Everything I wish I Knew about Biocontrol and Did Not Ask
I hear from clients daily, “these pesticides are just not working like they used too”. It is true, pesticides are not working as well any more. Even when the pesticides were working well, not all the pests were killed even with good coverage and there were dead bugs on the leaves. The surviving pests continued to survive in the pesticide environment and increased their populations. Chemical resistance in pests has been know for years, if not decades. The resistance situation is the driving force for growers to change to using biological pest control (BPC). It not likely that a pest will find a way not to been 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 predator.
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 (reference). 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 at the beginning. Once a crop has been sprayed with a pesticide there is a waiting period before beneficial can be used. The time can be as short as a few weeks or up to months. During this time, your pests that are resistant will explode as you wait. Start with bugs and not sprays.
Your stock plants or seedling should be managed by BPC so that each cutting will enter the growing cycle without pesticides and some beneficials already established. N. fallacis with pesticides 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 out side the pest box and use trap plants. Trap plants can be used to lure pests from your crop. Pest do have strong preferences for certain plants. Beans are usually more attractive than any other crop for spider mites. Bean 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. 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, if the pesticides are not working, stop using them. Pesticides do not work in biological programs. There is better way to manages your pests and means understanding how beneficial insects fit into you crop. Start your crop off crop of clean and with plan for when the pests to come. Think beyond the sticky cards for monitoring pests and look at using trap plants or banker plants.
