Organic methods for tackling grasshoppers – Organic Matters

Organic farmer columnist Ian Cushon is taking the summer off from writing to concentrate on production, house construction and his growing family. He will return to this space in the fall, with topics including his experience this season in organic direct seeding. Brenda Frick, prairie co-ordinator of the Organic Agriculture Centre of Canada, is filling in through the summer.

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

Knowing a few things about grasshoppers will make planning easier. First, grasshoppers aren’t all bad. They are important in natural ecosystems, efficiently converting grass to a high protein feed 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 environment we create, and breed and eat to excess.

This spring’s grasshopper pests are hatching from eggs that were laid last fall. The females mainly chose stubble fields, alfalfa, pasture, marshes and 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 pests. The pest species all hatch in the spring, and thus are tiny – about one centimetre – when they emerge. They develop only when soil temperature is above 10 C. The warmer it gets, the more quickly they develop.

When the small grasshoppers emerge, they must eat or 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 short- and long-term options. In the short term, spring tillage can eliminate weeds and volunteers that are grasshoppers’ food source as they hatch. Tillage in “hot spots” can also bury eggs and nymphs deep enough to prevent their emergence.

Crop rotation is crucial. Because 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, such as chickpeas, field peas, mustard, oats and B. rapa (Polish) canola.

Cereals might be considered on clean summerfallow. Lentils are particularly vulnerable, and should be considered only if the risk is low and other precautions are taken.

Barrier or guard strips of up to nine metres can be seeded around high-value, higher-risk crops. These strips might include the non-preferred crops. Barrier strips 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 nine m of tilled land. This can be effective in stopping young grasshoppers because they will have nothing to eat and will find it hard to reach the main part of the field. Older grasshoppers are more likely to cross a tilled strip, so seeding the strip to field peas 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. Early-seeded crops are larger by the time grasshoppers arrive to feed and 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. It may be helpful to discuss your management plan with your crop insurance office this spring, to avoid problems later.

In the long term, rotations are especially important. A diverse mix of crops, weeds, shelterbelt and natural areas will increase the diversity of insects found on a farm. This diversity may include important predators or pests of problem grasshoppers. Dan Johnson, entomologist and ecologist at the Agriculture Canada research centre in 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 hastening the decline of grasshopper populations.”

Grasshoppers are a reminder that nature works in cycles. In hot dry years, they can get ahead of their enemies. In cool wet years, natural predators and parasites will get the better of them. Our extensive cereal cropping feeds the population booms in grasshopper cycles.

By increasing biodiversity, maintaining natural areas, expanding crop rotations and relaxing weed control, perhaps we can

help foster the balance in the systems that sustain us.

Frick is the Prairie co-ordinator for the Organic Agriculture Centre of Canada located at the University of Saskatchewan. Frick can be reached

at 306-966-4975, at brenda.frick@usask.ca, or www.organicagcentre.ca.The opinions expressed in this column are not necessarily those of The Western Producer.

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