2003 Grasshopper Forecast for Alberta and adjoining regions of Saskatchewan

Grasshopper surveys conducted at the end of the summer of 2002 at over 1,900 locations in Alberta indicate that grasshopper numbers remain high in much of east-central Alberta and west-central Saskatchewan, and will increase in numbers in some southern regions.  The extent and timing of dry weather during the last three years has been a benefit to crop-eating grasshoppers that require sunny weather to breed in the late summer, and warm, dry conditions during hatch and growth of the immature stages in June.  The unusually cold spring in 2002 delayed grasshopper hatching, especially in southern Alberta.  Most grasshoppers had not hatched before the heavy rainfall that began around June 10.  The delayed hatch after the rain resulted in grasshopper attaining adulthood late in the summer, and laying fewer eggs than would have been possible in a normal year.  A higher than normal proportion of the eggs that were laid did not achieve full embryonic development before frost in the fall.  This means that the hatch will cover a longer period in the spring, for example four weeks rather than three, in some areas.  If spring warming is more normal than in 2002, grasshoppers can be expected to hatch during the last week of May, continuing into June.  Grasshoppers should not be controlled until as many as possible hatch.  Grasshoppers should not be controlled if they are not severely damaging crops, because some non-pest species that do not attack crops also increased in 2002, relative to their previous low numbers (such as the Big-head grasshopper, the tiny spur-throated grasshopper, the Russian thistle grasshopper, the club-horned grasshopper, the white whiskers grasshopper, snapper grasshoppers, and others).  The two-striped grasshopper was dominant across southern and central Saskatchewan, and southern Alberta, and the clear-winged grasshopper was much more common in east-central Alberta (see photos and map).  The recent warm weather has no impact on the grasshopper situation, because the eggs are protected in the soil, and normally not affected by cold weather. 

In addition to the normal survey at 1,700 locations in Alberta, conducted by the Association of Alberta Agricultural Fieldmen, over 200 additional sites were surveyed in greater detail for research purposes, with additional observations on grasshopper species, development, disease and breeding activity.  The additional investigation, and assessment of weather conditions later in the winter, allows more precise forecast updates during the critical hatching period coming in late May.  Forecast and monitoring updates will be provided over the spring and summer.  The survey monitored 6 species of crops pests, 8 species of potential range pests, and 15 other grasshopper species. (The additional survey was made possible by funding from Alberta Agriculture, Food and Rural Development, and was supervised at the Lethbridge Research Centre.) 

Fence lines, roadsides, pastures, fields with a known problem in 2002, and crops grown on stubble must be watched closely when hatching begins in the spring.  Ignore grasshoppers seen early in the season with clubbed antennae, or with coloured wings.  In most crops, grasshopper infestation in excess of seven to ten grasshoppers per square metre will justify control measures, but only if damage is obvious and widespread in the crop or at least along the edge.  When using insecticides, take note of precautions regarding user safety, label requirements, pre-harvest waiting periods, and proximity to wildlife.  The objective is to economically protect the crop, and not to achieve 100% removal of grasshoppers. 

Forecast contacts: Dan Johnson, Research Scientist, Agriculture & Agni-Food Canada, Lethbridge.

Jim Calpas, IPM Specialist, Alberta Agriculture, Food and Rural Development, Edmonton.