Striped cucumber beetles often fly from their hibernating sites early in the season, even before plants emerge. As soon as the cucumber, squash, pumpkin, melons and related seedlings push up through the soil, beetles can eat off the stems and cotyledons, frequently killing them. Adults later feed on the leaves, vines and fruits of plants that survive. Sometimes, deep pits are gnawed into the rind, making the produce unfit for consumption or market. Damage is also caused by the larvae feeding on the roots of host plants, which weakens the plant and makes it susceptible to other problems.
Adults also feed on beans, peas, corn and blossoms of other plants.
Most important, these beetles are vectors of a serious cucurbit disease known as bacterial wilt. Plants infected with the disease wilt quickly with leaves drying out prior to plant death. These beetles introduce the bacteria into the plants through the fecal contamination of feeding wounds. This is the only natural method of infection known. Beetles also spread squash mosaic virus.