AgricultureNewsProvincial

Grasshopper Damage

By Ashley Willms, PAg, Crops Extension Specialist, Humboldt

There are about 180 grasshopper species in Canada, and 85 of those are found in Saskatchewan. Of the 85 species, only four, sometimes five in northern Saskatchewan, are considered pests. It’s important to be able to identify these species so proper management can be done while avoiding harming beneficial insects or misusing pesticides.

The four pest grasshopper species in Saskatchewan include:

  1. Migratory grasshopper: Adults can be identified by two prominent black bands on their hind legs. They are omnivores and prefer forbs, grasses, wheat, barley and other crops. They will also scavenge on dead insects, ground litter, dried manure and in an outbreak may also consume trees or ornamental plants.
  2. Packard’s grasshopper: One of the largest grasshoppers in Saskatchewan. Distinguishing characteristics include two light-coloured stripes that extend from just behind the eyes to the end of the thorax and the last two leg segments are a blue-green colour. They prefer legumes in open habitats with light textured soils but will also feed on other crops.
  3. Two-stripe grasshopper: Has two pale stripes extending back from the eyes to the tip of the forewings. This grasshopper prefers lush vegetation in lush habitats with heavy textured soils, specifically in sloughs and ditches. They will feed on a wide range of broad-leaf crops (often alfalfa), cereals and grasses.
  4. Clear-winged grasshopper: Yellowish to brownish with mottled dark patches on the wings. They also have two stripes beginning at the thorax and converging at the tip of the forewings. Clear-winged grasshoppers prefer grass and rangeland areas and will feed on grasses and cereal grains. Broad-leaf plants are usually avoided.

Note that economic threshold may vary depending on conditions. Weather conditions, current market value of crop, input costs, crop stage etc. may influence your decision to spray from year to year. Grasshoppers in the third to fifth nymphal stage is when the most serious economic damage begins. Adults are also very damaging and highly mobile. Considering this, the economic threshold in cereals ranges from 8-12 grasshoppers per square meter.

Cultural Control

Early seeding can assist with withstanding feeding pressure as actively growing plants are more resilient than young seedlings.

Trap strips are a cultural control method that allows for a separate perimeter crop around the field that is more attractive to the grasshoppers than the main crop. A cultivated gap is worked on the outer edge of the field as well as between the perimeter and the main field, creating a ring of crop around the field edge. The goal is to have the grasshopper population be in a more localized area so that minimum insecticide use is required. For detailed instructions on how to create a trap strip, read about Grasshopper Overview, Control Methods and Economic Thresholds.

Weather – Will rain reduce populations?

Areas of the province that already have higher populations of grasshoppers may wonder how rain may help their situation. A downpour of rain may result in drowning some small nymphs but will not solve the problem altogether. However, high-humidity conditions contribute to increased fungal infections that help regulate grasshopper populations. They include Entomopthora grylliMetarhizium, and Beauveria bassianaEntomopthora fungi attacks the grasshoppers through the cuticle and colonizes in the main body cavity. If toxins are produced, the grasshopper dies quickly, or else a slow death occurs from nutrient depletion or organ damage.

For more information on grasshoppers and control measures, please contact your local crops extension specialist or the Agriculture Knowledge Centre at 1-866-457-2377.

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