Grand Rapids area small fruit regional report – September 10, 2013

With increased use of insecticides for small fruit pest control, along comes a “spider:” the two-spotted spider mite and the blueberry bud mite?

As a result of the intensive pest control program conducted across Michigan’s small fruit fields, an old pest is making its come back: the two-spotted spider mite. So far, raspberries and strawberries seem to be the most seriously affected. In blueberries, it is very likely that blueberry bud mites may become an issue in fields with a previous history of bud mite infestations.

As of Sept. 10, 2013, the blueberry harvest is wrapping up in most places in southwest Michigan, but it may continue for another two more weeks in counties north of Allegan County. Fruit harvested still maintains good quality and prices are going up in relation to previous weeks. This provides an incentive for growers that were discouraged by the low prices and the high expenses of pest control to battle spotted wing Drosophila (SWD) infestations. With the end of harvest in sight, blueberry growers need to turn their attention to post-harvest issues such as preventing blueberry bud mite infestations and leaf rust infections that can cause serious problems for the next season. It is also important to pay attention to the nutritional program and irrigation.

After intensive pest control conducted in most fields to prevent SWD infestations, populations of natural enemies and other “good guys” may be depleted. That can create secondary pest problems that we need to be ready to tackle. One of these secondary pest problems are blueberry bud mites. This year, Michigan State University Extension recommends taking shoot samples of those fields that in the past suffered from blueberry bud mite problems, especially Rubles and Elliott fields. As in previous years, the small fruit team is offering assistance to those interested in scouting their fields for bud mite problems. Remember, shoot samples should be taken before the buds close. To be effective, blueberry bud mite control needs to be applied when the blueberry buds are still open to allow the insecticide to penetrate into the bud’s scales and onto the mites.

If you suspect your field might have bud mites, please bring your samples to the Trevor Nichols Research Center at 6237 124th Avenue Fennville, MI 49408 if your field is located in Allegan and Van Buren counties. In Ottawa County and counties north of Ottawa County, bring samples to the Ottawa County MSU Extension office at 12220 Fillmore Street, Suite 122, West Olive, MI 49460.

In preparing the samples for blueberry bud mite inspection, please follow these instructions:

  1. All samples need to be collected fresh. Samples should be taken throughout a field that is suspected of being infested.
  2. Collect 20 shoots no more than 6 Inches long of this year's growth. If a particular area of the field has symptoms that have raised suspicion of bud mite infestation, a separate sample should be taken from that area and marked appropriately.
  3. Samples should be placed in a plastic, zip-lock bag without any water, clearly labeled with the date, farm, field and blueberry variety. It is important to collect samples early in the morning and to submit them immediately. This allows sorting of samples while the material is still fresh.
  4. Please provide your contact information with a daytime phone number and address and the location of the field from where the samples were taken.

Another issue is nutrition. With the high volume of fruit harvested this year, the nutritional demand on the blueberry plant has been extraordinary. Thus, reviewing the nutritional program for the next season is important to prevent a drop in productivity.

In raspberries and strawberries, the intensive use of insecticides to prevent SWD infestations means we are seeing two-spotted spider mite problems. It is important growers control this pest before it causes substantial damage to plants and fruit production. In raspberries, Tanagoshi, Murray and Gerdeman from Washington State University provide a complete description of two-spotted spider mite symptoms and damage. In strawberries, Celeste Welty from Ohio State University provides a complete description of two-spotted spider mite symptoms and damages.

In addition to these useful links, consult MSU Extension Fruit Management Guide (Bulletin E-154) for insecticide recommended for control. If you need assistance with these pests, please visit your local MSU Extension office or call Carlos Garcia at 616-260-0671 or e-mail


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