Female Pheromone Containing Compounds
As noted earlier (Section ll.l)). there is evidence to suggest that the female pheromone secretion contains compounds additional to EEOH. Mating can occur in EEOH- treated areas when adult density is exceedingly high (as in the cages of Cardé et al.“), and close range encounters between the sexes in such circumstances may involve other compounds. However, it seems unlikely that other components would contribute significantly to a breakdown in disruption as release rates of EEOH as low as 1 to 2 mg/ ha/hr prevent males from locating calling females at population densities normally encountered in the field. Additional components in the female pheromone blend could in the long-term lead to a breakdown in disruption if constant treatment with EEOH led to the selection of individuals communicating by means of these compounds (or other cues). However, it seems unnecessary to speculate on this possibility at present as disruption control with EEOH is still at a very early stage of development. Presumably EEOH treatments designed to achieve moderate rather than total control of codling moth would permit some mating and reduce selection pressure for alternative means of sexual pheromones communication. Check out http://pheromones-work.weebly.com/home/pheromones-for-men-2015
Immigration of Adults Into Treated Areas
Immigration of mated females appears to be a major cause of failure to achieve control within EEOH-treated blocks. The experimental plots described in this chapter have generally been small; none have exceeded 0.9 ha in area, and the average is no more than 0.3 ha. Treated plots were frequently within 150 m of other pome fruit orchards. Most recent work on codling moth dispersal has been confined to males, and there is only limited information on female movements. In the often-cited work of Steiner” and Van Leeuwen,“ catches in trapping grids were not sexed. The earlier observations by Worthley,” based on mark release and recapture data, indicated that most females did not disperse further than 100 m from a release point but that some individuals were recaptured at the outermost limits of the trapping grid at 400 m. On the basis of field experiments, Wildbolz and Baggiolini“ concluded that codling females were highly dispersive, but Geier“ considered that their experimental data did not support this conclusion. https://www.rebelmouse.com/.
In a similar test, White et al.” noted that 90% of the damage produced by the progeny of released females in a previously uninfested orchard was within 300 m of the release point.
From estimates of adult numbers, Wearing’ was able to demonstrate that immigration from neighboring areas influenced population trends in any one site to a greater extent than most other factors. Adults appeared to disperse away from areas with high population densities; however, most plots in his experiments were within 100 m of one another. There is thus firm evidence that local short-range dispersal of females could lead to a breakdown in disruption, but further information is required on the extent of long-range movements. Does max attraction silk work | http://mikesthoughts.drupalgardens.com/content/does-max-attraction-silk-work
Work on other species” raises the possibility that males could be attracted into plots receiving EEOH treatments, and that resident males do not emigrate from such areas. This would tend to increase the ratio of males to females, and perhaps lead to greater opportunities for encounters between the sexes — particularly in any residual pheromone-free sites within the EEOH-baited block. in untreated orchards it has been found that egg densities are high at times when males predominate, suggesting that a greater proportion of females are mated in these circumstances.”