How pheromone mating disruption works: In nature, female moths release pheromone perfumes to attract males for mating.
(continued from last issue)
For codling moth, this happens just after sunset when there is just a little light in the evening sky. For OFM, it is a little earlier in late afternoon.
Males follow the pheromone trails upwind, turning back and forth in the plume. In this way, they can accurately reach the female (see Figure 1).
When they get close, they swing into the next phase in which they perform a dance which involves wing fluttering in the vicinity of the female, followed by mating.
Mating usually happens on the first night after moth emergence from the pupal cases. After mating, the females can lay fertile eggs that give rise to the problem larvae a few days later.
Codling moth
Pheromone dispensers (for example, the PheroKlip CM mating disruption dispensers) contain synthetic nature identical pheromone and continuously release thousands of times as much as female moths.
Male codling moths react in the same way that they do to female pheromone trails.
Codling moth males home in on the dispensers and perform their ritual wing fluttering mating dance on branches and leaves close to the dispensers. They know the female must be there somewhere but cannot find her. The same procedure happens for three or four nights, after which the males are exhausted (see Figure 2).
Unmated females waiting around use up their energy reserves and the unfertilized eggs are resorbed.
If there is a high population of codling moth in the orchard, mating disruption must be supplemented by an insecticide program.
The combination of the two seems to be synergistic and is an excellent way to get on top of a high resistant population of codling moths that do not come down under either a spray program or pheromone mating disruption alone.
Oriental fruit moth
For OFM, the response of the male moths to PheroKlip OFM and tube type mating disruption dispensers is a little different from codling moth.
OFM males are overwhelmed by the quantity of pheromone coming from the PheroKlip OFM dispensers. The sensors on their antennae become saturated with pheromone and can no longer detect presence or absence of pheromone—so the signal reaching the brain of the OFM male is ‘nothing out there; all very boring’. For this reason, mating disruption of OFM is not highly influenced by moth population density.
(cont. next month)
See this article in Tree Fruit September 2018
