Issue 1, April 28, 2022
Biological Control in Home Landscapes
I love just about every part of the summer except for the bugs. Flies and mosquitos are my least favorite. However, in the garden, there are several critters I could do without, such as tomato hornworm, aphids, and squash bugs, to name a few. Nevertheless, these insects have their place in an ecosystem and are someone else's food! How do we get the good predatory insects to control those pesky problematic pests? It takes going back to essential integrated pest management.
Integrated pest management utilizes cultural, biological, mechanical, or chemical controls against pests. Cultural controls include fertilization, plant variety and selection, soil pH, and watering. Mechanical controls are hand-pulling weeds or insects, pruning, or even mowing. Biological is using other insects, fungi, or bacteria to control pests. Chemical is the use of pesticides.
The definition of biological control is the control of a pest by the introduction of a natural enemy or predator. An advantage of this control measure is that it requires no chemicals. Introducing the predator will allow nature to take care of itself, and it also does not require much of our effort or time. There are also some disadvantages to consider. Introducing predators to an infested site is easy, but having them stick around to keep the pest population in check can be an issue. The predatory insects often move on after the food source is gone, so if a pest resurgence were to occur, the predators might not be there to take care of the pest. The other concern is that this is not a fast control option, and it will also not eliminate the pest.
Many predatory insects are also pollinators, which is lovely in that they survive on pests and pollen or nectar. There is a great need to protect and encourage pollinators into the landscape. A major preparatory step in landscapes is to have a diverse planting that accommodates predator populations. This will allow them to live in your landscape awaiting prey and encourage them to "stick around" since a food source is continually available. We can not say that creating this habitat for one will not eliminate the other since both prey and predator can exist within the same habitat. However, it does allow for a nice circle of life situation to occur.
Within IPM, scouting is critical to correctly identifying the problem pest. It will also allow us to identify if the predatory insect is already available or if we need to introduce a predator.
| Natural Enemies | Favored Prey Species |
|---|---|
| Green Lacewings | aphids |
| Lady beetles | aphids |
| Minute Pirate Bugs | aphids, scales, spider mites, thrips, small caterpillars and insect eggs |
| Chinese Mantid | Generalist feeder tend to eat larger insects like grasshoppers opposed to aphids |
| Assassin Bugs | Generalist feeders |
| Predatory mites | feed on eggs, nematodes and fly larvae |
| Spiders | generalist feeders |
| Velvet ants (mostly southern IL) | beetles, caterpillars, flies, bees and wasps, cockroaches |
| Parasitoid wasps | lay eggs on caterpillars, armyworms, cabbage loppers, hornworms |
Another way to attract natural enemies is to incorporate garden features to protect your predators. This includes cracks and crevices for them to hide. Mulch is a great way to provide a habitat for ground-dwelling predators, like spiders and soil-dwelling mites. Consider creating areas within the lawn/turf with these diverse plantings and structures. This will help create a balance of habitat for both the predator and prey.
| Examples of pollinator-friendly plants |
|---|
| Coneflower |
| Spiderwort |
| Aster |
| Iron weed |
| Bee Balm |
| Lupine |
| Liatris |
| Lobelia |
| Clover, sweet alyssum, thyme, daises |
Knowing that biological control will never eliminate the pest population, remember that IPM has other control options. If considered, chemical control is best to wait until May or June to make applications to avoid exposure to early season pollinators. Utilize granular formulations to fall to the ground and are not on flowering portions of plants. A cultural control practice should be selecting and planting species that are resistant to pests. The mechanical and cultural practice maintains a high mowing height for grass to promote deeper root systems that enhance the plants' ability to tolerate stress and injury from pests. Using an integrative approach can increase your success, reduce cost, and create an aesthetically pleasing landscape. Your yard will become a haven for pollinators and predatory insects, allowing you to enjoy the space in harmony.
Resources
https://academic.oup.com/jipm/article/8/1/18/3934663?login=false
Good Garden Bugs: Everything you need to know about about Predatory Beneficial Insects- Mary M. Gardiner
https://www.amazon.com/Good-Garden-Bugs-Everything-Beneficial/dp/1592539092
Author:
Maria Turner