Leafhoppers are small, wedge-shaped insects that feed on plants by sucking sap. This activity causes light-colored stippling on leaves, which reduces photosynthesis and weakens the plant. Certain leafhopper species also transmit harmful plant diseases, such as aster yellows or the curly top virus, which can devastate crops. Biological control (biocontrol) offers a natural, targeted solution to manage these pests by leveraging their natural enemies, minimizing the need for chemical intervention.
Primary Predators and Parasitoids Targeting Leafhoppers
The most effective biological agents for managing leafhopper populations fall into two main categories: generalist predators and specialized parasitoids. Among predators, the minute pirate bug (Orius species) is highly valued, actively preying on leafhopper nymphs, thrips, and mites. Green lacewing larvae and adults are aggressive generalist predators that consume soft-bodied leafhopper nymphs.
Lady beetles (ladybugs) also consume leafhopper nymphs, contributing to population control early in the season. Various species of spiders, including jumping spiders and crab spiders, capture both adult and immature leafhoppers. Specialized parasitoid wasps are potent control agents because they target the leafhopper’s protected egg stage. Wasps in the Mymaridae family, such as Anagrus species (often called “fairy flies”), are key egg parasitoids for pests like the grape leafhopper. Other parasitoid wasps, such as the Dryinid wasps (Aphelopus species), target the leafhopper nymph directly by injecting an egg into its body.
Biological Mechanisms of Control
Predation and parasitism work together to suppress pest populations at different points in the leafhopper life cycle. Predation involves a direct attack, where insects like the minute pirate bug or green lacewing larvae actively hunt and consume leafhopper nymphs and adults. These predators pierce the leafhopper’s body and suck out its internal fluids, resulting in immediate death.
Parasitism is a more specialized mechanism that prevents the next generation from emerging. For example, tiny Anagrus wasps locate leafhopper eggs inserted into plant tissue and deposit their own egg inside the host egg. The developing wasp larva consumes the leafhopper embryo, and an adult wasp emerges from the host egg instead of a leafhopper nymph.
Other parasitoids, like Dryinid wasps, perform internal parasitism on the nymph or adult leafhopper. The wasp larva develops internally; in the case of Aphelopus, the later stages become partially external, forming a visible sac on the host’s abdomen. The parasite eventually consumes the host completely, killing the leafhopper before it can reproduce.
Strategies for Attracting and Sustaining Beneficial Insects
A successful biocontrol program depends on creating an environment that encourages and retains beneficial insect populations.
Providing Floral Resources
The most effective strategy is providing supplemental food sources for adult parasitoids and predators. Adult parasitoid wasps often require pollen and nectar to sustain themselves and lay eggs. Planting a diverse range of flowering plants with small, open blossoms provides easily accessible nectar and pollen. These include plants in the aster, carrot (Apiaceae), and buckwheat (Polygonaceae) families. Interspersing these plants throughout the field ensures a continuous food supply, which increases the rate of parasitism by key wasps.
Offering Shelter
Providing suitable shelter is another important factor, as many beneficial insects, including spiders and ground beetles, are nocturnal and need daytime hiding spots. Organic mulches, such as straw or wood chips, offer humid, protected refuges on the soil surface where these predators can rest and overwinter. Maintaining permanent, non-crop vegetation near growing areas serves as a long-term habitat and overwintering site for many beneficial species.
Managing Pesticides and Augmentation
The careful management of pest control products is paramount, as broad-spectrum insecticides can decimate beneficial insect populations more severely than the target pests. When intervention is necessary, growers should opt for selective products with short residual activity, such as insecticidal soaps, horticultural oils, or neem oil, which minimize harm to natural enemies. For severe outbreaks, purchasing and releasing commercially available species, such as green lacewing eggs or Anagrus wasps, can augment the natural population if timed properly to coincide with the leafhopper life cycle.