Bagrada Bugs

Every year around St Patrick’s Day, cabbage becomes a hit again thanks to the traditional meal of corned beef and cabbage. There is typically a 50 to 75% increase in demand for green cabbage beginning about two weeks before the March 17 holiday. California leads the nation in cabbage production accounting for about 24% of total U.S. production. Most of the cabbage from California at this time of the year comes from the state’s southern coast and southwestern desert. In 2010, a new pest of cabbage, the Bagrada bug, made its grand entrance into these desert cabbage fields and threatened the availability of cabbage for St Patrick’s Day.

“2010 was a year that many winter cole crop vegetable growers in the Desert Southwest would rather forget, thanks to the bagrada bug which attacked plant seedlings en masse.

Since then, research conducted at the University of Arizona and the University of California has led to a better understanding of the pest, its biology, and has helped reduce yield and income losses for growers.

When the bagrada bug made its 2010 grand entrance, winter vegetable growers, pest control advisers, and entomologists were stunned.

“The pest caught us blind. Suddenly the bagrada bug was everywhere in the desert,” says John Palumbo, University of Arizona (UA) Extension specialist and entomologist based at the Yuma Agricultural Center.

The pest attacks the underside of leaves during the day, and hides at night in the soil and under dirt clods.

The bagrada bug can quickly destroy a seedling. In Palumbo’s trials, a single insect placed on a cotyledon killed the plant in about 60 hours under laboratory conditions.

In another lab test, small pots were lined up in a row, each containing one of 12 different vegetable seedlings. The bagrada passed right by the head lettuce to feast on cole crops. Its feeding favorites include green cabbage, red cabbage, and radish.

If the plant lives, the damaged plant develops multiple unmarketable small heads instead of a single large marketable head or floret.

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.

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.

Looking to the future, Palumbo says the best insecticidal control of bagrada may lie in neonicotinoid seed treatments, based on trial findings.”

Author: Blake, C.
Affiliation: Reporter
Title: Researchers making strides against bagrada bug
Source: Western Farm Press. 2013-11-20. Available at: http://westernfarmpress.com/vegetables/researchers-making-strides-against-bagrada-bug