Articles
PEACH BLOSSOM AND FRUIT THINNING WITH CGA 15281 AND A POSSIBLE MODE OF ACTION
Terminal fruits were larger than basal and middle node position fruits in Bicentennial.
In 1981, all applications of CGA 15281 (0 – 3000 ppm) to Candor and Jefferson thinned blossoms and resulted in an increase in fruit size, when compared to the hand-thinned control.
Treatments of 2250, 2500 and 2759 ppm to Candor resulted in adequate thinning and increased yields.
Applications at 1400 and 1750 ppm resulted in overthinning and reduced yields in Jefferson.
Fruit tissue was treated with concentrations of 0, 240, 360, 480, 600, 720, 840 and 960 ppm of CGA 15281 applied to 1/3, ½ and 2/3 of the fruit surface.
Increased abscission of fruit occurred as ovule length increased from 3.5 mm to 13.3 mm when fruit alone were treated.
Foliage sprays of the same concentrations, with the fruit protected, generally had no effect on fruit or leaf abscission.
Application of 0.01 ml droplets of CGA 15281 to the abscission zone, peduncle, and fruit cheek caused little fruit removal, but produced chlorosis of the treated area on the fruit.
The data suggest that fruit contact with CGA 15281 is necessary for fruit thinning.
The mode of action of CGA 15281 seems to lie in its effect on carbon transport into young fruit.
Application of 960 ppm CGA 15281 substantially inhibited carbon transport into young fruit of peach 4 to 5 days before visual symptoms of senescence occurred.
Carbon transport was unaffected 4.25 hours after treatment, but was greatly reduced after 24 hours.
Reduced carbon transport continued through 144 hours following CGA 15281 application.