Winter canola producers in the Southern Plains states of Texas, Oklahoma and Kansas should be scouting fields for the presence of turnip and green peach aphids, according to Heath Sanders, Oklahoma State University Extension Assistant for winter canola production.
"Winter canola requires more management than wheat," Sanders said. "Make sure you are watching your canola in its period of semi-dormancy it is in right now. Start scouting your fields for these pests. Aphids have become the most important insect problem for winter canola in the southern plains states."
Turnip and green peach aphids have been frequently observed to colonize fields during fall growth, Sanders said.
"They are able to survive mild winters and increase to damaging levels during the early spring," he said. "They will feed on the underside of the canola leaves, so make sure you flip the leaves over and check those leaves laying closest to the ground."
To sample for the presence of the aphids in canola fields, Sanders suggests farmers walk diagonally across each field and stop 10 times. At each stop, check three plants. Count the aphids on three consecutive plants by looking under the leaves.
Also, look for other spots with dead or dying plants, he said.
"It is important to remember canola plants can handle large numbers of aphids before it is necessary to use a costly insecticide for control," Sanders said. "For every aphid per plant, 0.5 pounds of seed is lost in a field. It is important to delay insecticide applications until aphids approach a lever where important income is being lost."
Sanders points out research done by Dr. Kris Giles, OSU entomologist, indicates applying inseciticides to control aphids in canola requires some good information and judgement on the part of the farmer.
For specific answers on aphid control in winter canola, Sanders urges farmers to contact their local OSU County Extension office.
Sanders also urges canola producers to topdress their fields by applying the remaining two-thirds of nitrogen with sulfur to their crop. Herbicide applications also may be needed if weeds are competing with the crop and to avoid any weed second growth.