NEWS for North Dakotans
Agriculture Communication, North Dakota State
University
7 Morrill Hall, Fargo, ND 58105-5665
June 25, 1998
Orange wheat blossom midge are emerging from the soil in much of the state where midge are present, according to Phil Glogoza, entomologist with the North Dakota State University Extension Service. The farther north, the later midge emergence begins. Males emerge first, females a few days later.
"These first detections do not mean that activity levels of the midge are at the point where treatment to protect wheat is warranted," said Glogoza. "They do mean that growers should start monitoring wheat fields that have heads emerging. Growers farther north should begin making preparations to monitor fields now for the presence of midge, to determine if the treatment threshold has been reached."
The decision to treat wheat for midge should be determined by growth stage and the number of midge found on wheat heads during evening scouting activities, he said.
Glogoza warns that there is another insect, commonly found in North Dakota wheat fields, that is similar to wheat midge, but larger, and harmless. Growers should take care not to confuse the "lauxanid" fly, which has a plump body and is tan in color, with the orange wheat blossom midge, which has a slender body and is bright orange. The lauxanid is likely to be in wheat fields everywhere and all day long, while the orange wheat blossom midge will be found only in evening hours and after dark.
The big question: if growers find wheat midge in their fields, how long should they wait before taking action against them?
"The action threshold," said Glogoza, "is one adult midge per four to five wheat heads inspected, including both primary heads and first tillers. At this level of infestation, potential yield reductions are estimated to be 15 percent."
Monitoring is essential. Here's how to go about it:
Monitor wheat fields for the presence of wheat midge from heading through flowering. Field scouting must be in the evening from 9 p.m. until midnight. Wind speeds should be below 6 miles per hour and temperatures above 59 F. Wheat midge adults can be seen laying eggs on the wheat heads.
Monitor fields from head emergence until 80 percent of the heads have anthers visible. When anthers are visible, a wheat head is flowering.
Visit three or four different sites in the field. At each location, count the number of midge on several sets of wheat heads (four to five heads per set). Record and calculate your average for the field.
"The only registered product in North Dakota with wheat midge on the label is Lorsban 4E-SG, at a rate of one pint per acre," said Glogoza. "Ground or aerial application can provide effective control when timed properly. Refer to the label for specific-use recommendations before applications are made."
Timing a treatment is critical for getting the best results, he said. Apply insecticides after 6:30 p.m. and when the crop is in the period from heading to flowering.
n If monitoring shows that the action threshold has been reached, said Glogoza, producers should consider the following guidelines for taking action:
n If 30 percent of the wheat is heading, wait up to four days and then treat with Lorsban 4E-SG.
n If 70 percent of the wheat is in the heading to flowering stage, optimum control should be achieved by treating.
n If 30 to 60 percent of the heads are flowering, and at least one anther is visible, spray immediately, though control is likely to be reduced.
n If 80 percent of the heads are flowering, treatments are not recommended. Applications at this time are no longer effective because larvae will already be feeding on kernels and will be well-protected inside the glume, or else the plants will be no longer be as attractive to adult midge and further infestation of primary heads and first tillers will be unlikely.
For further information regarding wheat midge, contact your local office of the NDSU Extension Service, and listen for updates regarding midge activity in your area.
###
Source: Phil Glogoza (701) 231-7581
Editor: Barry Brissman (701) 231-7866
Click here for a pdf version of this graphic.
Click here for a pdf version of this graphic.