Joy detergent can be used as an insecticide on garden and house plants. Insecticidal soap kills a wide range of insects. But, according to Colorado State University Extension entomologists, it works best on small, soft-bodied insects such as aphids, mealybugs, psyllids and spider mites. However, to work effectively, insecticidal soaps must make direct contact with the insects. You must spray plants frequently to rid them of the infestation.
Mix a 2 percent dilution of Joy detergent soap and water in a clean spray bottle. Add 5 tablespoons per gallon of water, 4 teaspoons per quart of water and 2 teaspoons per pint of water.
Test the Joy detergent spray on a plant. Spray a few leaves with the detergent early in the morning or late in the evening when temperatures are at their lowest. Leave the spray on for three hours, then rinse it off. If no damage occurs to the foliage in 48 hours, it is safe to use on the plant.
Spray the insects--again early in the morning or late in the evening. Thoroughly wet insects you spot on the plant with the solution. Look under leaves and in the junctures between stems where insects like to hide. If the insects are not thoroughly coated, they will not die.
Spray the treated plants with plain water to wash the detergent off three hours after you treat them.
Re-spray plants every four to seven days until the insect infestation is gone.