A comparison of high- and low-volume spray techniques in the thinning of ‘Golden Delicious’ apples

Abstract

SummaryA trial at the Grove Research Station, southern Tasmania in 1989-90 examined the thinning of mature ‘Golden Delicious’ apple trees. High-volume sprays were applied at 6,0001 ha-1 as air blast or vertical boom using NAA at 10mg l-1 4d after full bloom (AFB) and 18 d AFB. Carbaryl at 1,000 mg l-1 and thiram at 1200 mg l-1 were also applied as combined sprays, 30 and 38 d AFB. These high-volume sprays were compared with unsprayed controls and Micron and Micronair low volume sprayers at 200 and 1,1000 l ha-1. The dosages of the low volume applications were equilibrated to apply the same rates of chemical per hectare as the high-volume sprays, and the timing was the same. All spray treatments reduced crop load to acceptable levels when compared with the overcropped controls. There were no consistent differences between treatments for number of fruit per cm2 limb area except that the lowest volume Micron spray thinned significantly less than most other treatments. Considering the number of fruit per 100 ...