NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
March 19, 1998
Many North Dakota growers have bought Lindane-treated canola seed from Canada this year. Planting it is now legal in North Dakota, according to the Environmental Protection Agency. But growers who plant this seed should be especially alert to possible insect problems during the growing season, according to Mike Weiss, entomologist at North Dakota State University.
Lindane-treated seed will protect against crucifer flea beetles for only 11 days after seeding, or about 5 or 6 days after emergence. In many situations, however, two weeks of protection after emergence will be required.
Canadians typically combine a granular-formulated insecticide with the seed at planting to ensure plant protection for two weeks after emergencebut that formulation has not been labeled for use in the United States.
In short, at the moment U.S. growers who plant Lindane-treated seed have no option but to plant as early as possible and hope for ideal growing weather. Once the canola plant has true leaves, flea beetle injury is often not significant.
"Our data from NDSU studies and field observations at Carrington, Minot and Langdon," says Weiss, "indicate that cool and wet conditions are ideal for plant growth during seedling emergence. It would not be unusual, under these conditionsand with low to moderate beetle populationsfor canola seedlings not to require any insecticide treatment whatever."
On the other hand, Weiss notes that if conditions are dry, canola growth can be severely retarded and plants can remain for an extended period in the cotyledon stage, which is the stage when they are most vulnerable to injury by the crucifer flea beetle.
If conditions are not only dry but sunny, beetles will feed even more voraciously and damage will be even greater, says Weiss.
"Fall surveys conducted by NDSU," he says, "indicate that crucifer flea beetle populations are relatively high west of Highway 20, and that populations east of Highway 20 have been increasing. The big unknown variable is what the weather will be during seedling emergence. If the weather's cool and wet, no problem."
And if the weather's wrong?
"Officials at NDSU and the North Dakota Department of Agriculture are investigating the possibility of obtaining permission to use certain insecticides as a rescue treatment in the event crucifer flea beetle injury to canola should become significant," says Weiss. "But growers should not count on this. Getting this permission for a rescue treatment is far from certaineven if beetles are causing significant damage in some fields."
Source: Mike Weiss (701) 231-7924
Editor: Barry Brissman (701) 231-7866