Only a few of the insects in the vegetable garden are harmful, but they do a lot of damage. Tomato cutworms, cabbage worms, whiteflies, mealy bugs and squash bugs eat vegetables before they reach the table. Some plants are natural insect repellents. Catnip, coriander, basil, larkspur, petunias, radish and thyme repel whiteflies, beetles, aphids, fleas and flies. Homemade sprays containing garlic, onions, pepper, yarrow, marigolds and castile soap also control insects.
Homemade Insect Sprays
Garlic spray is an effective homemade solution for aphids, cabbage worms, June bugs, leafhoppers, mites, squash bugs and whiteflies. Garlic contains naturally occurring sulfur, which prevents fungus and acts as an antibacterial agent. To make the spray, mix 3 oz. of minced garlic and 1 oz. mineral oil. Strain the mixture and allow it to soak overnight. Combine 1 tsp. fish emulsion with 16 oz. of water and 1 tbsp. castile soap. Blend the two mixtures in a sealed glass container. When ready to use, put 2 tbsp. into a pint of water and spray all plant surfaces.
Herbs Repel Insects
Harmful insects are repelled by certain strong-smelling herbs planted nearby. Thyme repels carrot flies and cabbage worms, tansy keeps cucumber beetles and squash bugs away, and summer savory deters bean beetles. A vegetable garden with a variety of herbs smells good and keeps plants healthy. Members of the mint family, such as catnip and spearmint, are invasive growers but also provide protection from ants, rodents, flea beetles and aphids. Radish planted among cucumbers and squash keeps damaging beetles away.
Native plants co-evolve with local insect communities, providing help and protection. Sage is native to all regions of the country and provides a strongly aromatic barrier to insects that damage vegetables. Sage keeps away cabbage moths, beetles and carrot flies, but do not plant it near cucumbers. Sweet alyssum is a native plant that attracts the hover flies that eat aphids. Native purple coneflowers attract bees that are essential for pollination.
More Homemade Sprays
Peppers contain the compound capsaicin, which is general insect irritant and repellent. Pulverize dried cayenne, chili, red or black peppers in a food processor and sprinkled the powder around the vegetable garden soil. Mix the dust with water and sprayed on foliage. Orange and other citrus contain compounds called limonene and linalool that repel aphids, fungus gnats, mealy bugs and ants. The alkaloids in tomato leaves, when soaked in a pint of water overnight, kill asparagus beetles and fleas.