Cottony Scale on Blueberry

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cottony scale 2Cottony Scale ( (Pulvinaria sp./spp.) has been observed again this Spring on several commercial blueberry farms in southeastern NC. The insect is very difficult to see in winter but becomes highly visible in late April when egg-laying occurs and the females produce white egg sacs. The following images and quotes are from an image-only sample I sent to the NC State Plant Disease and Insect Clinic in 2021. The pest was identified by entomologist Matt Bertone, with additional comments on control measures from Hannah Burrack. Thank you, Matt and Hannah!

cottony scale 1 cottony scale 4 cottony scale 5 cottony scale 6

From Matt Bertone:  This is one of the cottony Pulvinaria–type scales, a type of soft scale (Coccidae). There are a few species that will feed on Vaccinium, including more specific Pulvinaria ericicola and the polyphagous Pulvinaria floccifera. This seems a little darker than P. floccifera, but I have not identified P. ericicola before to know that it’s that species. Regardless, they are commonly seen this time of year when the females produce their long egg sacs filled with eggs and both species should respond to similar treatments.

From Hannah Burrack:  In general, we get the best control of scale insects with dormant season oil treatments rather than in-season contact insecticides. This is because coverage is better without foliage, and oils suffocate scale insects as they coat them. There would need to be crawlers present for an in-season foliar insecticide to have real efficacy against scale, and that is hard to effectively time without intense monitoring. If growers are truly interested in making an in-season application, a material with some systemic activity would be a better choice than malathion. Movento is a newer, locally systemic material that is applied as a foliar treatment in blueberries can be used post-harvest and is effective against scale insects in other systems. This would be a better choice than malathion for a post-harvest treatment in my opinion.