Mating disruption is where large amounts of sex pheromone is released into the crop in order to prevent males locating the females, whereas mass trapping involves insect pests being attracted to a site where they can be removed Foster and Harris, The physiological mechanism behind mating disruption is unknown but many theories have been suggested Foster and Harris, Both mating disruption and mass trapping incorporating the use of sex pheromones have been successfully implemented within pest management programs for many species of pest, especially Lepidoptera.
Large amounts of the synthetic sex pheromone, E,E -8,dodecadienol codlemone McDonough and Moffitt, , can be introduced into the crop by the use of several different pheromone-delivery systems, that is, isomate polyethylene-tube dispensers Thomson et al.
This prevents the males from locating the females. Examples of successful mass trapping of pests with sex pheromones include Prays citri the citrus flower moth on lemons in Israel Sternlicht et al. The aphid sex pheromone has potential to be used in pest management systems. Nepetalactone and nepetalactol are commercially available. A commercial system has been developed where 30 kg of essential oil, comprising 85— This formulation maintains a slow and consistent release rate of the active ingredients as well as preventing UV degradation and oxidation Birkett and Pickett, The use of essential oils from renewable stocks is not only cheaper and sustainable compared to synthesis using fine chemicals from mineral oil stocks, but would also be more readily accepted by organic growers.
If further research shows that dolichodial is an important component of the aphid sex pheromone, a similar system could be used to extract 1S,2R,3S -dolichodial VIII from T.
Although the components of the aphid sex pheromone are readily available, the use of the aphid sex pheromone in direct aphid control programs has not been commercially developed. One limiting factor is the biology of the aphid pest.
Aphids which alternate between hosts are generally an agricultural pest on the summer secondary host. It is in the autumn on the primary host where the sexual morphs occur Blackman and Eastop, and where the farmers generally cannot implement control measures. Also, the opportunity to exploit the aphid sex pheromone for control purposes is limited to a 2-month period.
In addition, when conditions in winter permit the survival of an aphid, and a suitable food quality is found, the aphid may continue to produce parthenogenetic generations Blackman, Direct control measures using the sex pheromone can generally only be implemented where the aphid is a pest on the primary host, that is, in fruit orchards.
In the autumn, gynoparous winged females that produce oviparae on the winter host and male D. It is in the following spring, when the fundatrices hatch, that the new population of D. Substantial damage to the fruits occurs even when aphid densities are so low as to defy visual monitoring Blommers et al.
This selection pressure has lead to the development of insecticide resistance Delorme et al. The spring population could be reduced by controlling the autumn population by utilizing the sex pheromone and therefore less damage will occur. Only one investigation into the use of direct control measures using the aphid sex pheromone has been reported. The sex pheromone of R.
A significant increase in the number of males landing on the trees was observed but whether the behavior exhibited by the males locating conspecific oviparae was affected was not conclusive. The use of the aphid sex pheromone could also be part of an integrated pest management IPM scheme. In IPM, the sex pheromone could be used to monitor male or gynoparous see below populations, used together with the exploitation of biological control agents Hockland et al.
Currently, the most common strategy to control D. Kehrli and Wyss reported that insecticide applications against the oviparae in autumn strongly inhibited the threat of an outbreak the next spring. As the window of opportunity is small, aphid monitoring systems using the sex pheromone components of D.
Gynoparae appear first in the crop with the males following approximately 2 weeks later Blommers et al. The sex pheromone components have been shown to attract gynoparae as well as male aphids Gabrys et al.
Thus information on when the gynoparae are present and when the first males start to appear in the crop can be collated. Spraying insecticides in the autumn will reduce the number of sexual females; therefore, as a consequence less or no eggs are laid thus lowering the damage the following spring. The lure and infect mechanism involves the insect being lured into a trap where it is infected with a pathogen, then allowed to escape.
When it is released, the insect locates other conspecific aphids which it then infects with the pathogen. Finally, the aphid sex pheromone has been shown to elicit a positive behavioral response by aphid parasitoids Glinwood et al.
The response of Aphidius ervi to 4aS,7S,7aR -nepetalactone I was found to be innate, thus not easily modified by learning experiences Vet and Dicke, Therefore, the aphid sex pheromone could be used to manipulate natural populations of parasitoids to control aphid populations.
In order for parasitoids to be used as an effective control system it is necessary to achieve early-season synchrony between the aphid and parasitoid populations Powell et al. Unfortunately synchronization tends not to occur in the field, consequently large aphid colonies develop before the parasitoids arrive into the crop. To combat this problem, a parasitoid management system using the aphid sex pheromone has been developed.
In the autumn when the parasitoids are forced to leave the harvested crop, sex pheromone lures are placed around the field in order to attract the parasitoid into the field margins where they overwinter as pupae. The following spring, the parasitoids emerge and rapidly recolonize the crops, therefore better synchrony occurs with the invading aphids Powell et al. Field studies have been conducted which demonstrate the feasibility of this approach Pickett et al.