Many Ontario growers may be noticing that insect pests this year are more abundant than usual. They may have also noticed that the last 12 months have been uncharacteristically warm and dry. Well, it turns out there may be a relationship between these two occurrences. 

National records indicate that last winter was the second driest and warmest in the last 65 years. Snowfall was also at a record low and spring-like weather came earlier than usual. 

Weather plays an important role in controlling insect populations. Cold winters with freezing temperatures and snowfall help reduce pest numbers during that part of the year. Generally, the insect populations start growing again when warm weather returns. 

However, if the winter is mild, then there will be more insects left over from last season when the population starts to expand again in the spring. 


Pests in fields, lawns and gardens

As the weather warms up, various insect populations begin to feed on agricultural, lawn and garden plants. These pests can include insects like aphids, the bean leaf beetle, moths and armyworms. Other pests, like fleas and ticks, present problems to farm animals, pets and humans.

The aphid is a very small insect that swarms around growing plants, which they can harm by feeding on the juices found in the plant’s soft new growth. Tick populations also rise with warmer weather and they play an important role in the spread of disease. Ticks like to dwell in the dark areas under vegetal growth and they are parasites that subsist on blood sucked from an animal host. 


Beneficial insect populations also benefit from warmth

Warmer than usual weather is not all bad news though. In addition to boosting the numbers of pest insects, the warm weather can also help with beneficial insects. These insects consume the pests and keep their populations in check. 

Growers can monitor their fields to see which populations are flourishing to gauge whether pests will likely be a major problem. For example, if populations of beneficial predator insects are high, then it is less likely that pests will flourish. Obviously, if the predator population is healthy, the grower may not want to employ insecticides as this could reverse a favorable situation. 

Lack of moisture can also inhibit insect populations in general since healthy rainfall creates conditions needed for insect breeding. Many pests, like mosquitoes, actually reproduce in the water or otherwise rely on moisture for breeding. 

Some insects cannot survive when environmental conditions are too dry. Since there has been record dryness over the past 12 months, this could help in keeping these specific population numbers down. The combination of heat and lack of moisture is especially harmful to tiny insects that rely more on ambient moisture. 


Diamond back moth affecting Ontario canola

The diamond back moth appears in Ontario canola fields periodically, and reports indicate that it is breeding this season in certain fields. Farmers are observing this activity closely because the larvae of the moth feed on the flower buds, leaves and pods of the canola plant. 

The moths come with storms from the United States in May and June, so it is difficult to get a handle on their numbers. The larvae can feed for 10 to 21 days during which time they can cause serious damage to canola plant flower buds and pods. They strip off the plant’s outer protective coating leaving it more vulnerable to disease and other problems. 


Controlling pests

Many insect pests have waxy exoskeletons that are vulnerable to a number of countermeasures. Natural insecticides like neem oil, soap and organic enzymes can break down the exoskeleton of these insects. 

Organic and natural farmers use methods that avoid artificial pesticides and meet regulations for specific product labeling. Another approach to controlling insect populations is to interfere with their breeding cycle. 

Introducing predator populations can also keep pests under control. The nematode, for example, is a popular beneficial predator that helps control a number of pests from fleas to white grubs. To inject nematodes into an area, the soil must be very moist. This will usually require watering for a few days. 

One popular way to introduce nematodes into a lawn or garden is to place them in a lawn sprayer to maximize moisture during deployment. 


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