Insect – agronomic interactions in canola integrated pest management

Much previous research in pest management in canola has focused on developing strategies for reducing infestation levels of single pest species (e.g., bertha armyworm), or individual pest groups (e.g., insects) without regard to possible detrimental effects of these control strategies on other pests. The aim of our research has been to integrate insect management strategies with agronomic practices to ensure that control recommendations are compatible among different pest groups and lead to integrated crop management. Field studies were undertaken in Alberta, Canada, to determine the effects of fertility regime, crop cultivar, time of weed removal, seeding date, and seeding rate on seed yields and infestations of insects and weeds. Increasing soil fertility resulted in improved canola seed yields, but produced plants with larger root systems that made them more vulnerable to attack by root maggots (Delia radicum (L.)). Altering seeding date from ‘normal’ spring planting times to fall or early spring seeding had no effect on root maggot infestations. Nevertheless, the higher seed yields derived from early seeding more than compensated for insect feeding damage. Delaying weed removal from the twoto the six-leaf stages of canola development increased interspecific plant competition and depressed yields, but root maggot damage declined when weeds were removed later. Some canola cultivars were less susceptible to yield losses from insect pest attack than others, presumably because they could better compensate for herbivory. To date, we have identified several practices that are effective against multiple pests, or at least are effective toward one and without impact on others. Such research will serve as an important foundation toward integrated crop management in canola.