Semiochemical-based pest management programmes comprise of three major approaches to control insect pests: (1) mass trapping, (2) “attract and kill,” and (3) mating disruption. Mass trapping can be used in short and long-term pest management, the eradication of invasive species and has good potential to suppress or eradicate low-density, isolated pest populations. However, its full potential in pest management is in combination with a chemical program that fits into the grower’s IPM programme.
The main purpose of mass trapping with pheromones is catching as many insects as possible to reduce the overall numbers. (See illustration below). The most commonly used pheromones are female-produced sex pheromones that attract only males. Hence, any attempt to suppress the population by mass trapping would require a sufficient number of trapped males so that nearly all females would remain unmated.
Mass trapping both sexes of a species using plant volatiles or aggregation pheromones should be more effective than mass trapping only males or females. Similarly, food lures used in combination with pheromones may also enhance the effectiveness of the mass trapping system.
Layout guidelines for Water Traps baited with Pherolure. – Mass trapping based on 20/25/30 traps per hectare.
20 traps per hectare
25 traps per hectare
30 traps per hectare
Theoretical considerations of mass trapping males take into account the density of males in the population as well as its ability to mate during its lifetime. If a male can mate with six to ten females in its lifetime, then up to 90% of the male population can be trapped without affecting the number of mated females as well as the subsequent larval generation.
Under high population levels, the rate of female encounters would be high and mass trapping would be more difficult to achieve. However, under low population levels, males would locate females less frequently and intensive trapping could conceivably reduce male populations to biologically significant levels.
In practice, the effectiveness of the mass trapping technique can be reduced by factors such as: inefficient trap design; saturation of traps (especially in situations of high pest density); poor pheromone release or duration; attraction of only one sex; inappropriate positioning of traps or the extensive immigration of new pests from outside the area treated with pheromones.