Friend or Foe?

— Written By Susan Brown and last updated by

Did you know that fewer than 10% of insects are what we as gardeners would consider harmful? The remaining 90% of them are either benign or beneficial. Even the seemingly bad guys serve a function. They may be pollinators, decomposers, or food for other creatures higher up in the food chain, but they are bad to us because they damage and consume our plants. To gardeners, benign insects are those that play no key role in our gardens, they just happen to be there and beneficial insects are, well, good for the garden because they either pollinate plants or prey upon pest insects. caterpillar on leaf margin

It’s important to properly identify any insects you encounter and place them into one of these three categories: bad, benign or beneficial. To do this, you will need to watch them in action. Observe if they are munching on leaves or buds or, if you’re lucky, other insects. Are they flying or crawling? What is their physical appearance? Identifying the insect is important otherwise you may be doing more harm than good.

When most people think about insects they immediately think that they are pests. What a lot of people do not know is that not all insects are pests. In fact, many of them can be used to pollinate our flowers, and reduce the population of insects that are harmful to plants. The effectiveness of controlling pests with beneficial insects is determined by the volume of food available as well as the proper habitat to support them.

Beneficial insects need a stable habitat in order to stay happy and healthy. If care is taken to provide shelter where the insects can find protection from disturbances, they will be more likely to stick around. Plots of cover crops, perennial flower beds, and hedgerows near flower and vegetable gardens all provide excellent shelter for your beneficial insects. Just like anything else insects need water to survive. Providing a small, shallow container will work but be sure to change the water every 2-3 days to discourage mosquitoes from breeding. Small sticks or rocks should also be placed in the water to give the insects a place to perch. When pests populations are low, beneficial insects will feed on pollen, nectar or plant juices to supplement or replace their insect diet. They will even hold off laying eggs even though they have been fertilized if no pests or prey are present or if pest populations are not high enough to feed the hatching young.

In order to sustain their food source, beneficial insects must allow some of their prey to feed and reproduce. They may not always be able to solve all your pest problems. Choosing the right plant for the right place as well as choosing plants that are resistant to pests is always a good idea. Pesticides would be another option but always a last resort for me. Before using any pesticide it is important to know if there will be any adverse effects to the environment as well as to beneficial insects. Often times when we spray we kill the pests as well as the beneficials and it takes beneficial insects longer to build their populations back up. That is why when pesticides are used you see an increase of pests a few weeks after you spray. The eggs of the pests have hatched and the beneficial insects have all been killed.

assassin bug

In most cases when you ask someone to name a beneficial insect they will say lady bug or butterfly and those insects are typically easy to recognize in the garden. There are many less popular beneficial insects in the garden that may not be as easy to identify. Be sure that when you find an unknown insect in the garden you begin with the proper identification of the pest and plant host. Observe if the insect is munching on leaves or buds or if they are feeding on other insects. Are they flying or crawling? What is their physical appearance? All these questions can help you to determine what insect you are encountering and how to manage them effectively. Then you can place them into one of three categories:  bad, benign, or beneficial. Ninety percent of the insects we encounter in the garden are either benign or beneficial. Even the seemingly bad insects serve a purpose whether it be for pollination, decomposition or food for other creatures higher up the food chain. The most effective way to manage pest insects is to grow healthy plants and enrich the soil.