Insecticidal soaps kill garden pests on your plants in a natural manner without the need to use pesticides. A homemade pest-killing soap made with dish detergent costs only pennies per application, and spraying garden pests directly with dish soap spray kills them on contact to prevent excessive sap loss that injures and kills plants.
1 Measure liquid dish detergent at a 2 percent dilution and add it to a garden sprayer. Use 5 tablespoons per gallon, 4 teaspoons per quart or 2 teaspoons per pint.
2 Add water to the garden sprayer from a garden hose while swirling the liquid to mix it and make soap bubbles.
3 Screw the top clockwise on the garden sprayer. Pump the handle on top up and down to add pressure to the mixture. Shake the sprayer to add more bubbles to the solution.
4 Turn the sprayer handle clockwise to lock it in position.
5 Walk to the garden and look for soft-bodied insects such as spider mites, aphids and mealy bugs using a magnifying glass. Spider mites are either brown or red and have eight legs as adults with a pair of needles at the front of the mouth. Aphids resemble small grasshoppers in green or black with a 1/8-inch-long pear-shaped body. Mealy bugs are about 1/4 inch long with a white wax covering, and they resemble tiny cotton balls.
6 Squeeze the trigger on the garden sprayer to deposit the detergent spray on the insects. Soak each insect with the solution thoroughly. Coat the tops and bottoms of foliage as well as the stems down to the ground level. Pump the sprayer handle as needed to add pressure to the tank when there is a slow flow from the applicator tip or wand.
7 Allow the soap solution to remain on the plants for about two hours. Wash the soap residue off the plants on all surfaces with a strong spray of water from a garden hose. Dish detergents contain fragrances that can harm some plants if left on the foliage.
8 Reapply the dish detergent solution about once a week as long as the insects return to the plants.