Most recommendations about pesticides include an economic threshold — if you have more than the specified number of pests per square metre, spraying could be an effective option for you. So before you can make your decision, you’re going to need to take a census.
At Saskatchewan Agriculture’s Crop Diagnostic School at Indian Head in July, Saskatchewan Agriculture’s provincial insect/vertebrate pest management specialist, Scott Hartley was on hand to give farmers and agrologists a live demonstration of taking an accurate insect count.
Three steps to counting hoppers
Hartley demonstrated a simple way to count grasshoppers.
Step 1: Step off a distance. If you use a yard stick at home to check how long a step you need to measure off one metre, you can easily step off a close-enough distance out in the field. A good distance to use is 25 metres (long enough for a representative sample, not so long you need to carry a compass and water bottle.)
Step 2: Once you’ve stepped out the distance, walk the length of the distance, counting every grasshopper you see in a one-metre strip right in front of you. Make sure you’re shuffling your feet, to scare up everything your path.
Until you’ve done this a few times and you’ve got the hang of the distance, you could carry a metre stick out into the field to make sure you’re counting in an accurate range.
Step 3: Divide the number you counted by the distance in metres (25 in this case) to get a count per square metre.
This method is fast and easy. It might not be scientifically accurate down to the last decimal point, but Hartley says, “It gives a pretty good indication.”
- More Grainews: Getting those grasshoppers
Six sweepnet tips
While you can spot grasshoppers visually, other insects are easier to count if you catch them in a net. Using a sweepnet to count the number of bugs in a certain area seems pretty straight forward. But here are some tips to help you get a closer count.
Tip 1: When you walk through the field, be sure to sweep the area 180 degrees in front of you.
Tip 2: Be strong. Hartley says you should use “a good firm sweep with a little flick at the end to shake everything down.”
Tip 3: Keep your net level, at about waist height. “You do not just want to go just over the top,” Hartley says. You might want to work out before scouting season, as pushing and pulling that net through at that height can be a bit of a test. “It isn’t always easy to keep it exactly at that level.”
Tip 4: Hang on. “You need a good, firm sweep,” Hartley says. “Or you’ll flip the net over.”
Tip 5: “Take it out of the field to bag it,” Hartley advises. Turn the net inside-out to put the contents directly into a plastic bag.
Tip 6: Having trouble getting a count on the bugs in the bag when they’re all moving around? Hartley has a solution for this. “Throw it in the freezer overnight. They become a lot more cooperative.”