Pheromone formulation development

Finally, new types of aerosol dispensers ejecting pheromone at very high rates onto pads were developed so that formulations were developed in which the number of dispensers could be reduced to only 10-15 dispensers per hectare (Mafra-Neto and Baker 1996 Shorey and Gerber 1996 Shorey et al. 1996 Baker et al. 1997 Fadamiro et al. 1999). Efficacy in disrupting sex pheromone communication of a number of different species was clearly demonstrated. 

Rauscher, S. and Am, H. (1990). Field tests to develop a sex pheromone formulation for Hyphantria cunea in Northern Italy. Abstracts, Pheromones in Mediterranean Pest Management, L Organisation Internationale de Lutte Biologique/ Section Regionale Ouest Palearctique, Granada, Spain, Sept. 10-15,1990. p.43. 

Although pheromone traps are now widely used for monitoring insect populations, the use of synthetic pheromones in control of insect pests by disruption of pheromone-mediated communication has been much slower to develop, at least in part because of the difficulties of formulation. There are three main types of formulation currently available - hollow fibres, plastic laminates and microcapsules. For several years, the UK Overseas... 

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 increased use of pheromones to monitor and/or control insect pests is directly related to the development of efficacious controlled release formulations. In order for such formulations to be effective it is necessary to know the rate of release of the pheromone and the longevity of the formulation. 

The emission of a pheromone from a controlled-release formulation can depend on the diffusion through holes in the matrix or on the penetration of the compound through a wall or membrane by absorption, solution and diffusion (8). Thus variation in the parameters of the formulations, such as film thickness, particle size, solvent, pore dimensions, etc., alters the release rate. The design of the formulation must therefore take into account the effect of each variable on the emission rate in order to develop a system that is effective during the appropriate cycle of the target insect. 

Early experiments in our laboratory were concerned with methods for sampling and analysis of TDAL from formulations (6), insects (7) and from the forest atmosphere (8). This work was largely founded upon concepts developed previously by Beroza e t al. (9, 10, 11). Since then, several other groups have applied these concepts to the measurement of a number of different insect pheromone release rates (12, 13). On the basis of our early findings, we were convinced that the existing laboratory techniques for release rate determination from formulations were inadequate. Laboratory tested formulations did not experience the extremes of climatic variation which are the norm in the field and consequently the release rate results were not transferable to field performance. 

Our first step was to develop a simple effective wind tunnel which allowed us to age formulations in the laboratory under very nearly natural conditions. Rather than attempt to control all climatic parameters - temperature, pressure, humidity, light intensity, wind speed, turbulence, etc. - which would have been a formidable engineering task, a very simple design was chosen in which only air speed, temperature and illumination were controlled The only real deficiency in this system is the lack of control of humidity. However, that aspect was addressed separately by measuring the pheromone release rate of each formulation under conditions of very high and very low humidity. To date, none of the candidates tested has shown a major humidity dependence. 

Several years of research were spent developing formulations that would release pheromone at a satisfactory rate through the mating season (about 8 weeks). 

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. 

Utilization of lead as a promoter has been developed further by the formulation of true Pd-Pb alloy catalysts these have even higher seleetivities than the Lindlar analogs, in the hydrogenation of 11-hexadecynyl acetate and 12-tetrahydropyrany-loxy-3-tetradecyne (insect sex pheromones) [2] ... 

Attempts to alleviate this damage problem usually involve the use of poison bait to reduce or eliminate the rodent population. However, the resiliency of gophers (and voles) to depopulation, hazard of poison to nontarget species, and increased resistance of rodents to poison formulations make the development of new control techniques highly desirable. The use of semlochemlcals (pheromones and kairomones) is one such avenue which might provide effective protection for fruit tree orchards. 

Control of insect pests and invasive weeds has become very sophisticated. Knowledge of the interaction between insects and host plants is critical to development of effective control strategies diat are friendly to the environment. We must also understand how insects communicate with each other. What are the semiochemicals (signal substances such as sex pheromones) and how do they function Research efforts in this fast-growing field involve organic chemists, analytical chemists, entomologists, biochemists, microbiologists, formulation experts, and statisticians. 

A more successful application of terpenes in crop protection has been found with the development of (4aS,7S,7aK)-nepetalactone 40 from catmint as an insect attractant. As well as luring male aphids, nepetalactone serves as an attractant to numerous aphid predators such as lacewings (Birkett Pickett 2003). Formulations of catmint oil distillate, impregnated into a polymer which releases nepetalactone over a period of months, are now commercially available. This represents the first example of plant cultivation on a large scale for insect pheromone production - less than 35 tonnes of plant material yield over 301 of nepetalactone-rich oil at a production cost of approximately l/g. 

Permeation with the 3-component pheromone over a 0.81 hectare plot prevented the beetles from being trapped on traps baited with the same pheromone in the center of the treated area 536), When verbenone was released from formulations attached to ponderosa pine trees that were also baited with the pheromone, no mass attack occurred on these trees, in contrast to the mass attacks that occurred on trees that were simply baited with the pheromone. Further development of this approach is warranted to develop a method for protecting individual high-value trees. 

Satisfactory formulations of pheromones that afford a constant release rate over a long period of time are not likely to be achieved without the cooperation of the chemical industry. Controlled release of pheromones is discussed in the Proceedings of a recent symposium (623). Fortunately, several organizations in the U. S. have been interested in the possibilities of the use of pheromone formulations on a commercial basis. One company (605) has supplied formulations for several investigators, and in addition has carried out extensive field tests with their own personnel. It has developed the use of hollow fibers, which are simply microcapillary reservoirs that serve to contain a vaporizable material and mediate evaporation of the material into the atmosphere . The fiber wall is essentially impermeable. One end is sealed, and the release rate essentially depends on diffusion from the surface of the liquid-vapor interface to the open end of the hollow fiber. Fibers are supplied in two forms. A tape form consists of a parallel array of fibers on an adhesive tape this form is used to establish point-source evaporators. The chopped fiber form is used for dissemination with a ground rig or from the air. 

SPLAT formulations have been developed to release a variety of compounds, including sex pheromones, kairomones, attractants, phagostimulants, and insecticides. Several mating disruption and attract-and-kill formulations are commercially available. SPLAT Verb and SPLAT AGP Repel represent our first successful attempts at developing repellent formulations and will be registered and marketed in the United States. 

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