Grasshoppers are common garden pests known for their voracious feeding habits, causing significant damage to many types of plants, including grasses, vegetables, trees, and shrubs. As generalist herbivores, they chew on a wide variety of plant material, often leaving large, irregular holes in leaves. For gardeners seeking environmentally friendly methods, using specific plants as natural deterrents offers a practical strategy for controlling grasshopper populations and protecting vulnerable crops. This approach utilizes the plants’ defensive chemistry to make a garden less appealing to the pests.
How Plants Naturally Deter Grasshoppers
Plants have evolved defense mechanisms that rely on the production of phytochemicals, also known as secondary metabolites. These compounds are not involved in growth or reproduction but serve as deterrents, toxins, or digestion inhibitors against insects like grasshoppers. The effectiveness of a repellent plant is linked to the concentration and type of these natural chemicals, such as terpenes, alkaloids, and phenolics.
These secondary metabolites interfere with the grasshopper’s ability to feed by targeting their sensory and digestive systems. Strong volatile oils can overload the insect’s chemoreceptors, making it difficult for the grasshopper to locate preferred food plants. Bitter compounds can trigger a feeding aversion response or, if ingested, cause physiological disorders that slow growth and reduce reproductive success. Introducing these chemically armed plants into the garden creates a biological defense system that reduces feeding damage.
Aromatic Plants That Confuse Pests
Aromatic plants primarily deter grasshoppers by releasing volatile compounds that mask the chemical cues insects use to identify preferred food sources. The intense scents emitted by these plants overload the grasshopper’s olfactory system, effectively hiding the presence of nearby crops. This strategy relies on confusing the pest rather than poisoning it.
Members of the mint family, such as rosemary and sage, are particularly effective due to their strong, characteristic scents. Rosemary contains volatile oils that work as a natural repellent. Similarly, the strong scent of sage discourages grasshoppers from landing and feeding. Other aromatic herbs like lavender and basil also emit strong odors that grasshoppers find unappealing, making them useful additions near susceptible plants.
Toxic and Unpalatable Barrier Plants
A different set of plants defends itself by containing compounds that are unpalatable, bitter, or mildly toxic when ingested, discouraging grasshoppers through taste rather than smell. These plants function as effective barrier crops because grasshoppers actively avoid consuming them, seeking out less protected foliage instead. This kind of deterrence is known as antixenosis, where the plant prevents the insect from feeding.
Marigolds and calendula are frequently used because they contain chemical compounds repellent to a variety of pests, including grasshoppers. The bitter taste of these compounds discourages feeding on contact. Neem trees produce azadirachtin, which, when applied as an oil, acts as a feeding repellent and disrupts the grasshopper’s ability to molt and breed. Strongly flavored culinary herbs like garlic, used in a spray application, can also reduce grasshopper populations due to the unpleasant taste and scent.
Strategic Placement for Effective Control
The success of using repellent plants depends heavily on their strategic placement within the garden layout, a practice often referred to as companion planting. Interspersing aromatic plants among vulnerable crops is an effective method, using their strong scents to confuse the pests. This technique disrupts the grasshoppers’ ability to home in on their target plants, reducing feeding pressure.
Planting barrier rows around the perimeter of the garden is another useful tactic, utilizing the toxic or unpalatable nature of specific plants. Shrubs like forsythia or crepe myrtle, which grasshoppers are not attracted to, can form a physical and chemical barrier along the edges of the growing space. For localized protection, concentrated plant extracts, such as a homemade garlic or hot pepper spray, can be applied directly to the foliage of highly susceptible plants to make them unappealing.