Biological Control
Biological control involves a number of different management tactics. All, however, use some aspect of the pest’s biology to combat it. One traditional method involves the use of natural enemies-parasites, pathogens, or predators that attack the pest. A natural enemy is a biological agent that controls a pest. Turfgrass managers have two options:
- Enhance or preserve natural enemies present.
- Introduce commercially produced biological organisms.
Take steps to support diverse populations of beneficial soil organisms-those that make loose, fertile soil and recycle nutrients. When possible, maintain healthy populations of organisms that compete with, eat, or parasitize pests.
One type of natural enemy is a predator. As a rule, insect predators must be present in large numbers to manage a pest population. Releases of predatory insects usually work best in closed settings where the predator will find adequate food. They do not work well on single plants or in large open areas. For that reason, releases of predatory insects are not often used in turf.
Entomopathenogenic nematodes are effective in some situations in turf. In addition, some naturally occurring insect predators may help to control turf pests. For example, ground beetles and rove beetles readily attack pest caterpillars and the eggs of sod web• worms and white grubs. Big-eyed bugs are predators of chinch bugs. Predators may not control large populations. However, in some cases, they will keep small populations small.
Biological control also includes the use of pheromones or juvenile hormones to control insects. Pheromones in traps can monitor pest populations. Applications of juvenile hormones can prevent immature insects from becoming normal adults. Since only adults reproduce, exposure to juvenile hormones can lower pest populations. Juvenile hormone applications are most useful when the pest does damage in the adult stage.
Remember that no all insects are damaging. Also remember that proper identification is critical. You can attract and sustain some types of beneficial insects with flowering plants. Flowers in borders can serve as alter• native food sources for many predators and parasitoids.
The active ingredients in some registered pesticide products are organisms or their by-products. Examples include milky spore disease (Bacillus popilliae) and Bacillus thuringiensis (Bt) toxins.
Some pesticides are compatible with biological control organisms if used as directed. These include insecticidal soaps, petroleum oils, and Bacillus thuringiensis formulations. If other pesticides are used, they must be managed with care so biocontrol agents are not exposed to them. Remember that indiscriminate or preventive pesticide use may kill beneficial insects.
Biological control agents usually target specific pests. Biological control agents must be able to move to – or be placed in contact with-the target pest. For that reason, application techniques influence success. Adoption of biological control measures usually takes careful planning and timing. Biological control organisms must be able to tolerate conditions at the site. To be sustainable, they must persist from season to season. Biological control systems using natural enemies work best when they have time ‘to become established. In ideal situations, the number of beneficial organisms comes into balance with pest populations at a level below the visible injury rate. Once a biological control program involving predators or parasites is established, you may need to make additional releases.
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