Whitefly controls tested in strawberries

(Editor's Note: Mark Bolda, UCCE Santa Cruz County; and Mike Nelson and Luis Rodriguez, both of Plant Sciences, conducted the following research and prepared this report.)

Greenhouse whitefly has been a serious pest of strawberries in recent years in the Monterey Bay strawberry-growing region. Feeding of whiteflies weakens plants, deposits honeydew on leaves and fruits and has additionally been implicated in the dispersal of several viruses in strawberries.

Although there are many pest control materials registered for the control of greenhouse whiteflies, a number of them have become ineffective at least in some areas of the Monterey Bay production area.

This trial was designed to test the efficacy of the newer insecticides Esteem, Oberon and Prevam in controlling greenhouse whitefly in strawberries grown on the Central Coast of California.

The trial was done as a randomized complete block design of four replicates of three 30-foot long by 4-foot wide beds per treatment on PS592 variety strawberries in a field in Salinas, Calif.

An application of all materials and mixes was made on Aug.11, 2005. Subsequent applications of certain materials were made on Aug 21, Aug. 31 and Sept. 9.

Counts of adult whitefly were made by randomly sampling and turning over, without detaching from the plant, 40 medium-aged strawberry leaflets per replicate plot and counting the number of adults present. Adult whitefly counts were made from all of the treatments just prior to first application, 1-day after each application, and 10-days and 20-days following the final application.

In addition to the adult counts, separate counts of whitefly eggs and whitefly nymphs were made using a random sample of at least 10 medium-aged leaflets per replicate plot, taken at each evaluation interval specified for the adult evaluations.

Treatments of Prevam and Brigade limited numbers of whitefly eggs, nymphs and adults to levels significantly lower than the untreated control on many evaluation dates. Esteem and Oberon mixed with either Prevam or Kinetic gave exceptional control, with consistent and significant control over other treatments of whitefly eggs, nymphs and adults over the course of the study.

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