December 16, 2008

2 Min Read

As harvest on cole crop and lettuce fields in the Arizona and Imperial Valley regions was moving forward, sources reported that crop quality was excellent and pests were generally light.

“Perfect” growing conditions early on, with warm days and cool nights, were ideal both for crops and pests, though PCAs generally reported that the light worm year throughout most vegetable growing regions was translating into the desert deal as well.

Entomologist John Palumbo with the University of Arizona’s Yuma Agricultural Center says worm pressures were heavy during September and October, but dropped off in November, despite above-average temperatures.

Some PCAs were making treatments for thrips and whitefly, he said. Thrips were just coming into the Arizona desert as temperatures cooled late in the fall.

“Thrips were heavy in some areas, requiring insecticide sprays, particularly in lettuce adjacent to or near melons and alfalfa,” Palumbo says. “Whiteflies were heavy in some areas on cole crops and some areas have required intense management.”

Careful attention areawide to whiteflies seems to have helped reduce incidence of cucurbit yellow stunting disorder virus on melons compared to last year.

Green peach aphids have been reported in very light numbers in both lettuce and cole crops and have required sprays in fields not treated with an at-planting, soil-systemic insecticides.

Despite these pockets of activity, Bill Fox, independent consultant with Seven Ag Consulting at Yuma, says the combination of cooler nights and better chemistries with longer residual have helped keep lepidoptera pests in check.

“This is a different year pest-wise,” he says. “I don’t think I can remember backing off sprays this early. Usually we’re fighting lepidoptera until the end of the month. It looked like it was going to be a tough year and then it just fizzled, so we’re probably off by one or two sprays this year.”

Imperial Valley independent PCA Clyde Shields says pest pressures were similarly light in the California desert regions.

“Worm pressure has been very light. With so many new chemicals, if you select the right one, you have long residual. We’re getting 14 to 18 days between applications, and that’s pretty good for vegetables.”

Shields says new thrips materials are also helping in the fight against impatiens cecrotic spot virus and other thrips-vectored viruses that might pose a problem in desert lettuce crops.

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