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Biocontrol Reference Center

Beneficial Arthropods

Courtesy of the International Pest Management Institute.
Currie Enterprises


Naturally occurring biological control organisms have always existed. If potential animal and plant pests were not already being managed, neither we nor our food production or landscape systems could survive. Through the millennia, arthropod herbivores have been held in check by arthropod predators and parasites, bacteria, viruses and other organisms.

The term "biological control" was first used in 1919 to indicate use of natural enemies (pathogens, predators, parasitoids) to control insect pests. There are over 1,500 naturally occurring macroorganisms or their products that hold promise for the control of insect pests. More recently the term "biorational" has begun to be used to describe other nonchemical forms of control: resistant crops, sterile male releases, genetic techniques, use of attractants/pheromones, or repellents.

Biological control was 100 years old in 1989. In 1889, USDA imported 129 vedalia beetles from Australia to manage cottony cushion scale attacking citrus trees in California. The young citrus industry was saved and able to greatly expand. Remarkably, the scale insect has never again built up in numbers to cause economic injury. The program to find and import vedalia beetles cost $2,000 in 1889.

In 1989, it was estimated that over 600 species of potentially useful biological control organisms have been released in the U.S.; 223 have become established (290 on a world wide basis). In the last 20 years, over 145 species have been released against 84 different insect pests. Biological management involves both introductions and augmentation of natural predators.

Insect populations are affected by the environment; biotic and abiotic factors influence rates of reproduction, survivorship and population densities. Natural enemies, particularly parasitic Hymenoptera, regulate insect populations by utilizing insects as prey or as sites for reproduction. This is why most plant feeding insects are not pests. Biological management has already proven successful in over 200 cases worldwide. It is essentially permanent and environmentally safe because in most cases because in most cases natural enemies are being reunited with pest species that have escaped natural regulation by invading new territory.

The major insect pests in the U.S. are nearly exclusively alien species that have successfully invaded new territory and then exploited particular resources. Invading pest insects escape population regulation when their specific natural enemies are left behind, enabling a pest population to grow virtually unchecked. In order to implement biological management, it is best to determine if and what natural enemy species exist in the original, natural habitat of the pest species that could be imported to regulate the pest species.

Surveys first conducted to determine if there are parasitic or predatory insects attacking eggs, larvae or adult pest populations. These studies also provide adult pest species for taxonomic study so as to correctly determine the origin of the pest and associated natural enemies. Next, searches for the natural enemies are conducted to locate the natural enemies in its home habitat. Then, geographic distribution and reproductive biology of natural enemies are determined.

Controlled populations of pest species, host species, and parasites or predator species are conducted in glass greenhouses to study interactions. Field release authorization is obtained from USDA-APHIS before particular natural enemies are released. Then, monitoring and sampling of the introduced parasite or predator species and pest species are conducted in natural environments. The objectives of biological management are not to eradicate the pest species, but to reduce pest species below the economic or aesthetic thresholds.

One pest management "tool" which should not be overlooked or underestimated, is the commercial production and release of predatory insects, predatory mites and parasitoids. Biological management by augmentation cannot be used as a "lone tool" either; it must be part of an integrated pest management system.

The challenges faced by biological management agents such as natural enemies differ from those faced by chemical and some microbial pesticides such as Bt. Natural enemies are living, heterogeneous and genetically plastic organisms; they have unique relationships with the components of the urban and agro-ecosystems where they will be applied. Commercially produced natural enemies cannot be "canned or bottled" as a magic biological bullet that performs equally in all habitats. Natural enemies must be used considering their inter-relationship with the environment where they are applied.

Natural enemies will not become economically competitive with broad spectrum chemical or microbial pesticides until the external costs caused by these pesticides is considered. For example, and chemical pesticide may appear cheap when its effect on the fauna of beneficial organisms and pollution is not considered. However, if the effects of the chemical pesticide on a valuable natural resource (the natural enemy complex) and pollution are considered, the cost of the chemical or microbial pesticide may be too high compared to the cost of using natural enemies.

Natural enemies will become more cost competitive as they are integrated with new technologies such as computers, phernomes and selective chemical and microbial pesticides and application methodology. The long term benefit must be calculated when making any cost comparison; such as fewer problems of resistance and secondary pests.

Biological management will be successful if a bio-compatible management strategy is practiced. It is important to actually identify your pests and monitor their distribution and abundance to insure proper timing and placement of appropriate biological measures. Use cultural and physical practices whenever possible, and use bio-compatible chemicals, if pesticides if necessary.

Changing your management strategy from one that relies solely on chemicals to an IPM approach involves common sense practices.

  • Plan your strategy four to six weeks in advance for the site. Consult suppliers, other growers, and university researchers and extension personnel.

  • Determine pest thresholds in advance. These are your maximum allowable limits of pest damage. This will enable you to make management decisions quickly when pest problems arise.

  • Use physical and cultural pest management wherever possible. Isolate new stock and kill incoming pests before they infest your operation. Screen vents and doorways, rotate crop plants, and keep site area free of debris and weeds (pest havens). Adjust temperature, humidity and light to be optimum for beneficial arthropods.

  • Pest monitoring, proper identification, and record keeping are essential to well-timed, effective management. This requires a person to carefully check the site on a weekly or semi-weekly basis. We recommend that you hire an experienced pest management consultant or train and dedicate one of your employee's to time this task.

  • Manage pesticides to encourage survival of beneficial arthropods. Ask for a list of chemicals and their effects on beneficial organisms. Many beneficials are tolerant to some of the pesticides you currently use. SPOT treat isolated outbreaks when necessary and before the entire site is infested. TEST NEW, BIO-COMPATIBLE PESTICIDES IN ADVANCE for phytotoxicity on a small number of plants.

  • Begin release of the biological agents at the first sign of the pest. These releases will frequently occur four to twelve weeks before you would normally consider spraying pesticides.

Although chemical pesticides are an important tool in many agricultural systems, the complete reliance on chemicals is no longer a feasible approach to pest management for the following reasons:

RESISTANCE: The major disadvantage which continues to erode the effectiveness of conventional insecticides is the ability of the pests to develop resistance. Approximately 500 insects and related pests (mites) have shown resistance. In fact, some cannot be controlled with today's chemical arsenal. The latest research has indicated that some insects are now beginning to show resistance against the popular Bt products.

SECONDARY PEST PROBLEM. Chemicals which are effective against pests often kill or interfere with beneficial organisms. The situation created then allows an insect (not the usual pest, but another insect taking advantage of the available food) to rapidly increase in number since no predators are in the field to prevent the population explosion. Sometimes the resulting (long term and economic) damage is greater by the secondary pest than by the pest originally targeted.

ECONOMICS. The combination of resistance, secondary pests and legal limitations brought about by safety and environmental concerns has increased the cost of insecticides. Also, a matter of economics to commercial producers and pest managers, is the demand for pesticide-free food and living environments.

The solution is to optimize pest management.

  • Identify the pest (not all insects are pests).

  • Establish the correct level of acceptable damage (not all pests are of economic importance).

  • Monitor the pest situation on a regular basis (sometimes no action is required).

  • If the pest population is high enough to cause economic damage, use all available means of management (biological, cultural, mechanical, selective chemical).

  • Record results to use in future strategy (preventive measures require planning ahead).

When we farm or garden (especially in a monoculture), we are changing the environment to favor that which we wish to grow. We may remove "weeds", "fertilize" the soil, provide additional water, etc. However, our first visitors are sure to be attracted by this new food. Generally, the plants attract a variety of plant feeders which EVENTUALLY attract predators and parasites. The time between arrival of the pest and the arrival of the enemy can be costly. Scientists worldwide are continuously searching for natural enemies to introduce into pest situations (i.e., parasites to combat Russian Wheat Aphid). Commercial insectaries mass produce a number of predators and parasites that have already proven to be successful in reducing pest populations enough to greatly reduce or eliminate pesticide use.

Read the next installment of Beneficial Arthropods,
My Enemy's Enemy is my Friend
Webkeeper: E. W. Acosta - mailto:info@biconet.com Last Update: May 06
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