On several occasions in the past, we have mentioned that pests can sometimes be effectively controlled biologically. Not surprisingly, Mother Nature has a system of checks and balances for insects just as she does for the larger ecosystem. Thus, it would be in our best interests to learn how to work with nature to control pests. Today we are going to take a deeper look at using biological pest control rather than pesticides in our gardens.
Biological pest control is simply using nature rather than chemicals to control pests. It can include using predatory insects, parasites, pathogens or even competitors to suppress pest populations. This happens to be an area of interest that we as a community are actively researching and learning more about every day. Biological pest control is becoming more and more important. Pesticides are becoming less effective due to pests developing resistance. New research keeps showing pesticides to be unsafe and harmful to the environment. Plus consumers want pesticide free food.
Biological pest control is wonderful because it is easy and safe to use. It reduces or eliminates the use of pesticides, and it avoids harming non-target species. Perhaps best of all, predatory insects can establish self-sustaining populations. These populations can continue to keep pest under control long after you initially introduced them.
In many cases, your garden pests are already being kept below damaging levels by native populations of biological pest control.
You might have seen this biological control taking care of tomato hornworms. This is one of the most obvious visual examples we can think of. Quite often hornworms will appear in a garden. Shortly thereafter you will see dead larvae with large white things hanging off of them. There is a parasitic wasp that reliably shows up in our garden along with the hornworms. This wasp is busy killing the larvae for us. In this case, the worst thing we could do would be to spray a pesticide. Rather, we can help encourage the beneficial insects by leaving the larvae she has laid her eggs in on the plant.
Another example of a pest commonly controlled by natural predators is spider mites. As you might know, spider mites can be a difficult to control menace on greenhouse crops or house plants. And yet, though we know they are present in the environment, there are rarely spider mite outbreaks outdoors. Plants that spent the entire summer outdoors often have a spider mite outbreak when moved indoors for the winter. Why? Because the natural predators do a fantastic job of keeping spider mite populations low until you move plants into an artificial environment.
The only other time we typically see large spider mite outbreaks in the garden is following the application of broad spectrum pesticides.
There is a lesson to be learned here. This shows just how easily we can disrupt the balance in nature. In this case, the broad spectrum pesticide killed off all of the spider mite predators. What it did not kill off was the the spider mites. This allows the spider mite population to explode to devastating proportions almost overnight. Then you must spray to save the plants from spider mites. This kills any predators that survived the first spray creating a viscous cycle. Sadly, the problem your pesticide created might not re-balance itself until winter when the spider mites are killed off by cold.
This is why it is extremely important only to use pesticides if absolutely necessary. It is also equally important to make sure you are using them appropriately, and are using the correct pesticide for each pest. Select pesticides carefully with the beneficial insects in mind. Choose pesticides most likely to harm the pest while doing the least harm to predators. So for example, rather than spraying a broad spectrum contact insecticide, use Bt or a systemic that requires ingestion of plant material to kill.
Another Important Note: It is not necessary to eliminate every single pest from your garden.
This is part of cultivating a habitat that is full of resources for the predators so that they can establish breeding populations. Sometimes we get carried away with an almost obsessive need to have a ‘sterile’ garden. ‘Sterile’ is not necessary or even ideal. You simply need to keep the pest populations suppressed to a level at which they are not causing any real damage.
Understanding this can be an important part of establishing a predator population. Unless your biological control is something like a pathogen, it needs to feed on something. If you eliminate the food source the predators will either die of starvation or move elsewhere looking for food.
Many predator adults also require food sources such as pollen, nectar, or even honeydew from aphids throughout the season. They also require overwintering sites. Therefore, adding diversity of plants and leaving natural areas can help the predators to establish a population in your garden. Many of these insects benefit from the same types of plants and natural areas that our native pollinators do, so by working towards creating a pollinator haven, you will also be working towards establishing habitat for healthy, stable, biological pest control populations.
What to do if you have a pest problem natural biological control is not taking care of
Unfortunately, sometimes Mother Nature needs some help. This can be because we have created an unnatural monoculture of plants, used too many pesticides, or planted plants in a bad location which makes them stressed and prone to problems. Or maybe our predator population died out over the winter. Some predators are not capable of overwintering in all parts of the country. Others might not have had appropriate habitat available to them in your garden.
If you have found yourself in a situation with a pest problem, fortunately, there is a dizzying variety of biological control options available to purchase. Many of these are beneficial insects you simply sprinkle around the problem areas. Sometimes you need to do a knock down spray of a mild insecticide such as Neem Oil to reduce the populations prior to adding predators.
Some pests have a variety of predators available. Others have only a few. Some predators are generalists. Others have a very specific target. There are sometimes even different ideal predators for different temperatures, seasons, and climates.
It is important to do your research prior to purchasing predators.
Unfortunately, it is beyond the scope of this article to discuss details of all the different options for each pest. However, there is a wealth of information online available both from University publications, and also from the companies producing and selling the beneficial insects. An extension agent, or biological control sales rep should be more than willing and able to help you select the correct predator and release schedule for your specific pest.
So next time you have a pest problem in your garden we encourage you to stop and consider other options before you pull out the pesticides!
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