Calling in Reinforcements – Biological Controls

Landscapes and gardens have natural populations of helpful organisms at work. These “workers” are the beneficial predators, parasites and pathogens that naturally target pest organisms in the environment. Beneficial organisms include a wide assortment of organisms such as: bacterial and/or fungal diseases; spiders; mites; centipedes; nematodes; various lady beetles; ground beetles; rove beetles; lacewings; predacious
bugs (minute pirate bugs, big-eyed bugs,damsel bugs, stink bugs); and numerous parasitic wasps.

Lacewing

Most pest management practices are designed to manage against the pests; instead, manage for beneficial organisms that are already providing valuable pest control. Why is biological control important? The preservation and use of common beneficial organisms ensures that the natural ecological balance is maintained and promotes a safe home landscape by reducing pesticide use. The misuse of pesticides can impact directly on beneficial organism/pest interactions. Pesticide resistance develops in pest organisms that were once killed by a specific application of pesticide and through genetic evolution can now survive the application. Increased rates of application may not provide greater control either, making a once reliable pest control weapon useless.

Lady Bug

Pest resurgence occurs when natural biological control organisms are reduced by broadspectrum pesticides, either by one that persists in the environment for long periods of time or by numerous applications of chemicals with short residual times, to a level where they can no longer keep the pests in balance. This causes an increase in the pest populations. A disruption of natural enemies can also lead to secondary pest outbreaks. Pesticides reduce the natural enemy populations and a pest insect, that was not causing the original problem, increases in population to a damaging level.

Pesticides also affect non-target organisms such as wildlife, pets and humans. One method of biological control is augmentation. This practice involves the purchase and release of beneficial organisms, usually insects, into the infested area. In order for this practice to be effective, the correct organism must be purchasedand released at the appropriate time. Many beneficial insects choose specific hosts or prey as food sources. Anyone considering this tactic must have the knowledge to select the proper beneficial insects. Conservation of natural enemies present in the environment is the easiest and most cost-effective method of biological control available for gardeners. Conservation involves changing and improving management practices to either reduce harmful effects on beneficial organisms or to improve the environment to increase their populations. Reducing pesticide impacts would be the first and most important change to conserve natural enemies.Many insecticides and some fungicides directly affect natural controls by killing them at the
time of application. Others have long residual activity and harm beneficial organisms that later move into the treated area. Pesticides can also indirectly harm beneficial organisms by causing lengthened development time of the immature stages, reduced prey consumption, reduced reproductive capability, and repellency, where beneficial organisms are driven away from the treated plants by the chemical pesticide. An easy and colorful method of promoting beneficial insects is to grow a wide variety of plant materials in the home landscape or garden. An herbaceous perennial border, with a variety of species that flower at different times during the growing season, will provide alternate food sources (i.e. pollen) for some beneficial insects when there are no prey insects available.