Bio Controls for the Garden
by Emily Gatch

1. Conservation and enhancement: modifying the local environment to conserve beneficial species and encourage their activities; modifications would include but are not limited to providing shelter, food sources (insectary plants, alternate hosts), and overwintering sites. This is the most obvious and most economical biocontrol method, and a wealth of information exists on the topic (see "Further Reading" below).
2. Augmentation: supplementing the numbers of existing biocontrol agents by releasing "more of the same" in the form of laboratory-reared or field-collected populations.
3. Importation (also known as classical biocontrol): deliberate introduction of an exotic natural enemy into an area where it did not previously occur. This is a tactic employed only by university and government agencies, and is used to control exotic (introduced) pests. This approach involves identifying the origin of the pest and then finding the naturally occurring biocontrol agents of that pest in the region of origin. After quarantining and screening the potential control agent for possible invasiveness in the area of introduction, controlled releases are made and the effects are closely monitored. While viewed as too risky by some, there have been striking successes with this biocontrol tactic (for example, the control of cottony cushion scale, which damages citrus, with the imported Australian ladybeetle Rodolia cardinalis). This is not a tactic available to individual gardeners and growers, although introduced exotic control agents already present can certainly be conserved, as described above.

1. Parasite: an organism that lives in or feeds on a host. Parasites tend to be very host specific, which is a desirable trait in a biocontrol agent. Nonspecific control agents may affect nontarget organisms as well, in the same way that a broad-spectrum pesticide will harm natural enemies. Many species of nematodes, which are microscopic roundworms ubiquitous in the environment, are parasites of various insect pests such as bark beetles, grasshoppers, and black flies.
2. Parasitoid: a subclass of parasites, parasitoids are organisms that are parasitic only in the immature stage and are free-living as adults. Typically, adult parasitoids lay their eggs in the larvae of pests. The parasitoid eggs hatch and complete their larval development within the pest larvae and then emerge as adults, killing the pest larvae in the process. Parasitoids are most typically members of the wasp (Hymenoptera) and fly (Diptera) insect orders, and are one of the most effective biocontrol agents. Trichogramma wasps, which are available through our Garden Variety Insect Package, are parasitic wasps that lay their eggs inside the larvae (caterpillars) of moths and sawflies. These wasps have been shown to be very effective against tomato fruitworm, European corn borer, and codling moth. This spring in the greenhouse, we released the parasitic aphid wasp Aphidius colemani, and the aphid midge (a type of fly), Aphidoletes aphidimyza, to control an aphid outbreak. These insects are available commercially through Planet Natural and Rincon Vitova. A thorough knowledge of the target pest's life cycle is important for timing the release of beneficial parasitoids. Mexican bean beetles, which have crippled attempts to grow beans on the Seeds of Change Research Farm in New Mexico, can be controlled by the parasitic wasp Pediobius foveolatus, but the release of the wasps must occur when the beetle larvae are present.
3. Predator: a free-living organism that feeds upon other organisms, typically devouring them quickly and completely. The unlucky prey may be either immature or adult, and many prey may be required for the predator to reach maturity. Insects and mites are the most important predators in biocontrol systems. Examples of predaceous biocontrol agents include ladybird beetles, lacewings, and praying mantises (all included in our Garden Variety Insect Pack). Predators tend to have a wider prey range than the more host-specific parasitoids; this is an advantage when dealing with a diversity of pests on a low level, but not necessarily with a rapidly growing population of a single pest. While there is debate about whether parasitoids or predators are most effective as biocontrol agents, it is agreed that a good management program will rely on the activities of both types.
4. Pathogen: a microorganism that causes disease or outcompetes a pest for space or nutrients. The disease may kill the pest, reduce its reproductive capacity, or slow its growth and development. There are many pathogens that naturally reduce the survival of pests. Augmenting populations of these pathogens is an established biocontrol practice.

• Microbes controlling microbes: Commercial preparations of various microorganisms that control plant pathogens are available. For example, a strain of the bacteria Bacillus subtilis has antimicrobial activity that destroys various disease-causing pathogens by disrupting germination of fungal spores and reducing growth of fungal tissue. When applied as a spray early in the season, the bacteria is effective against many rusts, downy and powdery mildews, fire blight, botrytis, and bacterial spot on many crops. A preparation of this bacteria called Serenade is now on the market and approved by OMRI for organic use. Mycostop is another product available from Peaceful Valley Farm Supply that contains live strains of the soil bacteria Streptomyces griseoviridis, which colonizes plant roots and protects against various soil pathogens, including Fusarium, Alternaria, Phytophthora, and Pythium. These products, known in the industry as "biologicals," add to the tools available to organic growers who, while in the process of creating a functionally diverse and self-regulating farm ecosystem, may need some help in the meantime. Because the products contain living organisms, they must be stored and handled carefully. Thorough coverage and proper timing of application are essential for all microbial pesticides.
• Microbes controlling insects: Microbial insecticides capitalize on naturally occurring pathogens that infect various insect pests. Many of these microbial products are quite host-specific and do not harm beneficial insects. The soil borne bacteria Bacillus thuringiensis (Bt) is one of the most widely used microbial insecticides. The bacteria produces a protein that acts as a stomach poison when ingested by larvae of the target pest. Various subspecies target specific insect classes, such as subspecies kurstaki for lepidopteran control (available commercially as Dipel), israelensis for mosquitoes and fungus gnat control (available commercially as Gnatrol), and tenebrionis for Colorado potato beetle control (no formulation of this subspecies is currently available for organic use). Another microbial insecticide we use on the Research Farm is Mycotrol, a formulation of the fungus Beauveria bassiana, which mummifies various insect pests but does not harm bees and other beneficial insects. Semaspore bait is a product that targets grasshoppers (an annual scourge in the desert Southwest) through the ingestion of a grasshopper-specific, disease-causing protozoan called Nosema locustae. When grasshoppers sickened by this disease die, they are consumed by other grasshoppers and thus spread the pathogen throughout the farm. Tell me that's not high drama!