producers, 75 percent of the voters representing 73 percent of the volume of production favored continuance. For processors, 79 percent of the voters representing 74 percent of the volume favored continuance. - Jim Nugent, NWMHRS Coordinator.

Apple thinning for 2003

Phil Schwallier
District Hort Agent and CHES Coordinator

For apple growers, the most critical and difficult annual practice to perform is chemical thinning. Chemical thinning directly impacts the crop load and therefore, fruit quality for the current season's crop. It also impacts the return bloom for next year's crop. It is difficult to perform due to the need to apply chemical thinners before fruitset is truly known. Nevertheless, fruit growers of high quality apples perform chemical thinning annually and adjust their plan as trees, crops and weather conditions dictate.

This year it appears that most orchards have an abundant numbers of flower buds. This is due to last year's light crop. Growers should plan on applying chemical thinners early at aggressive levels this year, under good conditions and at the right time.

Standard thinning recommendations for 2003

1)   Apply chemical thinners at the beginning of a warming trend when temperatures are forecasted in the 70's and 80's.
2)   Target the 8-12 mm king fruit size for most thinners.
3)   Heavily clouded periods during fruitset will increase the thinning response.
4)   Consider aggressive thinning combinations for this year.
5)   Start your thinning program early, perhaps at petal fall.

Research has shown that all chemical thinners work better when warm temperatures follow the spray application within two to three days after the application. Temperatures near 80° are excellent to achieve a chemical thinner response. Research has also shown that the temperature at the time of application is not important.

At the 8 to 12 mm size, fruitlets are very vulnerable to any kind of stress. Stress will cause them to not set. Long cloudy periods during this time will cause stress and fruitlets will drop. If fruitlets run out of energy at this time, fruitset is reduced. Chemical thinners will cause a stress and increase fruit drop. The 8 to 12 mm stage is the time when the fruitlets respond to thinners the best.

This year we will most likely experience a heavy crop. Starting thinning early will be important. Early thinning helps produce two crops, this year's crop and next year's crop. On difficult to thin varieties and varieties prone to biannual bearing, consider applying first thinners at petal fall. At petal fall, fruit thinning generally is less responsive -- applying a full rate of thinners at petal fall will only reduce fruitset slightly. Most years, inadequate thinning occurs and later additional thinning is required. However, this is the first real window when fruits will respond to thinners, and in some years weather conditions are very favorable at petal fall for thinning.

Thinning at petal fall has three important effects. First, it reduces the crop somewhat. Secondly, it helps promote return bloom. And third, it improves fruit size and quality early on this year's crop. On difficult to thin varieties such as Fuji, Gala, Golden and Red Delicious consider applying a combination thinning application such as Sevin plus another material. Most likely inadequate thinning will occur, but perhaps as much as 10 to 15 percent thinning will occur. However, return bloom will be promoted and some thinning will help reduce a potentially heavy crop load.

A follow-up thinning application will be required at the 8 to 12 mm size of the king fruits. Most years that occurs ten days later. On these varieties consider a second application where thinning is needed of a combination spray again of Sevin plus perhaps 6-BA or Sevin plus NAA. These two applications of aggressive combinations will provide adequate thinning most years to difficult to thin varieties, especially if weather conditions are favorable.

On moderate to thin varieties, consider just a straight application of NAA and/or Sevin alone to provide some early thinning at petal fall. On moderate to thin varieties, consider an aggressive spray at 8 to 10 mm of Sevin plus NAA and/or Sevin plus 6-BA. This will be important, especially if it's the first thinning application and fruitset looks heavy. Where fruitset looks moderate to heavy and a first application was made at petal fall, consider a moderate combination at 8 to 10 mm stage. On easy to thin varieties consider a single application of chemical thinners applied alone such as Sevin, 6-BA, or NAA alone at the 8 to 10 mm stage.

Most likely this year, our crop load will be heavy. Consider aggressive combinations of thinners and start early. Plan on two sprays on the moderate to thin and the difficult to thin varieties. Apply chemical thinners at the beginning of a warming trend when temperatures are forecasted in the 80's. Heavy cloudy periods increase thinning and reduce fruitset. Target traditional thinning applications at the 8 to10 mm stage of the king fruits.

We have had numerous years in a row that weather conditions have been unfavorable for fruitset and chemical thinning. The odds are this year we will experience very favorable pollination bloom and fruitset conditions that will promote fruitset. It will be important to reduce this potentially large crop to a manageable crop and insure return bloom. The nation could easily have a very large crop this year due to the national light crop last year. It will be important to produce high quality apples this season.

Apogee on apples

Phil Schwallier
District Horticulture Agent

Apogee was labeled in 2000 on apples and has since been used by growers to control vegetative growth on most varieties. Apogee also has a side benefit of suppressing fireblight infections and canker growth. Apogee will reduce vegetative growth of shoots, laterals and water sprouts when the correct rate per acre is applied. Apogee is only locally effective. Coverage is very important to achieve desired results. Apogee benefits include control of vegetative shoot growth, suppress fireblight infections and reduce pruning time.

Table 1 lists suggested use rates and timing for different size trees. These rates are a guide for moderately vigorous trees and need to be adjusted up when used on highly vigorous trees. Table 2 lists factors to consider when selecting a rate to use. Apogee is compatible with all typical materials used during the time Apogee is applied except for calcium, boron and thinners. Don't mix Apogee with calcium and boron in the same tank. Table 3 lists suggested Apogee use on various varieties. Apogee will sometimes increase fruitset. More aggressive thinning is suggested when using Apogee. Apply thinners separately from Apogee. Separate thinner treatments by two to three days before or after an Apogee treatment.

Apogee must be mixed with AMS or a substitute in equal amounts and with a surfactant. Empire and Winesap fruit can be checked by Apogee.

Pheromone-based management programs for codling moth and oriental fruit moth

Larry Gut, David Epstein and Peter McGhee
Entomology

Factors to consider when implementing a pheromone-based control program broadly consist of site selection, pheromone application, product performance and monitoring. The best opportunity for control is achieved where physical characteristics and environmental conditions --topography, size and shape, canopy structure and wind -- allow for uniform distribution of pheromone. For example, orchard sites that are even canopied are better candidates for mating disruption than sites with large numbers of missing trees. Using mating disruption in a large, contiguous area is considered a better strategy than in small, individual orchards. However, mating disruption can be successfully combined with other management strategies for control of moth pests in small orchards and where physical conditions are less than optimum.

Experience teaches us that orchard borders require extra attention when implementing mating disruption programs. Two processes are thought to contribute to the development of border infestations. First, mated females immigrate from adjacent orchards that are not treated with pheromone. Second, it is suspected that pheromone concentrations are lower on the borders than the interior and so increases the likelihood of males locating females and mating along borders.

Several tactics can be used to protect orchard borders. Additional pheromone can be applied to border trees or extended into adjacent orchards if possible. This approach appears to be most effective when initial pest densities are low. In orchards that historically have a pest problem, it is best to treat borders with insecticides in addition to applying more pheromone to the borders or extending pheromone treatments into neighboring orchards. An effective border treatment (insecticides or extra pheromone) in most orchards would be an area equivalent to three or four rows around the orchard perimeter or along the problem border. Treating large contiguous areas with mating disruption is the best protection against border damage, as this strategy decreases the amount of border space relative to orchard interior.

Mating disruption, like any other control, is most effective if the application is well timed, the rate is high enough, and coverage is good. Effectiveness of mating disruption is reduced if dispensers are applied late since this tactic provides no control once mating has taken place. Most moths begin mating immediately upon emergence into the orchard. Dispensers should be in place prior to the predicted start of adult activity for the target pest. Coding moth and oriental fruit moth are currently the principal candidates for control by disruption in fruit orchards. Both pests have more than one period of adult activity, the overwintering generation and at least one summer generation flight. The best strategy for controlling codling moth in apple and oriental fruit moth in peach is to apply dispensers prior to the start of the first flight period. In contrast, targeting only the late-season activity of oriental fruit moth is a viable approach for using pheromones to manage this pest in apple.

For hand-applied disruption products, the rate of application corresponds to the number of dispensers applied per acre. Dispenser densities that can provide satisfactory control for orchard pests at a reasonable cost range from 100 to 400 dispensers per acre. The recommended application rate for most oriental fruit moth disruption products is about 100 d/a or one per tree. An exception to this is Isomate MRosso, a rope dispenser that has a recommended application rate of 200 units per acre. To successfully disrupt codling moth, the history of pest pressure within an orchard should be considered when determining the number of dispensers to apply per acre. Treat at the high end of the recommended rate if pest pressure is moderate to high. Regardless of pest pressure, experience over the past ten years strongly suggests that a minimum of 200 dispensers per acre is needed to result in worthwhile suppression of codling moth mating. Good coverage for disrupting codling moth or oriental fruit moth entails a more or less uniform distribution of dispensers throughout the orchard. If two or more dispensers per tree are applied, it is best to spread them out within the canopy.

Proper placement of dispensers within the tree canopy can be a critical component of a pheromone-based control program. Positioning dispensers in the upper portion of the canopy generally provides the best chance of interfering with mate location. However, good control of oriental fruit moth can be achieved by placing dispensers in the middle of the canopy. In contrast, successful mating disruption of codling moth requires placing dispensers within two feet of the top of the canopy, but near foliage to protect them from UV radiation and high temperatures. In orchards with canopy heights greater than 10 feet, optimum placement of dispensers cannot be achieved from the ground. A very good method for applying dispensers is with the assistance of a pole and clip. Application entails pushing a clip holding a dispenser onto a selected branch and leaving it there when the pole is twisted and pulled away. It takes less than 2 hours to treat an acre of apples with this technique.

Monitoring target pest activity is difficult in orchards treated with mating disruption products. Adult capture in pheromone traps provides some measure of the effectiveness of mating disruption. In pheromone treated orchards where control is being achieved, moth catch in pheromone-baited traps should be very low or shutdown completely. The rationale behind this measure of effectiveness is that if males are incapable of finding a lure releasing relatively large amounts of pheromone, then they are probably unable to find female moths releasing much lower quantities of natural pheromone. For oriental fruit moth, trap shutdown appears to be a good indication that a high level of control is being achieved. However, for codling moth, unacceptable levels of fruit injury often occur where moth captures in traps are zero or very low. A pheromone trap baited with a "high load" lure improves the utility of trapping to determine the effectiveness of codling moth disruption. Another option for monitoring disrupted orchards is to use traps baited with a DA lure (Trécé Inc.). The DA lure releases a volatile that is attractive to both female and male codling moth and is not impeded or suppressed by pheromone-based mating disruption.

For all orchard pests, however, monitoring with pheromone traps should not be relied on as a stand-alone method for assessing the effectiveness of mating disruption. Trapping should be used in conjunction with visual inspection of fruit for damage. Concentrating visual examinations of fruit to the upper canopy, orchard borders and susceptible varieties increases the chance of early detection of fruit damage.

Various hand-applied dispensers are currently the most widely used products for pheromone-based control of fruit pests. At least four products are commercially available in the USA for control of codling moth or oriental fruit moth: Isomate C Plus and CTT (Pacific Biocontrol, Corp., Ridgefield, WA), CheckMate (Consep, Inc., Bend, OR), NoMate (Scentry, Inc., Billings, MT) and Disrupt (Hercon, Inc., Emigsville, PA). Modifications to these formulations over the past few years have focused on improved longevity and ease of application. A new oriental fruit moth dispenser, Isomate MRosso, provided season-long disruption in trials conducted in Michigan in 2002.

Hand-applied mating disruption formulations employ either a single or multiple application strategy. These strategies are designed to ensure the adequate release of pheromone throughout the mating period of a target pest. All registered formulations are sensitive to temperature, releasing more pheromone when it is hot and less pheromone during cool periods. This variation in release rates due to temperature difference makes it difficult to determine the effective field life of a dispenser. Control problems have occurred when dispensers have run out of pheromone earlier than expected, leaving gaps when there is no pheromone dispensed. Dr. Jay Brunner (WSU, Wenatchee, Washington) and other researchers have been evaluating pheromone emission rates for various codling moth disruption products. Among the products registered for use in the US, the two rope dispensers, Isomate C Plus and CTT, had the highest and most consistent release of pheromone. Consistent releases of pheromone were also provided by the Checkmate CM and Disrupt CM dispensers, but at very low rates per day. The NoMate CM dispenser released pheromone at a very high rate initially, but ran out of pheromone after about 90 days. I encourage you to discuss the expected field life of products to ensure proper use and performance in the field with the dispenser manufacturers or an extension specialist.

Pheromone can be formulated into tiny capsules or beads and then applied through standard spray equipment on an as needed basis. We have been testing microencapsulated formulations manufactured by 3M Corporation or Suterra LLC. Sprayable pheromone offers the opportunity to be readily incorporated into current programs that include a number of sprays for diseases, insects and mites. A sprayable product could be used on an as-needed basis rather than as an expensive preventative control. The current use pattern for sprayable pheromones is one to two applications per flight at a high rate, generally greater than 10 gm AI/acre. Good control of oriental fruit moth has been achieved using this strategy. However, on-farm trials conducted in Michigan and in other states suggest that high rates are not the most effective or economical way to use sprayable pheromones. Significant rain events (> 0.5 inches) wash off a portion of the microcapsules that contain the pheromone, thus reducing the effectiveness of the treatment. Very low rates (e.g., 2.5 gm AI/acre) appear to be as effective as high rates for up to two weeks post-treatment. Frequent application (every 10 to 14 days) of very low rates of pheromone -- only a few grams per acre -- appears to be the most economical and effective strategy for using sprayable pheromone to manage oriental fruit moth. To date, both high rate and frequent low rate sprayable pheromone strategies have proven to be substantially less effective than hand-applied dispensers for codling moth control.

View dispensers

Pest monitoring in apple from bloom to petal fall

This article is part of an ongoing series in the Fruit CAT Alert newsletter. It has been adapted from the script of an orchard scouting video being produced at MSU. Video team members include: John Bakker, Doug Murray, Jim Laubach, Jim Koan, John Wise, Dave Epstein, Larry Gut, Peter McGhee, Mark Whalon, Bill Shane, Amy Irish-Brown and Jeff Andresen

Rapid tree growth and increased pest activity often mark the bloom period in apple, with a greater diversity of pests being visible. Many of the pests first seen at the tight cluster to pink stage are now becoming more prevalent. The focus of orchard management at this time is disease control and ensuring good pollination. Protection of pollinators will limit insecticide use to those compounds that will not harm bees. Just the same, the pest information gathered at this time will be critical for good insect management decisions at the petal fall stage. Fireblight control measures are critical in the bloom period if conditions become favorable for infection.

Monitoring for fireblight entails using models that integrate moisture, temperature and tree phenology to predict when potential infections may occur. In the field it is important to look for overwintering cankers on twigs, bacterial oozing from these cankers and new blossom infections. Any visible symptoms should be reported immediately.

Apple scab and powdery mildew are increasingly active during this period as foliage expands and temperatures rise. Apple scab lesions will become larger and may be found on both upper and lower leaf surfaces. Powdery mildew can cover entire leaves or terminals.

The insect and mite pests that should be visually scouted for are rosy apple aphids, green apple aphids, leafrollers, and European red mite nymphs. Rosy apple aphid colonies are expanding and feeding damage is visible as curled leaf clusters and petioles exhibit a reddish discoloration. Rosy aphids will now take on a deeper red body color with a dusty covering. Green apple aphids will continue to colonize clusters, but without the distinctive damage seen with rosies. Obliquebanded leafroller larvae are now larger and more active, moving throughout the expanding flower cluster and consuming more leaf surface. European red mite eggs have mostly hatched by this time and nymphs will be readily visible on leaves. Spotted tentiform leafminer eggs have now hatched and are becoming visible as sap feeding mines on the underside of older spur leaves.

Leafminer flight is now in decline, and trap information is less important as a management tool.

Continue to monitor traps for oriental fruit moth, and note the first sustained catch for biofix purposes. If pheromone baited traps for codling moth have not been placed, then they need to go up now. Plum curculio adults are also beginning to emerge from their overwintering sites. Traps for this pest can be placed in the orchard at this time to provide preliminary information on movement of adults into trees and to estimate population levels.

The tarnished plant bug spends the winter as an adult, and on warm spring days can be seen feeding on flower clusters. High populations of tarnished plant bug may cause limited injury to flowers. Most economic injury to the fruit will occur over a two-week period beginning at petal fall.

Inspect flower clusters to assess pest populations. Select a total of 100 flower clusters from inside and outside of 10 to 20 trees throughout the block. Inspect each cluster and record the damage and the total number of each kind of pest present.

Uses of Dacthal herbicide canceled

Eric Hanson
Horticulture

Uses of Dacthal 75W and other products containing the herbicide DCPA have been canceled in Michigan. Dacthal has been used for many years for preemergent weed control in strawberries. The Michigan Department of Agriculture (MDA) canceled all uses of the herbicide following detection of metabolites of DCPA in well water in Coloma, Homer, Three Rivers, Wixon, East Lansing, Portage, Jackson, Summit Township, Ionia and Waterford Township. Levels at several sites exceeded the US EPA health advisor level (70 ppb). Growers who have purchased Dacthal should attempt to return the product to the manufacturer, or dispose of the product through the MDA's "Clean Sweep" program.

Dacthal has been particularly useful to strawberry growers because so few herbicides are registered on this crop. Dacthal provides a high degree of crop safety and could be used during the planting year. Note that the label for Sinbar herbicide was modified this year to include planting year use. Apply 2 to 3 oz Sinbar 80W per acre after planting. If new leaves have emerged, be sure to wash Sinbar off the foliage with 0.5 to 1.0 inches of irrigation.

Protecting blueberries from frost

Eric Hanson
Small Fruit Specialist, and
Mark Longstroth
District Horticultural Agent

After watching blueberry growers protect against widespread frosts in 2002, the blueberry team focused some of their winter programming on using sprinklers to reduce spring frost damage in blueberries. We discussed irrigation for frost control in detail during the Great Lakes EXPO last winter and in a workshop last month. Here are some important points to consider.

The system's irrigation rate and uniformity determine the freeze protection that sprinkler systems can provide. More water is needed to protect at lower temperatures and higher wind speeds (see accompanying table). Most systems in Michigan are designed to deliver 0.12 to 0.15 inches of water per hour. These systems can protect to 22^oF under very still conditions, but only to 26^oF if there is a slight breeze (2-4 mph). If you do not know your delivery rate, catch water in 6 to 8 cans placed on the ground throughout the planting.

Most systems cannot easily be changed to deliver more water and protect to lower temperatures. Increasing the operating pressure is not advisable because the volume is not increased substantially (increase from 60 psi to 80 psi may provide only 15 percent more water). Higher pressure can also break lines. Higher pressures also generate considerable mist and change the uniformity of application. Larger nozzles can be installed in some systems but only if the capacity of the mainlines, well and pump can handle the added volume. For example, 9/64-inch nozzles that deliver 0.12 inches water per hour require 60 gallons per minute per acre of blueberries. Switching to 5/32 inch nozzles would deliver 0.15 inches per hour but require 68 gallons per minute per acre. Even if systems can provide adequate volume to protect from temperatures in the low 20's, breakage from ice accumulation can be considerable.

When to attempt to frost protect

Blueberry flower buds and flowers become more sensitive to cold as they develop. Swollen but closed buds tolerate 15 ^o -20 ^oF. At tight cluster or early pink bud (individual flowers are visible but still tight in bud), injury will occur between 18 ^o and 23^o F. Once flowers have separated from one another but the corollas (petals) are still closed, 22^o-25^oF may be lethal. By the time the corolla is half their full length, they are damaged at 25^o to 26^oF. Fully open flowers are killed at 27^oF. The most sensitive stage is just after the petal fall, when 28^oF may cause damage.

Dr. Mike Mainland from North Carolina State University provided a useful rule of thumb during our workshop last month. He suggested not even attempting frost control until at least a few flowers are open. He reasons that most flowers are tight enough to tolerate 22 ^o-24^oF until the first flowers open, so protecting before the first bloom is not useful. This rule of thumb is especially useful when there is a wide difference the emergence of buds on a shoot. If most of the flower buds on a shoot are terminal (at the end of the shoot) and are opening at the same time, then you might want to frost protect in late pink bud. But there is no reason to try and protect flower buds at temperatures below 23 ^o or 24^oF.

Another consideration is wind. Don't attempt to frost protect if the combination of wind and temperature will exceed to capacity of your system to protect (see accompanying table). Dr. Mainland suggested studying the weather forecast closely, and hanging colored flagging in the field to indicate wind strength.

When irrigation begins, air temperatures are initially reduced due to evaporative cooling. The amount of cooling depends on the relative humidity. If the air is very dry (dew point 15 ^o -20^oF), start the irrigation when the air temperature drops to 36^oF. If the relative humidity is high (dew point above 24^oF), start irrigating when air temperature falls to 34^oF.

Stop irrigating when the ice is melting and temperature is rising. Ice breaking free from branches indicates water is forming under the ice and it is likely safe to quit. Normally this is when temperatures are above freezing and rising. Beware of sudden dips in the temperature soon after sunrise.

Some frost avoidance can be gained by keeping the soil surface clean of vegetation, moist and packed. Moist soils have a large capacity to capture and store heat energy during sunny days, and release heat to maintain air temperature during cold nights. Weeds, sod, and plant residues insulate the soil from the sun and reduce heat capture. In addition, tall grass and weeds raise the effective ground level. This is important since cold air is heavier than warm air, and settles along the ground and in the lowest areas of fields. If fields are covered with foot tall grass or weeds, flower buds a foot higher in the canopy may be injured during a frosty night. Mowing fields with tall weeds is worthwhile.

Another consideration is that moist soils have a higher heat capacity than dry soils, and packed soils absorb more heat than recently cultivated soils. It is not worthwhile to cultivate just before a frost. Some growers attempt to irrigate during the day prior to predicted frosts in order to increase the capacity of the soil to absorb heat. This may be of some value if water is applied early in the day, and there is ample sun to warm the wet soil. Irrigating late in the day or on cloudy days will not increase soil temperatures and provide more heat at night. The bottom line is that clean, moist, and packed soil surfaces absorb the most radiant energy during the day, and protect from frost by releasing this heat during the night.

Focus on early sprays for Phomopsis control in grapes

Annemiek Schilder
Plant Pathology

Phomopsis cane and leaf spot, caused by the fungus Phomopsis viticola is a disease of continued concern in Michigan grapes. The first symptoms of Phomopsis are usually small brown spots with yellow halos on expanding leaves. The leaves may have a wrinkled appearance around the spots. Later, dark brown to black lesions on shoots, petioles and rachises appear. Infected tissues become brittle and break easily. Infected rachises turn brown and shrivel up, resulting in premature berry drop. Berry infection is usually first noticed several weeks before harvest. The fungus can infect the berry directly or through the berry stem. Infected berries turn brown and rubbery (not hard like black rot).

The fungus overwinters in diseased canes and pruning stubs. The spores ooze out from fruiting bodies on the canes during wet weather and are dispersed by raindrops. While cane and leaf lesions are common, rachis infections contribute most to yield loss, because they lead to premature berry drop. The rachis is susceptible from the moment it becomes visible (when the first leaf has expanded) until harvest. In years with rainy springs, Phomopsis spores are exhausted by bunch closing. Last year, however, we did see some spore release after the drought period in July (though spore numbers were lower than during peak spore release in April/May), which could have contributed to additional infections on the rachis and berries.

Since the fungus overwinters in diseased canes, rigorous pruning can help reduce overwintering inoculum. Fungicide protection of the rachis and developing berries is crucial for control of this disease. Since there may a fair amount of overwintered inoculum this year (owing to reduced fungicide programs last year), it will be important to stay on top of the disease this year, especially in Niagara grapes. Early fungicide protection is crucial for control of rachis infections, which accumulate during rainy periods in April and May. A sensible approach would be to apply mancozeb from 1-3" shoot growth until bloom (at least two sprays in Concords and three to four sprays in Niagara), and then switch to strobilurins or ziram from bloom to bunch closing. Strobilurins have consistently shown improved disease control after bloom than protectant fungicides, presumably because of better coverage of the clusters as the canopy fills in.

Using bees for pollination of small fruit crops

Rufus Isaacs
Entomology

According to calculations developed by Robinson and co-workers in 1989, the annual value of honey bee pollination to agriculture in the United States is as high as $US 14.6 billion. In Michigan alone the total value to the main fruit and vegetable crops dependent on honey bee pollination is about $270 million per year. Bee pollination provides the essential cross-fertilization of plants that promotes larger, earlier berries and increased percentage of fruit set.

Generally, flowers of small fruit crops are less attractive to honeybees than some other flowers due to the shape and the relatively low 'reward', so a different strategy is required that you might use for apples which need bees early. You want to have your crop starting to bloom before bringing bees in so that bees tend to forage more on your crop. If brought in too early, bees will learn to forage eleswhere and when your crops bloom, they are not attractive enough to get the bees "back" to where you want them. Blueberry flowers have about 3 days to be pollinated after the flowers open, but you want the bees to stay in the field, so move bees into blueberry fields after 5% bloom but before 25% percent of full bloom. The "late" strategy is especially important for cranberries, which is not very attractive to bees. Luckily, craneberry flowers will stay open for a while if not pollinated, and the petals will turn to a rosy color if not pollinated in time. In cranberries, it is better to wait until 10% bloom in order to maximize the yield. If you see too many flowers turning rosy, this means you did not have enough pollinators, so make sure you increase the number of bee hives next year.

Expect to pay anywhere from $40-60 per colony for spring fruit pollination. There is a range here because if you only need 10 hives, you might be expected to pay a higher price than the other grower who is renting 500 hives. Colonies might be also of different strengths. Try to deal with the same beekeeper year after year in your area so you know what to expect and can build a good working relationship. If the beekeeper is new in the pollination business, make sure he/she knows your requirements and make sure you sign an agreement for pollination purposes.

The invasion of Varroa mite has decimated the numbers of feral (unmanaged, wild) honeybee colonies that used to contribute to pollination in addition to rented colonies. The proportion of pollination caused by feral bees relative to managed colonies is unclear, but it is safe to say that we need higher densities today than when feral bees were present. Recommended densities of managed bees are 3 hives per acre for cranberries, and 1 hive per acre for strawberries and raspberries.

Research in blueberries has shown variation in their needs for bee pollination. This is mainly because cultivars with short open flowers and good nectar production are easier to pollinate. Because of this, varieties like Rubel require 1 strong hive on 2 acres, whereas Jersey may benefit from increasing hive densities to 5 per acre. The average is around 2 hives per acre. In general, a good rule of thumb is that you'll need 4 to 8 bees per plant in the warmest part of the day during bloom to achieve good pollination.

Do not cut corners with respect of putting enough bees in your crops. Investing some money to have enough colonies there at the right time will provide returns in the form of improved yields.

If possible, place the colonies in a sheltered location with the entrances facing east. This will encourage earlier activity as the hive warms in the morning sun. Hives should be spread out around the field to maximize floral visitation, with a maximum of 300 yards between colonies.

Many other helpful insects are active in your fruit crop, and with 20,000 species of bees, some local native bees are probably active in Michigan's small fruit crops providing free pollination. Bumblebees and other native species can be seen looking for flowers already in and around fruit crops, and their activity generally remains high when weather conditions turn too cold or wet for honeybees. These native bees may be insufficient to provide adequate pollination for good yields, however, and cannot be relied on to stand alone as your sole pollination source. By providing the right nesting habitats, and food for the bees after your crop has flowered, you can enhance the local populations of native bees around your crop. This is a long-term process and you'll need several years of experimenting before these bees can become a reliable part of your pollination planning. For more information on native bees, visit the ATTRA (Appropriate Technology Transfer for Rural Areas) website:
http://attra.ncat.org/attra-pub/nativebee.html

Pest management during pollination

Do not apply broad-spectrum insecticides when flower buds are open or you may kill a significant number of pollinators. Beehives should be removed immediately after pollination if post-bloom pesticide applications are planned. By monitoring for pest problems carefully during bloom, growers can help minimize the need for pest control. If an insecticide application is necessary during bloom, the compounds that are least toxic to bees should be used, with careful observation of the pollinator-restrictions on the label. Two insecticides that can both be applied during bloom for control of moth larvae in blueberry and cranberry are the Bacillus thuringensis (Bt) products, and the insect growth regulator tebufenozide (Confirm^®). Good coverage is required for both, and a spreader/sticker should be used to improve effectiveness.

Although it is a little outdated (printed in 1976), the book Insect Pollination of Cultivated Crop Plants covers nearly all crops (fruits and vegetables) and is the best reference available for pollination to-date. It has been out of the print for many years, but the book is available free online at http://gears.tucson.ars.ag.gov/book/

Indar Section 18 granted for blueberries in 2003

Annemiek Schilder
Plant Pathology

An emergency exemption (Section 18) has again been issued for the use of Indar 75WSP (fenbuconazole) for mummy berry control in blueberries in Michigan. The exemption runs from April 25 to September 1, 2003. You have to be in possession of the supplemental label at the time of application.

While the material is locally systemic, it only has a limited amount of back action. Therefore, it is best used on a preventative basis. The recommended application rate is 2 oz per acre using ground or air equipment. Sprays should begin at early green tip and subsequent applications should be made at 7 to 10 day intervals. Spraying immediately after a frost appears to improve disease control, since temperatures of 28° to 30ºF may predispose the shoots to infection. Do not make more than five applications per season or use within 30 days of harvest. Do not use any spray adjuvants with Indar 75WSP. Applications are not permitted within 75 feet of streams, rivers, ponds, lakes or reservoirs. Carefully read the label before use.

Michigan fruit Section 18 pesticide labels posted on the Internet

Mark Longstroth
District Horticultural Agent

Within the last week Indar and Mycoshield have received Section 18 labels in Michigan. Every year several Michigan fruit crops receive special pesticide labels. In order to be used on a crop, the EPA must register a pesticide for use on that crop. Pesticides are also registered with the Michigan Department of Agriculture before they can be used in Michigan. National labels (Section 3) labels are included in the manufacturer's product packaging. Pesticide applicators need to read and follow the pesticide labels when using pesticides. Pesticide labels sometimes have additional Special Use labels for specific states. Section 18 (Emergency Exemptions, one year) and Section 24c (Special Local Needs, 5 year) labels are examples. Growers are required to read and have these special labels in their possession at the time of use. The MSU Fruit Team posts these special labels on their website at http://web1.msue.msu.edu/fruit/

There is a link to the Special label page at the top of the index on the web page.

New job responsibilities for Amy Irish-Brown

Amy Irish-Brown
MSUE District Fruit & Vegetable ICM Agent

To help balance the budget for MSU Extension in the West Michigan area, I have chosen to broaden my crop responsibilities as a district Integrated Crop Management (ICM) agent. I will now be working half-time with the commercial tree fruit industry and half-time with the commercial vegetable industry in the following West Michigan counties: Allegan, Barry, Ionia, Kent, Montcalm, Muskegon, Newaygo and Ottawa. I will continue to focus my extension programming efforts in the area of ICM.

I am excited about this new challenge and see it as an opportunity to broaden my knowledge base about Michigan horticultural food crops. My goal for this "new" position is to help fruit and vegetable growers find new and innovative tools that they can incorporate into an integrated cropping system to ensure that the bottom line will result in a profitable, yet environmentally sound agribusiness for them and their families.

Regional udates

1 - Southwest

Mark Longstroth
Bill Shane
Al Gaus

The last two weeks have been dry. Temperatures have been warm with highs often in the 60s and 70s. Frosts on April 23 and 24 with lows ranging from 28° to 23° F caused scattered damage. Lower sites and advanced crops were hurt most. Southern Berrien and central Van Buren counties seem the worst affected. Soil temperatures are in the 50s. Soils are dry as plant growth has used the available water. This week is forecast to be warm and mild.

There has been scattered loss to frost. Some sites and advanced varieties are hit worse than others are. With no rain, conditions have been too dry for brown rot or other fruit diseases. Rain this week may cause a brown rot infection in peaches and plums. Stone fruit growers need to scout for plum curculio as fruit emerges from the shuck and is exposed. Generally two warm humid days with highs in the 70s are needed before egg laying begins.

Peaches are blooming. Leaves are emerging well and trees appear healthy. Peach leaf curl symptoms have not been seen yet. Oriental fruit moth began to emerge last week. Oriental fruit moth trap catches were down with the cold frost but they are up again. We are biofixing Oriental fruit moth on Thursday April 24 at about 250 GDD base 45.

Cherries are blooming. Leaves are unfolding and growers need to protect against cherry leaf spot. Crop potential is still good.

In plums, brown rot and black knot management programs should be underway. Black knot fungicide sprays are most important from white bud through shuck split and especially during bloom. Black knot infections are favored by rain and temperatures above 55°F. Captan may cause injury on Stanley and Japanese-type plums if used repeatedly in early season sprays. Bravo is not labeled for use on plums after shuck split.

Apples are beginning to bloom. Spur leaves are crinkling from frost and damage is severe in some sites. Reports of damage include Delicious, Jonathan, Empire and McIntosh. Flower set appears heavy for most varieties. European red mites are scarce. Spotted tentiform leafminer adults are out in large numbers. Redbanded leafroller trap catches are down. Some leafroller larvae are attacking fruit buds. Aphids have also been found in apples. Apple scab symptoms from the April 3 infection period have not been found. A scab infection period occurred on April 20 (pink tight cluster). With the beginning of bloom, growers need to prepare for fireblight. We are not at significant risk early in the bloom period. We need warm temperatures with highs in the 70s for bacterial populations to build up on the open flowers. We need high bacteria population as well as warm temperatures and rain during bloom before there is risk of fireblight infection. Mycoshield has been granted a Section 18 label for use on fireblight in Michigan apples where streptomycin resistance is a problem. See the article in this newsletter for details. Mycoshield has no back action and needs to be applied before an infection occurs.

Pear growers need to protect against pear scab and fireblight. Pear psylla adults are lying eggs.

Blueberry growers have been spraying for mummyberry. Indar has been granted a Section 18 label for use in blueberries to control mummyberry. See the mummyberry article in the last Fruit CAT Alert. The tip die back we seeing in blueberries seems to be both winter damage and phomopsis strikes from late last year. Whether the winter damage occurred as a result of early cold in December, a deep frost in the ground or poor vigor in some plantings late in the fall is open to debate. There does seem to be less damage in blocks that are vigorously pruned annually. Growers should be scouting for leafroller larvae eating fruit buds.

Grape growers should begin control of black rot and phomopsis as the leaves unfold. Apply protectant materials before rains to keep flower bud clusters protected. There have been few reports of cutworms and flea beetles in grapes and we are moving past the stage where the young buds are vulnerable.

Strawberry flower buds are emerging from the crown. Once flower buds emerge, growers should be alert for tarnished plant bug and strawberry clipper.

Many raspberry varieties are showing lots of cane dieback due to winter cold. In the variety trial at SWMREC there is little damage to Boyne, Latham, Nova, Prelude and Killarney. Canby and other varieties show significant dieback.

The next Monday Fruit Management meeting will be at Borge's Fruit Acres Farm, at the corner of Friday and Carmody roads, approximately 2 miles south of the Coloma exit I-94, on May 5 at 5:00 PM.

There will be several Grape IPM Meetings in the Southwest this year. The first will be April 30. These meetings will be held in both Berrien and Van Buren counties on the same day. On April 30^th, the first meeting will be in Lawton at 10:00 AM and the second at SWMEC at 1:30 PM. The focus of this first meeting will be early season insect and disease control in grapes. For more information check the Fruit hotlines at Van Buren County (269)657-6380 and Berrien County (269)944-4126 ext. 1.

2 - Southeast

Bob Tritten

With temperatures ranging in the 60's to mid 70's many days over the last two weeks, our plant growth and development has been pushed ahead considerably. We had some frost on the mornings of April 23 and 24, but temperatures were mostly in the low 30's and should not have caused any damage to fruit buds. With a prediction of much needed rainfall later in the week we may even be back to our normal time frame in terms of plant growth and development. Our season had been running behind the last three seasons and a bit behind normal. Our soil temperatures remain cool, mostly in the high 50's to low 60's and very dry. The soils have been dry enough that many farms have been planting both tree fruits and small fruits over the last two weeks. We've had a good number of tree fruits and small fruits planted at many farms this year in contrast to light plantings the last couple of years.

Apples are mostly at early pink in the southern part of the region to tight cluster in the northern part of the region. Ida Red's are a bit ahead and mostly at pink. It appears that we have a strong crop of flower buds this year on all apple varieties, with a possible exception of Golden Delicious, which appear to be a bit lighter. For the most part insect activity has been slow to develop this year due to continued cold nighttime temperatures. Spotted tentiform leafminer trap catches have continued to climb, now averaging around 200 per trap. Redbanded leafroller trap catches are continuing to build with averages in the range of 5 to 6 per trap. Oriental fruit moths have been caught in just a few traps across the region, however most of our traps are empty at this time. There are very few leafroller larvae in apples. Tarnished plant bugs have been seen feeding on apples. With little to no dandelion bloom at this writing, it appears that tarnished plant bug could be a problem in early flowering apples. No aphids to report now. European red mite numbers are fairly low this year, and the mite eggs that are there have been heavily parasitized last fall and this spring, with 90 percent of the mite eggs being fed upon by predators. Apple scab infection