Whiteflies

For the last five or 6 years mid-Septemeber marked the mass arrival of Whitefies to the urban areas. The last couple years their numbers have dropped so dramatically that we in the urban sector think of them of as history. This makes it safer to go ahead and do fall planting in the garden with few thoughts of damage to the young tender plants.

Even though their presence in the mid 90's was counted in the billions they caused little damage to the landscape. Unlike agriculture where they were and still are a major pest of concern for vegetable and cotton growers.

The reduction from those galactic numbers of yore comes about by a concentrated and multipronged attack by agriculture.

Responding to the devestation to melons and cotton due to Whiteflies researchers and cooperation from the growers has made our life nearly Whitefly-free.

The attack launched by agriculture included:

The judicious use of a new and highly selective insecticide on the melon crops. Nursery operations used similar chemicals in the growing to make the stock Whitefly- clean;

Cotton growers stated using Insect Growth Regulators (IGRs) that are not toxic to anything except Whiteflies. They simply disrupt the normal life cycles of the Whitefly to they never mature and reproduce;

Melon and cotton growers also cooperated and separated their planting areas so the Whiteflies would have further to fly when one crop ended to get to another crop; And indirect use of B.t. Cotton over most of the acerage effectively controlled Pink Bollworm without chemicals. By this strategy few sprayings For bollworm meant not killing the natural predators of Whitefly.

If you do plant and Whitelies show up control is relatively easy. Their numbers should be much lower than times past. Before spraying be sure to check the undersides of the leaves. The ones flying around are not feeding. Its the flightless ones clinging to the undersides of the leaves doing the damage. If more than 5 are seen on the leaves' underside, spraying a mild dishwashing soap solution on the undersides of the leaves suffices.

The solution should never exceed a 1% concentration of liquid soap. In reality about one tablespoon per gallon is fine. Repeat only as needed remembering as the nights and days get cooler their numbers will slow even more until they will be gone when Orion is visible in the eastern sky in early evening.

Our battles against a once tough foe are greatly reduced. Without a doubt hugh kudos go out to the research and farming community to let us live in relative insulation from the ravages of Whiteflies.

Written by Terry Mikel, College of Agriculture and Life Sciences, the University of Arizona, 602-470-8086.
Material originally appeared in Arizona Republic
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