CORVALLIS, Ore. – If silent, uninvited guests with voracious appetites have been eating your vegetables and other plants, the good news is that ingredients to stop the intruders can be found at home in the kitchen or medicine cabinet.
The most likely culprits can range from minute aphids to the more obvious ground squirrels and deer.
A few of several safe household chemicals to use are vinegar, dishwashing soap and rubbing alcohol, according to an Oregon State University Extension Service publication called "Using Home Remedies to Control Garden Pests," (EC 1586). The publication, complete with photos, is available free of charge online.
As a precautionary measure, test your mixture on a small number of plants or part of a plant to evaluate toxic effects. Plants with hairy leaves tend to hold soap solutions on their leaf surfaces where it may burn. The greater the strength of the solution, the hotter the day, and the more a plant is water-stressed, the greater the likelihood of burning.
Here are tips from the publication on how to control some of these pests.
Aphids are soft-bodied insects that show up on new shoots, crowns and undersides of leaves. They insert a needlelike stylet into the plant and remove the sap. Symptoms of aphid damage are curled leaves, yellowish spots and glossy leaves from sticky honeydew. A “weeping” tree that drips a sticky substance commonly has an aphid infestation. Black sooty mold may develop on leaves and reduce photosynthesis.
Insecticidal soap, available at most garden centers, controls aphids by clogging their breathing holes. Alternatives: Mix a teaspoon of vegetable oil, a teaspoon of dishwashing liquid and a cup of water. Or, mix three tablespoons of liquid soap and a gallon of water. Spray to wet the entire plant thoroughly, particularly the undersides of leaves, because aphids must come into contact with the soap solution to be affected. After a few hours, wash off the oil and soap with a garden hose to protect sensitive plants. Repeat the application every few days as necessary.
Slugs and snails like damp places and usually feed at night, preferring tender new growth and seedlings. Although they are ground dwellers, they can climb plants and cause damage well above the ground. Confirming damage by slugs or snails can be difficult but you may see them early mornings or evenings or find their glistening slime trails on hard surfaces.
Cultivate the soil and remove weeds, debris, and decaying organic matter that provide breeding and hiding places. Shaded areas beneath decks can be slug “heaven.” Keep shaded areas weed- and litter-free. You can remove slugs and snails by hand or trap them in shallow pans containing beer throughout the garden. Beer is effective for about three days.
Spider mites are very small pests that are difficult to see without a magnifying lens but can cause substantial plant damage. Most is caused by two-spotted spider mites, recognized by the two spots on their upper backs. They are particularly damaging late in the season or on plants near a dusty road or during hot days. Plants or leaves damaged by spider mites appear off-color or have speckled green and light-colored spots.
An easy way to confirm spider mite damage is to tap the plant while holding it over a sheet of white paper. Look at the small spots on the paper with a magnifying glass to identify spider mites. To get rid of them, mix three tablespoons of dishwashing soap with a gallon of water. Wet leaves thoroughly and reapply every five or six days if necessary. Rubbing alcohol also can treat plants infested with spider mites, aphids and whiteflies. Apply with cotton balls. After a few hours, wash off the soap solution or alcohol with a garden hose. After a few applications, these pests should be eliminated.
The OSU publication also recommends treatments for other insects, as well as moles, gophers and ground squirrels.