Both the larval stage and adult ladybird beetle are beneficial. They prey mainly on aphids, but will also feed on scale insects, whitefly larva, mealybugs, spider mites, insect eggs, and other small insects.
If you find ladybird beetles or larva on your plants, that is an indication that you also have one or more of the above mentioned plant pests on the same plant. If the plant can tolerate the aphid, mealybug, etc. infestation, it is best to allow “nature” to take its course, as, in time, the ladybird beetles will suppress the pest infestation. Unfortunately, many times the pest infestation gets out of hand before the ladybirds arrive and become present in sufficient numbers to adequately suppress the pest. In this situation you may have to treat the plant with a plant protection product to prevent the pest from causing economic or aesthetic damage to your garden landscape. Fortunately, there are now plant protection products on the market, which are “soft” on predators and parasites while still controlling the pest.