By Marco Peña, UA Research Specialist

Those involved in vegetable production know that whiteflies damage and kill crops by sucking sap, spreading viruses, and excreting a sticky substance called honeydew.

In 1992, the sweet potato whitefly (SPW), Bemisia tabaci, was considered an occasional virus vector. Today the SPW is one of the main pests in desert melons and vegetables.

Spraying is a fairly effective control method. But whiteflies could develop resistance and new biotypes have been discovered recently. John Palumbo, UA research scientist and extension specialist, is conducting efficacy experiments developing new methods to improve whitefly population management.

There are different methods to monitoring the adult SPW. Yellow sticky traps can monitor adult flight activity. Sampling for adults and immature SPW should be centered on young foliage.

The most practical method to sample for SWF is to turn the leaves carefully when the insect is active in the early morning. This method is also used in UA experiments for evaluating the efficacy of the new chemicals against SPW.

I would like to describe a different method used by researchers inside and outside the UA to sample cantaloupe whitefly efficacy with a vacuum. This is done at the Yuma Agricultural Center using a heavy duty two-gallon cordless wet dry vacuum powered by an 18-volt battery. Plastic cups are properly labeled with the treatment and replication number for insect collection.

Cups are placed in the suction hose. The cups have a nylon mesh at the bottom which prevents the insects from going into the vacuum deposit. Each plant is vacuumed for three seconds. Usually five plants are sufficient with a good whitefly population. Lids are placed on the cups.

To identify by species and count numbers, the cups are placed in a freezer for about one hour. The contents are then evaluated under a stereomicroscope. The data is analyzed by the researcher. The lower numbers are the most efficacious products for whitefly control. Recommendations are available to pest control advisers and growers.

Contact Peña: (928) 782-3836 or marcop@ag.arizona.edu