By KAREN BINDER
Illinois Correspondent URBANA, Ill. — A couple of devastating crop marauders are now lurking in Illinois fields: Goss’s wilt and the red-shouldered stink bug.
Goss’s wilt was discovered at the University of Illinois Plant Clinic in late July. This pathogen and the stink bug each can reap enough damage to cause yields to diminish, UoI officials say, adding that both typically have not been observed in recent years.
Prompting these possible outbreaks have been Illinois’ “tropical” weather patterns, which follow last year’s cooler summer temperatures. Carl Bradley is a UoI plant pathologist. He noted Goss’s wilt has been observed in Illinois cornfields in past years, but it is not typical for this region.
This condition is commonly found after hail storms, high winds and heavy rainfall, and symptoms of this disease appear as large tan to gray lesions on the leaves with dark spots, often referred to as “freckles,” within the lesions, Bradley explained.
“Some plants may wilt, as the pathogen can infect the xylem,” he said. “In some cases, darkening of the vascular tissue can be observed in affected plants if a cross-section is cut through the stalk.”
He warns that symptoms of Goss’s wilt may be confused with other foliar diseases such as Stewart’s wilt, northern corn leaf blight or Diplodia leaf streak. The best method for identification is to send suspicious samples to the UoI Plant Clinic – details are at http://plantclinic.cropsci.illinois.edu or call 217-333-0519.
Once set in, there’s nothing to protect against infection or its spread. But Bradley noted one way to control its spread is to plant corn hybrids with high levels of resistance. If an infected field is identified, he also suggests tilling it under after harvest to bury any residues, and rotating to a non-host crop.
Likewise, coping with the stink bug in soybeans has been a challenge for extension advisors because an actual specimen has not been located. What they do know is the red-banded stink bug has been observed in several states, including Arkansas, Louisiana, Mississippi, Missouri and Tennessee.
Now Illinois farmers are asked to watch for the red ones, as well as green and brown stink bugs, since a red-shouldered stink bug was observed south of Champaign in central Illinois. Mike Gray, UoI extension entomologist, said the bugs are especially damaging to soybean plants in the bloom to early pod-fill stages and use their piercing and sucking mouthparts to remove plant fluids.
“Because of their ability to damage tender plant tissues, especially developing seeds, they are capable of causing economic losses to soybean producers,” Gray said.
“The economic threshold of one bug per row foot during the pod-fill stage has been suggested.”
Advisors in Illinois are especially vigilant, since the red-banded stink bug has caused enough damage in Louisiana to extend to economics, Gray explained. He said the threshold for the bug is 24 insects per 100 sweeps, as compared to 36 insects per 100 sweeps for the brown stink bug.
Any suspicious stink bug resembling the red-shouldered, red-banded or brown-marmorated species should be reported to Kelly Estes, state survey coordinator with the Illinois Cooperative Agricultural Pest Survey Program, by calling 217-333-1005 or e-mailing invasives@inhs.illinois.edu |
