Good Bugs

By Tracy McLellan, Master Gardener Volunteer

Question: What can I do to encourage beneficial insects in my garden?

Answer: We tend to notice the insects that damage our plants.  However the vast majority of insects and related animals called arthropods are either harmless or beneficial.  They perform the useful functions of pollination, predation, parasitism, and decomposition.

Bees and some flies transfer pollen from one flower to another, ensuring that the plants produce fruit. Pollination is particularly important for fruit trees and squash plants.  

Familiar and easily seen, ladybugs and praying mantises are predators on other insects that eat plants.  Spiders, centipedes and green lacewings are predacious and can devour pests. Ladybug and lacewing larvae look similar, rather like striped worms.  Both prey on aphids, sucking insects with soft bodies that are common on many kinds of plants. 

Tiny parasitoid wasps and some types of flies lay their eggs in the bodies of other insects and digest them from the inside. Parasitoids are often highly specific to one host animal, so they might help out with only one pest species.

 

Ichneumonid parasitoid wasps
Enicospilus spp.
Merle Shepard, Gerald R.Carner, and P.A.C Ooi

We can provide beneficial insects with a good home by making our gardens comfortable for them throughout the season they are active.  Provide flowers for pollinators at times in addition to when our fruit trees and vegetable plants need them, and plant those flowers close to those plants.  Provide food plants for the other life stages, which might eat leaves when they are juveniles and visit flowers when they are adults. Flowers in the carrot (parsley) and daisy families are good hosts for pollinators. Cover crops such as buckwheat and clover are great if you have enough space.  Have water available at all times.  Use straw mulch or leave pulled weeds on the soil surface, as long as the weeds do not have seeds, to give insects places to hide from their predators.

A high diversity of plants provides a variety of habitats and food sources.  That means lots of different varieties within species, and a large number of species.  Many different plant types, from ground hugging to shrubs and trees, encourage good insects.  Mixing plantings of vegetables, ornamental, trees and shrubs is a great way to provide good homes for good bugs and makes for an interesting garden. A huge, closely mown lawn does nothing to enhance the good insects in your garden.

If you do use insecticides, do not spray everything heavily, but focus on the infestation you are aiming to eliminate.  Even the less toxic, organically approved insecticides are broad spectrum and will kill most insects, including those that it would be good to keep around.

For more information on beneficial insects, visit the Cornell Garden-Based Learning website:

Beneficial Insects