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NAA is commonly used for post-bloom apple thinning. However, occasionally with `Delicious', excessive small fruit (50 - 67 mm) may be produced, regardless of crop load. This effect has been associated with late and/or low volume applications, however the cause is not known. A preliminary study (1991; fruit diam., 11 mm; 15 mg·L-1 equivalent at 234 - 2104 L·ha-1) resulted in a high incidence (19 - 40 %) of small fruit. A later application (fruit diam., 20 mm, 701 L·ha-1) had a lower incidence and fruit size approached that of hand thinned controls. In 1992, NAA (15 mg·L-1,equiv.) was applied (fruit diam., 8 mm) at 250 - 2000 L·ha-1. Time of application was assessed by applying NAA (15 mg·L-1, high vol.) at 5 - 21 mm fruit diameter. At harvest, there was no significant amount of small fruit in any treatment. Fruit from NAA treatments were smaller than hand-thinned, but larger than non-thinned controls. Fruit size distribution showed no significant effect of spray volume or time of application. In a related study, a higher concentration (17 mg·L-1) of NAA induced small fruit. The possible involvement of seasonal/environmental factors will be discussed.

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Abstract

Naphthaleneacetic acid (NAA) ethyl ester was applied as 0.5% aqueous spray 7 cm below the grafts of 9-month-old avocado (Persea Americana Mill.) prior to graft growth. No growth occurred on the grafts and plants were dead 4 months after treatment. Volatilization of ethyl ester of NAA applied as 0.3% to 1.0% aqueous spray, 7 cm below grafts that had grown out 12 cm, caused the new growth to wilt for 36 hours. The 0.4% spray caused slight bark burn of the seedling trunk. The higher the concentration the greater the burn. Sprays of 0.3 or 0.4% sodium salt NAA did not cause wilting or bark burn. Both formulations of 0.3 and 0.4% gave good control of sprouts on the seedlings trunks. The 0.3 and 0.4% ethyl ester treatments reduced total graft growth.

Open Access

Abstract

Parthenocarpic fruit development was induced in ‘Montmorency’ sour cherry (Prunus cerasus L.) with AC 94377. The biological activity of AC 94377 was increased significantly by NAA. The development (Stages I, II, III, “June drop”, ripening) of parthenocarpic fruit was similar to that of open pollinated controls except for smaller fruit size. Ovules enlarged during Stage I in AC 94377-induced parthenocarpic fruit, but lacked embryos; all ovules aborted during Stage II or III of fruit development. The primary action of NAA appeared to reduce abscission of AC 94377-treated ovaries with no significant effect on fruit size. Chemical names used: 1-naphthaleneacetic acid (NAA); N-(phenylmethyl)-1H-purin-6-amine (6-BA); 1-(3-chlorophthalimido)-cy-clohexanecarboximide (AC 94377); polyoxyethylene sorbitan monooleate (Atlox BI).

Open Access

In spring 1999, a commercial NAA (1-naphthaleneacetic acid) preparation for trunk sprout inhibition was compared with a corrugated plastic trunk wrap, aluminum foil wrap, bimonthly hand removal of sprouts, use of NAA preparation plus bimonthly hand removal when sprouts appeared, and a nontreated control. Three recently planted groves on three different rootstocks [`Midsweet' orange (Citrus sinensis)] on Swingle citrumelo (Citrus paradisi × Poncirus trifoliata), `Valencia' orange on Volkamer lemon (Volk, Citrus limon), and `Minneola' tangelo (Citrus paradisi × C. reticulata) on Smooth Flat Seville (SFS, Citrus hybrid) received each of the treatments in a randomized complete block experimental design with trees blocked by initial height and circumference. Every 2 months, sprouts were counted on each tree and removed from the hand removal treatments. After 1 year, all sprouts were removed and counted and height and circumference of trees was determined. Across all experiments, 82% to 100% of nontreated trees produced trunk sprouts and all sprout control methods significantly reduced sprouts per tree. NAA treatments were never significantly less effective at sprout suppression than the wraps at the P = 0.05 level, although in two experiments, wraps were more effective than NAA at P = 0.10. Time of sprout appearance varied between the three experimental blocks. Plastic and foil trunk wraps enhanced development of trunk circumference compared with nontreated controls in `Midsweet'/Swingle and `Valencia'/Volk. Greater trunk circumference resulted from use of wraps versus NAA in all three experiments, which appeared unrelated to differential sprout suppression. In these experiments, it appears that either wraps enhanced tree development beyond the suppression of sprouts or NAA influence on tree metabolism somewhat reduced trunk growth. The economics of the sprout suppression methods are also discussed.

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Abstract

Pre-June drop sprays of naphthaleneacetic acid (NAA) applied to apple trees increased the radial pedicel-xylem ratio, the % tracheary cells that were lignified, and the number of mature treacheary cells on the 7th day following treatment No significant response for these characters were obtained with sprays of 1-naphthyl methyl carbamate (Sevin). Both NAA- and Sevin-treated pedicels had a higher percentage of sclereids that contained nuclei. Neither material affected pedicel diameter, width of phloem or xylem, size of newest lignified tracheary cells, number of immature secondary tracheary cells, or the radial xylem-phloem and pedicel-phloem ratios.

Open Access

Abstract

A 1% ethyl ester or sodium salt formulation of naphthaleneacetic acid (NAA) in 30% aqueous solution of white latex paint sprayed below the grafts effectively controlled trunk sprouts in topworked avocados (Persea americana Mill). Regrowth was suppressed over a 7-month growing period with no adverse effects on the grafts.

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In Washington and other western states Elgetol, a blossom thinning agent was previously used before the postbloom NAA and Sevin applications and there was no need for an earlier timing of NAA and Sevin treatments. In 1989, Elgetol was removed from the market by the manufacturer because of minor crop use and the high cost of re-registration. Without a blossom thinner it is impossible to guarantee a return bloom on severe biennial bearing cultivars such as Golden Delicious and Fuji. Even though adequate fruit thinning occurs with the postbloom thinning sprays, flower Initiation may not occur for the next years crop because the application is made too late.

NAA and Sevin are used as postbloom sprays for reducing fruit set of apples. The usual time of application is when the largest fruit are from 10 to 15 mm in diameter. Sprays applied at the 10-15 mm fruit diameter stage take advantage of warm weather after spraying which increases stress and maximizes reduction of fruit set with a minimum effect on the seed number, however, when temperature is cold seed abortion occurs without adequate reduction of fruit set.

This report compares the efficacy of the postbloom thinners NAA and Sevin as early petal fall sprays for reducing fruit number and increasing return bloom the following year. Sevin is most effective as an apple fruit abscission agent when applied at petal fall. In trials for 2 years there was no reduction in fruit seed number, no reduction in fruit size and no effect on fruit shape. In comparison NAA applied at petal fall tended to reduce seed number, reduce fruit size, flatten or distort fruit shape and cause leaf curling.

Free access

Abstract

Treatment of headed-back 1-year-old dormant shoots of ‘Monroe’, ‘McIntosh’ and ‘Wayne’ apple (Malus domestica Borkh.) with 1% naphthaleneacetic acid (NAA) in latex paint was relatively ineffective and gave inconsistent results; however, treatment of mechanically hedged shoots on established trees gave statistically significant reductions in regrowth, by reducing bud break of dormant buds on older wood. Regrowth in ‘Monroe’ trees was reduced with daminozide primarily by reducing shoot length.

Open Access

Abstract

We previously reported a method for shoot tip micropropagation of the Vitis hybrid ‘Remaily Seedless’ (1, 2). In preliminary trials, rooting of subcultured shoots was erratic and shoots deteriorated after 2 weeks in culture. Herein we report the effects of sucrose and naphthaleneacetic acid (NAA) concentrations on the physical condition of subcultured shoots and subsequent root production in an attempt to increase the efficiency of grape micropropagation.

Open Access
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Abstract

As the concentration of the exogenously applied gibberellin GA4+7 increased from 1 to 100 ppm, 3 significant correlations were observed: 1) the number of days to first flowering decreased; 2) the peduncle length of the first flower increased; and 3) the number of visible peduncles on the primary phyllomorph increased. A subsequent application of 10 ppm naphthaleneacetic acid (NAA) generally had no effect on these results.

Open Access