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Everything I Wish I Knew about Biocontrol … but Did Not Ask

Oct. 31, 2017 - I hear from clients daily, “these pesticides are just not working like they used to.”
It is true, pesticides are not working as well any more. Even when the pesticides were working well, not all the pests were killed despite good coverage and dead bugs on the leaves.

October 31, 2017  By Stacey Hicks

The surviving pests continued to survive in the pesticide environment and increased their populations.

Chemical resistance in pests has been known for years, if not decades. The resistance situation is the driving force for growers to change to using biological pest control (BPC). It’s not likely that a pest will find a way to avoid being eaten by a good bug. The use of beneficial insects in the long run can be cheaper and more effective than pesticides. Using good bugs is not an easy path and it requires monitoring and patience as balance is achieved between pests and predators.

If you are having trouble getting off the spray treadmill, think about using just water. Water will wash away some of chemical residual and also reduce plant stress. A stressed plant will attract more pests. In the case of spider mites, a stressed plant is a welcome sign for an easy meal. Plants can be stressed in many ways, such as by pesticide residuals and improper watering.

To help growers move between a pesticide program and beneficial insects (BPC) there are a few insects that can be used right away to ease the transition. Consider Neoseiulus fallacis, which is a generalist predatory mite that is resistant to organophosphates and pyrethroids. N. fallacis has a strong preference to tetranychid mites such as two-spotted spider mite, Tetranychus urticae.


The soil mites Stratiolaelaps scimitus and Gaelaelaps gillespiei can provide control for fungus gnats, thrips pupae and sciriade flies at the soil level. These mites are protected somewhat from foliar applications of pesticides and residuals.

The best advice I can give when dealing with beneficial insects is to start with them at the beginning. Once a crop has been sprayed with a pesticide there is a waiting period before beneficials can be used. The time can be as short as a few weeks or up to a few months. During this time, your pests that are resistant will explode as you wait. Start with bugs and not sprays.

Your stock plants or seedlings should be managed by BPC so that each cutting will enter the growing cycle without pesticides and with some beneficials already established. N. fallacis with pesticide resistance can establish on plants without pests by feeding on wind blown pollen. These predator mites will provide spider mite control when populations are low.

Think outside the pest box and use trap plants. Trap plants can be used to lure pests from your crop. Pests do have strong preferences for certain plants. Beans are usually more attractive than any other crop for spider mites. Beans can be grown in the crop and sacrificed as they become full of spider mites. Spider mite damage can be seen easily on the leaves of beans and in some cases can act as an early warning system to pest problems.

Some experienced growers use beans as banking systems for predatory mites. Banker plants can be thought of as mini breeding systems for beneficial insects.

These same bean plants can also attract whiteflies and thrips, again serving as the early warning flag of pests.

There are many things I wished I knew before starting with biocontrol. For example, if pesticides are not working, stop using them. Pesticides do not work in biological programs.

There is a better way to manage your pests and this means understanding how beneficial insects fit into your crop. Start your crop off clean and with plans for when pests do come. Think beyond the sticky cards for monitoring pests and look at using trap plants or banker plants.

Stacey Hicks is entomologist at Natural Insect Control in Streetsville, Ont. She has worked with Natural Insect Control as the lead greenhouse consultant for biological controls for the past 18 years. She has been on the cutting edge of biological controls and has worked closely with marijuana and cut flower growers in developing new and effective methods for biological control – always with an eye for maximizing yields while still staying away from harmful pesticides.

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