The squash bug, Anasa tristis, is a common insect pest specializing in feeding on the Cucurbitaceae family, often called cucurbits. These true bugs use piercing-sucking mouthparts to extract sap from the leaves, vines, and fruits. This feeding disrupts the flow of water and nutrients, which can severely damage or kill young plants.
The Preferred Host Plants
The squash bug exhibits a strong preference for plants within the Cucurbita genus, which includes most squashes and pumpkins. These plants are not only the main food source but are also the preferred location for the bugs to lay their bronze-colored, barrel-shaped eggs. Young squash bugs, or nymphs, have the highest survival rates when reared on pumpkins and squash varieties, demonstrating the high susceptibility of these plants.
Specifically, yellow summer squash varieties like yellow straightneck and yellow crookneck are highly attractive to the pests. These varieties are frequently sought out for both feeding and egg-laying, making them particularly vulnerable to rapid population growth. Hard-skinned winter squashes, such as ‘Hubbard’ squash, as well as pumpkins, are also among the most severely damaged plants.
Feeding damage on these preferred hosts results in yellow spots that eventually turn black and dry out. This condition is sometimes called “Anasa wilt” due to the wilting that occurs beyond the feeding point. Some varieties, such as butternut and royal acorn squash, demonstrate a higher tolerance to feeding damage.
Occasional Meal Sources
While the squash bug shows a clear preference for pumpkins and squash, it will feed on other members of the Cucurbitaceae family if its primary hosts are unavailable or overcrowded. These secondary targets include cucumbers, various melons, and gourds. However, the damage inflicted on these plants is typically less concentrated and severe compared to the primary hosts.
Research indicates that the survival rate of squash bug nymphs drops dramatically on these less-favored hosts. Nymph survival is considerably lower on watermelon and cucumber plants than on pumpkin or squash. While these plants provide sustenance, they are not optimal for the pest’s life cycle. Damage can still occur, especially when populations are high or during periods of drought when host plants are stressed.
Melons, such as cantaloupe and muskmelon, are the least preferred food source among the common cucurbits, offering the lowest survival rates for nymphs. This difference in preference can be utilized by gardeners who may choose to plant a highly preferred variety, like ‘Blue Hubbard’ squash, as a “trap crop” to draw the pests away from their less-tolerant plants.
Plants That Deter Squash Bugs
Plants that deter squash bugs can help protect nearby host plants through companion planting. These plants actively discourage the pest’s presence due to their strong scents or chemical composition. Growing these deterrent plants near susceptible squash and pumpkins offers a non-chemical method of pest management.
Companion Flowers
Nasturtiums and marigolds are frequently cited as effective companion plants that can repel squash bugs. Nasturtiums sometimes act as a trap crop, drawing the insects away. The distinct aroma of marigolds is generally unattractive to the pests.
Aromatic Herbs and Vegetables
Aromatic herbs can also be beneficial in reducing infestations. Herbs like basil and mint produce volatile oils that confuse or repel the squash bug. Basil’s sharp scent, caused by compounds such as citronellal and limonene, makes it an unfavorable location for adult bugs to settle and lay eggs. The distinctive aroma of radishes, particularly when planted as a border, can also help deter squash bugs from approaching the main crops.