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- The western cole crop industry is gaining much needed information to manage the bagrada bug insect in cole crop seedlings, thanks to researchers at the University of Arizona and the University of California.
Fun and fellowship at the California Association of Pest Control Advisers’ Agri-Expo. Seated from left - Mike Mendoza, Sandy Creighton, and Jason Haught. Standing, from left: Larry Liggett, Greg Hallquist, Jose Silva, Riley Reynolds, and Robert Hornyak.
Pest marches into Central California
Since its 2010 debut, the bagrada bug has marched in heavy numbers into some Ventura County cole crop fields. Bagrada is found in isolated areas in the Salinas Valley and on the Central Coast. This year, Palumbo received numerous queries from the Fresno County area.
First found in South Africa, the insect arrived in the western hemisphere in the U.S. in 2008 in California; possibly as a stow-a-way on a cargo ship arriving at the Port of Long Beach. The insect then scurried into neighboring Orange County and kept moving.
Some desert PCAs call the starburst-shaped feeding marks left on plants “tattoos.”
The bagrada bug does not always feed on the cotyledon. It will attack the plant’s first true leaves. If the plant survives, then split, forked, or multiple terminals lead to the unmarketable produce.
Pesticide use during the first 20 days of stand establishment from August through November averaged 4.3 sprays in 2010; 3.4 sprays in 2011, and 4.1 sprays in 2012, according to the survey results from PCAs.
A common question growers pose to Palumbo is when does the bagrada bug stop damaging the plant so growers can discontinue sprays. Trials conducted in Yuma County and the Coachella Valley in 2011-2012 young broccoli plantings revealed a possible answer.
“The bottom line is once the plants get to about the 6th leaf stage then you are probably out of danger,” Palumbo said. “Most of the PCAs I’ve talked with in the desert agree with this.”
The late morning and afternoon are the best times for PCAs to scout for bagrada. Yet since PCAs must cover a lot of ground daily, early morning scouting should look for pale-colored feeding marks on plants. If found, look for damage on the surrounding plants.
Palumbo has conducted several trials with synthetic insecticides and natural predators. While he said bio-control is a ways off, pyrethroid insecticides currently provide the most effective control.
“Newer pyrethroids on the market appear to be more consistent with good knockdown and residual control.”
Residual activity usually lasts about five days. He estimates that the cost of each spray in the desert totals about $20-$25 per acre.
Looking to the future, Palumbo says the best insecticidal control of bagrada may lie in neonicotinoid seed treatments, based on trial findings.
“This might help minimize yield losses and the number of needed sprays,” Palumbo concluded.
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