Check blueberry fields for scale infestation

Isolated detections of scale in blueberry fields have been reported in west Michigan. Now is a good time to check fields during scouting for scale.

These scale insects are covered with a white covering that is evident on this mature bluebery cane.
These scale insects are covered with a white covering that is evident on this mature bluebery cane.

A few isolated cases of scale infestation have been reported in the past few weeks in west Michigan, and this would be a good time to be checking blueberry fields during regular scouting to see whether scale is present in your farm. These are small insects that survive on older woody canes through winter, grow in spring usually under protective covers, and then start egglaying in spring and summer followed by those eggs hatching into a crawler stage that spread throughout the plant looking for new places to settle and feed.

Scales have piercing mouthparts they use to suck sap from the plant, and the honeydew they produce can be tended by ants, so looking for ants crawling up and down the canes is another approach for detecting these scales. Blueberries are most often susceptible to Putnam scale, Lecanium scale or Terrapin scale, but the current specimens seem to be Azalea bark scale based on our preliminary identifications.

If scales are detected, the best option for control is to identify the timing of the crawlers emerging from under the protected waxy covering. This can be done using double-sided tape checked each week, and this can identify when an in-season scale control product could be used. Other strategies that are important for preventing outbreaks of scale in the first place include regular pruning of old canes, a dormant oil application in the early spring and protecting scale-parasitizing wasps through careful selection of insecticides.

Please send reports of scale to your local Michigan State University Extension fruit educator, and if you have specimens that need identification, remove an infested piece of stem and send to MSU Diagnostic Services.

Close-up photo of scales infestation on a blueberry cane.

A closeup image shows multiple scales clustered in a depression on a bluebery cane. Removal of the white covering from two sclaes in the bottom left of the image reveals the dark purple female scale and the numerus pink eggs.

Dr. Isaacs work is funded in part by MSU’s AgBioResearch.

Did you find this article useful?