Winter oil application in Australian pistachio production

Sustainable future food production is faced with the challenge of changing environmental conditions, especially global warming. In the past 10 years, pistachio production in Australia has experienced a number of winters with low chill accumulation resulting in late bloom and crop reduction. To overcome environmental threats, chemicals are now being used to promote bud break. Winter oil has been applied to pistachio trees since the winter of 2005. To determine optimum application dates, field trials and shoot dipping trials were conducted. To determine the flowering difference between winter oil applications and no oil applications, plastic was used to cover control trees during winter oil application treatments. Daily flowering records were used to determine treatment effects. To compare the effects between high concentration (6%) and low concentration (3%) dormant oil treatments, an experimental trial was established in 2008; an 8.6 ha block with 5 replications in a randomized complete-block design. In the 6^th year trial, when chill portions were below 59 critical portions for 'Sirora' pistachio trees, the 6% treatment showed early bloom and better crops than the 3% treatment. When chill portions were above 59 portions, yield differences were not as marked. However, during low heat accumulation springs the 6% treatment induced flower opening earlier and neater. The possible reasons have been discussed.