Beneficial Insects in the Garden

When we think of insects in the garden, we typically think of pests which eat and spoil the produce we have worked so hard to grow. However, there are many insects which can improve the health and productivity of an at-home garden.

We visited the Southington Educational Agriculture Farm (LEAF), in central Southington, Connecticut to learn more about how growers use pest management and beneficial insects in agriculture, and to learn about how people can make these processes more sustainable.

LEAF is known in town for its youth agricultural educational programs and its popular CSA (Community-Supported Agriculture) food share program.

During our tour of LEAF, Executive Director and Farmer Mark Ramsey explained the typical pest issues that gardeners face in CT, and told us about the typical strategies one can use to mitigate them.

For example, white flies and their green relatives, aphids, are a typical pest in the garden. They can damage any crops with large leaves, especially leafy vegetables like kale and lettuce. White flies can quickly infest crops, leaving powdery stains behind and spoiling them. Both pests eat tiny holes in the leaves and can reproduce quickly.

Aphids and whiteflies are preyed upon by ladybugs and praying mantises. Thus, promoting these in the garden will naturally lower these pests. Also, gardeners can try planting strong-smelling plants like garlic, chives, and petunias next to their leafy crops, which has been known to repel these pests. If these methods do not work, spraying with pesticides is a final resort, which should remove the last of them.

Various caterpillars can damage crops in the garden as well. The tomato hornworm is an especially destructive caterpillar that eats tomato plants. Given its large size, it can easily be picked off plants. Parasitic wasps naturally kill these pests by laying their eggs on them, so tolerating wasps in the garden can be beneficial. In addition, tilling the soil and removing weeds can decrease the number of caterpillars and their eggs in a garden.

Another pest common to the garden, especially potted plants, is the fungus gnat. These insects thrive in moist, wet soil, so watering intermittently once the soil dries out is a natural solution to reduce their numbers. However, if heavy watering is necessary, the gnats can be controlled with a gentle neem oil spray from a hardware store or garden center. Some species of beetles will also prey on them.

Leafy vegetables are frequently prone to damage from moth larvae, such as the Cabbage Looper and the Cabbage White Moth. These insects lay their eggs under large leaves, then the worm larvae eats the plant. They have some natural predators, like birds and other predatory insects. The adult moths can be blocked from the garden with netting, and removing large weeds can discourage them from laying eggs near their garden.

So if all these garden predators are good for the garden, how can they be attracted? First, start by knowing and being able to identify them, their larvae, and their eggs so you do not disturb or kill them. See our "Helpful Links" page for more info on identifying them. In general, these are the major predators:

-praying mantis

-ladybugs

-ground beetles

-dragonflies

-assassin bugs

-parasitic wasps

-some birds

Generally, they can be attracted by creating a healthy garden habitat. Cover your plant beds with organic material such as mulch. Plant flowers nearby as a source of nectar. Birds can be attracted with a bird feeder and a bird bath. Insecticides will kill all insects, including the beneficial ones, so only apply them lightly as a last resort. In short, by providing all the resources an insect would need in the wild, you should attract them.

For more information on pests, beneficial insects, and starting a garden, please see our "Helpful Links" page.