Insects that use special sucking mouth parts to feed on sap and plant cells include some of the most diverse and interesting insects in the garden. They can also be some of the most destructive pests in home landscapes. Unlike the beetles and ants with their chewing mouth parts, insects that feed on sap have piercing/sucking mouth parts. Damage from sap feeders can be difficult to spot at first. After a while, however, plants being attacked by sap-feeders will take on a shiny look and sticky feel. Eventually these sticky plants may turn black with a coating of black sooty mold, a type of fungus that grows on the sugars in the drippy droppings of sap-feeders. Common sap-feeding insects include mealybugs, scale insects, aphids, true bugs and whiteflies.
Not all plant-feeding insects with sucking mouth parts feed on sap. Some feed on the inner tissues of leaves, called mesophyll (MEEZ oh fill). Mesophyll includes the food producing (photosynthetic) cells layers of a leaf that lie between the upper and lower epidermis. Symptoms of mesophyll feeding include a stippled pattern of yellowish, gray or whitish dots on the plant surface. This damage causes the leaf color to dullen, turn yellow or gray, and eventually brown. Other mesophyll feeders may leave pits or sunken areas of leaves that eventually turn brown and die. Spider mites, leafhoppers, lace bugs and yucca bugs are examples of mesophyll-feeders common in Texas landscapes.
- What is sap?
- What are mouthparts on insects like, and how can I see them?
- What is a systemic insecticide?
- Aphids in Texas Landscapes (E-311) Aphids are among the most common sucking insect pests on Texas landscape plants. Found on leaves, stems, and even roots of plants, aphids feed on the phloem (sap) and leave behind weakened plants and sticky honeydew.
- Box elder bugs (E-453) Box elder bugs feed with their piercing sucking mouthparts fmaple and box elder seeds. While this does no damage to the tree, their presence in and around the home is a concern.
- Chili thrips (EEE-000412) Though not a true sap-feeding pest, these tiny insects are becoming an increasingly important and serious pest in roses.
- Crape Myrtle bark scale (Insect Update May 10, 2010) A new scale pest on crape myrtle turns bark black and is tough to control. Learn more about control.
- Pink hibiscus mealybug – New Texas pest (E-454) This new mealybug pest attacks over 300 species of plants and forms dense colonies with heavy wax buildup.
- Scale insects (B-6097) One of the more important, sap-feeding pest groups. Some scales are very difficult to find and control. This publication provides an overview of scale insects and control recommendations.
- Cycad aulacaspis scale (ENT-00038) Another recent scale pest, this is a major pest of sago palms.
- Wax scales on holly (L-5479) Large white scales on holly and many other plants.
- Whiteflies (E-432) Very small insects that feed on the undersides of leaves and produce honeydew, the name comes from the tiny, white adults that hover around infested plants.
- Spider mite control by CSU Colorado State University provides a good summary of spider mites and control options.
- Lace bugs by University of California. Lace bugs are common pests of ornamental trees and shrubs in Texas. This publication tells how to identify these insects and offers control options.