THE CONSTRUCTION, VALIDATION, AND BEHAVIOR OF A POLLINATION AND FRUIT SET MODEL FOR 'DELICIOUS' APPLES (HONEY BEES)

A computer based, interactive, simulation model has been developed to predict pollination and fruit set in 'Delicious' apples. Predictions are based upon updates on the number of honey bees cross-pollinating apple blossoms, and the probabilities that blossoms in various age classes will set fruit if cross-pollinated. The rate of blossom aging is based on temperature, while the size of the cross-pollinating honey bee population is a function of temperature, wind, solar radiation, honey bee population size, and stage of the apple bloom.;The pollination and fruit set model (REDAPOL) demonstrated that the strongest effects on fruit set were weather and the availability of compatible pollen. Weather influenced both the intensity of honey bee foraging activity and the duration of 'Delicious' and pollinizer bloom. The latter affect the degree of bloom overlap and the number of open 'Delicious' and pollinizer blossoms at any given time. Blossom number affected the availability of compatible pollen, as did orchard design and the ratio of 'Delicious' fruit set under the widest range of weather conditions was predicted to occur in orchards with one-to-one ratios of 'Delicious' and pollinizer trees. The arrangement of trees did not strongly influence fruit set according the the model's predictions.;During the model's construction, field estimates on the size of the honey bee population carrying cross pollen were needed to validate this component of the program. Field data indicated that this population was of considerable size. Previously, pollen from unrelated apple varieties was thought to be transferred by honey bee movement from tree to tree due to competition for nectar. Our simulations predicted that competition for nectar could not create a cross-pollinating population as large as that found in the field, and that these bees were originating from another source. It has been concluded that honey bees were transferring compatible pollen in the hive through contact between nestmates. The model bases its predictions on the size of the pollinator population on both competition for nectar, and in-hive pollen transfer.