Q: Are all grasshoppers crop pests?
A: In Canada, there are approximately 200 different species of grasshoppers. Of these 200 species, more than 85 are found in fields and pastures on the Prairies. With so many species, it can be difficult to know which ones to be concerned about.
On the Prairies, there are four species that are economically damaging to crops. The first three are the migratory grasshopper (Melanoplus sanguinipies), Packard’s grasshopper (Melanoplus packardii) and the two-striped grasshopper (Melanoplus bivittatus). These three species are part of the spur-throated grasshopper classification that can be identified by the presence of a knob between their front legs.
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The fourth species is the clear-winged grasshopper (Camnula pellucida), which has brightly coloured hind wings in the adult grasshopper and is part of the band-winged grasshopper group. Sometimes this species can be confused with leafhopper species, which can also have clear wings and be similar in size to smaller grasshoppers. Outside of these four, the majority of grasshopper species in Western Canada will not cause economic damage to crops.
All four species of concern listed above overwinter as eggs in the soil. Eggs are laid in the soil by females from mid-July until freeze-up. Grasshoppers need soil temperatures of at least 15 C for approximately 200 hours in the fall and/or spring to hatch. In normal years, this means most eggs will hatch at the end of May or early June. Newly hatched grasshoppers are referred to as nymphs and go through five instar stages before molting and becoming adults. Nymphs (three to five millimetres in length) are miniature versions of adult grasshoppers without developed wings, so they are less mobile and unable to fly. Control at this stage is key as nymphs are less able to escape from insecticide applications. Adult and older nymph stages (three to five instar) will feed on green biomass, resulting in more potential yield losses.
A grasshopper will take 35 to 50 days to mature to an adult, with the length of time affected by environmental conditions.
A good first step to identify grasshopper species is by using a sweep net tool. Economic thresholds for grasshoppers can be determined by using the metre-square method. For a metre-square count, find an area in the interior of the field that is approximately one square metre. Count the number of grasshoppers that jump or fly from that square metre as you walk toward the area. Complete this in four to five areas and take an average of the counts. Field edges can be assessed to determine if adult populations are moving into a field. Monitoring should be ongoing throughout the season from June to September particularly when populations are high. Economic thresholds for grasshoppers for different crops are available to determine when control measures are needed.
– Erin Campbell, PAg, CCA, is a manager of agronomic solutions in northwestern Saskatchewan for Nutrien Ag Solutions.
