Neem is best used preventively, before pests become a serious problem. For example, if your garden is always plagued by squash bugs, begin spraying plants with neem every seven to 10 days as soon as the first adults are spotted. Egg laying and overall vigor will be reduced, but you will still need to handpick adults and remove egg clusters regularly to get good control. Employ the same strategy when using neem oil to manage leaf-eating beetles, spraying weekly when the first adults and egg clusters are seen. Neem is best applied in warm weather.
Why are different strengths critical? The appropriate strength depends on many factors. For example, babies absorb topical steroids faster than adults, so they may require a low-potency steroid. Areas of the body where skin touches skin (think: armpits, rectal area, etc), as well as sensitive areas (like the skin on the eyelids), tend to absorb topical steroids more rapidly, so those regions of the body also usually require a low-potency steroid. However, thick, rough skin on the palms of the hands and the soles of the feet usually absorb topical steroids more slowly than other parts of the body, so those areas typically require a more potent steroid. Keep in mind: The greater the potency of the steroid (in other words, the lower its class number), the more likely it is to cause side effects .