Comparison of thiram, carbaryl, N.A.A. and N.A.D. as fruit thinning sprays on Granny Smith apples

Abstract

Evidence is presented that a single application of the fungicide thiram at 0.12 per cent, applied 14 and 21 days after full bloom on Granny Smith apples, reduced the fruit set highly significantly, and to about the same extent as carbaryl at 0.02, 0.04, or 0.08 per cent applied 14 days after full bloom. Either material resulted in good fruit thinning. Carbaryl caused about the same degree of thinning over a wide range of concentrations, the only significant difference being between 0.02 and 0.16 per cent (P<0.05). Applications of N.A.D. at 25 p.p.m., and N.A.A. at 5 p.p.m. caused more drastic reduction in fruit set than carbaryl at 0.02, 0.04, and 0.08 per cent, or thiram at 0.12 per cent, applied at the same time. Carbaryl resulted in the most uniform fruit thinning, followed by thiram, N.A.D., and N.A.A. All spray treatments improved fruit size, reduced fluctuations in cropping, and significantly increased fruit yields over a period of four years as compared with unsprayed, hand thinned trees.