Groups of Pests Pests of ornamentals may be divided into five groups according to the way they damage plants. Insects with Piercing-Sucking Mouthparts. These insects have beak-like mouthparts which are used for piercing the plant tissue and sucking the plant juices. They may feed on the leaves, flowers or attack the roots. These pests are not insects but closely related to spiders and scorpions.
Spider mites suck plant juices with their piercing-sucking mouthparts.
These are very small larvae of flies, beetles, or moths that tunnel between the upper and lower leaf surfaces. There are many species of insects which bore into the twigs or trunks of plants and trees. These are either the larvae of moths or beetles. Sometimes it is possible to remove pests and keep populations below damaging levels by spraying landscape plants with a forceful stream of water. Use a garden hose with an adjustable nozzle and spray undersides of leaves and stems when such pests as aphids, mealybugs, spider mites, thrips or lace bugs appear.