7/18 Thursday

Beneficial Insects

​Beneficial insects are those helpful little critters that eat other insects that damage and attack our plants. There are far more beneficial insects than bad ones. Scientists estimate that more than 95 percent of the insect species we see in our landscapes are beneficial.
​Many beneficial insects are predators that consume other insect pests. Some well-known predators include lady bird beetles (lady bugs), praying mantis, and ambush bugs. While most of these insects are pretty easy to identify in their adult form, they are not as easily recognized in their juvenile or larval stages. Lady bird beetles, for example, are pretty scary looking when young. They look like little black and red alligators! It is important to correctly identify an insect before taking any action. If you need help identifying an insect, place it in a jar and bring it to your local Cooperative Extension office for identification.
Spiders are pretty easy to identify, but are often overlooked as predators. They are invaluable at keeping backyard insect populations in check. Resist your urge to kill every spider you see. They are the top predators in your garden and you WANT them there!
Many parasitoids are also beneficial. These insects lay their eggs inside or on top of an insect host. A parasitoid wasp must have been the inspiration for the movie, “Alien.” These tiny wasps inject their eggs into a host, where the larvae eat the host from the inside out. Many parasitoid wasps are no bigger than a grain of rice. Some species lay their eggs exclusively in aphids, infamous for munching roses and many other landscape treasures.
Attracting beneficial insects to the garden is easy. Some gardeners even plant special “insectaries” near their vegetable garden to ensure good pollination and natural pest control. Two of our founding fathers, Thomas Jefferson and George Washington, were farmers and relied on their insectaries to pollinate and protect their crops.
The best way to create an insectary is through plant diversity. Flowering plants, such as yarrow, black-eyed Susan, milkweed, Cosmos, sunflowers, and pincushion flower, provide nectar and pollen that attract many beneficial insects, while ornamental grasses and woody shrubs provide cover and ambush areas.
It is important to note that predator populations often lag behind those of their prey. However, when nonselective pesticides are used to control pest populations, predators are also killed. The pests will usually recover pretty well, and can go through two or three population explosions before the next pesticide application. The predators, however, are usually less resilient and have a more difficult time recovering. Therefore, less toxic control methods, such as spraying water to knock off and kill aphids, are often recommended for additional control when predators are not quite keeping up with pests. That way, you keep the beneficials around to continue helping with the problem. 
Remember that 95 percent of the insect species in your backyard are beneficial. As you become familiar with the natural cycles of your garden, you can actually shape the ecology of your backyard, attracting and encouraging beneficial insects to work for you!
Here are excellent resources from Montana Cooperative Extension on two very important beneficial garden insects. 
​This is a reprint of an article I wrote when I was the commercial horticulture program coordinator for the western area of University of Nevada Cooperative Extension. For more specific gardening and horticulture advice be sure to visit your local Cooperative Extension office.

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