Early field scouting activity confirms that aphids are present in Ontario soybean fields, although in low numbers.
“This however could change quickly, as winged aphids could move in from other regions or from the few heavily infested fields already present in Ontario at any time,” says Tracey Baute, field crop entomologist with the Ontario Ministry of Agriculture, Food and Rural Affairs.
Baute reports that about three or four sites had exhibited heavy populations early on and that they are showing a high percentage of winged aphids. A storm front could pick them up and move them through eastern Ontario or Quebec.
Baute says that in some fields planted around May 5, aphids have already reached threshold levels and require spray treatment. Because of the absence of natural enemies after the first application, she says some of these fields may require a second treatment.
“However, in other early planted fields, natural enemies have brought the aphid population from near threshold to nearly zero again, demonstrating the importance of scouting and determining if management is indeed necessary,” she says.
Producers should examine between 20 and 30 random plants across the field, taking care to avoid field edges, and estimate the average number of aphids per plant in the field. Baute says a minimum of two field visits is required to confirm an increasing aphid population.
Spray action should be taken if the aphid populations are “actively increasing” above 250 aphids per plant on 80 per cent of the plants from the R1 up to and including the R5 stage. “If aphid populations are not actively increasing above the threshold, this is an indication that natural enemies are keeping up with the aphid population,” says Baute.
Scouting should continue until the plants are well into the R6 (full seed) stage when the top pod seeds of the plant fill the seed cavity. Insecticide application is not likely to yield any economic return beyond the R6 stage.
Baute says that the most common question she receives is what and how to spray. “My response is that it depends on the field and the conditions that year as to which product works better.” No matter what product is used, Baute says spray coverage is the most important consideration.
More information is available by calling 1-877-424-1300 or via e-mail: [email protected]
~Anne Howden Thompson~