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Monday, July 26, 2010

Whiteflies in blueberries - should we be concerned?

I'm attending the North American Blueberry Research and Extension Workers Conference in Kalamazoo, MI today and tomorrow, so I thought it would be a good time for a blueberry post.

I have been noticing large numbers of an unusual looking whitefly in blueberries for the last 2 years and now have an ID for it. Tetraleurodes ursorum does not have a common name, although the Florida Department of Agricultural & Consumer Services suggests it be called the bearberry whitefly. These whiteflies usually appear after harvest and are present on new growth. They are unique in their dark blueish black coloring, which almost makes them appear parasitized. Although many of the nymphs and pupae I collected in 2010 were parasitized, the dark color is their natural appearance. Whiteflies have a complex life cycle. Eggs hatch to a mobile 1st instar, termed a crawler. They then mature through a few stationary nymph stages to what is generally called a pupa but is really just a final, non-feeding nymphal instar. Because whiteflies do not undergo complete metamorphosis, the term pupa is a misnomer.

Whitefly nymphs and pupae on the underside of blueberry foliage in 2008. Photos: HJB

These whiteflies can reach extremely high numbers in NC blueberries. I have seen the back of leaves entirely covered in nymphs and pupae and their associated honeydew. Because they appear to be a post harvest feeder, it is unclear if they are causing any damage to the plant. This late summer, I plan to treat some of my new planting for whiteflies (assuming they are present there) and to then compare flower clusters next spring. Hopefully this will starting giving us a sense of what, if any, importance this unusual insect has for NC blueberries.

Whitefly adults on young blueberry foliage. Photo: HJB

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