Limitations of Potential Use of Mass Trapping for Insects Population

For mass trapping to adequately reduce pest populations, a large number of very efficient traps are usually needed.

Because pheromone traps are so effective for catching certain insects, numerous traps placed throughout a pest's environment can sometimes remove enough insects to substantially reduce the local population and limit the damage it causes. Efforts to "trap out" insect pests (a process also termed removal trapping or mass trapping) have utilized species-specific aggregation pheromones that attract both male and female beetles or species-specific sex pheromones that attract male moths. When aggregation pheromones are used to attract adult beetles of both sexes, traps may reduce the feeding damage caused by the adult insects and reduce reproduction by capturing adults before they lay eggs. When sex pheromones are used to capture moths, success depends upon capturing males before mating occurs.

Efficient traps capture a high percentage (and often a very large volume) of the target insects that are drawn to the area by the attractant. For many insects, the efficiency of commonly used traps is not known; however, low efficiency seems to be a limiting problem in some instances. Removal trapping is also most likely to succeed when the density of the target pest is low and immigration into the trapped area is minimal.

The following examples illustrate conditions that favor or limit the potential use of mass trapping.

Codling Moth

Larvae of the codling moth tunnel into apples and pears, leaving the fruit scarred, contaminated, and unsuitable for most commercial markets. Although pheromone traps are used to monitor the seasonal timing and sometimes the density of codling moth populations in commercial orchards, mass trapping has not been widely adopted. In experimental programs, high numbers of pheromone traps (14 and 72 traps per acre) in some trials provided less control of subsequent larval damage than did fewer traps (4 per acre) in other trials. These seemingly contradictory results appear to have resulted from different conditions in and surrounding the test orchards. Available data indicate that mass trapping for codling moth control is likely to be successful only in reasonably isolated orchards (at least 100 yards and preferably further from the nearest source of moths) where codling moth populations are already low. Where nearby fruit trees harbor codling moth infestations, mated female moths can disperse into the trapped orchard and lay eggs even if the local males have been trapped. (Immigration also prevents the successful use of mass trapping to protect fruit on one or two backyard trees in most urban situations.) Where initial moth populations are high, some males will locate and mate with a nearby female even if a great number of traps have been used; in these orchards the mated females produce enough fertile eggs to damage a measurable portion of the fruit. Despite these limitations, mass trapping can reduce codling moth damage in some orchards. Although damage may not be limited to the extremely low levels required by most commercial markets, producers who sell to "organic" markets might use mass trapping along with other steps (such as removal of dropped fruit and banding of trunks) to substantially limit codling moth damage. Because the number of traps needed for mass trapping of codling moths has not been determined, the economic feasibility of mass trapping is unclear. However, Trece, Incorporated manufactures a pheromone TRAP-Pherocon® ICP TRAP that can be used to monitor the insect population during control measures.

Japanese Beetle

Adult Japanese beetles eat the leaves of many different ornamental plants (both trees and shrubs), and the larvae (grubs) or this species feed on the roots of grasses. Can- or baglike traps for Japanese beetles contain a feeding attractant alone or in combination with a sex attractant. These traps are sold under claims that they will reduce beetle numbers and protect nearby plants from feeding damage. Although their lures are indeed very attractive to adult Japanese beetles, the use of these traps in areas where the Japanese beetle is prevalent has been shown to increase beetle numbers and damage to host plants in the area around the trap. This outcome apparently results from the fact that many beetles are attracted by the lure but not captured by the trap. In areas where the Japanese beetle is a serious pest, only very widespread use of many traps (several traps per homeowner by a majority of homeowners in an area) is likely to reduce damage to plant foliage. In contrast, in areas where Japanese beetle densities are low, traps placed several yards away from valuable plants can reduce the damage caused by adult beetle feeding on foliage or flowers. Additionally, these traps have been used at densities of one or two per acre to remove adult beetles from golf courses and to reduce turf damage caused by the subsequent generation of grubs. To monitor populations place lures at the perimenter of property. Trece, Incorporated manufactures a product called Japanese Beetle-3-way Lure. It containes a chemical (Eugen) that is highly attractive to adult Japanese beetles.

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