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- Author or Editor: Fenton E Larsen x
Abstract
The growth retarding effect of N-dimethylamino succinamic acid (Alar) on certain deciduous fruit trees in the orchard was first reported in 1964 (1). Its value for size control in the nursery where tree size is sometimes excessive was subsequently reported in 1967 (3). It was reported in 1954 (2) that certain growth regulators applied prior to the application of a nursery stock defoliant reduced the effectiveness of the defoliant.
Abstract
Following publication in 1965 (9) of the identity of Abscisin II isolated from cotton by Addicott's group, it was established that sycamore dormin and Abscisin II have the same structure (3). Abscisin II was later named abscisic acid (1). This and other research (4, 8, 10) shows that this is apparently a widely distributed compound.
Abstract
Nurserymen often wish to dig plants prior to natwl leaf abscission. Plants for some areas could be shipped for fall planting if digging could be done early enough. In other areas an extended digging period would lessen harvest pressure or make better use of labor. Early digging would also de crease danger of losses from early fall freezes. Some plants (i.e. Weigela) retain their leaves extremely late in the season
Abstract
Cycloheximide (CHI) [3-(2-[3,5-dimethyl-2-oxocyclohexyl]-2 hydroxyethyl)-glutarimide] and Retzanol TD-8 (RTD-8) [tridecyl alcohol derivative] surfactant alone and in combination stimulated significant leaf abscission on cherry, peach, pear and apple nursery stock. RTD-8 alone was sometimes more effective than CHI alone, and combination treatments were rarely better than either material alone. CHI but not RTD-8 induced bud and shoot tip damage.
Abstract
The results of 4 years work with Bromodine show that it is an effective nursery stock defoliant for several species and cultivars. Thorough wetting (200-300 gal/A) with 1 to 3 applications at 6 to 7 day intervals of 0.25% Bromodine on cherry and pear and 0.50% on apple and prune was sufficient for 70 to 100% leaf abscission. Experimental work was confirmed with commercial trials.
Abstract
Work with 2-chloroethylphosphonic acid (Ethrel) 3 over a two year period to stimulate leaf abscission of deciduous nursery stock showed that this chemical has potential for this purpose. Satisfactory rates for apples were generally 3 applications of 2000 ppm at weekly intervals. ‘Italian’ prune required two applications of 2000 ppm. Single applications of 500 ppm and 1000 ppm were sufficient for ‘Bartlett’ pear trees and Prunus mazzard cherry seedlings respectively. A 5 or 10 ppm NAA spray two weeks prior to Ethrel application materially reduced the effect of Ethrel. Combining NAA with Ethrel in the same application had less effect than a pre-spray but still often reduced leaf abscission. Combining 5 and 10 lbs. urea/100 gal with Ethrel occasionally increased abscission. ‘Elberta’ peaches were killed back almost to the bud union with single applications of 2000 ppm Ethrel and serious bud damage occurred on ‘d'Anjou’ pear at 4000 ppm. Apple, prune, and cherry were not damaged by 4000 ppm.
Abstract
Combinations of ethephon and D-WK (Dupont-WK) surfactant were effective in stimulating leaf abscission of 20 cultivars in 5 species of tree fruit nursery stock. Species and cultivars varied considerably in sensitivity to mixtures of these chemicals, but 1 to 3 applications at weekly intervals of 200 to 400 ppm ethephon + 1 to 2% D-WK were generally effective. These treatments caused little xylem, phloem or bud damage except to ‘Early Redhaven’ peach and ‘Early Italian’ prune. ‘Rome’ apple was sensitive but was not damaged by concn of 200 ppm ethephon + 1% D-WK. D-WK stimulated leaf abscission when used alone at 1 to 2% but acted more slowly than when combined with ethephon. Ethephon alone at 200 to 400 ppm was usually relatively ineffective.
Abstract
Ethyl 5-(4-chlorophenyl)-2H-tetrazole-2-acetate (PP528) applied in early summer to apple (Malus domestica Borkh.) and pear (Pyrus communis L.) trees stimulated lateral branching the first year in the nursery. Concentrations of 25 to 50 ppm were effective, while 100 ppm or more sometimes killed shoot terminals and stopped or retarded further vertical growth for the season. Branch angles were not measured, but when terminal meristems were not killed, branch angles were wide. If terminal meristems were killed, the uppermost branch angles were narrow. Double applications 2 weeks apart of 25 or 50 ppm were sometimes more effective than single applications. Timing, uniformity of growth, and application during active growth were important to produce maximum branching effect and branching in suitable locations. PP528 caused more branching in 2 nonspurred ‘Delicious’ apple cultivars (up to 9 times control values) than in ‘Oregon Spur Delicious’ (up to 3 times the control). Treatments with up to 200 ppm were largely ineffective on sweet cherry (Prunus avium L.). Use of 100 or 250 ppm GA was of little benefit in overcoming the stunting effect of high concentrations of PP528.
Abstract
A 2,4-dichlorophenoxy acetic acid (2,4-D) application in September, 1972, to a grass cover crop and most of a weed free 1.2 m wide strip under the tree row followed by sprinkler irrigation within 24 hours injured 8 year-old pear trees. Fall leaf abscission was inhibited and foliage development was abnormal the following spring. ‘Bartlett’/imported French seedling had no apparent damage while ‘Bartlett/Pyrus calleryana Decne., ‘East Mailing Quince A’ and ‘Provence’ quince was seriously damaged. ‘d’Anjou’/imported French seedling was damaged the least of the 9 combinations and was most seriously damaged on the same 3 rootstocks as ‘Bartlett’. Fruit yields were correlated with damage ratings.
Abstract
D-WK (Dupont-WK surfactant with the principal functioning agent being the dodecyl ether of polyethylene glycol) can be used to stimulate leaf abscission of some deciduous tree fruit nursery stock. One to 3 applications of 1 to 2% D-WK were satisfactory for most cultivars tested of apple, pear, cherry, and prune. ‘Early Red Haven’ peach was particularly sensitive to damage, and required lower concentrations.