Mealybugs and scales
produce honeydew (on which moulds grow) resulting in considerable damage in ornamental and fruit crops and loss of value. Armoured scales do not produce honeydew [...] of mealybugs feed on the aerial parts of the plant, some species extract their nourishment from roots, whilst others are gall-formers. A few species can [...] the product unfit for sale. A very small population can thus cause considerable loss of value. Soft scales feed mostly on leaves and twigs, causing di