PREDICTING THE VERTICAL DISTRIBUTION OF PHEROMONE INORCHARDS.

D.M. Suckling¹, G. Karg^1,2 and S.R. Green³
HortResearch, ¹PO Box 51, Lincoln, New Zealand, ²PresentAddress: Dept. Biology, Univ. Kaiserslautern, Germany, ³PO Box11030, Palmerston North, New Zealand

A Langragian model was developed to predict the vertical distributionof pheromone in apple orchards treated with polyethylene tubing dispensersreleasing synthetic pheromone, to better define the requirements for matingdisruption. Measurements of tree canopy form, dispenser application height,air temperature, and wind speed were used to parameterize the model. Partialmodel validation was achieved using air sampling and capillary gas chromatography.Moth trap catch, wing fanning behaviours, and electroantennogram traceswere also recorded. The highest atmospheric concentrations of pheromonewere predicted in the plane of the dispensers. The range of measured valueswas from 0.5-5 ng/m³. Predicted atmospheric concentrations ofpheromone at 1.85 m above ground at dusk in plots treated with 1000 dispensersper ha varied between 2-40 ng/m³ over several months. Mean windspeed had the largest influence on pheromone levels within the canopy.Wing fanning was significantly reduced by increasing numbers of point sourcesper ha, but was not completely eliminated at 1000 dispensers per ha withpredicted values of <10 ng pheromone/m³. Electroantennogramrecordings showed a higher frequency of pheromone fluctuations in the treatmentswith more point sources.