By RON ARMSTRONG
Many vegetable gardeners are turning to flowers as a way to reduce or eliminate chemical pesticides. The problem with broad-spectrum conventional insecticides is that they not only kill the bad bugs, they also often kill the good ones, too.
The use of companion plants is a simple way to help eliminate the bad insects and nematodes while attracting beneficial insects and pollinators. In addition, companion plants may reduce insecticide use and increase yields through better pollination.
Many companion plants are adapted to our area. Here are several plants to consider and the pests that they control.
Borage, Borago officinalis, is an excellent plant to attract the green lacewing. Lacewing larvae are voracious eaters of the eggs and immature stages of many insect pests, including aphids, mites, thrips, whiteflies, leafhoppers, beetle larvae, mealybugs, tomato hornworm, and cabbage looper.
Zinnias, Zinnia spp., are great for attracting hummingbirds, hover-flies, parasitic wasps and flies, ladybugs, pollinating bees and butterflies.
Other plants with similar properties to zinnias include anise hyssop, Agastache foeniculum; bee balm, Monarda spp.; black-eyed susan, Rudbeckia spp.; purple coneflower, Echinacea purpurea; mountain mint, Pycnanthemum spp; golden marguerite/Dyer’s chamomile, Anthemis tinctoria; and basket of gold, Alyssum saxatile.
Garlic, tansy, catnip and marigold repel Japanese beetles. Painted daisy, Tanacetum coccineum, contains a natural insecticide, pyrethrum, that drives away Japanese beetles and root nematodes.
French marigolds, Tagetes patula, have roots that exude a substance which spreads in their immediate vicinity killing nematodes. There have been some studies done that showed this nematode killing effect lasted for several years after the plants died back.
Marigolds also help to deter whiteflies when planted around tomatoes, melons and squash while attracting butterflies and hover-flies.
Nasturtiums, Tropaeolum, planted near tomatoes and cucumbers can fight off aphids, white-flies, squash-bugs and cucumber beetles. The flowers, especially the yellow blooming varieties, act as a trap for aphids. Plant them as a barrier around tomatoes, squash, cabbage and cucumbers.
Petunias, Petunia spp., repel aphids, tomato hornworm, asparagus beetles, leafhoppers and squash bugs.
To protect potatoes from scab, I put dried comfrey, Symphytum officinale, leaves in the soil with the potato sets at planting time.
Ornamental grasses provide excellent summer shelter and overwintering sites for ground beetles, ladybugs and other beneficial insects. When I cut them back to about four inches in the spring, I often catch the ladybugs waking up ready to eat the bad bugs in my garden.
I plant perennial flowers all around my vegetable garden and annual flowers in and among the rows of vegetables. I also plant radishes around my squash hills, which seems to protect them from squash borers.
I encourage you to try companion plants to control insects. My vegetable garden is much more colorful since I have been using companion plants and I can enjoy my harvest without concern over eating pesticide residues.
For additional information on companion planting, I recommend http://blogs.cornell.edu/horticulture/insects/.
Armstrong is an Ohio State University Extension, Hancock County, Master Gardener volunteer.
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