Why is it important to conserve beneficial insects? When is it time to “pull the trigger” on an insecticide application, and how does choice of insecticide influence populations of beneficial insects?
John Gavloski, provincial entomologist at Manitoba Agriculture and Resource Development, says that to farm most economically and efficiently, the way insects are viewed and reacted to is very important.
Sure there are pest species that at high enough levels will do damage to a crop but, “at any given farm, there will be a myriad of insects that contribute to the profit of the farm through services such as predation, parasitism, decomposition, pollination, and some actually consume weed seeds — ground beetles do a very good job that way,” says Gavloski.
When it comes to spraying, and helping to protect beneficials, Gavloski says that the damage the pest insect would cause to the crop needs to outweigh the cost of controlling that insect — the expected value of crop loss equalling the cost of management is called the economic injury level.
For example soybean aphids can be viewed as an economic problem in some years, but it takes a very high population for it to be damaging. The economic injury level is 670 aphids per plant, explains Gavloski, but because aphid populations can increase rapidly, and the beneficial insect might not control them adequately, the economic threshold is actually set at 250 aphids per plant.
The main message is that it’s important not to panic when the pest insect is there, and is below the economic threshold.
In this episode of the Pests & Predators podcast, Gavloski explains how the miniature labour force of beneficial insects out there can help increase profit on-farm, how to make the most of this valuable resource, and much more.