Beneficial insects are thought of as any insect that assists in pest control or pollination, without harming humans, plants, or pets. Many organic gardeners will rely on beneficial insects as an alternate or complementary method of pest control, rather than using pesticides. It should be noted that using pesticides can kill all kinds of insects in your garden, both beneficial and harmful. Therefore, if you are using both pesticides and beneficial insects, you will need to be careful about your timing of releasing the insects, so that your pesticides do not kill them.
There are many different kinds of beneficial insects, each targeting specific harmful pests. Companies will specialize in producing these insects or catching them in nature. You can mail order these insects and learn more about each one from suppliers such as:
Guides will advise on what time of year and what time of day is best for release of each insect type. For example, it is recommended to release ladybugs in the early morning or evening, so that it is cooler and more likely that they ladybugs will acclimate and survive. Sometimes, it is recommended to release your beneficial insects over a period of a few days.
The most common beneficial insects sold for release:
Trichogramma wasps (Trichogramma) are one of are many varieties of beneficial parasitic wasps, ranging from tiny sizes no longer than one millimeter to wasps about an inch long. Parasitic wasps need to find a host to complete their metamorphosis. This will vary depending on type of wasp, but many will use caterpillars and will paralyze their host and then lay their eggs in or on them. When the egg hatches into a larva, the larva will feed on its host until it is ready to pupate, and by then the host is either dead or moribund. Adult wasps mostly feed on nectar from flowering plants, so good pollinator plantings are key for retention. Trichogramma are a very tiny wasp species that are an effective control for codling moth, a common pest for apples, pears, and sometimes peaches and plums. Use codling moth pheremone traps to determine the best time for release.
Ladybeetles/Ladybugs (Hippodamia) are voracious predators of aphids, the soft bellied pests that suck the juice out of your plant leaves. Ladybugs will also eat mites and scales, other types of pests in your garden or orchard. Unfortunately ladybeetles rarely stay where they are released and in many cases aren’t sustainably harvested by suppliers. For this reason, purchase and release of ladybeetles is not recommended. . . but welcome them in your landscape when they arrive on their own!
Lacewings (Chrysoperla) are tiny green or black insects with clear, lacy wings that commonly fly around at dusk. Their larvae are known as “aphid lions”, but they also eat a wide variety of other garden and orchard pests including scales, mites, moth eggs, and small caterpillars. Their survival rate in shipping is low, but the survivors are effective and can be retained on site with good pollinator garden plantings. Not to be confused with Lacebugs, a common pest!
The praying mantis is a vicious predator, with the unique ability to turn its head 360 degrees. They also have extremely strong front arms with sharp spikes on them, which are used to hold on to prey. They will send out a special nerve impulse that can track down their prey by angle and distance. After catching their prey, the praying mantis will take a bite from their neck, thus killing the pest. Unfortunately, praying mantis are indescriminate predators, killing more beneficial insects and spiders than pest insects. For this reason, purchase and release of mantids is not recommended. In recent years, they’ve also become quite common in the city on their own!
As evident from the descriptions above, most beneficial insects releases are only marginally effective, although trichogramma wasps and lacewings might be worth introducing. A much more important strategy is to build habitat in your orchard or garden that will attract and retain a wide variety of beneficial insects. For this reason, we strongly recommend including pollinator garden plantings adjacent to all orchards or establishing food forest style plantings that include beneficial habitat right around the fruit trees and berry bushes.
There are particular plant species that will attract beneficial insects into your garden, a strategy that some call farmscaping. In particular, many beneficial insects are drawn to the flowering plants that will easily provide nectar and pollen. Some examples of these plants are yarrow, coneflowers, asters, goldenrod, cosmos, plants in the mint family, buckwheat, plants in the mustard family, and plants in the carrot family. For best beneficial retention, it is important to include spring, summer, and fall blooms. You can find a full list of attracting annuals and perennials from this page of the Mother Earth News.
This same internet source guide has an excellent essay on types of beneficial insects, which will give you more information on this topic.
There are also some beneficial insects which target fruit tree pests in particular. The following article written by the Penn State Extension explains these pests, as well as the beneficial insects that will help you combat the pests.
This edition of POP TIPS prepared with assistance form 2015 POP Intern Rachel Baltuch.
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