Stink bugs belong to the insect family Pentatomidae and are easily recognized by their distinct, broad, shield-shaped bodies. Species like the invasive brown marmorated stink bug are significant agricultural and garden pests across the United States. While a major infestation rarely kills a mature plant outright, the insects cause severe quality damage to fruits and vegetables, often rendering the produce unmarketable or inedible. Young plants and seedlings are significantly more vulnerable to feeding pressure and can be stunted or killed by a heavy presence of these pests.
How Stink Bugs Cause Plant Injury
Stink bugs feed using specialized, needle-like mouthparts known as stylets, which form a piercing-sucking proboscis. The insect uses these stylets to penetrate the plant tissue, reaching deep into the fruit, seed, or stem. This mechanical puncture is only the first step, as the insect also injects saliva into the plant.
The injected watery saliva contains potent digestive enzymes, such as proteases and nucleases, which liquefy the plant’s internal contents. The insect then sucks up this pre-digested, liquid material, leaving behind collapsed and damaged plant cells. To facilitate this process, the bug also secretes a gel saliva that hardens to form a salivary sheath. This sheath stabilizes the stylets and seals the feeding site. The combination of the physical puncture and the enzyme injection causes the long-lasting, internal tissue injury.
Recognizing Stink Bug Damage and Severity
Visible signs of stink bug feeding vary, but damage is often concentrated on developing fruits and seeds. On fleshy produce, such as tomatoes, peaches, and peppers, the injury appears as sunken, cloudy, or white-yellow spots on the surface. Beneath the skin, the affected tissue will be dry, pithy, and corky due to internal cell collapse caused by the salivary enzymes.
Feeding on young fruits often results in a severe cosmetic deformity known as “cat-facing,” leaving the fruit scarred, dimpled, and misshapen. This injury makes produce unfit for fresh market sale, leading to significant economic losses. When stink bugs feed on seeds, such as soybeans or nuts, the kernels may become shriveled, aborted, or fail to develop properly.
On leaves and stems, stink bug feeding can leave small, circular, necrotic spots or give leafy greens a tattered appearance. Infestation severity is highest when bugs are present during the plant’s reproductive stages, such as fruit set or pod fill. While mature plants typically tolerate the feeding, the small size and tender tissues of seedlings mean they can quickly succumb to a relatively small number of feeding insects.
Management Strategies for Infestations
Managing stink bug populations relies on an integrated pest management (IPM) approach that combines multiple strategies to limit their numbers. Non-chemical control methods should be the first line of defense, particularly in home gardens. Physical exclusion is highly effective, involving covering vulnerable plants, such as vegetables and berries, with fine-mesh netting or row covers to prevent adults from landing and laying eggs.
For small infestations, hand-picking bugs and dropping them into a container of soapy water is a practical method of removal. This is easiest in the cool temperatures of the early morning when the insects are less active. Removing common overwintering sites, such as tall weeds, garden debris, and brush piles near the garden, can reduce the number of bugs that survive to emerge in the spring.
Chemical control is generally reserved for severe infestations and is most effective when targeting the young, wingless nymph stage, as they are more sensitive to insecticides than adults. If a pesticide is necessary, choose a product labeled for stink bugs and apply it precisely, such as using border treatments to intercept bugs moving from surrounding areas. Broad-spectrum insecticides should be used cautiously, as they can unintentionally kill beneficial insects that prey on stink bugs and their eggs.