Overview
Bertha armyworm (Mamestra configurata) is one of the most significant insect pests of canola in Canada. The pest occurs throughout Manitoba, Saskatchewan, Alberta and the interior of British Columbia.
Severe infestations can occur throughout most of this area, but are usually (but not always) limited to the Parkland area of the Prairies and the Peace River region of British Columbia and Alberta.
Background
Bertha armyworm is native to North America and belongs to a group of insects referred to as "climbing cutworms." Also included in this group are the true armyworm and variegated cutworm.
In most years, populations are kept low by unfavourable weather conditions such as cold winters and cool, wet weather as well as by parasites, predators and diseases. However, when these natural regulators fail, populations can increase dramatically, creating the potential for widespread damage to a variety of broad-leaved crops.
In extreme situations, infestations of more than 1,000 larvae per square metre have been reported while densities of 50 to 200 larvae per square metre may be common.
Infestations may be localized or spread over millions of acres. Widespread crop losses can be minimized with insecticides if the infestation is detected early. However, failure to detect infestations early may result in insufficient time to apply the chemicals before severe damage is done. Also, there may be temporary insecticide shortages if suppliers are not aware of the potential outbreak.
Monitoring programs are now in place to help forecast outbreaks and to act as an early warning signal for farmers, crop scouts and industry.
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