Testing for viruses in blueberries

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.  

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. If you have seen unusual symptoms in a blueberry field, such as sudden death or blight of all leaves and blossoms on one of more shoots of a blueberry bush, please contact Dr. Richard Kaitany (.(JavaScript must be enabled to view this email address)) of the Michigan Department of Agriculture, so that the bushes can be tested. You can see pictures of typical symptoms of scorch and shock in the Blueberry Pocket Scouting Guide and at: http://www.blueberries.msu.edu/diseases.html.

With respect to other viruses, we invite growers who suspect a virus infection in their fields (other than blueberry shoestring, which is very common and easy to diagnose) to send in samples this week or next week to: Dr. A. Schilder, 104 CIPS Building, Michigan State University, East Lansing, MI 48824. Phone number: 517-355-0483. The last day to send in samples is Wednesday August 16. The main thing is to keep the sample as fresh as possible by sending them overnight or hand-delivering them. The best way to take samples is to take living, symptomatic leaves and shoots and place them in a plastic bag. Refrigerate/cool the sample immediately. If you add ice packs, be careful that the sample is not crushed. Whole plants can also be dug up and potted or whole canes can be cut and placed in a plastic milk jug with water.

Symptoms that may indicate a virus disease include: mosaic or mottling of leaves , crinkling or malformation of leaves and other plant organs, stunting, poor fruit set, generally poor growth, and plant decline or death. Some of these symptoms can also be caused by herbicides, such as Round-Up or 2,4-D, as well as nutrient deficiencies. He re are a few pointers that may help you decide whether symptoms that you are seeing may be due to a virus or another cause:

  1. Are the symptoms present in a few scattered plants or in many plants over a large area? If present over a large area, it is more likely to be caused by an abiotic disorder like drought stress, herbicide injury or nutrient deficiency.
  2. Did the symptoms show up suddenly or have they been worsening over the past couple of years? Symptoms of virus diseases usually become worse over time, and may eventually result in the death of the bush.
  3. Does the disease seem to be spreading? If so, it may be a virus disease. Virus diseases vectored by nematodes usually spread in a more-or-less circular pattern in a field, whereas viruses vectored by aphids spread more readily down the row.
  4. Did you apply Round-Up last fall? This herbicide may get transported into the roots and may not show symptoms until the following year.
  5. Are symptoms showing up in a newly planted or young field? Consider your source of plants. Did you buy virus-tested planting stock? If not, you may have imported a virus disease with the planting material.

Pictures and descriptions of virus diseases and other disorders can be found in the Blueberry Pocket Scouting Guide and at: www.blueberries.msu.edu.

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