Flea beetles have been feasting on canola seedlings in Manitoba. Heavy infestations have warranted foliar insecticide treatments, Manitoba Agriculture, Food and Rural Initiatives says in a June 13 report.
“Even if Helix or Prosper seed treatments have been used, some minor feeding to leaves and cotyledons is normal, as the flea beetles needed to ingest the seed treatment to be killed. Such feeding is normally not heavy enough that further control would be needed,” the report said.
In years when germination and early development of the canola is delayed, seed treatments can lose their effectiveness before the canola reaches the three-to four-leaf stage, where it can better tolerate flea beetle feeding.
“When doing early-season scouting in canola, consider the level of feeding that is occurring and the stage of the plants. If seed treatments are losing their effectiveness, heavy feeding can occur if flea beetle populations are large, particularly on warm, calm days,” the province advises.
John Gavloski, provincial entomologist, said some farmers have asked whether flea beetles come in flushes. For the species of flea beetles that feed on canola, there is one generation per year, although adult beetles appear twice. “The beetles you see now are the ones that overwintered. They feed in the spring, lay eggs and then die. When the eggs hatch the larvae feed on the roots in early and midsummer. This feeding is believed to not be economically significant.”
Then in late summer adults will appear again, which will overwinter and emerge to feed on crucifer seedlings the following spring.