Two methodological approaches were applied to estimating the number of non-bearing trees in the absence of such data using data for the Southern USA pecan industry. The first approach distinguished between bearing and non-bearing phases of a tree life and directly estimated the number of non-bearing trees. The second focused on indirect estimating of the non-bearing tree number from changes in production. This approach relaxed the assumption of maintaining maximum yields for infinite period as used in earlier studies. Empirical applications used two data sets from the pecan industry. The comparison of empirical results suggested that the first method was more accurate than the alternative approach in predicting the number of newly planted trees over an extended period of time. Additional data collection will allow for further application of available methodology to the pecan industry.

Spray distribution in an apple tree canopy using an adapted knapsack mistblower fitted with a spinning disc, with the provision of an induced electrostatic charge on the droplets was studied.

Droplets were sampled using uvitex fluorescent tracer on Kromekote cards positioned in different areas of the canopy.

Droplets were highest on the outer surface and decreased sharply into the canopy. Uncharged spray droplets gave the poorer deposition with better distribution, but by adding an electrostatic charge, droplet deposition was significantly improved in the outer parts of the canopy. An average of 3 ml/tree of spray liquid was used in all applications. The larger variety (Red Victoria) required about 50% more spray liquid, but distribution was still lower than that achieved by the smaller Keswick variety.