by Paul Schattenberg, Texas A&M AgriLife Communications
SAN MARCOS — The Bagrada bug, Bagrada hilaris, an invasive stink bug that has been slowly spreading through the southwestern U.S. for the past decade, has recently been reported in Hays County, said a Texas A&M AgriLife Extension Service entomologist.
“This bug can cause serious crop damage as well as cause damage to plants in commercial nurseries and home gardens and landscapes,” said Molly Keck, AgriLife Extension entomologist and integrated pest management specialist, Bexar County.
Keck said adult Bagrada bugs have the same coloring as harlequin bugs, but are about one-third to one-half their size with smaller orange markings and no white markings.
She said the Bagrada bug is primarily a pest of cole crops in the mustard family, or Brassicas, including brassicaceous weeds such as wild mustard.
“Bagrada bug prefers plants such as broccoli, cabbage, cauliflower, collards, kale, radishes and brussels sprouts,” she said. “However, it is also known to feed on cotton, Sudan grass and Bermuda grass.
Keck said the bug has needle-like mouthparts used to penetrate and feed on plants and young seeds. They can cause a range of damage from leaf spotting, wilting or stunting, which can result in the plant not producing a flower, heads not forming, or even death of the plant.”
She said a high concentration of Bagrada bugs can significantly damage young broccoli and cabbage plants left unprotected in as few as two to three days.
“This pest is certainly capable of producing the kind of numbers needed to cause this type of damage,” she noted.
The recent identification of the pest in Hays County, however, is not the first instance of the bug being found in South Central Texas, said Wizzie Brown, AgriLife Extension entomologist for Travis County.
“The Bagrada bug has also been identified in the Austin area,” she said. “We’ve had reports of the bug from residents who have home gardens or who tend community gardens. The bugs appear to have shown up sometime late last year and then sprang up again on some cole crops this spring. Some people reporting them thought they were baby stink bugs.”
Bagrada bugs gather on plants and lay their eggs one at a time or in small clusters on the underside of leaves and stems or in soil beneath the plant. The eggs start out white and turn an orange-red as they get older. Young Bagrada bugs change color from bright orange-red to near black with red markings as they get older. Newly molted nymphs are also red but quickly darken to a near-black color with the white and orange markings.
Keck said early detection is important as bug populations can build quickly, but can be difficult because they are small compared to other vegetable pests and may be easily overlooked until populations become large.
“It’s usually difficult to observe Bagrada bugs until there’s been some damage, so look carefully for damage like light green lesions, which are easier to spot than the insects during the early period of infestation,” she said. “If you’re a home gardener, be sure to inspect plants and shipping containers for the bug or signs of possible bug infestation before you plant.”
More frequent monitoring for the bug may be necessary when temperatures rise above 75 degrees, as the bugs are typically more active and visible during the warmer parts of the day. In gardens where the pest is present in large numbers, Keck said it may be advisable to remove host plants and replace them with plants not in the mustard family.
Keck said while some control methods may include picking the bugs off by hand or using a hand-held vacuum cleaner to remove them from the plants, it is often easier to tap the plant and let the bugs fall onto a cloth in order to collect them. Also, pyramid traps baited with crushed sweet alyssum inside polypropylene bags can be used to catch and destroy these bugs, especially when in large numbers.
In larger production systems, cultural control methods such as weed control and planting transplants as opposed to seeds may reduce populations and damage by Bagrada bugs.
“Stink bugs are difficult to manage with insecticides and repeat applications are often necessary,” Keck said. “Adult bugs usually fly away before they contact the insecticide and return later. Home vegetable growers will probably have better control by using plant covers or screening to exclude the bugs — or by removing host plants from the garden.”
Keck said if insecticides are used in a home garden or landscape, be sure to check the pesticide label to make certain the product is registered for use in that specific application. She noted there has been some success using pyrethrum to suppress adults while azadirachtin and insecticidal soaps have been shown to help reduce nymph populations.
She said experience with the bug on commercial cole crops in conventional field vegetable production in Arizona and California has shown success using carbamate, neonicotinoid, organophosphate or pyrethroid insecticides for control.
However, she noted, most Organic Materials Review Institute-approved pesticides are unable to control Bagrada bug.
For agricultural purposes, pesticides with quick-acting contact activity such as pyrethroids may provide good short-term protection against Bagrada bugs feeding on emerging leaves and transplants, Keck said. Once transplants become established, foliar sprays of pyrethroids and neonicotinoids should help prevent further feeding damage.
“Of course, while these bugs may move to other areas on their own, it is important people don’t help them by inadvertently transporting infested plants or produce into new areas,” she said.