Environmental conditions this year are certainly conducive to grasshopper population growth, and some areas of the Prairies are finding this pest a major cause for concern.
Dr. James Tansey, provincial entomologist for Saskatchewan Ministry of Agriculture, joins host Shaun Haney in this episode of the Pests & Predators Podcast, to chat about the common species of grasshoppers that do cause damage, the conditions they prefer, and how to get ahead of them this year.
“In Western Canada, we’ve got 85 species of grasshopper,” says Tansey, but typically only four are going to be pests on the Prairies: clearwing, migratory, Packard’s and two-striped grasshopper. These common pest species all overwinter as eggs, and won’t be present as adults until mid-July to August. Currently, Tansey says there are some populations of clearwing grasshoppers that have emerged early in Saskatchewan.
Typically, dry conditions contribute to population increases, says Tansey, and although there are differences in preferences between pest species for moisture, as a general rule, they all do well in drought. Migratory, Packard’s, and two-striped grasshoppers are broad generalists and will attack the majority of crops. Clearwing grasshoppers tend to prefer cereal crops and other grasses, and occasionally flax. (Story continues below video)
Late instar nymphs and adults emerge around mid-July to early August and start feeding. The recommended method for scouting is to look at a 50 metre section, either in a field or in the ditch next to the field says Tansey. Walk for a metre and try to count the grasshoppers in the peripheral that get stirred up. Having a clicker counter or a piece of paper is handy for this step because after walking the 50 metre-increments, divide by 50 and that’ll be the square metre count.
In mid-summer, when temperatures get hot and the humidity is higher, grasshoppers are susceptible to a fungal pathogen. There are different lines that affect different species of grasshopper. The fungus causes the grasshopper to climb to the top of a plant, grab on tight, and then die there, causing fungal spores to fall on other grasshoppers.
There are a lot of vertebrates that love to eat grasshoppers, including burrowing owls and garter snakes, and Tansey says there are also arthropod predators such as robber flies, that will snatch grasshoppers out of the air. There’s also a wasp that will dig burrows and purposely sting grasshoppers, in order to lay eggs on them in their burrows. Carabid beetles and wolf spiders are also important predators of grasshoppers.
Tansey says that when it comes to control, don’t spray unless it’s necessary and the population is at the economic threshold. There are a lot of registered products for different crops to control grasshoppers, and some of these contain ingredients that will affect beneficial populations.
Finally, Tansey says it’s a good idea to keep an eye on the size of grasshoppers by mid-July — if they’re over a half inch, and the population is as high as 10 to 12 per square meter, for most crops, it’s time to take action.