by Dan Johnson
The Canadian Prairies grassland and farmland are home to more than 80 different species of grasshoppers. Some of them (around 10 of these) may cause severe damage to emerging crops, in years with warm, dry springs that follow warm summers the year before.
Not all grasshopper species are considered pests, and some of the types that are seen earliest in spring have an unusual life cycle, feed on native plants, and rarely reach significant numbers. The early species that appear in March to mid-May have no impact on agriculture, but do serve as food for wild birds. Their timing and numbers do not forecast pest species later.
With more effort to make farming science-based, and with crop production margins getting tighter, learning to identify the type of grasshoppers is worth while. Reducing unnecessary pesticide applications also reduces the potential for harmful impacts on the environment, including natural enemies that can help to hold down insect pests.
The booklet, Grasshopper Identification and Control Measures, published by Agriculture and Agri-Food Canada and Saskatchewan Pulse Growers includes some basic rules of thumb concerning early grasshoppers:
- Small hoppers appearing in March or April (even early May) in Canada are not pests.
- Any grasshopper flying before June 1 is not a pest.
- Crop pest grasshoppers hatch in late May and early June, are brown or black, and always have tiny triangular wing buds, not large wings that can be folded back when examined closely.
- Any grasshopper with coloured hindwings (under the forewings that serve as covers) visible in flight is not a pest.
- Any grasshopper that sings, calls, clacks, clatters, or makes any other song is not a pest.
- Grasshoppers that inhabit a crop on a warm day without feeding on the vegetation may be a temporary resident that is moving to more preferred vegetation, and may not eat crops at all.
- Grasshoppers that remain in rangeland, headlands, or other grassland without moving into crops are likely to be species that do not damage crops. This is common with many types, although a few may move back and forth, and do easy-to-see damage.
The most common spring species this year in Alberta and nearby are usually found already hopping around on warm days after the snow melt begins. A few overwinter in active stages, and one species hatches months earlier than pest grasshoppers, and can cause confusion during surveys early in the spring. The hatching grasshoppers that may damage pulse crops, forages and cereals (such as the two-striped grasshopper) can be distinguished because they are small when hatching (around 1/8th inch, 2 to 3 mm, in late May and early June), and tan, black or brown. Many overwintering grasshoppers are silver, green or rust-coloured, and much larger.
Pest grasshoppers to watch for during June and July
About 10 can cause some damage, but five or these are the most common, and lately two have been the most common grasshopper pests in the Canadian prairies. These are the two-striped grasshopper and the clear-winged grasshopper. Both of these can occur in large numbers, and tend to eat crops down to the ground around the edge of the field or other choice spots. If a forecast predicts high densities in an area, it may be prudent to check fields in late May and early June. Forecasts typically indicate the abundance of grasshopper observed during the previous August, for example, 2-4 per square meter. This does not represent the expected hatching abundance in early spring. An adult female grasshopper can easily lay over 100 eggs (50+ per pod), and the potential number that hatch the following spring depends in part on weather and survival. the two-striped is a tiny tan hopper at first, and the youngest stages of the clear-winged grasshopper are black with a white stripe.
Remember that the two-striped grasshopper feeds on a wide range of grassy and broadleaf plants, and the clear-winged grasshopper is mainly restricted to cereal crops and grass. They both overwinter as eggs and hatch in time to grow in June, so the date can help to separate them from the harmless species that overwinter and emerge in April and early May. In the last decade, the lesser migratory grasshopper and Packard’s grasshopper ranked a distant third and fourth in pest status, although they were bigger problems in past outbreaks.
The on-line booklet discusses these key early spring grasshoppers:
- club-horned grasshopper (Aeropedellus clavatus),
- velvet-striped grasshopper (Eritettix simplex tricarinatus)
- brown-spotted range grasshopper (Psoloessa delicatula)
- dark brown or charcoal-colored grasshopper called the speckled rangeland grasshopper (Arphia conspersa).
- northern green-striped grasshopper (Chortophaga viridifasciata)
- red-shanked grasshopper (Xanthippus corallipes latefasciatus)