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Don C. Elfving and Dwayne B. Visser

A new bioregulator, cyclanilide (CYC, Bayer Environmental Science, Montvale, N.J.), was tested for growth-related effects on apple trees over three years. Although treatment with CYC produced small reductions in shoot length, its principal effect was to stimulate the formation of lateral shoots on current-season's shoot growth and from spurs on older wood. CYC treatment of `Scarletspur Delicious' apple trees in the nursery more than doubled the formation of well-developed feathers with wide crotch angles (≈60°) and with no effect on final tree height. CYC appeared to flatten the apples and reduce fruit size in one trial. CYC appears promising for lateral branch induction in apple, especially in the nursery. Chemical names used: 1-(2,4-dichlorophenylaminocarbonyl)-cyclopropane carboxylic acid (Cyclanilide); calcium 3-oxido-4-propionyl-5-oxo-4-propionylcyclohex-3-enecarboxylate (prohexadione-Ca, Apogee); N-(phenylmethyl)-1H-purine-6-amine + gibberellins A4A7 (Promalin); polyoxyethylenepolypropoxypropanol, dihydroxypropane, 2-butoxyethanol (Regulaid).

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Don C. Elfving and Dwayne B. Visser

A new bioregulator, cyclanilide (CYC, Bayer Environmental Science, Research Triangle Park, NC 27709), was compared with a proprietary formulation of 6-benzyladenine and gibberellins A4 and A7 [Promalin (PR), Valent BioSciences, Walnut Creek, Calif.] for branching effects on sweet cherry trees. CYC stimulated the formation of lateral shoots on current-season's shoot growth under both orchard and nursery conditions. In the nursery CYC was as effective or better for feathering compared to PR in all cherry cultivars tested. There were no synergistic effects of CYC/PR tank mixes on feather development. Crotch angles of induced feathers were not different from the angles of feathers that formed spontaneously. The growth of CYC-induced feathers was sufficient to produce acceptable quality feathered trees. Trunk caliper of nursery trees was either not affected or reduced to a very minimal degree. CYC is effective for lateral branch induction in sweet cherry, especially in the nursery. Chemical names used: 1-(2,4-dichlorophenylaminocarbonyl)-cyclopropane carboxylic acid (cyclanilide); N-(phenylmethyl)-1H-purine-6-amine + gibberellins A4 and A7 (Promalin); polyoxyethylenepolypropoxypropanol, dihydroxypropane, 2-butoxyethanol (Regulaid).

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Don C. Elfving and Dwayne B. Visser

Improving lateral branch development in young sweet cherry trees without reliance on pruning is a desirable component of tree training programs, especially for high-density systems. Applications of two proprietary formulations of 6-benzyladenine and gibberellins A4 and A7 (Promalin, Valent Biosciences, Walnut Creek, Calif.; and Perlan, Fine Americas, Walnut Creek, Calif.) to individual buds or intact bark of unpruned sweet cherry central leader shoots at green-tip had little effect on lateral shoot growth from buds or on distribution of new shoot growth along the treated leader shoots. Scoring, nicking, or notching cuts alone also had inconsistent effects on shoot development and distribution. In some trials, bud removal (or disbudding, removing every fourth bud on 1-year-old shoots) produced limited improvement of lateral shoot development and vertical distribution. Combining nicking, notching, scoring, or bark scraping with the application of cytokinin–gibberellic acid solution to the cut area greatly improved both number of shoots developed and the numbers originating from the lower portions of treated leader shoots. Removing the physical barrier to bioregulator product contact with active tissues was a primary factor in improving treatment efficacy.

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Don C. Elfving and Dwayne B. Visser

The height above the bud union at which induced feathers develop on fruit trees in the nursery is an important determinant of tree quality for an intended market. The bioregulators cyclanilide (CYC; Bayer Environmental Science, Research Triangle Park, NC) and a proprietary formulation of 6-benzyladenine and gibberellins A4 and A7 (Promalin [PR]; Valent BioSciences, Walnut Creek, CA) affected the final height above the union of the lowest induced sylleptic shoot (feather) differently in apple and sweet cherry trees in the nursery. In apple, both products resulted in the lowest induced feather developing at approximately 4 to 20 cm below the height of the central leader shoot tip at the time of bioregulator application. In sweet cherry, the lowest induced feather typically originated starting approximately 2 to 20 cm above the central leader shoot tip height at the time of bioregulator application. Nursery tree height can serve as a suitable criterion for timing bioregulator applications to obtain feathers starting within a specific range of height above the bud union as long as species-specific feathering response characteristics are taken into account. Chemical names used: 1-(2,4-dichlorophenylaminocarbonyl)-cyclopropane carboxylic acid (Cyclanilide), N-(phenylmethyl)-1H-purine-6-amine + gibberellins A4A7 (Promalin), polyoxyethylenepolypropoxypropanol, dihydroxypropane, 2-butoxyethanol (Regulaid).

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Don C. Elfving, Gregory A. Lang and Dwayne B. Visser

Prohexadione-Ca (P-Ca) and ethephon (ETH) were evaluated as potential inhibitors of growth and promoters of early flowering for high density orchard management of sweet cherry (Prunus avium L.) trees on vigorous rootstocks. Single applications (P-Ca at 125 to 250 mg·L-1 active ingredient (a.i.) or ETH at 175 to 200 mg·L-1 a.i.) to young, nonfruiting sweet cherry trees produced short-term, generally transient reductions in terminal shoot elongation, and did not stimulate flower bud formation. Tank-mix applications (P-Ca + ETH) usually produced a stronger, possibly synergistic, reduction in shoot growth rate. Single tank-mix applications either increased subsequent flower bud density on previous season shoots or had no effect; when a second application was made three weeks later to the same trees, subsequent flower bud density on previous season shoots and spurs on older wood increased ≈3-fold over untreated trees. Yield efficiency (g·cm2 trunk cross-sectional area) also increased nearly 3-fold. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon); calcium 3-oxido-4-propionyl-5-oxo-3-cyclohexene carboxylate (prohexadione-Ca); polyoxyethylene polypropoxypropanol, dihydroxypropane, 2-butoxyethanol (Regulaid); aliphatic polycarboxylate, calcium (Tri-Fol).

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Don C. Elfving, Stephen R. Drake, A. Nathan Reed and Dwayne B. Visser

A sprayable formulation of 1-methylcyclopropene (1-MCP; AgroFresh, Spring House, PA) was applied to ‘Scarletspur Delicious’ and ‘Cameo’ apples in the orchard 1 to 3 weeks before harvest and compared in different postharvest studies with the commercial postharvest 1-MCP fruit treatment (SmartFresh; AgroFresh) and with aminoethoxyvinylglycine (AVG; ReTain; Valent BioSciences, Walnut Creek, CA). Treated apples were held in air storage for 50 to 60 d or in controlled-atmosphere storage for 120 to 125 or 215 to 225 d. With increased concentration, sprayable 1-MCP treatments were effective at controlling flesh firmness loss and internal ethylene concentration (IEC) up to 225 d of storage as well as during a 7-d poststorage shelf life simulation at room temperature. Application closer to harvest improved the effect of sprayable 1-MCP on control of flesh firmness loss and IEC. Concentrations of sprayable 1-MCP above 90 mg a.i./L produced similar fruit effects to 1-MCP. Treatment with 1-MCP showed little effect on soluble solids concentration (SSC), titratable acidity (TA), or skin or flesh color in ‘Delicious’ but slightly increased SSC and TA in ‘Cameo’ apples. AVG applied 4 weeks before commercial harvest controlled IEC nearly as well as either sprayable 1-MCP or 1-MCP during storage, but AVG-treated fruit allowed to ripen for 7 d at room temperature after storage lost much more flesh firmness regardless of storage regime. Sprayable 1-MCP also reduced starch hydrolysis, IEC and fruit drop at harvest. Sprayable 1-MCP may offer new opportunities for effective preharvest management of apple fruit condition, storability, and poststorage fruit quality.