Effects of Dichlorprop and MCPB on Preventing Preharvest Drop of Apples
1990 Volume 59 Issue 1 Pages 107-114
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1990 Volume 59 Issue 1 Pages 107-114
The influence of 2, 4-dichlorophenoxy propionic acid triethanolamine salt (dichlorprop) and 2-methyl 4-chlorophenoxy butyric acid enthylester (MCPB) sprays on preventing preharvest drop of apples was examined. The effects of concentration, number of applications and time of applications were investigated. In addition, the dose response of the cultivars (‘Tsugaru’, ‘Starking Delicious’, ‘Jonagold’ and ‘Oorin’), variability due to year, influence of soil moisture, and fruit quality were studied.
1. Sprays of 30 or 45ppm dichlorprop applied 25 and 15d. before harvest significantly reduced preharvest drop of all cultivars tested. A spray of 15ppm dichlorprop reduced preharvest drop of ‘Starking Delicious’ but not ‘Tsugaru’. Double applications of dichlorprop at 10-day intervals were more effective than a single application for preventing preharvest drop of ‘Tsugaru’ and ‘Starking Delicious’. But with ‘Jonathan’, single and double applications had the same effect.
2. Double applications with 30, 50 or 70ppm MCPB similarly reduced preharvest drop of ‘Tsugaru’. The triple application treatment of 30ppm MCPB was more effective than the double application for ‘Tsugaru’. A double application of 30ppm MCPB reduced preharvest drop of ‘Tsugaru’ and ‘Starking Delicious’ but was not effective for ‘Jonagold’. With ‘Oorin’, preharvest drop was promoted by this treatment.
3. No fruit quality differences were detected between the dichlorprop treatments and the control, but double or triple applications of 30ppm MCPB enhanced fruit color development and seemed to accelerate fruit maturity.
4. The effectiveness of dichlorprop spray for prevention of preharvest drop of ‘Tsugaru’ was clearly demonstrated by the 10 year trial, but effectiveness varied due to annual variation (C.V. of 45ppm double application=78.8). The effectiveness of dichlorprop treatment was reduced in the years with low August rainfall, but was enhanced by irrigation in dry years.
5. The application of dichlorprop in a lanolin paste to the peduncle did not prevent preharvest drop, but application to the bourse, bourse shoot or the zone where abscission occurred reduced it significantly.
