Deposition and vertical distribution of odors

Very little work has been done on the rate of pheromone adsorption and reentrainment by vegetation and other objects in nature. Various studies have documented reduced trap catch of insects to pheromones in heavy vegetation. These results, however, may have easily been caused by disruption of the flight behavior by the vegetation rather than pheromone adsorption. Adsorption to vegetation may be substantial (Wall et aL, 1981). 

An additional aspect of the vertical distribution of pheromone has been considered by Schal (1982). The odor dispersion models discussed in this chapter all assume that the mean wind flow is horizontal. The occurrence of buoyant or convective transport of odors is treated by increasing the rate of dispersion to that characteristic of unstable conditions. On the relatively small scale of odor communication this description may not be adequate. Schal demonstrated that air currents at night beneath a Costa Rican rain forest move predominantly upward in response to a substantial lapse rate. He found that male cockroaches of various species positioned themselves in trees at levels above that of pheromone producing females of the same species. 

Our research on pheromone dispersion has been supported by NSF Grant PMC 7912014 and by a grant from the USDA Expanded Gypsy Moth Program. We are greatly indebted to Conrad Mason, John Murlis, Roger Shaw and Ralph Charlton for invaluable discussion and review of this paper. 

(1976) Estimating peak concentrations of pheromones in the forest. In Perspectives in Forest Entomology (Anderson, J. F. and Kaya, M. K., eds) pp. 177-88. Academic Press, New York. 

Parlange, J.-Y. and Grannett, J. (1976) Turbulent dispersion of disparlure in the forest and male gypsy moth response. Env. Ent, 5, 1026-32. 

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