Microencapsulated pheromone

Figure 6. Communication disruption of Pectinophora gossypiella in 0.01 ha plots in Egypt with microencapsulated pheromone applied at 5 g a.i./ha. Key control...

Hall DR, Nesbitt BF, Marrs GJ, (ireen ASJ, Campion DG, Critchley BR. 1982 Development of microencapsulated pheromone formulations, pp. 131-143 in Insect pheromone technology chemistry and applications. ACS Symp Scr 190, Washington DC. 

Slow release formulations incorporate nonpersistent compounds, eg, methyl parathion, insect growth regulators, and sex pheromones, in a variety of granular, laminated, microencapsulated, and hoUow-ftber preparations. 

One particular example of controlled release is sustained release. In this form the desired material is continuously released over a period of time at a constant rate. Two timely publications (3)(4) cover the general area of controlled release, which can also include the controlled release of agricultural materials and biological materials, far example, pheromones. In using the term microencapsulation in this article, the author intends to refer to capsules in the size range of 1 micron to 1000 microns. Capsules below 1 micron in size are frequently referred to as nanocapsules and they are made by one or more very specialized methods (5). The term capsule refers to macro objects in the order of 1 millimeter or larger. This term of capsule is frequently used in the delivery of pharmaceuticals. 

Development Administration and ICI Ltd. have been involved In a collaborative project to develop microencapsulated formulations of lepidopterous sex pheromones for control of insect pests by mating disruption. 

The extent of pheromone degradation under field conditions was investigated with a microencapsulated formulation containing a saturated hydrocarbon and acetate (octadecane and tetradecyl acetate (14 Ac)), the corresponding monounsaturated hydrocarbon and acetate ((Z)-4-octadecene and (Z)-9-tetradecenyl acetate (Z9-14 Ac)) and a diunsaturated acetate ((Z,S )-9,ll-tetradeca-dienyl acetate (ZE9,ll-14 Ac)), chosen so that all the components had similar volatilities. On exposure to sunlight, loss of the diene was more rapid than loss of the monounsaturated components which in turn disappeared faster than the saturated components (Fig. 1). All components disappeared at a similar, slower rate when shielded from direct sunlight. 

The above studies were carried out using the simple, exposed thin-film system. Microencapsulated formulations of Z9-14 Ac and 14 Ac were made up containing the N,N -dimethyl UOP 688 and/or Waxoline Black, and tested in exposure experiments in Egypt. The N,N -dimethyl UOP 688 alone stabilised the pheromone but seemed to have little effect on the degradation of the capsule walls (Fig. 3), while the Waxoline Black alone had a greater effect on the stability of the capsules than on that of the pheromone (Fig. 4). Combination of the two had a synergistic effect on the stabilities of the microcapsule wall and the pheromone (Fig. 5). 

The pheromone of the rice stem borer, Chilo suppressalis, is a mixture of two aldehydes, (Z)-ll-hexadecenal and (Z)-13-octa-decenal. Field-cage trials carried out in the Philippines at the International Rice Research Institute showed that the fully stabilised microencapsulated formulations of these aldehydes persisted for over 30 days and virtually eliminated the laying of fertile eggs during this period (6). 

Ilichev, A.L. Stelinski, L.L. Williams, D.G. Gut, L.J. Sprayable microencapsulated sex pheromone formulation for mating disruption of oriental fruit moth (Lepidoptera Tortricidae) in Australian peach and pear orchards. Journal of Economic Entomology 99(6), 2048-2054, 2006. 

Microencapsulated and hollow fiber formulations of the pheromone were shown to disrupt mating of both the RBLR and the GBM (578). However attempts to disrupt mating for the complex of moth pests were less successful improved formulations with better control of release rates of individual components are needed. Tumlinson et al. (579) and Roelofs (580) have dealt with the problems involved in manipulating complexes of insect pests. Roelofs and Card6 (21) have analyzed communication systems and their disruption by pheromones and para-pheromones. 

The sex attractant of several tick species have been identified, but only three examples of attempts to apply the attractant have come to our attention. Sonenshine has demonstrated (620) mating disruption by dusting a tick-infested dog with a microencapsulated formulation of the pheromone, 2,6-dichlorophenol the ticks used were the dog tick, Dermacentor variabilis, and the Rocky Mountain wood tick, Dermacentor andersoni. Gladney (621) applied a mixture of pesticide and male extract to a shaved area on the shoulders of cattle and found that the Gulf Coast tick (Amblyoma maculatwn) could be attracted to the spots and killed... 

Two companies (626, 627) provide microencapsulated formulations of pheromones. This is a very flexible system in that encapsulating materials and particle size can be varied over a wide range. The microcapsules can be applied as solid particles or sprayed as a slurry. A study with microencapsulated disparlure (536) on the gypsy moth showed that the field life of disparlure could be extended to approximately six weeks (628). 

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