Since the Bagrada bug’s first appearance in low desert cole crop fields three years ago, University of Arizona research on the quarter-inch-long stink bug is now yielding answers to help farmers and pest control advisers (PCAs) better understand and control the pest.

The Bagrada bug, Bagrada hilaris, stunned farmers, PCAs, and chemical company representatives when it first appeared in the fall of 2009 in huge populations in California’s Imperial County and neighboring Yuma County in Arizona.

Bagrada bug adults and nymphs feed on young cole crop plants including broccoli, cauliflower, cabbage, brussel sprouts, kale, turnip, mustard, and radish. The insect’s needle-like stylet mouthpart sucks the sap from leaves; essentially killing or maiming cotyledons and growing points.

Feeding at the growth terminal can cause branching which produces small, unmarketable multiple heads of broccoli and cauliflower. Heavily attacked plants have a scorched appearance. The bug feeding causes large stippled or wilted areas on leaves. Newly formed central shoots or heads often become stunted.

The Bagrada bug, also known as the painted bug or harlequin bug, is a serious pest of vegetable crops in East and Southern Africa, Southern Asia, and Southern Europe.

The insect was first found in the U.S. in 2008 in California in Pasadena (Los Angeles County). The Bagrada bug then crawled into Orange and Ventura counties before pole-vaulting into low desert cole crop fields.    

So far, Bagrada bug numbers have been low this fall. It was the September-November period over the last two years when numbers quickly increased.

“PCAs and farmers should not become complacent just because they are not finding any Bagrada bugs yet,” said John Palumbo, University of Arizona research entomologist based at the Yuma Agricultural Center, Yuma, Ariz.

“It would be wise to assume the bug will eventually show up in some intensity and to prepare for the insect accordingly.”

Such pest challenges breathe fire into the bellies of entomologists including Palumbo. Since the first infestation, Palumbo has worked many long days and nights seeking answers to perplexing questions about the pest.

Palumbo shared the results of his most recent YAC Bagrada bug trials with farmers, PCAs, and industry members during the 2011 Preseason Winter Vegetable Workshop in Yuma.

Palumbo’s preliminary research conducted over the past year suggests that direct-seeded and transplanted crops are most susceptible to Bagrada bug infestations during stand establishment.