What’s up with grasshoppers in the 2024 growing season?

Many Alberta farms experienced significant grasshopper damage in 2023. The most severe damage occurred at the south and eastern borders of the province, along with the south and central portions of the Peace Region. With such high grasshopper pressure last year, it poises several questions for 2024 including what is the forecasted trend of grasshoppers in 2024 and how can growers best manage grasshoppers this upcoming growing season?

In the south and eastern border regions of Alberta, we have seen a buildup of grasshopper population since 2021. In 2023, due to warm and dry spring, the hatching and development of grasshoppers were around two weeks ahead of average. Feeding on the crop started earlier, causing more severe damage. By the end of the season, an open fall provided adults with longer periods to lay eggs.

Looking ahead, if the mild winter persists and leads into a warm spring, grasshoppers are again likely to hatch early. This may, once again, lead to significant pressure, especially in areas with that saw high populations in 2023.

If this occurs, what can be done to mitigate grasshopper damage?

Scouting is the key to monitoring grasshopper risks. The eggs start to develop when soil temperature reaches 10C, so start scouting in early May to mid- June. Growers should pay special attention to the fields that had high populations the previous year.

Additionally, grasshoppers tend to lay eggs near areas of green growth in the fall, such as field margins, roadsides and fence lines. Scouting these areas can give early indications of potential problems.

Grasshopper scouting techniques are described by the monitoring protocol on the Prairie Pest Monitoring Network blog. Measure a 50m by 1m strip across a field, count the total number of grasshoppers in that strip, then divide the total count by 50. This will give you the number of grasshoppers found per square meter. Be sure to check multiple locations in the field. Remember, field boundaries can sometimes be much worse than interior field areas.

In addition to counting, take note of grasshopper species while scouting is also beneficial. Only five out of 85 grasshopper species in Alberta are considered pests. The major pest species found in Alberta include migratory, Packard’s and two-striped grasshoppers. More information on species identification can be found in the Grasshopper Identification & Control Methods booklet (visit bit.ly/3Vs3kHr), developed by the University of Lethbridge.

Integrated management measures can reduce the risks of grasshopper damage. Cultural practices include weed control, trap strips and early seeding. Weed control can reduce egg laying in the fall and hatchling survival in the spring. Trap strips planted on the edge of the field attract grasshoppers to concentrate in narrow zones. They can then be monitored and managed with insecticides within the trap strips, rather than the whole field. Seeding early helps the crops to be established earlier. Older plants that are growing vigorously can withstand more grasshopper feeding than younger plants. It helps to reduce the amount of crop damage and allows time to arrange for other control measures.

If chemical control is needed, grasshoppers are easier to control when they are in earlier stages, before reaching half an inch in length. To be proactive, one can monitor and treat field edges before grasshoppers move to the whole field. The threshold in the field is 6-12 grasshoppers per sq. metre. Thresholds are on the lower side if conditions favour grasshopper development.

For example, in hot and dry weather, grasshoppers develop faster and cause more damage, so the threshold for control is lower. The same goes for crop species. For crops that are preferred by grasshoppers, such as wheat and lentils, the threshold is lower than for non-preferred species like oats or peas. When the population is over the threshold, a control measure may be required. Growers should be sure to follow pesticide labels for best efficiency and safety. If more than one spray is needed, always ensure rotation of chemical groups based on label recommendations to discourage resistance development.

Overall, grasshoppers might pose considerable risks to the 2024 growing season, especially if the conditions are hot and dry. Early scouting will be key to monitoring the population and making management decisions. In addition to scouting, use resources such as Prairie Pest Monitoring Network to keep track of the overall trend and timely management tips. When control is needed, integrating cultural management with the use of insecticides can make the control more effective.

References

Overview: Government of Alberta grasshopper management 

Survey and maps: Government of Alberta grasshopper forecast

Outlook: 2023 Western Canadian grasshopper populations and prospects for 2024

Monitoring protocol: Monitoring Protocol for Grasshoppers

Thresholds and scouting tips: Canola Watch

Grasshopper identification & control: Grasshopper identification & control methods to protect crops and the environment