Encouraging Beneficial Insects on your Farm
Posted: May 3, 2012
Lady beetles, syrphid fly larvae, and lacewing larvae eat soft-bodied pests like aphids and scale crawlers. Some parasitoid wasps lay eggs on aphids and the developing young wasps kill their aphid host. Minute pirate bugs eat thrips and aphids. These beneficial insects and others are part of the natural fauna of your farm.
Here is link to a great fact sheet from the University of Maine that shows what some of the most common beneficial insects look like -- http://umaine.edu/publications/7150e.
I recently heard Carol Glenister of (Integrated Pest Management) IPM Laboratories talk about "Guardian" plants and how they can be used to enhance beneficial insect populations. This article summarizes some of the things I learned from her.
Many people are interested in having populations of beneficial insects inhabit their fields, high tunnels and greenhouses. One strategy is to purchase beneficial insects from a commercial supplier and release them. This is known as augmentation, and can be an effective way to manage pests. Keys to successful augmentation include properly identifying the pest, choosing a beneficial that is proven to be effective, having an adequate ratio of prey to beneficial, and following all the directions carefully. Even if you do all these things exactly right, there are no guarantees that augmentation will always work. There are so many variables that it is impossible to always get it exactly right.
If you can enhance the populations of naturally occurring beneficial insects on your farm, you may be able to get a lot of pest control with less effort. So, what can you do? Of course you want to use pesticides judiciously. Choose the least toxic pesticide possible with short residual activity. Spot spray or time your sprays to minimize contact with beneficials. What else can you do? Many beneficial insects eat nectar or pollen. Provide habitat by planting flowering plants, especially sweet alyssum, sunflowers, lantana, marigolds or fennel. Plant a row or two in your vegetable field. It is easy to do, you will probably be able to see beneficials like syrphid flies hovering over the flowers…and it is pretty too!
Researchers are working to figure out ways to encourage natural beneficials in greenhouses and high tunnels. One system involves growing "banker" plants which can support natural enemies and their prey. Briefly, the researchers grow barley in containers, and then they intentionally infest the barley plants with a cereal aphid, one that will only colonize only grasses. After the aphid population reaches a certain level, they introduce an aphid parasitoid. This parasitoid is a small wasp that lays an egg on the cereal aphid and the developing young wasp kills its aphid host. The young wasp pupates inside the dead "mummified" body of the aphid, and emerges as an adult wasp in several days, and the females will seek out other aphid hosts. This gives greenhouse growers a portable "bank" of pupating aphid parasitoids that can colonize and kill the aphids on broadleaf host plants, such as annual bedding plants or vegetable transplants.
Here is a link to a fact sheet from University of Massachusetts, which describes the aphid banker plant system and how you can produce banker plants yourself -- http://extension.umass.edu/floriculture/sites/floriculture/files/pdf/AphidBankerPlantSystem.pdf.
Researchers are also working on 'Black Pearl' peppers which will support populations of a type of beneficial minute pirate bug called Orius insidious. Orius will eat thrips and aphids, but can also survive on the pollen of the 'Black Pearl' pepper. Keeping a few flowering 'Black Pearl' peppers around will encourage populations of Orius to live there. To read more about one of these research projects, go to http://www.southernsare.org/News-and-Media/Press-Releases/Exploring-Biological-Control-of-Greenhouse-Pests.
Another interesting system is using bush beans in a high tunnel where tomatoes are being produced. Two spotted spider mite is often a problem on tomatoes in high tunnels. Bush beans are very attractive to spider mites, so bush beans planted in a tomato high tunnel can serve as a sentinel or indicator plant to monitor for the pest. When spider mites are found on the bush beans, a predatory mite can be introduced. This predatory mite can provide biological control of the spider mites throughout the high tunnel. To read more about this system go to http://www.bugwood.org/arthropod/day2/matteoni.pdf.
Growers should not rely on enhancing natural enemies as their only form of pest management. These systems are intriguing, and definitely worth considering as an addition to your regular pest management strategy, but they cannot replace diligent monitoring and other interventions. Leaving a heavily infested plant in your production area can quickly lead to a pest population getting out of control. You should have a plan, and should know your options before common pest problems arise so you can react to them.
I'm planting some 'Black Pearl' peppers and sweet alyssum this year. It can't hurt, and I am interested to see what kinds of beneficial insects I will find on them.