METAMITRON REPLACING CARBARYL IN POST BLOOM THINNING OF APPLE TREES

Abstract

ABSTRACT Carbaryl or the mixture of carbaryl with NAA (naphthalene acetic acid) or BA (benzyladenine) are the post-bloom chemical thinners most widely used in apple thinning in Brazil. The marketing restriction of carbaryl demands new options of apple post-bloom thinners, requiring the evaluation of others compounds for this purpose. Metamitron is one of the substances that may be used in chemical thinning of apples. Metamitron was evaluated at two concentrations, alone or in mixture with BA, in ‘MaxiGala’, ‘Fuji Suprema’ and ‘Fred Hough’ apple cultivars. Applications of metamitron at 384 mg L-1 and at 768 mg L-1 in a mixture with BA, ranging from 40 mg L-1 to 80 mg L-1, sprayed on fruits with diameter ranging from 5 to 25 mm were compared with the standard treatment and hand thinning. The experimental design was a randomized complete block with 4-6 repetitions of a single plant. The variables analyzed were: fruit set (%); percentage of floral clusters with 1, 2, 3, 4 or more fruits; fruit yield (kg); average fruit fresh mass (g) and percentage of dropped fruit after thinning. Metamitron alone or in combination with BA reduced production per plant and significantly increased the fresh weight of fruits in all cultivars tested. Metamitron at 800 mg L-1 resulted in excessive fruit thinning, especially in ‘MaxiGala’ cultivar. Metamitron or metamitron + BA have potential to compose the program of chemical thinning of apple trees to replace carbaryl.