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  • Author or Editor: Jeannie K. L. Garth x
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Abstract

Paclobutrazol (PP333) was applied to dormant ‘Heritage’ primocane fruiting red raspberry (Rubus idaeus L.) plants at dosages of 0, 6, 12, 24, 48, and 96 mg a.i.·0.37 m−2 ·hill−1. After 29 days of fruit production, the average cumulative fruit yield of primocanes treated with 24, 48, or 96 mg of paclobutrazol was 92% greater than for control primocanes. The cumulative fruit yield of primocanes receiving the 24-mg dosage remained significantly greater through 50 days of production compared to that of control primocanes. Cumulative fruit yield was not adversely affected at any time during the production season by any of the dosages applied. The 24-mg dosage suppressed final primocane height by 19% but did not significantly decrease primocane diameter or the number of nodes formed. The vegetative responses to 48- and 96-mg dosages were similar, with an average reduction in primocane height, diameter, and total number of nodes formed of 36%, 25%, and 14%, respectively. Early onset of anthesis was positively correlated (r = 0.72) with suppression of vegetative growth. Production midpoint occurred 60 ± 3.7 days after initial anthesis and varied (r = 0.85) with the date of first anthesis. Chemical name used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Open Access

Abstract

Butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) (2000 and 4000 ppm) was applied to ‘Heritage’ primocane fruiting red raspberry (Rubus idaeus L.) primocanes at combinations of several dates, when the canes averaged 19, 42, 65, and 79 or 91 cm in height. Daminozide-treated plots achieved 50% of the eventual final yield an average of 8 days earlier (averaged for 5 treatments involving daminozide application at 42 cm) than controls. This advance of the production curve resulted in an average yield increase of 51% during the first 28 days of production. However, while early yields were increased, total yields were unaffected. Increasing the concentration of daminozide from 2000 to 4000 ppm did not increase the effects. Double application of daminozide (2000 ppm) at 65 and 79 cm and single application at 91 cm reduced yield during the 14 to 28 day harvest period compared to that of the single 65 cm application. This reflects, in part, the reduced berry size during the early harvest period resulting from the later (79 or 91 cm) applications of daminozide. Daminozide reduced the number of nodes formed and advanced the date of anthesis. Application of (2-chloroethyl)phosphonic acid (ethephon) (300 ppm at 19 and 42 cm) increased the number of nodes formed, delayed anthesis by about 13 days, delayed fruiting, and reduced total production.

Open Access

Abstract

Treatments to modify the available photosynthetic assimilate supply and partitioning pattern of developing laterals were imposed on canes of red raspberry (Rubus idaeus L.). Removal of alternate buds on the entire floricane or all buds on the lower half of the floricane did not influence productivity of the remaining fruitful nodes. Removing upper buds substantially increased the productivity of lower fruitful nodes (150–184%). The increased number of fruit produced by laterals at the lower nodes arose from an increase in the percentage of fruitful nodes on the laterals (lateral nodes), and from an increase in the number of fruit per lateral node. The region of fruitful lateral nodes itself was not extended. The increased number of fruit produced at the lower fruitful cane nodes was a response by initiated buds during the early stages of spring growth. The increase in berry size (weight) was favored in 1 of the 2 experiment years after upper bud removal. Training canes horizontally, to balance the exposure to light of laterals along the cane, did not influence yield.

Open Access

Abstract

Petiole and scape elongation, leaf expansion, and runner formation were reduced by soil application of paclobutrazol (PP333). Runner number was reduced 90–100% by paclobutrazol dosages of 0.2–0.4 mg a.i. per 15-cm pot, accompanied by smaller reductions in leaf expansion (14–29%), petiole elongation (31–59%), and scape elongation (24–47%). Subsequent foliar applied gibberellic acid (GA3) at 50 ppm alleviated the effects of paclobutrazol. Lateral crown formation was promoted in several experiments. Fruit weight was not affected at 0.6 mg a.i. paclobutrazol per pot, but scape elongation was reduced by 51%. Chemical names used: β-[(4-chlorophenyl)methyl]α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Open Access

At two-week intervals from 17 June to 15 July, three groups of `Meeker' red raspberry plants were infested with two-spotted spider mites (Tetranychus urticae) in a greenhouse. While populations on individual plants were allowed to develop freely, control plants were kept free of mites with a chemical miticide. Gas exchange measurements were made on 27 July prior to visible mite damage, and on 7 October after injury was apparent. The relationships between mite populations and leaf gas exchange and chlorophyll characteristics were described using a logarithmic function.

Physiological responses to mite feeding were observed prior to visible leaf injury. On both dates, CO2 assimilation rates decreased (p ≤ 0.001) with increasing mite numbers per leaflet. On 27 June, a significant relationship (R2 = 0.61***) was found between mite number and mesophyll conductance (gm). On 7 October, significant relationships (p ≤ 0.001) were also observed with gm, stomatal conductance (gs), and transpiration (E). Total chlorophyll content of leaves decreased with increasing mite populations, but chlorophyll a/b ratio and dry weight per leaf unit area were unchanged.

Free access