Wednesday, November 21, 2007

Greenhouse - Whitefly Biotypes

Whiteflies can be difficult to control in greenhouses. The silverleaf whitefly in particular is a problem due to the ineffectiveness of some control measures. In addition, there are different biotypes of these whiteflies that respond differently to control measures. The following is an article on the subject.

The Q biotype whitefly is a new variant of the common A and B biotypes of Bemisia whiteflies, the silverleaf whitefly and sweet potato whitefly. Biotypes are genetically distinct strains of a species, similar to varieties of plant species, although some have been given species designation. Q and B biotypes are visually indistinguishable and require lab tests for accurate identification. Growers' first indication that they have Q biotype is that the usual insecticides are less effective on what appears to be silverleaf whiteflies, not the common and more easily controlled greenhouse white fly. However, it is possible to have mixed populations of B and Q so lack of efficacy may not be clear-cut.

There were at least 6 cases of Q biotype reported from New York State greenhouses in 2006, on poinsettia and hibiscus. If you suspect that you have Q biotype whiteflies, contact your local Extension personnel and they can help you get the necessary lab analysis and treatment options.

Following are some suggestions to growers on managing whiteflies, particularly the Q-biotype whitefly:
  • Carefully check plant shipments for even low levels of whiteflies.
  • Use good non-chemical controls.
  • Correctly identify the whitefly species present!
  • Monitor whitefly population levels as the crop is growing.
  • Use sentinel plants to check for pesticide performance.
  • Consider using biological control right from the start.
  • For unusual silverleaf whitefly control problems, contact a regional Extension specialist for more information on preparing and shipping samples.

From the article "Whitefly Update Q & A (Biotype B too)" by Betsy Lamb NYS IPM in the Ornamental Crops IPM E-newsletter, Spring 2007, Cornell University

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