Squash Bug Damage

Squash plant on right wilts due to squash bug mechanical damage to its water transport system.
Inset: Squash bugs on a squash leaf.

Squash bugs, Anasa tristis, are lacerate and flush feeders. They have sucking mouthparts that can probe inside a plant and excrete enzymes that digest and liquify plant tissue. Squash bugs do most of the damage to plants when stylets enter and destroy the vascular tissue of the plant. In heavy infestations, all transport of water to the a leaf can be blocked and the leaf will wilt.

Squash bug can transmit a strain of the bacteria, Serratia marcescens that causes cucurbit yellow vine disease. The bacterium enters the plant with the squash bug saliva. This disease is spreading Texas and Oklahoma.

Serratia marcescens is an interesting bacterium. It is opportunistic and can colonize tissues of both plants and animals. A strain distinct from the one that cause cucurbit yellow vine disease causes soft rot in bell peppers. Yet another strain can be pathogenic in humans. In insects, Serratia is generally not fatal. It is considered an opportunistic infection that occurs in insects suffering from viral infection including silkworms and cockroaches. Squash bug is not known to suffer ill effects from Serratia marcescens. Squash bugs don’t bite people and do not transmit Serratia marcescens to humans. Serratia marcescens appears to be an opportunistic infection acquired by direct contact with the bacteria.