Pest management today is about more than just a blanket application of chemical insecticides. It’s an integrated approach of mechanical, biological and chemical controls, as well as establishing thresholds and monitoring insect populations. “Our objective is to find alternatives to manage insect pests using more environmentally friendly ways instead of relying completely on insecticides,” says Héctor Crcamo, a research scientist at the Lethbridge Research Centre.
For Crcamo, integrated pest management is the foundation of his research. He says such strategies help reduce the amount of insecticide needed and the risk to crop production systems.
“Integrated pest management requires a lot more knowledge about the basic biology and life cycle of the pest so you can identify weak links,” says Crcamo.
He says it goes beyond monitoring to follow economic thresholds – that is, we need to learn what tolerance the plant has for the insect pest, what density of pests reduces yield and whether
“Our objective is to find alternatives to manage insect pests using more environmentally friendly ways instead of relying completely on insecticides.”
that loss in yield is worth the cost of insecticides to spray. When crop prices are high, for instance, it could “pay to spray.” When prices drop, a small loss in yield might be worth the cost of insecticides.
One area of integrated pest management that Crcamo and other researchers have been looking at as an alternative to insecticides is host plant resistance. For example, to reduce the impact of wheat stem sawfly, researchers have developed solid-stem wheat varieties to block larval movement within the stem, such as AC Lillian.
Crcamo says there is concern that solid-stem lines have lower yields but research at Lethbridge shows that solid-stem wheat out-yields even the best hollow-stem wheat when grown in sawfly-affected areas. Solid-stem varieties are considered tolerant rather than resistant, since some sawfly may still survive and cause cutting damage. Crcamo says research has also shown that female sawfly that emerge from solid-stem wheat are smaller and lay fewer eggs than sawfly that emerge from hollow-stem wheat.
Another example of host plant resistance is a trait developed for wheat that makes the kernel toxic to wheat midge larvae. The problem, though, is that kind of trait has the potential to allow the development of resistance in the insect, says Crcamo. So, for the first time, a mixture of lines (90 per cent resistant and 10 per cent vulnerable) is being allowed. The idea, says Crcamo, is to allow some of the wheat midge from vulnerable lines to mate with adults from the resistant lines to prevent complete resistance.
Good bugs, bad bugs
Conservation biocontrol is another alternative method to insecticides. The main focus here is on promoting beneficial insects that eat target pests. Researchers are exploring options for the pea leaf weevil, a relatively new insect pest in Alberta that feeds on the roots (larvae) and leaves (adults) of cultivated and wild legume species. In southern Alberta peas are the major crop at risk of economically significant damage. While conservation biocontrol emphasizes using native natural enemies, the pea leaf weevil has no natural enemies, or egg parasitoids, in Alberta, as it has in Europe.
Crcamo says the pea leaf weevil represents a concern for field pea and faba bean growers in the area, as some commercial field trials report losses of one to two bushes per acre. The adults feeding on foliage is not the issue but rather the larvae laying eggs at the base of the plant, which in turn feed on the nodules and destroy the bacteria that fixes nitrogen.
Lethbridge Research Centre is working with the Southern Applied Research Association in a crop trapping study, where winter peas are planted around the perimeter of a field of peas, so as to concentrate the weevils along the border and reduce the spraying required.
Crcamo and his team are also considering an agronomic approach to integrated pest management that involves planting flowers around a cereal crop to provide nectar and pollen for the parasitoids of certain crop pests. He says he’d like to experiment with buckwheat this year, since it flowers early and for the entire summer, although actually implementation by producers may be a challenge.