Many gardeners limit their use of commercially available chemical sprays and instead use homemade brews. Homemade garden bug spray can be inexpensive, safe for soil and septic systems and effective. However, the fact that a spray is natural and homemade does not mean it can't damage plants. Test any homemade bug spray on a small number of infected plants and wait for results before spraying on a wide scale.
Garlic, Pepper and Soap Spray
A spray made from commonly available foods and household items may help protect garden plants from chewing and sucking insects such as aphids, cabbage-worms, horn-worms, caterpillars and flea beetles. The ingredients for a batch can include six garlic cloves, a tablespoon of the hottest dried chili pepper available, one onion minced and a teaspoon of non-detergent soap flakes mixed into a gallon of hot water. Blend in a blender or food processor. Allow the mixture to sit for a day or two then strain it thoroughly so that it can be applied with a spray bottle. Remember to spray the leaf undersides. Do not spray in direct sunlight. Reapply about every two weeks and after a rain.
Detergent and Salad Oil
A mixture of about a tablespoon of canola oil and a few drops of liquid detergent such as laundry detergent in a quart of water may help control and discourage aphids, meal bugs and mites. The spray bottle needs to be shaken before being sprayed to emulsify the oil. Spray during non-direct sunlight evening hours or on cloudy days. Rinse the spray residue after about two hours to minimize leaf damage.
Baking Soda, Peroxide and Soap
The baking soda and hydrogen peroxide combination in this mixture helps keep fruit tree pests such as waxy exterior insects and damaging fungus at bay. The spray is applied before the tree or shrub is in full bloom, while it remains dormant. The mixture is made with 2 tablespoons of baking soda to 5 tablespoons of hydrogen peroxide and 2 tablespoons of a natural soap such as a castile or olive oil soap all combined in a gallon of water. Use a garden sprayer. Shake the mixture vigorously immediately before applying. The spray can be applied immediately after pruning to seal the cut against entry of insect pests.
A few other homemade sprays and concoctions may be useful in the garden to combat pests. A diluted mix of antiseptic mouthwash and water may discourage insects. A simple spray mixture of water and baby shampoo or liquid dish detergent may make plants not taste good to insects. A mist made from a mixture of rubbing alcohol or vodka and water may discourage white flies.
Wait for calm weather to spray and especially avoid spraying on windy days. Do not apply bug spray in the heat of afternoon sun. Protect eyes and skin while spraying. If mist lands on hair, wash hair before sleeping. Wash hands after handling homemade sprays.