Biological Control of Pests

Protecting Plants and Trees from Invasive Pests

Biological control (bio-control) of pests relies primarily on reducing pest numbers below damaging levels using natural methods like predators, parasites and pathogens to control pests. Unlike pests that originate in the United States and have "natural enemies" and predators, these non-native, invasive species lay their eggs, eat and damage ecosystems, and repopulate without natural enemies and predators to keep them in check. Left uncontrolled, invasive pests run rampant on farms and in home gardens, forests, nurseries and parks, crippling the health of the natural ecosystem and interfering with the ability of plants and trees to produce and survive.


Bio-control is an integral component of both organic farming and Integrated Pest Management. The following strategies are successful biological controls:

Mating Disruption

Many insect pests have short lifecycles – they are born, grow, reproduce and die within 60 to 90 days. One of the most targeted and least environmentally disruptive ways to manage pests is by interfering with their reproductive cycle. When the success rate of mating is reduced, the entire population of an invasive pest can be eliminated in a fairly short timeframe.


Mating disruption techniques work by confusing insect pests searching for mates. In nature, female insects release pheromones to attract mating partners. The release of large quantities of synthesized sex pheromones makes it very difficult for male pests to locate a mating partner by making everything – trees, roads, even structures – appear to be a partner. The result is a decline in pest numbers as the insects naturally reach the end of their lifecycle and the number of pests in the next generation is drastically reduced or eliminated.


A key benefit of pheromone-based programs is that they are highly selective. Typically, only the targeted insect pest and a limited number of closely related insects will respond to the pheromone. There is also virtually no detectable residue, negligible health risks to humans and other animals, and no accumulation in wildlife or groundwater.


There are a few main methods to disperse the pheromones:


Twist Ties

Pheromone-infused "twist ties" provide a timed-release method of dispersing pheromones. Similar looking to garbage bag ties, twist ties are placed on trees, shrubs and objects such as fence posts or telephone poles in infested areas. They contain an odorless, synthetic pheromone and work best in very small geographic areas. They are less effective at reducing the presence of pests in an area where the invasive pest population has grown to great numbers, due to the manual labor involved in twist tie application. A twist tie is effective for 60-90 days, at which point it is removed or replaced.



Pheromones may be sprayed from ground applicators, such as puffers, or from the air via helicopters or airplanes. Spraying allows larger geographic areas to be covered more thoroughly and rapidly. This reduces the likelihood of "hit-or-miss" coverage and the resulting spread of infestations. Puffers use timed-release technology that allows the pheromones to be released over a period of time, confusing male pests over the course of their reproductive peak.


Sterile Insect Technique

The Sterile Insect Technique (SIT) is a method of pest control using area-wide inundative releases of sterile insects to reduce the fertility of a field population of the same species. The SIT involves raising large numbers of sterile insects in a lab and releasing them in infested areas to mate with fertile insects and thus produce infertile eggs. The sterile insects compete with fertile insects for mates. Mating still occurs but each subsequent generation is smaller as reproductive success decreases. This process can be repeated until the natural population is progressively reduced and eventually eliminated.


Many countries have used mass sterile insect releases since the 1960s to eradicate dangerous invasive species, including Argentina, Canada, Japan, Mexico, several countries in Central America and the Middle East, New Zealand, North Africa, South Africa and the United States. The technology was originally developed to manage the animal pest called screwworm fly and has been used successfully in California for decades with the Mediterranean fruit fly, Mexican fruit fly and Pink bollworm moth. The United States Department of Agriculture (USDA) is currently developing the facilities and technologies necessary for Light Brown Apple Moth (LBAM) sterile insect releases, though the project will take years to fully develop. Although SIT is an effective pest management method, the number of years that it takes to develop an effective SIT program for a specific pest makes it difficult to implement quickly.


Male Attractant Technique

A "male attractant technique" that combines a pheromone with a pesticide in a mixture applied in small splotches on utility poles and trees may be used for intermediate infestations, defined as a limited number of pests spread over a large geographic area. This method is effective with fruit flies, like the Oriental Fruit Fly. This method is also somewhat labor intensive but may be more targeted. It can be used in both urban and rural settings.


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Last Modified: May 3, 2010