Plan to Reduce Grasshopper Risk

Brenda Frick, Ph.D., P.Ag.

The grasshopper forecast for the prairies indicates severe risk in many locations. Sound planning is the key to managing this grasshopper risk, especially on organic farms.

Knowing a few things about grasshoppers will help make the planning easier. First, grasshoppers aren't all bad. Grasshoppers are important in natural ecosystems, efficiently converting grass to a high protein feed; they are food for a variety of creatures from burrowing owls to coyotes. Of nearly 100 grasshopper species on the prairies, only four are considered serious pests. These four can be a problem because under ideal weather conditions, they can take advantage of the conditions we create, and breed and eat to excess (at least it seems excessive to us!).

This spring's grasshopper pests are hatching from eggs that were laid last fall. The females mainly chose stubble fields, alfalfa, pasture, marshes or roadside ditches to lay their eggs. Females generally don't lay eggs in areas without plants, such as clean summerfallow fields.

Some species hatch in the fall, and spend the winter as "nymphs", but these species are not a pest problem. The pest species all hatch in spring, and thus are very small (0.5 in) when they emerge. They develop only when temperatures in the soil around them are above 10°C. The warmer temperatures get, the more quickly the little hoppers develop.

When the small grasshoppers emerge, they must eat or they will die. Only after they have fed and grown, are they able to travel to distant fields. This makes their first few days critical.

How can a producer take advantage of this vulnerability? There are both short and long term options. In the short term, spring tillage can be helpful, to eliminate weeds and volunteers that are the food source as grasshoppers hatch. Tillage in "hot spots" can be used to bury eggs and nymphs deep enough to prevent their emergence.

Crop rotation is crucial. As most hoppers will emerge from stubble, crops seeded on stubble are most at risk. If the grasshopper risk in your area is severe, it would be wise to seed something grasshoppers don't like on these areas. Possibilities include chickpea, field pea, mustard, oat or B. rapa canola. On clean summerfallow, cereals might be considered. Lentil seems to be particularly vulnerable, and might be considered only if the risk is low and other precautions are undertaken.

Barrier or guard strips of up to 30 ft can be seeded around high value, higher risk crops. These strips might include the non-preferred crops: chickpea, oat, mustard, field pea. The idea would be to discourage grasshoppers from crossing through the crop they dislike to get to the crop they do like, something like hiding the dessert table behind the salad bar.

If grasshoppers emerge in ditches near crops, the crops can be protected by a barrier strip of up to 30 ft of tilled land. This can be effective at stopping the very young grasshoppers from feeding in the strip, and thus reaching the main part of the field. Older grasshoppers are more likely to cross a tilled strip, so seeding the strip to field pea or some other less preferred crop, later in the spring is recommended to keep the strip undesirable to grasshoppers.

Early seeding is recommended in high risk grasshopper areas. Crops that are seeded earlier, and therefore are larger when grasshoppers arrive to feed, are more able to survive the damage. Older crops will also be less attractive to migrating grasshoppers later in the season.

For some producers, crop insurance will be part of the risk management plan. Crop insurance requires that all producers, whether organic or conventional, attempt to reduce risk from grasshoppers through management practices. Therefore, it may be helpful to discuss your management plan with your local crop insurance office this spring, to avoid problems later.

In the long term, rotations are especially important. A diverse mix of crops, weeds, shelterbelts, and natural areas on the farm, will increase the diversity of insects found on the farm. This diversity may include some important predators or pests of grasshoppers that are causing cropping problems. Dan Johnson, entomologist and ecologist at the Agriculture and Agri-Food Research Station at Lethbridge, says that "after the direct effects of weather on reproduction, growth and survival, the grasshoppers' natural enemies are the most important factor in controlling grasshopper populations. Weather affects insects like grasshoppers gradually, and also through extreme events. Natural enemies of grasshoppers are widespread, and with the right conditions they can be effective in the hastening the decline of grasshopper populations."

Grasshoppers are another reminder that nature works in cycles. In hot dry years, the grasshoppers can get ahead of their enemies. In cool wet years, the natural predators and parasites will get the better of the grasshoppers. Our extensive cereal cropping feeds the population booms in grasshopper cycles. By increasing biodiversity, by maintaining natural areas, expanding crop rotations and through relaxed weed control, perhaps we can help foster the balance in the systems that sustain us.

For more information, see Grasshopper Management, March 2003, AGRI-FACTS Agdex 622-27, Alberta Agriculture, Food and Rural Development. AND Understanding Premiums & Causes of Loss, Agriculture and Agri-Food Canada and Saskatchewan Crop Insurance Corporation.

Grasshopper forecast maps can be viewed at the following websites:
http://www.gov.mb.ca/agriculture/crops/insects/forecast/
grasshopper_map.html
http://www.agr.gov.sk.ca/
http://www.agric.gov.ab.ca/app21/rtw/index.jsp

Brenda Frick, Ph.D., P.Ag., is the Prairie Coordinator for the Organic Agriculture Centre of Canada and is located at the University of Saskatchewan. She welcomes your comments at 306-966-4975 or via email brenda.frick@usask.ca

Click here for futher information about grasshoppers

This article first appeared in The Western Producer, and is published here on the OACC website with permission.