What Is Neem Oil Soap?
Neem oil soap is an insect control product derived from the oil from the neem tree (native to Asia and Africa). It is extremely effective as an insecticide or in some cases as a fungicide. For insect control, the active chemicals in neem oil soap act in two ways, they either repel insects or kill them. Unlike synthetic pesticides, the neem oil soap molecules do not act as a nerve or stomach poison, but rather they degrade the protective, water-proofing insect exoskeleton. The neem oil soap breaks down this exoskeleton, disrupting normal membrane functions, often causing the insect to dry out and die. For foliage feedeers such as cabbage loopers, neem oil soap repels the insect by making plants unpalatable. As a repellent, it last for up to 30 days. Neem oil soap's dual role as a repellent and an insecticide may make it doubly difficult for insects to develop resistance to it.
Neem is a natural product and is very safe to use. In fact neem oil has been used in Southeast Asia as an insecticide, to clean teeth, to treat boils, and as a diuretic. Leaves from neem trees are eaten 'to purify the blood' in Hindu rituals. And neem oil is used in soap manufacture in India (the leftover neem oil cakes are fed to livestock). Neem oil soap can be used in the vegetable garden or orchard right up to the day of harvest. Needless to say; neem oil soap is safe.
What Insects Does Neem Oil Soap Control?
Neem oil soap repels or kills over 50 insect pests, most of which are never even seen in the home landscape.
The most common insect pests controlled by neem oil soap include: Aphids, Crickets, Flea beetles, Grasshoppers Japanese beetles, Lacebugs, Mealybugs, Mites, Mole crickets, Scales, Spider mites, Tent caterpillars, Thrips, and Whiteflies.
In the lawn it controls Chinch bugs, regular Crickets, Grasshoppers, and Mole crickets.
In trees and shrubs it controls Adelgids, Aphids, Gypsy moth caterpillars, Hemlock woolly adelgid, Japanese beetles, Lacebugs, Mites, Pear psylla, Pear slug, Psyllids, Scales, Spruce woolly aphids, and Tent caterpillars.
On flowers it controls Aphids, Earwigs, Flea beetles, Grasshoppers, Green stink bugs, Harlequin bugs, Japanese beetles, Lace bugs, Leafhoppers, Leafminer, Mealybugs, Mites, Plant bugs, Rose slugs, Rust mites, Sawflies, Scales, Thrips, and Whiteflies.
In the vegetable garden it controls Aphids, Cabbage loopers, Cabbage worms, Colorado potato beetle, Earwigs, Flea beetles, Grasshoppers, Green stink bugs, Japanese beetles, Leafhoppers, Mexican bean beetle, Mites, Squash bugs, Stripped cucumber beetle, and Whiteflies.
On houseplants, it controls Aphids, Mealybugs, Mites, Scale, and Whiteflies.
Using Neem Oil Soap - Precautions
First the no-no’s: Do not use neem oil soap on drought stressed plants. It should not be used on new transplants, and recently rooted cuttings. Because of potential phototoxic problems it is wise not to spray neem oil soap on plants while they are exposed to full sun. Use it early in the morning, better in the evening hours. Avoid using neem oil soap with the air temperature is much above 85F.
Because neem oil soap is in fact an oily substance, it can cause problems for certain plants because of the way it filters the sun to the leaf surface. This “phototoxicity effect” can cause the leaves to wilt and flowers to wilt. On most plants it is not a problem at all.
There are a number of the more delicate plants where sometimes it is a problem and sometimes it is not a problem. The trick is to try it on a few leaves and wait a day to see if any wilting occurs. If not it is safe to use. Use this technique on plants such as begonia, camellia, chrysanthemum, plants in the cucumber family, delicate ferns, fuchsias, grapes, impatiens, ivies, palms, peppers, schefflera, some conifers, and succulents such as cactus and bromiliads.
There are some plants that cannot tolerate neem oil soap under any conditions. They include bleeding heart, Crown of Thorns, Gardenia, Horse Chestnut, Jade Plant, Japanese Maple, Lantana, Mountain Ash, and Sweetpeas.
Generally it is wise to avoid spraying the neem oil soap directly on blossoms of most plants.