Annemiek Schilder and Timothy Miles...Conditions for mummyberry were favorable during the spring of 2009 with generally more disease pressure than in 2008. This was due to frequent rains and cool weather in spring and higher numbers of overwintering mummies from the previous season. In addition, overly wet fields and frequent rains prevented many growers from applying protective fungicides at critical times. Shoot strikes in four scouted fields were first noticed in mid-May and increased rapidly towards the end of May and into early June, followed by a decrease as old shoot strikes dried up and fell off the bushes. Conditions during bloom were moderate for dissemination of spores to the flowers as cool conditions reduced honey bee activity.

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Carlos García-Salazar...Since the discovery of the blueberry shock and scorch viruses around West Michigan, there has been a large volume of articles and information coming out of both MSU and the Michigan Department of Agriculture (MDA). This information has attracted national and international attention and has been disseminated all over the world. Communication between growers, scientists and regulatory agencies has been very effective in informing the Michigan blueberry industry and stakeholders about the danger that implies the spread of these viruses across the production area.

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By Rufus Isaacs, Keith Mason and John Wise...As harvest season comes to an end for some growers in southern counties, it is worth sampling fields that had poor bud development last season to determine whether treatment for bud mites is required in some fields during the immediate post-harvest period.

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By Rufus Isaacs and Keith Mason... Blueberry growers are reminded to continue their blueberry maggot monitoring program for any fields that still have berries to be harvested later this season.

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By Annemiek Schilder... Monitoring and eradication of two exotic blueberry plant diseases caused by blueberry scorch virus and blueberry shock virus, respectively, is underway. So far, the incidence has been localized and there is no need for growers to be overly concerned.

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Please follow this link to the press release sent out on July 27, 2009 regarding blueberry shock and blueberry scorch virus.

By Rufus Isaacs... A proposal has been made to the US Environmental Protection Agency (EPA) to slow down the speed of restrictions in the Guthion phase-out, so blueberry, apple, and cherry growers have more time to develop and adopt effective and economical alternative programs.

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By Rufus Isaacs... Blueberry aphid is the vector for blueberry shoestring virus, which can cause bush decline and significant yield reductions. Because of this, aphids should be managed to minimize the spread of the virus and its transmission to susceptible plantings.

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By Rufus Isaacs and John Wise... With blueberry bloom finishing in much of Michigan and beekeepers removing colonies from fields, grower insecticide options for fruitworm control expand. Blueberries are at risk from infestation by cherry and cranberry fruitworm, two moth pests whose larvae have the potential to infest fruit at harvest and which can cause reduced yield if populations are high.

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By Eric Hanson and Bernie Zandstra... Many blueberry fields in Southwest Michigan received heavy rains in late April that affected weed control. If fields were treated with preemergent sprays prior to the rains, efficacy may be reduced by runoff and leaching. Growers who did not get their preemergent treatments on before the rains could not get back into the fields until after many weeds had emerged, so control was reduced.

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By Annemiek Schilder and Timothy Miles... Due to excessive precipitation this spring and difficulty getting equipment into wet fields, growers were not able to put on critical fungicide sprays for control of mummy berry. As a consequence, mummy berry pressure is higher than average in many locations.

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By Annemiek Schilder... Fungal fruit rots, especially anthracnose caused by Colletotrichum acutatum, continue to be of economic concern in blueberries. Losses can occur before as well as after harvest. The cultivars Jersey, Bluecrop, Rubel, and Blueray are very susceptible to anthracnose fruit rot, whereas Elliott is quite resistant.

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By Carlos Garcia-Salazar...

Continuing with our series of Blueberry IPM meetings, we are conducting a pre-harvest meeting on Thursday, June 11 as part of the MSUE blueberry IPM program. During the meeting, we will discuss the following topics:

• Fruitworm and blueberry maggot control.
• Fruit root infections (mummyberry and anthracnose), and Phomopsis twig and shoot blight control.
  
• Weed management and nutrient monitoring.
  

The meeting will take place from 6:00 to 8:00 PM at the Carini Farms, 15309 Port Sheldon Road, West Olive, Michigan (West of US 31). A light dinner will be served at 6:00 PM. All blueberry growers are encouraged to attend this event. Growers’ participation is critical to provide feedback to improve the quality of our research and extension activities.

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By Rufus Isaacs and John Wise... Cranberry fruitworm is one of the key insect pests of blueberry in Michigan, infesting the crop during and after bloom. Moths usually start flying during bloom, and this year is no exception. The first male moths have been trapped over the past week in Van Buren and Allegan counties, coinciding with peak Jersey flowering.

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By Eric Hanson... There will be a blueberry weed control meeting on Thursday, June 18 from 6:00-7:30PM at Jim Getzoff's Farm, 7093 116th St., Fennville, Michigan.

All are invited to this meeting to view and discuss herbicide demonstration and research plots, with Paul Jenkins, Bernie Zandstra and Eric Hanson from MSU. Treatments include various new and old herbicides and herbicide combinations. A dinner of hotdogs or hamburgers will be provided. Many thanks to Jim Getzoff for cooperating with us on these trials.

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By Eric Hanson and Mark Longstroth...Some Michigan blueberry fields are showing quite a bit of winter injury to buds and twigs. This raises several questions about cold injury and fertilization. Not all of these questions have been researched adequately, but here are some related facts and thoughts.

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By Annemiek Schilder... A new fungicide, Omega 500F (active ingredient: fluazinam) has been labeled for blueberries, currants, gooseberries, and lingonberries. Omega is a reduced-risk fungicide in the chemical group of the 2,6-dinitro-anilines. These fungicides affect respiration in fungal cells by uncoupling oxidative phosphorylation.

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By Timothy Miles and Annemiek Schilder... Now is the time of year to begin scouting for mummy berry. Mummy berry is a serious disease of high bush blueberries in Michigan and is prevalent in most blueberry-growing regions throughout the United States.

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By Annemiek Schilder... Virus diseases of plants are systemic, and once plants are infected, they cannot be cured. Virus symptoms include plant stunting, leaf and flower malformation, reduced yield, progressive decline and even plant death. Viruses spread via a range of mechanisms, including insect and nematode vectors, cuttings, etc.

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Blueberry integrated pest and crop management meetings begin April 2. The first meeting will be held at the Trevor Nichols Research Complex, west of Fennville from 1:00 PM to 3:30 PM. Admission for the meeting is free. RUP Credits for the meeting have been applied for. RUP Credits have been applied for.

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Rufus Isaacs and John Wise...Over the past five years, blueberry bud mite (Acalitus vaccinii) has been identified as the cause of some problems with poor growth and low yield in Michigan blueberry fields. Sampling by grower groups, extension educators and the small fruit entomology program detected this pest across most of the major blueberry production regions in our state. However, only some fields have sufficient populations to cause economic levels of injury, and only some cultivars are susceptible.

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Rufus Isaacs...The blueberry gall midge, Dasineura oxycoccana (Johnson) (Diptera: Cecidomyiidae), is a pest of blueberries across the United States and Canada. This season, we have seen higher levels of damage from this pest than in recent seasons. Midge larvae have been reported to damage fruit buds and they can also injure vegetative growth. The vegetative growth seems to be the most commonly-injured tissues seen this year in Michigan fields, and this is most easily seen in the form of side branching by stems where the growing tip was killed back in late May and June. Distorted and blackened shoot tips are also a distinctive feature of the damage caused by gall midge.

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Eric Hanson and Mark Longstroth...Irrigation is vital for maintaining high yields in commercial blueberries in Michigan. Blueberries grow best in moist soils. Many Michigan blueberry plantings are located in areas with a high water table, so the bushes have ready access to water located close to the surface. But blueberries are shallow-rooted and sensitive to drought stress, and most Michigan plantings are on sandy soils that hold very little water. Drought prior to harvest reduces berry size and yield, but drought stress anytime in the summer or fall also reduces bud set for the following year.

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Eric Hanson and Bernard Zandstra...Spring-applied herbicides do not always provide adequate weed control through the harvest season. Summer flushes of annual grasses (crabgrass, fall panicum) or broadleaves such as pigweed often are problems. Some Michigan blueberry areas received large amounts of rain in early June, and this may reduce the effectiveness of preemergent herbicides by leaching materials below the weed seed germination zone.

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Rufus Isaacs and John Wise...With blueberry bloom complete in much of Michigan and beekeepers removing colonies from fields, grower insecticide options for fruitworm control expand. Blueberries are at risk from infestation by cherry and cranberry fruitworm, two moth pests whose larvae have the potential to infest fruit at harvest and which can cause reduced yield if populations are high.

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Rufus Isaacs and Steve Van Timmeran...The whitemarked tussock moth (Orgyialeucostigma) is distributed throughout eastern North America and can be a pest of blueberry fields in Michigan. This species feeds on hardwood and ornamental trees and is found in native habitats. When this insect moves into blueberry fields, growers may experience damaging levels of leaf loss on young bushes and contamination of fruit at harvest can cause economic hardship in mature fields.

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Annemiek Schilder...After seven years of granting emergency exemptions for the use of the fungicide Topsin M (thiophanate methyl) as a replacement for Benlate (benomyl) in blueberries in Michigan, the Environmental Protection Agency (EPA) has not granted our emergency exemption request for the 2008 season. Of the Topsin M Section 18s originally issued to multiple states for blueberries, the only remaining applicant in 2007 and 2008 was Michigan, indicating that growers in other states had found alternatives among the currently registered products.

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Rufus Isaacs, Carlos Garcia-Salaza, and John Wise...Cranberry fruitworm is one of the key insect pests of blueberry in Michigan, infesting the crop during and after bloom. Moths usually start flying during bloom, and this year is no exception. The first male moths have been trapped in the past few days in southern Van Buren County, coinciding with peak Jersey flowering.

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Eric Hanson...Some athletes have been consumed by scandal for taking hormones or other substances to improve their performance. Plants also produce hormones or plant growth regulators that can potentially be used to improve their performance as well. Gibberellins are one group of plant growth regulators that are also synthesized and sold as commercial products (ProGibb, ProVide). In blueberries, gibberellins can increase fruit set or decrease flower numbers, depending on when they are applied.

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Timothy Miles and Annemiek Schilder...Last week mummy berry shoot strikes, a result of ascospore infection of emerging leaves, were seen for the first time this season in four blueberry fields that are scouted as part of an IPM project (though there were some reports of shoot strike sightings at the end of the previous week). Shoot strikes are a blighting of developing leaves and shoots which often exhibit an “oak leaf” pattern of necrosis (Figure 2). All scouted plots were at late pink bud or early bloom.

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By Paul Jenkins, Rufus Isaacs, Annemiek Schilder... A Blueberry IPM meeting to kick off the season will be on April 23 from 12:00-3:00PM at the Trevor Nichols Research Complex in Fennville, MI. Lunch will be served.

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By Annemiek Schilder... It’s mummy berry season again. The mummy berry fungus enjoyed the snow cover this winter, which provided sufficient moisture for mummies to germinate.

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Eric Hanson...Several post-emergent herbicides are labeled for use in Michigan blueberries. Most can be useful as spot-treatments to control weeds in problem areas of fields. Each herbicide has different characteristics that need to be considered when making choices.

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Rufus Isaacs & John Wise...With blueberry bloom almost complete in Michigan, grower insecticide options for fruitworm control expand. Monitoring traps have detected increasing catches of cranberry fruitworm in the past week across southwest Michigan, and our scouting on Monday found fresh cherry fruitworm eggs in Van Buren and Ottawa counties. This emphasizes the need for protecting fruit from fruitworm infestation in the weeks after bloom. Once bees are removed from the fields, broad spectrum insecticides can be used.

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Annemiek Schilder...In 2002, the Michigan Department of Agriculture (MDA) established a quarantine for blueberry planting material to prevent the introduction into Michigan of blueberry scorch virus (BlSV), blueberry shock virus (BlShV), and Sheep Pen Hill virus (BlSV-NJ). These viruses are known to infect blueberries in Oregon, Washington, New Jersey and British Columbia (Canada). Cranberry plants can also be infected by blueberry scorch virus. Recently, blueberry scorch virus was also found in highbush blueberries in Connecticut and Massachusetts. These viruses spread from one geographic location to another over long distances through infected planting stock. To date, these viruses have not been found in Michigan, and it is therefore very important that we are vigilant and keep them out as they can wreak havoc on our blueberry industry.

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Annemiek Schilder...Blighted flower clusters were seen at low levels in several blueberry fields. In most cases, the blighted clusters looked like they were caused by Phomopsis, which is characterized by a dark brown discoloration of the twig that bears the flower cluster (photos 1, 2). Initially, the brown lesion is ¼-½ inch long, but can expand to several inches in length in a couple of weeks and can kill additional flower clusters on that same twig. Eventually, the lesion will stop growing and the blighted blossoms will fall off. The causal fungus, Phomopsis vaccinii, overwinters in dead twigs and canes, and in the spring infects the flower clusters, aided by long wetness periods and possibly by frost injury.

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Annemiek Schilder and Timothy Miles...This past week most mummy berry apothecia in four blueberry fields that are being scouted in Allegan and Ottawa counties appeared dried up. However, shoot strikes were found in all of the scouted plots and ranged from three to 29 per bush. The number of shoot strikes increased with the number of mummy berry apothecia found at the site. Since it takes about two weeks for symptoms to show from the actual time of infection, shoot strike incidence will likely still increase in the next week or two. In addition, a few flower strikes were also found. Both shoot and flower strikes are sources of infectious spores for fruit infection.

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Annemiek Schilder...Phomopsis twig blight is caused by the fungus Phomopsis vaccinii. This disease occurs in most blueberry-growing regions and is present at low levels in most fields. In some years and locations, twig blight can be severe, with over 100 blighted twigs per bush. The reasons for the outbreaks are not clear, but appear to be correlated with frequent or prolonged rains or irrigation events during bloom. Cultivars Jersey and Berkeley are particularly susceptible to Phomopsis twig blight. Bluecrop appears more susceptible to Phomopsis infection of newly developing canes.

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John Wise and Rufus Isaacs...Pheromone traps should already be out in Michigan blueberry fields for monitoring of adult cherry fruitworm (CFW) and cranberry fruitworm (CBFW). CFW flight is well underway in most areas of southwest Michigan and yesterday, May 14, we received the first report of CFW larvae entering fruit in a Bluejay field. We have also trapped the first CBFW moths in the past few days, one in Grand Junction, and one in Fennville. These were only single moths, but this does indicate the fruitworm management season is upon us.

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Eric Hanson...Compared to most fruit crops, a high percentage of blueberry flowers normally produce fruit. When bees are numerous and weather is warm and calm, 80-95 % of flowers may set fruit. However, cold, rainy weather during bloom restricts honey bee activity and pollination, resulting in lower fruit set and often reduced berry size. Flowers that are not pollinated within 3-5 days after opening are unlikely to set fruit. After normal pollination, berry growth is dependent on the production of gibberellin and perhaps other growth promoters in the ovary tissues and viable seeds. If flowers are not pollinated, they abort. If only a few ovules are fertilized, the fruit may set, but not contain enough seeds to grow to full size.

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Eric Hanson and Mark Longstroth...Blueberry growers can protect against spring freezes by using sprinklers to reduce damage to blueberry flowers. Sprinklers do not protect blueberries in all circumstances. In 2002, many growers used sprinklers to protect their blueberries when they were at swollen bud and the temperatures were forecast to fall to the upper teens. Sprinklers will not protect crops under these extreme conditions. Sprinklers are used near bloom time when the flowers are visible and the lows are forecast to be in the upper to mid 20s.

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Annemiek Schilder...The Michigan Department of Agriculture is doing a survey for blueberry scorch and shock viruses in Michigan . The scorch virus in particular causes a serious disease of blueberries that is responsible for major losses in the blueberry industry in the Pacific Northwest . As far as we know, these viruses are not present in Michigan ; however, the survey is being done to confirm this.

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Annemiek Schilder...Fruit rots in blueberries, such as anthracnose fruit rot (Colletotrichum acutatum) and Alternaria fruit rot (Alternaria spp.), are generally separated into two types: field rot and post-harvest rot. The former can be seen on berries in the field before harvest and is especially common when berries are left on the bushes too long. So timely harvesting is an important control measure. Post-harvest rot can develop on sound-looking berries, as spores from infected berries can infect them in the field before or during harvest or during processing.

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Rufus Isaacs...In June, EPA made an announcement regarding two important insecticides used by blueberry growers in Michigan. If their proposals continue as written, they will completely phase-out Guthion by 2010 in blueberries across the United States and also restrict Imidan use in this crop. The comment period, running until August 8, is a chance for growers to make their opinions of these proposed restrictions known to EPA.

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Rufus Isaacs...Blueberry maggot flies have emerged over the past few weeks with high catches (over 10 flies in a week) at some farms. At the six farms where we have been evaluating a reduced-risk IPM program for four years, we have not yet trapped any flies. This emphasizes the need to monitor fields for this pest, so sprays are directed at the fields where they are most needed.

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Rufus Isaacs...Checking monitoring traps for cherry fruitworm and cranberry fruitworm at three farms in Van Buren county yesterday (June 4) has revealed the expected increase in moth catches over the past week. Eggs of both species were also found during detailed scouting of the bushes, indicating that fruitworm pest development is progressing and blueberries are at risk from larvae penetrating the fruit.

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Annemiek Schilder...Fungal fruit rots, especially anthracnose caused by Colletotrichum acutatum, continue to be of economic concern in blueberries. Losses can occur before as well as after harvest. The cultivars Jersey, Bluecrop, Rubel and Blueray are very susceptible to anthracnose fruit rot, whereas Elliott is quite resistant. Alternaria fruit rot is sometimes found on Bluecrop berries before harvest and affects most varieties after harvest. Botrytis fruit rot is not as common in Michigan, but may be a problem in years when cool, wet weather prevails during the flowering and fruit development period.

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Eric Hanson...Compared to most fruit crops, a high percentage of blueberry flowers normally produce fruit. When bees are numerous and weather is warm and calm, 80 to 95% of flowers may set fruit. However, cold, rainy weather restricts honeybee activity. When extended periods of poor pollination weather occurs during bloom (such as this year), berry numbers or berry size can be substantially reduced. Flowers not pollinated within three to five days after opening are unlikely to set fruit.

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Rufus Isaacs and John Wise...In the past week, monitoring traps in commercial blueberry farms in Van Buren County have caught their first cranberry fruitworm (CBFW), but only single moths have been seen in a few traps. Cherry fruitworm (CFW) moths have been trapped for a few weeks in the same region, but also at very low numbers (one or two moths per traps per week). These first captures indicate the flights of these important early-season insects are just beginning, but this is a little too early and the number of moths is too low to warrant any insecticide sprays in response.

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Carlos García-Salizar, Chuck Pistis and Eric Hanson...Since 1996, blueberry growers with fields located alongside major highways in west Michigan observed that plants located in front of the roads were suffering extensive dieback and flower bud mortality. The damage followed a gradient with the heavier damage in plants within the first 30 meters from the road (in some cases up to 100% flower bud mortality) and slight damage or no damage at all 100 meters away from the road at the back of the field. With the aid of MSU Extension, growers tried to find the reason behind the damage and the only explanation, apart from natural winter damage, was the possible effect of deicing road salt applied to major highways during the winter.

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Eric Hanson...Bloom is a critical time for blueberry producers. When bees are numerous and weather is warm and calm, 80 to 100 percent of flowers may set fruit. Pollinated flowers drop their corollas (petals) while they are still white and fruit begin growing rapidly. Berry set and growth is dependent on the production of gibberellin and perhaps other growth promoters in the ovary tissues and viable seeds. Berries appear to require a minimum number of seeds to attain full size. If pollination is adequate, most all berries contain 20 to 60 seeds, well over this minimum seed number. If pollination is limited, final berry size may be proportional to the number of seeds.

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Eric Hanson...Most blueberries grown commercially in Michigan should be irrigated. Soils are often sandy and hold little water, and blueberries are shallow-rooted and relatively sensitive to moisture stress.

Every 10 to 20 years, droughts occur that are severe enough to kill Michigan blueberries or cause so much injury that plants require multiple years to recover. Severe events occurred in 1988 and 2005. The cumulative water deficit in the figures below illustrates the difference between rainfall and evapotranspiration in Grand Junction and West Olive, Michigan during the 2005 season. By the end of the season, non-irrigated blueberry fields had deficits of 7 to 10 inches.

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Julianna Tuell and Rufus Isaacs...Honeybees are by far the most economically important bees in our blueberry fields, and most growers know what these bees look like. However, there are many of other types of bees native to Michigan who nest in the soil and in cavities in old plants. This article provides some tips on identifying these “other” bees and some guidelines on how to improve the landscape in and around your farm to provide some help to build their abundance.

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