Using portable sap flow sensors, the onset and volume of sap moving up the branches of grapefruit (Citrus Paradisi Macfadyen) trees was monitored on an hourly basis. Reference evapotranspiration (ETo) data was obtained from The Arizona Meteorological Network (AZMET). Crop evapotranspiration (ETc) was estimated from soil moisture measurements using a neutron probe. The threshold temperature limits were delineated from an evaluation of the hourly sap flow responses to cold winter and extreme summer temperatures. The heat based crop curve was derived from a correlation of the crop coefficients with heat unit over one crop year. The heat based crop coefficients were found to be similar to crop coefficients derived by other researchers.

The life history of the citrus peel miner was investigated. The peel miner larvae were found in low levels in grapefruit throughout the summer. In September the infestation level rose to 10%. Peel miners were also found in oleanders, mesquites, grapes and tree cottons. Peel miners were found to infest at higher levels in the skirt of the tree (less than 32. A parasitic wasp of the larval stage was discovered