SOUTHPORT, Man. – An abundance of potato leafhoppers in Manitoba’s dry bean and soybean crops last year left growers wondering whether they would face a similar threat this year.
However, provincial entomologist John Gavloski told growers last week there is no way of knowing what to expect this year.
He said potato leafhoppers overwinter in U.S. states around the Gulf of Mexico and rely on wind to carry them north into Manitoba during the growing season.
Some years the wind is more co-operative than others.
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“They won’t be an annual threat,” he said during the Manitoba Bean Symposium in Southport.
“They will be hit and miss from year to year.”
Potato leafhoppers like to eat dry beans, soybeans, potatoes, alfalfa, clover and about 200 other plants.
They can arrive in Manitoba anytime during June, but Gavloski said early arrival is worse because host plants are immature and less able to withstand damage.
“Those will be your problem years, and luckily they don’t happen often.”
Adults and nymphs suck sap out of the leaves of host plants. They also inject a saliva, which is what damages the plants.
Damaged leaves of dry beans can turn from green to yellow to reddish brown. The damage can stunt plants or kill them.
However, producers who notice those symptoms should not automatically assume potato leafhoppers are to blame. Gavloski said other possible causes could be herbicide injury, a nutrient deficiency or drought stress.
“You have to play detective and figure out what is causing the problem.”
One strategy is to seed early, he said, so that the plants are bigger by the time the leafhoppers are most likely to arrive.
In years when the insect is present in counts high enough to cause concern, growers need to remember that nymphs cause more damage than adults, so they should not be overlooked when scouting to determine whether spraying is warranted.
The nymphs have a peculiar habit of running sideways to escape trouble, Gavloski said.
When danger approaches, they will try to run to the underside of the leaves, so growers need to check both sides of the leaves when scouting.
