The greenbug, Schizaphis graminum, is an aphid or plant louse that is one of the most destructive insect pests of small grains in the Midwest. Although it usually attacks wheat and oats, it also feeds on Kentucky bluegrass lawns. Areas of discolored grass, ranging from pale green to yellow to burnt orange, under shade trees or in sunny areas, may be caused by the feeding of these small sucking insects. In heavy infestations, as many as 30 of the little bugs may be found on a grass blade. Using a hose end sprayer, spray grass blades thoroughly with the soap, covering all surfaces every 2 to 3 days for 2 weeks. This should bring control.
Insecticidal soap is often used to confirm the presence of two turf pests; sodwebworms and chinch bugs. The soap is applied to the area that is suspect and if those pests are present, they will show up on the top of the grass blades trying to get away from the soap. Then other control methods are used to stop the problem.
Treating Flowers & Vegetables
Adjust the insecticidal soap sprayer bottle for a strong pressure with medium droplet size. Thoroughly wet all plant leaf and stem surfaces top to bottom. It is especially important to spray the undersides of leaves, where most pests congregate. Do not use soap spray on gardenia, bleeding heart, sweet pea, violets, and nasturtium, and do not spray poinsettias after they begin to develop colored bracts. Some varieties of azalea, fuchsia, geranium, impatiens and palms are sensitive to soap spray under certain conditions, so it is wise to test-spray these plants. Follow guidelines on the product package.
Treating Trees & Shrubs
Some soap products are made especially for spraying trees and shrubs, and these usually are more concentrated than soap products recommended for flowers and vegetable plants. It is more difficult to reach both the tops and the bottoms of tree foliage, especially on trees over 5 feet tall. In these cases, wear eye protection and cover bare skin when spraying. Better yet, hire a professional arborist to do the job properly. Do not use soap spray on mountain ash, Japanese maple, horse chestnut, and hawthorn. Follow guidelines on the product package.
Treating Fruit Trees
If a tree with pest insect problems is currently bearing fruit, avoid over-spraying and avoid spraying on foggy or very humid days when it takes longer for the soap to dry. This is because prolonged exposure to soap on fruit such as apples, pears, and citrus may cause spotting or russetting of the skins. Follow guidelines on the product package.
Insecticidal soap is an excellent pesticide for most of the common insects that attack houseplants, such as aphids, scale, mealybugs, whiteflies and spider mites. Move plants to an outside area on a nice day or to the sink or tub to minimize soap spray damage to household appointments. Spray plants thoroughly, taking care that the soap solution penetrates dense foliage to wet all infested surfaces. Do not use soaps on corn plant (Dracaena), wandering Jew, or crown-of-thorns (Euphorbia). Test spray parts of other euphorbias, jade plants, palms, and delicate ferns before treating completely. Follow guidelines on the product package.