Time to spring into 2007

As we put the finishing touches on this issue, it appears spring is moving ahead quickly. Today’s issue is packed with advice for your consideration regardless of whether spring flies ahead or chills down to a stand still again. For more information as you plan your 2007 pest and crop management, we also invite you to use the Internet and search the last five seasons of the Fruit CAT Alerts for specific topics at: http://www.ipm.msu.edu/fruitsearch.htm  

With this issue we say good-bye to assistant editor Rebecca Lamb. She has been a reliable and capable hand in production of this newsletter, and we will miss her contributions here at IPM Communications. Rebecca has been part of our team for six years and is leaving for new challenges as a graphic artist for a Michigan organization. Our best wishes go to Rebecca on her new career.
Next issue – April 10

If you have suggestions for our newsletters, please feel free to contact me at (517) 353-4951 or catalert@msu.edu. Internet readers can also sign up to receive a brief email when we post new issues on the Internet. See this site for details: http://www.ipm.msu.edu/email-fruit.htm   – Joy Landis, editor.

back to top

Value of pollination
According to a study conducted by Cornell scientists Calderone and Morse in 2000, the annual value of honey bee pollination to agriculture in the United States is as high as $14.6 billion. In Michigan , the total value to the main fruit and vegetable crops dependent on honeybee pollination was about $423 million in 2005 (Table 1). Bee pollination of fruit crops provides the essential cross-fertilization, which promotes larger, earlier fruits and increased percentage of fruit set.

Use the “early” strategy for tree fruit crops
For both cherries and apples, it is important for bees to pollinate the earlier blossoms. “King blossoms” in apples, and the first cherry flowers to bloom in a cluster, produce larger and better quality fruits. Because of this, it is important to move the bees one to two days before the first flowers are to bloom. Dandelion flowers are common in apple orchards and can compete with apple flowers for the bees, so it is important to remove them either by mowing or spraying.

Use the “late” strategy for small fruit crops
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 that 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 may learn to forage elsewhere, and when your crops bloom, they are not attractive enough to get the bees "back" to where you want them. Blueberry flowers have about three 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, cranberry 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.

Prices for pollination
Most growers will already have their pollination contracts set, but expect to pay anywhere from $40 to $80 per colony for spring fruit pollination. There is a range here because if you only need ten 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 they know your requirements and make sure you sign an agreement for pollination purposes. With this year’s Colony Collapse Disorder causing large number of honey bee die-offs (See article by Zachary in this issue), call beekeepers earlier than usual to make sure you have bees. You can locate a beekeeper on http://cyberbee.msu.edu (click on beebase, then find a beekeeper) by searching within a county, an area code or the zip code.

Hive densities
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 two hives per acre for apples and cherries, four hives per acre for high density dwarf orchards, three hives per acre for cranberries, and one 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 one strong hive on two acres, whereas Jersey may benefit from increasing hive densities up to five per acre. The average is around two hives per acre. In general, a good rule of thumb is that you'll need four to eight bees per blueberry bush 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.

Hive placement
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.

Native pollinators
Many other helpful insects are active in your fruit crop, and with 20,000 recorded species of bees worldwide, some local native bees are probably active in Michigan ’s fruit crops providing free pollination. Bumblebees and other native species 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. Ongoing research at MSU is investigating strategies for conservation of native pollinators in Michigan blueberries, and we expect this work to be relevant to many other Michigan fruit crops.

Pest management during pollination
Do not apply broad-spectrum insecticides when flowers are open or you may kill a significant number of pollinators. Bee hives 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.

Pollination information available online
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/. Other websites provide specific information on honeybees, native bees and pollination.

The recent honey bee crisis and its implications for Michigan fruit growers
Zachary Huang
Entomology

If you have been listening to radio or reading papers the last few weeks, chances are that you have already heard about the alarming honey bee die-offs around the country. The phenomenon is officially named “Colony Collapse Disorder” (CCD). This disorder has the media all excited because it is large in scale (25 states are affected), came in quick (colonies that were fine in August/September became collapsed around October/November), and hit people hard (many beekeepers with hundreds to thousands of colonies are losing 50-90% of their colonies). The worse of all of these? We do not know what causes it!

The symptom seems to be for bees simply to disappear, that is why initially peopled called it the disappearing disease (or fall dwindle disease). A colony with 40,000 bees in the fall, apparently healthy with lots of honey and pollen, suddenly has nothing or a handful of bees with a queen left. Very few dead bees are found inside the hive or near the entrance. Strangely, wax moths, small hive beetles are slow in moving in such newly abandoned colonies. Several possible causes come to mind. When tracheal mites (Acarapis woodi) first showed up in North American (circa 1983), we had bees disappearing also. The disappearing mostly happened during the over-wintering process – colony with small clusters or no bees in the spring because bees with their trachea plugged with mites could not make back to the colony after defecation flights or they simply fly out to die late fall.

A new species of nosema (Nosema ceranae, so named because it was discovered first in the Asian honey bees, Apis cerana) also showed up in the European bees (Apis mellifera, the only species we have in North America and Europe) in Europe during summer of 2006 and killed up to 60% of bees in some apiaries. Recently it is confirmed to be present here also in our bees in the United States. It could also be related to all the chemicals we have been throwing into bee colonies, which conceivably can weaken the immune system of honey bees and/or affect their learning and orientation. A few years ago, French beekeepers suspected that their “Mad Bee Disease,” where bees got confused and could not return home successfully, was related to the use of an insecticide called Gaucho. Unfortunately, most of these factors (tracheal mites and nosema disease) have been all ruled out as the cause of CCD. Scientists from Montana State University, Penn State University, North Carolina State University and USDA Beltsville Bee Lab have been collecting and analyzing a large number of bee samples. Hopefully we will have the answer soon.

Michigan will be impacted by this new disorder in several ways. First, Michigan is listed as one of the 25 states with CCD, which means some Michigan beekeepers are directed impacted by losing bees to CCD. A more widespread impact would be for beekeepers who do not experience this disorder but lose colonies anyway due to severe winter conditions. It is already common for beekeepers to lose 50-70% of their colonies during the wintering process because a combination of stresses: varroa mite, tracheal mite, nosema disease and residual pesticides inside colonies. Prior to the arrival of both mites, the normal winter loss is about 10-20% in the Michigan. This number has increased considerably the last few years. These beekeepers rely on buying package bees to replenish their lost colonies. There might be a significant increase of package bee price simply because of the bee shortage caused by the large CCD related die-offs. In 2006, the average price of 3 lb packages was already $65, compared to $45 five years ago. This price might increase again. A third way of impacting Michigan would be higher pollination fees for fruit and vegetable growers. In the past few years, apple, cherry and blueberry growers have been paying $35-50 a colony to pollinate their crops in Michigan. Again due to bee shortages, the fee per colony might be increased in Michigan. The extent of increase is not known.

Plum pox virus quarantine in southwest Michigan
Mira Danilovich and Bill Shane
District Fruit Educators

In July 2006, plum pox virus (PPV) was detected in a plum tree sampled at the Southwest Michigan Research and Extension Center (SWMREC) in Benton Harbor, Michigan. The Michigan Department of Agriculture (MDA) has worked very intensively since that time to test the Prunus trees at risk at this and other Michigan locations. After testing more than 50,000 samples in late summer, no new “positives” were found in Michigan.

PPV is a serious disease of stone fruit that can cause significant yield and quality loss. PPV has been the most significant disease of stone fruit in Europe for many decades and was detected for the first time in Pennsylvania in 1999 and Ontario in 2000 and in New York and Michigan in 2006.

In August of 2006, the USDA issued an Emergency Action Notification (EAN) to all landowners with commercial orchards identified within one mile of the infected tree. The EAN notified landowners that they may not move propagative materials from PPV susceptible plants off their properties.

On March 12, 2007, the MDA issued a PPV Quarantine, signed by MDA director Mitch Irwin, which extends beyond the scope of the EAN. Under the provisions of the PPV Quarantine, all plant material such as nursery stock trees, seedlings, rootstocks, scions, budwood, branches, twigs and leaves, except for the seeds and fruit of Prunus species susceptible to PPV Dideron strain (strain D), are “regulated articles.” Movement and sale of fruit free of any leaves and branches is exempt from the quarantine regulations.

Prunus species susceptible to PPV-D strain include types grown for fruit production and for ornamental uses. Fruit-bearing species susceptible to PPV-D include peaches, nectarines, all species of plums: European (P. domestica), American wild plum (P. americana), Japanese plum (P. salicina), Myrobalan or cherry plum (P. cerasifera), apricot and almond.

Ornamental species susceptible to PPV-D include flowering almond (P. glandulosa), Myrobalan plum/cherry plum (P. cerasifera), purple-leaf plum (P. cerasifera “Atropurpurea), black thorn, sloe (P. spinosa), flowering plum (P. triloba), flowering peach, purple-leaf peach (P. persica), sand cherry (P. pumila), Japanese flowering cherry, Kwanzan cherry (P. serrulata), Nanking cherry, Hansen’s bush cherry (P. tomentosa), and purple-leaf sand cherry (P.x cistena).

The quarantine consists of an inner quarantine zone of approximately two-mile radius (see below for description) and a larger nursery stock regulated area of 7.15 mile (11.5 km) radius around the positive PPV-site. Movement of restricted Prunus material within or to outside the quarantine zone is prohibited. Regulated material may not be planted in the Quarantine area. Regulated species of nursery stock originating from or growing within the quarantine zone or nursery stock regulated area cannot be used as a source of propagative material (either rootstock or scion or seed) unless it is grown under a compliance agreement issued by the Director of the MDA.

The quarantine may be cancelled when sampling of all susceptible fruit bearing and ornamental trees in the quarantine zone is negative for PPV for three consecutive years.

Neither the EAN nor the MDA quarantine will hinder the harvest and sale of fruit in this area since PPV is not transmitted through the fruit or the seed. The plum pox virus poses no human health risk. The MDA plans to resample all regulated varieties in the 7.15 radius zone and additional targeted locations in 2007.

PPV Quarantine area boundary (see map)
The current PPV quarantine area is in Berrien County in southwest Michigan. It includes parts of Benton, Bainbridge, Sodus and Pipestone townships. It is outlined starting at the intersection of Britain Avenue and Benton Center Road in Benton Twp.; south side along the Benton Center Road to Meadowbrook Road; continuing west to Yore Avenue; than south on Yore Avenue to Snyder Road in Sodus Twp.; than east along a line formed by Snyder and Union Roads to Britain Avenue; than west to the starting point.

Peach leaf curl
Mark Longstroth
District Extension Educator for Horticulture & Marketing

Peach leaf curl has become an important disease in Michigan. This disease of peach and nectarine can defoliate trees. Infections take place in the spring as the buds open. The fungus infects peach buds from bud swell to bud opening under wet conditions. Air temperatures between 50 to 70°F are ideal. Rain or dew moves spores into the opening bud allowing the infection of young tissue. Prolonged cool, wet periods during bud burst can result in severe infections. Effective controls include Bravo, Ziram, Ferbam (Carbamate) and copper compounds. Copper compounds have the benefit of providing some suppression of bacterial spot as well.

Early spring applications at or before bud break are effective in controlling this disease. Later applications can reduce the severity of the disease. Once leaves are infected, there is no effective fungicide treatment. The leaves are infected in the bud and once they have emerged they are not susceptible to infection. Infected leaves become thick and crinkled, turning orange or red. When the fungus sporulates, the leaves become powdery with spores. Infected leaves will eventually fall off. The tree will grow new leaves. Peach leaf curl weakens the tree by removing leaves during early growth. This reduces the size of the remaining fruit. Heavy fruit thinning will reduce stress on the tree and increase the likelihood of a marketable crop. Severely infected trees should receive an increased ration of nitrogen fertilizer. This will help maintain vigor and help replace lost leaves.

Begin psylla management early
Mike Haas and Larry Gut
Entomology and Trevor Nichols Research Complex

As the daytime temperatures start to approach 50ºF, it’s time for pear growers to initiate their pear psylla management programs. Applications of dormant oil with or without lime-sulfur is a common first step. Once adults are found, and before egg laying begins, many growers will make an application of oil combined with an insecticide. The insecticide kills the adults while the oil is thought to delay egg laying by females coming into the orchard from overwintering locations. By delaying egg laying, eggs will be deposited over a shorter time frame, and the resulting generation of psylla will be closer together in age. Then it should be easier to target a specific life stage with an insecticide.

Last year we looked at the effectiveness of the insect growth regulator Esteem (pyriproxifen) as part of a pear psylla management program at two farms in southwest Michigan. Bartlett was the variety with Bosc as the pollinator. Our first adult sample, on March 28, showed us that psyllas were already active. Both growers started their regular psylla programs the next day. Pre-treatment psylla numbers varied at the two locations, with one having a light infestation and the other with much higher numbers. Both growers had reported heavy infestations of psylla in the two previous years. Insecticide resistance to AgriMek (avermectin) was suspected by the growers at both locations.

The first application of Esteem (5 oz./A) with oil was made in mid-April. Monitoring for psylla eggs, nymphs and adults continued throughout the summer. After eggs were found, a second application of Esteem and oil was made on May 10 at the farm with the heavier infestation.

Psylla were kept well below damaging levels throughout the season. A variety of insecticides were used on both farms including pyrethroids, organophosphates, antibiotics, neonicotinoids and oil. A fruit evaluation was conducted on August 9 just prior to harvest. An examination of two hundred fruit in each management program found no damage. The program, which included Esteem, gave the same level of control as the grower standard program, showing that this insecticide is an important option for growers wishing to preserve current psylla materials by utilizing different pesticide modes of action.

Both growers agreed that if monitoring had started earlier we probably would have found adult psylla activity and been able to start oil/sulfur sprays earlier. Don’t wait for T-shirt weather to start looking for adults. If the temperatures are hitting 45 degrees for part of the day these insects are probably flying from their overwintering locations and landing in your orchard.

Fungicide label update for blueberries
Annemiek Schilder
Plant Pathology

Indar (fenbuconazole) has finally received a full registration for use in blueberries, which means that we do not have to request a Section 18 anymore. The fungicide will be available in two formulations: Indar 75WSP (water soluble packets) and Indar 2F (flowable). Indar 2F should be available at distributors in May, although quantities may be limited. They have the same active ingredient and are for all practical purposes the same. A fungicide efficacy trial in Michigan in 2006 showed that Indar 2F worked as well as Indar 75WSP. Both products list the following diseases on the label: Alternaria, anthracnose, leaf spot and blotch, mummy berry, Phomopsis, powdery mildew and rusts. In Michigan, however, we have not seen any efficacy of Indar against anthracnose, and we have not tested it against leaf diseases since these are not common in Michigan. The diseases that Indar has repeatedly shown good efficacy against are mummy berry and Phomopsis canker and twig blight.

The application rate for Indar 75WSP is 2 oz per acre; a maximum of four applications (8 oz) may be made per season. The application rate for Indar 2F is 6 fl oz per acre; a maximum of four applications (24 fl oz) may be made per season. Apply Indar in a minimum water volume of 10 gal/acre, if applied aerially, and 20 gal/acre if applied by ground. The pre-harvest interval is 30 days, and the re-entry interval is 12 hours. Do not make ground or aerial applications within 75 feet of streams, rivers, ponds, lakes or reservoirs. Since Indar is the least systemic of the sterol inhibitor fungicides, a non-polymer containing spray adjuvant approved for use with registered pesticide products, e.g., a crop oil, may be added to spray solutions according to the manufacturer’s use instructions to improve disease control by aiding penetration of Indar into the plant tissue. This may be helpful when applying the fungicide after an infection period to enhance curative activity. Reduced efficacy may occur if water containing suspended soil particles, such as water from ponds, streams or unlined ditches is used.

Indar belongs to the sterol demethylation inhibitor (DMI) class of fungicides (Group 3). Since certain fungi can develop resistance to this class of products, the use of Indar 2F should be part of a resistance management strategy that includes alternation and/or mixing with fungicides that have a different mode of action. Examples of fungicides to alternate with earlier in the season are Topsin M + Captan, Bravo and Captevate, whereas Pristine, Abound, Cabrio and Switch are good options when the weather warms up and more diseases need to be controlled (e.g., between pink bud and petal fall).

A Section 18 emergency exemption for Topsin M WSB (thiophanate methyl) has been approved for the 2007 season (April 1 - September 30, 2007). Topsin M breaks down to the same active ingredient as Benlate and is for all practical purposes similar to Benlate. Topsin M is a systemic fungicide that has excellent efficacy against Phomopsis and Fusicoccum canker diseases, good efficacy against Botrytis, and moderate efficacy against mummy berry. While usually tank-mixed with Captan for control of anthracnose, Topsin M only has fair efficacy against anthracnose and Captan does most of the work in this tank mix. The application rate is 1 lb/acre and a maximum of three applications is allowed per season. Application may be made by ground or air, but not through any type of irrigation system. Only use Topsin M in combination or rotation with a registered non-benzimidazole fungicide (e.g., Captan or Ziram). The worker re-entry interval is 12 hours and the pre-harvest interval is 7 days.

A new fungicide that is now labeled and may be of interest to blueberry growers is Prev-Am (sodium tetraborohydrate decahydrate, simply stated: boric acid). This is a fungicide as well as an insecticide/miticide, and can also be used as an adjuvant with other fungicides. In fungicide efficacy trials in Michigan in 2005 and 2006, Prev-Am showed good efficacy against anthracnose fruit rot. The application rate for disease control is 50 fl oz per 100 gallons and sprays should be applied every 7 to 10 days. The pre-harvest interval is 0 days and the re-entry interval is 12 hours. Do not apply this product aerially or through any type of irrigation system. The label lists Botrytis and powdery mildew as target diseases, and aphid, leafhopper, lygus bug, mealy bug and mite as target insects. However, we have not yet tested the product for these uses in Michigan. Be sure to read tank-mixing instructions on the label.

Enviro-weather is geared-up for the 2007 growing season
Mark Trent
Enviro-weather

Ready for its second season, the Enviro-weather website is all set to be your source for agricultural weather and weather-based plant and pest management decision making tools. Just visit http://www.enviroweather.msu.edu and you will have access to information and management products from 49 weather stations across Michigan.

Weather information such as National Weather Service local forecasts and real time radar, overnight temperatures and weather summaries, including temperature, degree days and rainfall can be accessed by clicking on the weather station of interest to you. In addition, you can get summaries and decision making products specific for your favorite crop or area of interest by choosing from links to fruit, forestry and Christmas trees, potato or turfgrass.

Decision making tools for fruit producers
 The fruit page has a host of summaries and pest management products designed to assist in fruit production decisions. In addition to regional and station disease reports and summaries based on wetting events, many specific disease and insect management models can be accessed to help you make timely fungicide, bactericide and insecticide applications and get the most out of your pesticide dollar. Disease management models now available on Enviro-weather include: apple scab, cherry leaf spot, fire blight of apple blossoms, and black rot of grapes. Insect management models include: tart cherry plum curculio, obliquebanded leafroller, codling moth, and Oriental fruit moth. In addition, there is a Concord grape berry weight model to help monitor the development of concord grapes. Don’t forget to look for “About this model” links that will lead you to information about the model. These links are found below each model. Links to the IPM Resources website can be found throughout the Enviro-weather website and will lead you to information about specific and general pest management.

Southwest Michigan 2007 Fruit IPM Meetings
Mark Longstroth
Bill Shane

The Monday Fruit IPM update meetings will be at Annette and Randy Bjorge’s Fruit Acres in Berrien County again this year. The weekly meetings will begin on April 9 and run until July 10. There will be no Monday meeting on Memorial Day (May 28). The meeting will run from 5:00 PM to 6:30 PM. Each meeting will be a review of the current fruit pest situation in Berrien County with displays of insects and fruit collected that day from area fruit plantings.

Bill Shane, Greg Vlaming and Mark Longstroth will share the results of their scouting and discuss current and upcoming pest events and emergences. (Each week will change with changing pest complex.) The meeting dates are: April 9, 16, 23, 30; May 7, 14, 21; June 4, 11, 18, 25; and July 2 and 10. One RUP credit is available for private pesticide applicators and commercial fruit (1C).

Southwest Michigan 2007 Grape IPM Meetings
Mark Longstroth

There will be Grape IPM meetings in Van Buren and Berrien counties again this year. The meetings will be on Thursdays. The meeting dates are April 17 and May 22. The morning meeting will be from 10:00 AM to noon at the Cronenwett Farm Shop at 70123 28th Street east of Lawton. The afternoon meeting will be at the Berrien County MSU Extension Office at the Southwest Michigan Research & Extension Center.

These meeting are co-sponsored by National Grape Cooperative and MSU Extension and are open to all grape growers. The format for the meetings will be a review of insect and disease control in grapes specific to either early season or late season, focusing on the pests of each season during that meeting. The April 17, 2007, meeting will review prebloom insect and disease control. The May 20 meeting will discuss bloom sprays and late season insects and diseases.

Mark Longstroth of MSU Extension and Terry Holloway of National Grape who will share the results of their scouting will host the meetings. Drs. Rufus Isaacs and Annemiek Schilder will be the featured speakers and discuss current and upcoming pest control windows. RUP credits have been applied for private pesticide applicators and commercial fruit (1C).

Regional reports
1 -- Southwest
Mark Longstroth
Bill Shane
Greg Vlaming