Flea beetles, expected to be a major pest this year, have not yet appeared this spring.
Agrologists say the cold, windy weather is likely only delaying the problem. Worse, it may be weakening seed treatments as time passes.
Murray Hartman of Alberta Agriculture said the late spring means “we haven’t reached outbreak levels, yet.”
The slow start to the season has resulted in only half of the canola acres on the Prairies being planted by May 15. Emergence has been limited to a few areas of southwestern Manitoba and southern Alberta.
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Canola Council of Canada agronomist David Blais, who farms in west-central Saskatchewan, said many producers who saw higher populations of flea beetles last fall treated with Helix Extra.
“But with this delay they shouldn’t get too complacent about what might be happening out there. The temperature is going to come up fast and we might see the plants come on in a wave, but so will the insects,” Blais said.
Flea beetles produce only a single generation each year on the Prairies. Young adults overwinter in leaf litter, tree rows, sloughs or other areas where soil trash is abundant.
Normally they emerge in April and early May, but the spring of 2004 has delayed their appearance.
In most seasons the first food sources for the insect are flixweed, volunteer canola and wild mustard. As canola seedlings appear, the beetles move to those preferred food sources.
Then they begin their breeding cycle and lay eggs in the soil. The mature generation dies off, usually late in June or early July.
Once hatched, the larvae feed on canola plant roots until they emerge in August to resume feeding on the now mature canola crop wherever it remains green.
Feeding takes place through the early fall until cold temperatures cause the flea beetles to hibernate.
Derwyn Hammond, a canola council agronomist in Portage la Prairie, Man., said “this spring, maybe more than most, farmers are going to need to scout those crops every day. The weather is really going to be a factor.
“The sooner you find out if you have a problem, the faster you’ll get control of it,” he said.
Agronomists suggest checking fields daily for the first 14 days after crop emergence. This year’s cold and delayed growth may extend that scouting period by a week because the seedlings are most vulnerable when smallest.
While damaged seedlings can lose half their leaves without significant impact to the plant or yields, Hammond said the decision to apply a foliar spray must be made “when you’re staring at 25 percent damage. By the time you spray a day or two later, you could have that 50 percent damage.”
Canola plants that lose all their leaves will die.
Moderate attacks of flea beetles, causing 25 percent leaf loss, may not have any impact on fall yields if the canola has good growing conditions after the insects depart.
Hot, dry weather that lowers plant populations or puts the seedlings under stress will result in greater plant damage and higher yield losses.
Blais said producers waiting to seed canola or those who have been delayed by weather should not scrimp on the seed.
“The more plants out there, the greater the number to share (among) a fixed number of insects.”
Delaying tillage or spraying summerfallow weeds and volunteer canola that have infestations of flea beetles may assist in control
Hartman said foliar spraying is always a last resort and should be applied to crops only where the damage is evident.
“If it is at the edges of the field, spray the areas affected,” he said.
Insecticides should be applied in warm, calm conditions when the insects are most active.
Agronomists suggest that more than one application may be necessary if nearby habitat is not also controlled.
