the most damaging effect sucking insects on crop is the

The most damaging effect of sucking insects on crops is the transmission of plant diseases, particularly viral diseases. Sucking insects such as aphids, whiteflies, leafhoppers, and thrips feed by inserting their needle-like mouthparts (stylets) into plant tissues and extracting phloem sap. During this process, they can pick up viruses and other pathogens from infected plants and inject them into healthy ones.

While the direct removal of sap weakens the plant, the indirect damage caused by disease transmission is far more devastating. A single aphid can infect an entire field with a viral disease such as cassava mosaic virus, maize streak virus, or groundnut rosette virus. These diseases can cause total crop failure, whereas sap loss alone rarely kills a plant.

Consumption of plant tissues is more characteristic of chewing insects (such as grasshoppers and caterpillars), not sucking insects. Lowering the nutritive value of seeds is a storage pest effect, not a field-level impact of sucking insects. Complete dehydration of crop plants is an extreme outcome that sucking insects do not typically cause, since their sap extraction is usually insufficient to fully dehydrate a plant. The role as disease vectors is what makes sucking insects particularly destructive.