The squash bug (Anasa tristis) is a persistent and destructive garden pest that targets plants in the cucurbit family, including squash, pumpkins, and gourds. These insects use piercing-sucking mouthparts to extract sap, which can quickly weaken and kill young plants. Gardeners often turn to companion planting, a natural, non-chemical strategy, to deter these pests by using other plants to confuse, repel, or trap the bugs. This method focuses on creating a diverse environment that makes it difficult for the squash bug to locate its preferred host.
Identifying the Squash Bug and Its Damage
The adult squash bug is a flat-backed, grayish-brown insect, measuring about five-eighths of an inch long, often displaying orange or brown stripes along the edges of its abdomen. Females lay clusters of small, oval, bronze to reddish-brown eggs, typically found on the undersides of leaves near the veins. The nymphs are wingless, starting light-colored with black appendages before gradually turning grayish-brown as they mature.
Squash bugs use straw-like mouthparts to suck out sap, disrupting the flow of water and nutrients. This feeding leads to yellow speckling on the leaves that eventually turns brown and brittle. Heavy feeding can cause “Anasa wilt,” where the vines collapse and die. Young seedlings are particularly vulnerable and can be killed quickly.
Aromatic Plants That Directly Repel Pests
Aromatic plants deter pests by emitting strong, volatile compounds that mask the scent of the squash plant, making it difficult for the squash bug to locate its host. Planting aromatic herbs like mint, dill, and catnip directly among the squash can significantly reduce the number of pests landing on the main crop.
Mint has a powerful scent that effectively deters squash bugs, but it should be planted in a container to prevent aggressive spreading. Dill is also an effective repellent and attracts beneficial insects like parasitic wasps. Marigolds (Tagetes species) release a distinctive aroma from their foliage that helps repel squash bugs and other beetles.
Nasturtiums are highly recommended, as their spicy aroma helps repel squash bugs and cucumber beetles. Radishes, especially the Daikon variety, are sometimes interplanted because their peppery scent discourages pests from laying eggs. These plants create a sensory barrier, overwhelming the pest’s ability to detect the chemical cues released by the cucurbit plants.
Using Decoy and Trap Crops
Trap cropping involves planting a highly attractive host plant to lure pests away from the main crop. The most effective trap crop is the Blue Hubbard squash (Cucurbita maxima).
Blue Hubbard squash is highly attractive to squash bugs due to its high concentration of the biochemical compound cucurbitacin. The trap crop acts as a sacrificial plant, drawing the majority of the squash bug population, including adults and egg-laying females. Success requires regularly monitoring the trap crop and destroying the congregating pests, often by hand-picking, vacuuming, or targeted insecticide application.
The trap crop must be established and growing before the main crop so it is larger and more attractive when adult squash bugs emerge. Planting six to eight Blue Hubbard plants can effectively protect a small garden of around 100 cucurbit plants. This method concentrates the pest population, making management significantly easier and reducing the need for broad-spectrum treatments.
Placement and Density for Maximum Protection
Strategic placement and density are crucial for the effectiveness of companion planting. For aromatic repellent plants, interplanting is the most effective technique, mixing the companion plants directly among the squash. This ensures the strong scent is dispersed throughout the main crop area, maximizing pest confusion.
A high density of repellent plants is necessary to create a sufficient scent cloud; for example, planting a ring of marigolds or clumps of mint around each squash hill. Trap crops like Blue Hubbard should be placed three to eight feet away from the main crop, often at the corners or ends of the rows.
Companions should be planted at the same time as the squash, or slightly earlier, so they are established when squash bugs first emerge. While creating a perimeter barrier can help, the most successful approach combines interplanting and border planting for a multi-layered defense.