White-knuckles are proof of the wild roller coaster ride for growers and pest control advisers (PCAs) this fall in low desert cole crop fields with the first-time appearance of the Bagrada bug, Bagrada hilaris.
The Bagrada bug – also known as the painted or harlequin bug – was first sighted in August in broccoli, cauliflower, and other cole crops in California’s Imperial and Coachella valleys, and southwestern Arizona.
“Bagrada bugs were everywhere; it’s not like we’ve had to look for them,” said John Palumbo, research scientist and Extension specialist, University of Arizona Yuma Agricultural Center, Yuma, Ariz.
Adult and nymph Bagrada bugs suck sap from young leaves. Feeding causes small puncture marks visible as white patches on leaf edges. A heavily-attacked plant has a scorched appearance. End results can include plant death, plants without heads, or double heads too small for the commercial market.
The Bagrada bug attack early this fall targeted young plants. Organically-grown cole crops took the hardest hit. One organic grower lost five acres of broccoli, says Palumbo.
Pyrethroid and neonicotinoid-based insecticides minimized damage in conventionally-grown fields, Palumbo said. Pyrethroid applications were repeated in some cases. Some neonicotinoids applied for whitefly control also provided Bagrada bug control. Palumbo conducted several quick research trials that demonstrated good efficacy with the products.
“Thankfully we caught this pest early,” Palumbo said. “Most conventional growers didn’t have an issue with the Bagrada bug except for the first few fields they weren’t watching closely. Some transplanted fields of cauliflower and broccoli got beaned up pretty good. People started treatments once they learned what the problem was.”
The Bagrada bug was found in the U.S. in Los Angeles County in June 2008 and then moved into Orange County. California and Arizona are the only states where the Bagrada bug has been found.
According to the University of California, Riverside’s Center for Invasive Species Research (CISR), adult Bagrada bugs are 5-7 millimeters long with black, shield-shaped bodies with distinctive white and orange markings. The adult female is larger than the male.
Palumbo reports inquiries from growers and PCAs have dropped off significantly with cooler fall temperatures which reduce insect growth and activity. Meanwhile crop growth is on the increase.
“We’ve started a culture in our lab to get a feel for the biology of this pest,” Palumbo said. “It seems like the lifecycle is long compared to other pests, but we don’t know that for a fact. We want to find out before next year’s cole crop season.”
The question growers and PCAs have asked Palumbo the most often is does the Bagrada bug have a feeding toxin?
“I don’t have an answer yet; we don’t think so,” Palumbo said. “Is the plant damage from the Bagrada bug feeding on the young kernel and sucking it dry, or is there something systematically occurring in the plant from the feeding?”
Major Bagrada bug damage was seen in an organically-grown red cabbage field in Holtville in late October by Eric Natwick, entomologist, University of California Cooperative Extension, Imperial County.
“I’d estimate about 30 percent of the early September-planted transplants developed single heads,” Natwick said. “The other plants (about 70 percent) had no head or two smaller, unmarketable heads.”
Natwick found higher single head numbers in mid-to-late September-planted cabbage. The field contained adults, nymphs, and eggs.
From 2 percent to 5 percent of Imperial Valley vegetable production is grown organically with a similar amount estimated in the Yuma area, sources report.
PCA Rick Klicka, Southwest Ag Service Inc., Brawley, found the Baraga bug in broccoli, cauliflower, cabbage, rutabaga, collards, and kale. He found the first bug in September.
“The bug yellows up the leaves and twists the plants up,” Klicka said. “In broccoli as soon as the cotyledons pop up the bug steals the growing point. It either kills the growing point or deforms it.”
The plant’s yellowed leaves resemble herbicide damage, notes Klicka.
“The Bagrada bug has deformed or killed some cole crops on the organic side,” Klicka said. “Be wary on the conventional side because it has the capability to do the same. We are spraying for worms and beetles and are inadvertently picking up the Bagrada bug. We have to grow the crops out to see the end result.”
The Bagrada bug has five-instar stages. First instar bugs have reddish-brown heads and thoraxes plus bright-red abdomens. Later instars develop the color black. Eggs are oval and creamy white and turn orange with age. All life stages are present on plants at the same time, according to CISR.
The Bagrada bug is found in East and Southern Africa, Egypt, Senegal, and Zaire. Pest distribution includes Southern Asia and Southern Europe.