The Brown Marmorated Stink Bug (BMSB) (Halyomorpha halys) is an invasive agricultural pest that poses a significant threat to home gardens and commercial crops. This insect uses piercing-sucking mouthparts to feed on over 170 plant species, including tomatoes, peppers, and tree fruits. Feeding damage results in discolored spots, pitting, and fruit deformation, often rendering the produce unmarketable. Since stink bugs are highly mobile and infestations can quickly overwhelm crops, finding effective and safe control methods is a major concern for gardeners dealing with edible plants.
Immediate, Non-Chemical Control Methods
The most direct method of eliminating stink bugs involves manual removal, which is highly effective for smaller garden infestations. This technique, often called the “shake and drop” method, capitalizes on the insect’s defensive behavior of dropping to the ground when disturbed. The bugs are collected by knocking them from the plant directly into a container filled with soapy water.
The soap works by quickly breaking the water’s surface tension, causing the insects to sink and drown, preventing them from flying away. A simple solution of water and liquid dish detergent, mixed at a ratio of about two teaspoons of soap per quart of water, ensures the bugs suffocate by clogging the pores they use to breathe. Collecting is most productive in the early morning when stink bugs are sluggish from cooler temperatures.
Another approach uses homemade sprays, which kill by direct contact rather than systemic action. Insecticidal soaps or simple dish soap diluted with water can be sprayed directly onto the insects. This application method disrupts the waxy protective layer on the insect’s body, causing rapid dehydration. These sprays must coat the insect entirely to be effective and offer no lasting protection once the spray dries. Trapping systems, such as light traps or pheromone-baited sticky traps, can also be employed to monitor or reduce localized populations just outside the main garden area.
Utilizing Biological Control Agents
A strategy for suppressing stink bug populations involves the use of natural enemies, which can provide sustained pest control. Generalist predators, such as spiders, praying mantises, and certain species of birds, consume stink bugs or their eggs, contributing to a natural reduction in pest numbers. Encouraging these beneficial organisms requires creating a diverse habitat with flowering plants and ground cover that provides shelter and alternative food sources.
A more specialized method of biological control involves parasitic wasps, which target the next generation of the pest. The Samurai Wasp, Trissolcus japonicus, is a tiny parasitoid that specifically attacks the eggs of the BMSB. The female wasp lays her own egg inside the stink bug egg, which prevents the nymph from developing.
This parasitism can lead to high mortality rates in the stink bug egg masses, with documented success rates as high as 90% in their native range. While the Samurai Wasp has established itself in North America, it helps to suppress the overall population over time. Gardeners can support the activity of this wasp by avoiding broad-spectrum insecticides that harm these beneficial insects.
Selecting and Applying Targeted Pesticides
When non-chemical methods fail to control a severe infestation, particularly when crops are highly vulnerable, targeted pesticides become necessary. The challenge is selecting a product that is effective against the tough-bodied stink bug while minimizing harm to the edible crop and beneficial garden life. Broad-spectrum pyrethroid insecticides are the most effective chemical option, but they also carry a high risk of killing non-target insects, including pollinators.
For gardeners seeking less disruptive options, active ingredients like pyrethrins and neem oil are available. Pyrethrins are fast-acting, derived from chrysanthemum flowers, and provide a quick knockdown of insects upon direct contact. Neem oil, derived from the neem tree, works by disrupting the stink bug’s feeding, egg-laying, and developmental processes; it is often more effective on nymphs than adults. Both organic-approved options have limited residual activity, meaning they break down quickly in the environment.
Any application of pesticides must adhere strictly to the product label, especially concerning the Pre-Harvest Interval (PHI). The PHI dictates the minimum number of days that must pass between application and harvesting to ensure the produce is safe for consumption. To protect pollinators, applications should be limited to the late evening or early morning when beneficial insects are not actively foraging. For high-value crops like tomatoes and peppers, physical exclusion using fine mesh row covers can prevent the pest from ever reaching the plant.