The potato leafhopper insect is certainly not the Easter Bunny. Yet the one-eighth-inch-long, lime green-colored pest hops into Western alfalfa fields each year delivering eggs which once mature threaten crop yield and quality.

Improving the management of hopper insects including the potato leafhopper (Empoasca-fabae) and the threecornered alfalfa hopper (Spissistilus festinus) in low desert alfalfa production is the goal of Vonny Barlow, University of California Cooperative Extension (UCCE) entomologist and crop production specialist based in Riverside County’s Palo Verde Valley.

The potato leaf hopper (PLH) and the threecornered alfalfa hopper (TCAH) can be found year round in the Southern California desert, Barlow says. The PLH is found in the Palo Verde Valley from March through September. The insect can invade Central Valley alfalfa fields from April through July.

The TCAH is an occasional pest in both regions.

Barlow discussed alfalfa pest management efforts with farmers, pest control advisers, and industry representatives during the 2011 Fall Desert Crops Workshop in El Centro, Calif. The workshop, sponsored by Western Farm Press, was conducted by UCCE Imperial County and the University of Arizona Cooperative Extension, Yuma County.

Commercial sponsors of the workshop included: Platinum Level – BASF, Bayer CropScience, and Syngenta; Gold Level - Dow AgroSciences and Valent U.S.A.; Silver Level - FMC; and Bronze Level - Westbridge Agricultural Products.

The PLH normally dies during the winter months from the extreme cold. A new infestation occurs in the early spring when PLH populations originating in the Gulf Coast states migrate westward.

Effective management of PLH is important to reduce the loss of alfalfa quality and yield from the insect. Barlow says the recommended pest threshold in the Palo Verde Valley is .2 leafhoppers when alfalfa plants reach three inches in height, .5 leafhoppers at 6 inches, and one-to-two insects on a 1-foot-tall plant.

“The potato leafhopper feeds on the plant and injects toxic saliva,” Barlow said. “If the saliva is injected high in the plant the result can be reduced growth at the plant’s top. If the saliva is injected at the plant base, severe stunting can occur.”

Early insect control is important.

“With a 1-foot plant, the loss of an inch is not a big deal,” Barlow said. “A 1-inch plant which loses a foot of growth potential is a big deal. That’s why the recommended threshold is lower when the plant is smaller.”

Insecticides can provide good hopper control in desert-grown alfalfa. One to two sprays are usually required annually for PLH control, but the number can increase based on larger populations. 

Reducing indiscriminate insecticide use lowers secondary pest outbreaks and pest resurgence (bounce back effect). It also reduces hazards to honeybees and other desirable insects and lowers crop phytotoxicity.

Barlow says integrated pest management (IPM) is a crucial tool to reduce control costs and maximize plant quality and yield. Since alfalfa is a perennial crop, insect management strategies generally last longer than with an annual crop.