Numerous insect species are repelled by active ingredients in the neem seed. As they find the taste and smell unpleasant they avoid the plants that have been treated with neem extracts. Other insects die some time after having eaten leaves or other parts of the plant treated with these substances. They alter the behaviour in some insects or reduce their ability to lay eggs. Other pest species are affected minimally or not at all by the neem substances, probably as a result of their hidden biology.

The neem extract can be applied in two ways: When using a sprayer, the rough particles must first be filtered out of the mixture to prevent clogging the nozzle. This is done by covering a bucket or similar container with a coarse cloth or gauze through which the mixture is poured. The sprayer is filled with the filtered solution and spraying of the vegetable crops can begin. If no sprayer is available the extract may be applied with a straw brush. In this case, it need not be filtered. A brush made with fine, flexible straw is simply dipped into the solution and shaken over the plants until all the leaves are moistened. The effect of the neem substance lasts between 3 to 6 days, regardless of how it was applied.

The neem extract can be applied in two ways: When using a sprayer, the rough particles must first be filtered out of the mixture to prevent clogging the nozzle. This is done by covering a bucket or similar container with a coarse cloth or gauze through which the mixture is poured. The sprayer is filled with the filtered solution and spraying of the vegetable crops can begin. If no sprayer is available the extract may be applied with a straw brush. In this case, it need not be filtered. A brush made with fine, flexible straw is simply dipped into the solution and shaken over the plants until all the leaves are moistened. The effect of the neem substance lasts between 3 to 6 days, regardless of how it was applied.