Agricultural aircraft are of great importance to the Australian cotton industry. Specialised

aircraft are used to apply selected herbicides and fertilisers prior to planting, insecticides throughout the growing season and defoliants prior to harvest. The use of agricultural aircraft has developed largely as a result of the greater speed, better timing and efficiency of application offered by aerial distribution. Aircraft are able to apply agricultural products rapidly over large areas within narrow optimum application windows. When crop height and irrigated areas restrict the passage of wheeled vehicles, aircraft are able to place pesticides strategically on crops in response to economic thresholds, without contributing to soil compaction and breakdown.

Ultra Low Volume (ULV) application from the air has been used very successfully around the world for nearly three decades. The technique is used to effectiveIy apply insecticides in a range of crops including cotton, field crops and forestry. ULV pesticides formulated in low-volatile oil-based carriers are usually applied 'straight from the can' at total application rates of about 2-5 L/ha. This low rate of carrier is achieved by generating small droplets with a Volume Median Diameter (VMD) of approximately 50-100 um, usually using rotary cage type atomisers. Such droplet sizes allow large numbers of droplets to be generated resulting in high droplet coverage

(expressed in terms of droplet number per square cm) and high efficacy and productivity. This technology is particularly suited to the control of airborne pests (such as locusts and mosquitoes), forestry and broad-acre agriculture. ULV technology has been successfully utilised in the production of cotton in Africa, Asia and Australia.

Restrictions to the application of endosulfan in cotton were implemented by the National

Registration Authority for Agricultural and Veterinary Chemicals, (NRA) during 1999. In

particular, mandatory buffer distances and nozzle configurations were introduced. Despite the widespread adoption of these management tools and a successful season where an extensive monitoring of 14,000 beef carcases revealed only one carcase that exceeded the 1/2 MRL export endosulfan level further restrictions were imposed during july it is noted that low pest pressure and the use of products may have contributed to this finding. new rules for season suspended registration ulv formulation but permitted application existing stocks provided that: a) protection downwind buffer zone was doubled from 1500 metres to 3000 metres b) maximum allowed rotational speed micronair AU5000 nozzles reduced 4000 to 2000rpm. Based upon data compiled recent public domain studies undertaken on behalf land water resources research development corporation cotton report comments current practice establishing down wind distances nozzle criteria aerial ec products. examines available deposition assesses performance two mathematical models in predicting relative drift profile formulations endosulfan.