TREE FRUIT NURSERY STOCK DEFOLIATION: CARBOHYDRATE LEVELS PRE-AND POST STORAGE AND SHOOT LENGTH OF DELICIOUS APPLE HAND-STRIPPED OR TREATED WITH 'DUPONT WK SURFACTANT' AND ETHEPHON
Whips of one year-old Delicious apple nursery stock were planted in April 1977 and 1978 at 1 x 3m, headed to 30cm, and trained to one vigorous shoot. Hand defoliation was done on 1, 15, or 30 October. One, 2, or 3 applications of Dupont WK Surfactant (principle a.i. is the dodecyl ether of polyethylene glycol) alone and plus ethephon were made at 5-day intervals starting 5 October. Trees were dug and stored 15 November. Some trees were replanted the following April to observe and measure shoot growth. Carbohydrate (sucrose, fructose, glucose, sorbitol, and starch) levels were measured in buds, stems, and roots, pre-and post storage. Shoot growth was measured at the end of the growing season the year after treatment. Hand defoliation on 1 October resulted in 50% post-storage tree mortality with almost no growth on the remaining trees. The second year, 1 October hand defoliation resulted in only about 50% of the control shoot growth. Shoot growth and carbohydrate levels pre-and post-storage increased as hand defoliation was delayed and, in general, tended to decrease as the number of chemical applications increased. Late hand defoliated trees and trees treated once with chemicals were not significantly different in shoot growth and carbohydrates. Shoot growth and carbohydrate were usually decreased by 3 chemical applications.
Abusrewil, G.S. and Larsen, F.E. (1981). TREE FRUIT NURSERY STOCK DEFOLIATION: CARBOHYDRATE LEVELS PRE-AND POST STORAGE AND SHOOT LENGTH OF DELICIOUS APPLE HAND-STRIPPED OR TREATED WITH 'DUPONT WK SURFACTANT' AND ETHEPHON. Acta Hortic. 120, 83-88