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M.A. Moura, S.R. Zanin, and F.L. Finger

The objective of the research was to determine the optimal concentration of ethephon treatment on anticipation of ripening in harvested tomato fruits. Mature-green fruits of cv. Santa Clara were sprayed with 0, 1000, 2000, and 3000 mg/L ethephon solution. In another set of experiments, the fruits were sprayed with 0, 500, and 1000 mg/L ethephon solution containing 1.0% surfactant (Dytrol) or not. The visual color and firmness changes during ripening at 24.1°C and 81.3% relative humidity were evaluated. Concentrations of 1000, 2000, and 3000 mg/L ethephon had similar effect on the anticipation of fruit ripening. The use of 500 mg/L ethephon delayed the fruit color changes when compared with the treatment of 1000 mg/L ethephon; however, firmness changes were nonsignificantly affected (P = 0.05). Treatment with 1000 mg/L ethephon hastened the color changes by 3 days when compared with control fruits, but no difference on color intensity was observed after 12 days. The use of 1.0% surfactant mixed to ethephon caused slight delay on color changes; therefore, 1000 mg/L ethephon solution in absence of surfactant was more efficient in hastening tomato ripening.

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Moritz Knoche and Martin J. Bukovac

Gibberellin A3 (GA) applied to virus-infected sour cherry (Prunus cerasus L., `Montmorency') trees inhibits flower initiation and promotes spur formation. However, response to a given dose may vary. Differential foliar absorption has been suggested as a major source of this variation. Therefore, we studied if surfactants would reduce variation in GA absorption. Uptake through the abaxial surface exceeded that through the adaxial surface by about one order of magnitude (adaxial surface 1.1 vs 7.8% in 1988, 0.7 vs 16.6% in 1989). GA uptake was markedly affected by surfactants. Over a 24-hr uptake period, Activator 90 and Ortho X-77 were most effective (abaxial surface 38.3 and 37.4% in 1989), whereas Regulaid did not affect GA uptake. L-77 significantly depressed absorption (abaxial surface 9.1% in 1989). In addition to the level of uptake, surfactants also changed GA absorption kinetics. Penetration increased linearly over a 96-hr time period when Regulaid was included. However, with Ortho X-77, uptake was rapid initially but levelled off within 96 hr. These findings will be discussed in relation to biological response data obtained in the field experiments.

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Moritz Knoche and Martin J. Bukovac

The effects of selected surfactants and surfactant blends, frequently used in spray application, on deposit formation and foliar absorption of GA3 by sour cherry (Prunus cerasus L. cv. Montmorency) have been investigated. Globular deposits were observed on droplet drying from solutions without surfactants or when the surfactants Activator 90, Tween 20, or Silwet L-77 were present, while annular-shaped deposits were observed with Regulaid, Ortho X-77, and Triton AG-98. Absorption of GA3 without surfactant was 5- and 17-fold higher by the abaxial (8.5% and 20.2% of applied in 1988 and 1989) than adaxial surface (1.6% and 1.2% of applied in 1988 and 1989). Over 24 hours, Ortho X-77 and Activator 90 (45.7% vs. 33.7% in 1988, 42.5% vs. 41.7% in 1989) were most effective in enhancing GA3 penetration through the abaxial surface, followed by Triton AG-98 (38.6% in 1988), Tween 20 (28.6% in 1989), and Regulaid (23.6% in 1988, 16.8% in 1989). Silwet L-77 significantly reduced GA3 uptake (10.7% in 1989) compared with the nonsurfactant control (18.2% in 1989). GA3 uptake increased at a decreasing rate during a 96-hour absorption period when GA3 was applied alone or with Ortho X-77. However, uptake increased linearly with time in the presence of Regulaid, yielding significantly higher GA3 penetration 96 hours after application (44.8%) compared with GA, alone (11.3%) or GA3 with Ortho X-77 (27.7%). GA3 penetration was independent of Tween 20 concentration in the range from 0.0313% to 0.25% but increased with increasing Ortho X-77 concentration (0.0313$%0 to 0.25%) over a 24-hour absorption period. Chemical names used: alkylpolyoxyethylene ether, free fatty acids, isopropanol (Activator 90); alkylarylpolyoxyethyleneglycols, free fatty acids and isopropanol (Ortho X-77); polyoxyethylenepolypropoxypropanol, alkyl 2-ethoxy-ethanol (Regulaid); polyalkyleneoxide modified polydimethylsiloxane copolymers (Silwet L-77); alkylarylpolyethylene glycol (Triton AG-98); polyoxyethylene (20) sorbitan monolaurate (Tween 20); gibberellic acid (GA3).

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W. Tietjen, P.J. Nitzsche, W.P. Cowgill Jr., M.H. Maletta, and S.A. Johnston

`Market Prize' and `Bravo' cabbage (Brassica oleracea Var. capitata L.), transplanted as peat plug and bareroot plants into a field naturally infested with Plasmodiophora brassicae, Woronin, were treated immediately after planting with a liquid or a granular surfactant. APSA 80™, applied in transplant water, significantly reduced percent clubbing and disease severity index (DSI) compared to control treatments. Miller Soil Surfactant Granular™ did not significantly reduce percent clubbing or DSI. There was a significant effect of cultivar on percent clubbing and DSI. There was no significant effect of transplant type on percent clubbing or DSI. This year's study culminates five years of investigation of surfactants for clubroot control. Specific surfactants have proven to be an effective control of clubroot in cabbage. Chemical names used: nonylphenoxypolyethoxyethanol (APSA 80™); alpha-alkanoic-hydro omega-hydroxy poly (oxyethylene) (Miller Soil Surfactant Granular™).

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H.B. Pemberton, G.L. Philley, and W.E. Roberson

Plants of Rosa L. `Peace' were field planted in Feb. 1995 in order to test black spot (Diplocarpon rosae Wolf) control efficacy of several compounds. Plants were protected from fungal infection by black spot with weekly sprays of chlorothalonil (Daconil) from 5 Apr. to 8 June 1995 to allow plant establishment. Spray treatments for efficacy testing were started on 23 June and ended on 1 Nov. 1995. All plants were uniformly weeded, fertilized, and irrigated as needed for the duration of the experiment. Plants were rated for defoliation and disease development on 18 July, 1 Sept., and 10 Nov. 1995. A wettable granular formulation of cyproconazole (Sentinel) controlled black spot significantly better when a surfactant, Latron B-1956, was added to the spray solution at 0.5 mL·L–1. Differences between treatments with and without surfactant were greater at lower rates vs. higher rates of cyproconazole. The most effective Sentinel rates with the surfactant were 0.13 g·L–1 applied every 14 days or 0.26 g·L–1 every 21 days. A formulated combination of chlorothalonil and thiophanate methyl (ConSyst) controlled black spot on a 7-day interval at 1.2 g·L–1, but not when applied at 1.8 g·L–1 every 14 days. Control was no better than the standard mancozeb (Dithane) treatment. Neem oil (NeemGard) was not effective on the 14-day schedule tested. Tank mixing neem oil with chlorothalonil or thiophanate methyl (Domain) did not significantly improve control. Neither myclobutanil (Systane) or a formulated combination of mancozeb and myclobutanil (RH 0611) was effective in controlling black spot.

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Royal G. Fader and Martin J. Bukovac

The plant cuticle is the prime barrier to penetration of foliar-applied plant growth regulators (PGR). Spray additives of various chemistries are frequently included in a tank mix to increase performance of PGRs. We have reported that urea and ammonium nitrate (AN) enhance transcuticular penetration of 14C-labeled NAA (pKa 4.2) from aqueous droplets (pH 5.2) and their subsequent deposits through enzymatically isolated tomato fruit cuticular membranes (CM). Studies on effects of Triton × surfactants on AN-enhanced NAA penetration showed an additional 25% increase in NAA penetration and the AN:surfactant interaction was significant. Also, some alkylamine hydrochlorides increased NAA penetration. Studies comparing NAA penetration through tomato and pepper fruit and Citrus leaf CM in the presence of 8 mM AN or 8 mM ethylamine HCl showed that all three species exhibited the same trend for penetration at 120 h: ethylamine HCl > AN > NAA only. Comparative NAA penetration for CM of the three species was pepper > Citrus > tomato, with significant differences (P > 0.006) in NAA penetration, as indexed by initial slope and penetration after 120 h. On addition of AN, NAA penetration was greater (range 3% to 40%) for Citrus and pepper CM than tomato CM. When ethylamine HCl was added, NAA penetration through Citrus and pepper CM was less (–37 and –27%, respectively) than tomato CM as measured by the initial slope, but 6% and 11%, respectively, more than tomato CM for penetration after 120 h. The differences in NAA penetration among the three species cannot be explained by cuticle thickness, since pepper and tomato CM are 2.5- to 3.5-fold thicker than Citrus CM. We have suggested that the enhanced NAA penetration mediated by AN and ethylamine HCl (and other alkylamine HCl examined) may be related to their hygroscopic properties leading to greater deposit hydration. The significance of the differences among the species CM and surfactant-enhanced NAA penetration will be discussed, in relation to diffusion in the non-living, non-metabolic plant cuticle.

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P.V. Blenis, L.B. Nadeau, N.R. Knowles, and G. Logue

Marasmius oreades, a causal agent of fairy rings, is one of the most important pathogens of turfgrass in the Great Plains region of North America. Following in vitro and greenhouse screening of surfactants and fungicides, two organosilicone surfactants, Silwet L-77 and Sylgard, together with the fungicide chlorothalonil, were evaluated in the field. Treatments were applied to healthy and infested turfgrass (Poa pratensis L., Festuca rubra L.) in either 1992, 1993, or in both years. Plots were sampled for grass production, canopy cover, mushroom production, grass chlorophyll content, soil water content, and phytotoxicity. Typically, there were no significant fungicide effects, fungicide by surfactant interactions or differences between Silwet L-77 and Sylgard. Relative to the water control, surfactants caused an approximate 3-fold increase in grass productivity on infested plots in the year of application. However, the difference in canopy cover between organosilicone-treated and control plots tended to be much less. Applying the surfactants to diseased plots in two successive years decreased the canopy cover but had no significant effect on grass production. Chlorophyll content tended to decrease in response to surfactants regardless of whether the turf was infested or healthy. Surfactants almost completely eliminated mushroom production and greatly reduced the occurrence of mycelium. Both organosilicones increased soil water content in infested areas; differences were detectable 2 years after application. Acute phytotoxicity from the surfactants was detected in infested but not in healthy plots. There was no direct evidence of chronic phytotoxicity. Organosilicone surfactants appear to have considerable potential for the management of fairy rings. Chemical names used: oxyalkylenemethylsiloxane (Silwet L-77); 2-(3-hydroxypropyl)-heptamethyltrisiloxane (Sylgard); tetrachloroisopthalonitrile (chlorothalonil).

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Eugene K. Blythe, Jeff L. Sibley, Ken M. Tilt, and John M. Ruter

In five experiments, singlenode cuttings of `Red Cascade' miniature rose (Rosa) were treated with a basal quick-dip (prior to insertion into the rooting substrate) or sprayed to the drip point with a single foliar application (after insertion) of Dip `N Grow [indole-3-butyric acid (IBA) + 1-naphthaleneacetic acid (NAA)], the potassium salt of indole-3-butyric acid (K-IBA), or the potassium salt of 1-naphthaleneacetic acid (K-NAA); a single foliar spray application of Dip `N Grow with and without Kinetic surfactant; or multiple foliar spray applications of Dip `N Grow. Spray treatments were compared with their respective basal quick-dip controls {4920.4 μm [1000 mg·L-1 (ppm)] IBA + 2685.2 μm (500 mg·L-1) NAA, 4144.2 μm (1000 mg·L-1) K-IBA, or 4458.3 μm (1000 mg·L-1) K-NAA}. Cuttings sprayed with 0 to 246.0 μm (50 mg·L-1) IBA + 134.3 μm (25 mg·L-1) NAA, 0 to 207.2 μm (50 mg·L-1) K-IBA, or 0 to 222.9 μm (50 mg·L-1) K-NAA resulted in rooting percentages, total root length, percent rooted cuttings with shoots, and shoot length similar to or less than control cuttings. Exceptions were cuttings sprayed with 0 to 2.23 μm

(0.5 mg·L-1) K-NAA, which exhibited shoot length greater than the control cuttings. Addition of 1.0 mL·L-1 (1000 ppm) Kinetic organosilicone surfactant to spray treatments resulted in greater total root length and shoot length. Repeated sprays (daily up to seven consecutive days) had no or negative effects on root and shoot development.

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K.G. Weis, S.M. Southwick, J.T. Yeager, W.W. Coates, and Michael E. Rupert

The years 1995 and 1996 were low chill years in California with respect to stone fruit dormancy. Advancing reproductive budbreak and flowering was accomplished in `Bing' cherry (Prunus avium) by single-spray treatments of a surfactant {a polymeric alkoxylated fatty amine [N,N-bis 2-(omega-hydroxypolyoxyethylene/polyoxypropylene) ethyl alkylamine]} and potassium nitrate in combination when applied at “tightbud,” ≈ 42 days (1 Feb. 1995) before full bloom and with surfactant and potassium nitrate in combination when 10% green calyx was apparent, 33 days before full bloom. Applying 2% surfactant (v/v) + 6% potassium nitrate (w/v) was most effective in advancing bloom, speeding progression through bloom, and advancing fruit maturity when applied at tightbud stage. Surfactant (2% or 4%) applied with 25% or 35% calcium nitrate (w/v) on 2 Feb. 1996 significantly advanced full bloom compared to nontreated controls. Fruit maturity (1995) was somewhat advanced by surfactant–nitrate treatments, but fruit set and final fruit weight were equivalent among treatments. No phytotoxicity was noted in foliage or fruit. In California, marginal and insufficient winter chilling often causes irregular, extended, or delayed bloom periods, resulting in poor bloom-overlap with pollenizers. As a result, flower and fruit development may be so variable as to have small, green and ripe fruit on the same tree, making harvest more time consuming and costly. Data indicate that this surfactant, in combination with a nitrogenous compound, has potential to advance reproductive budbreak and advance maturity in sweet cherry without reducing fruit set or fruit size. Advancing the ripening time of sweet cherry even 2 to 3 days can increase the price received per 8.2-kg box by $10 to $20.

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Esmaeil Fallahi, Bahar Fallahi, James R. McFerson, Ross E. Byers, Robert C. Ebel, Robert T. Boozer, Jim Pitts, and Bryan S. Wilkins

Effects of Tergitol-TMN-6 surfactant on blossom thinning (fruit set), fruit quality, and yield were studied in different cultivars of peach (Prunus persica [L.] Batsch) during 2003 to 2005, and in one cultivar of nectarine Prunus persica [L.] in one orchard and one cultivar of plum (Prunus domestica [L.]) in two orchards in 2004. In addition to Tergitol-TMN-6, effects of Crocker's fish oil (CFO) alone in three peach cultivars or in combination with lime sulfur in a nectarine cultivar were studied on fruit set, quality, and yield. Tergitol-TMN-6 at 5 mL·L–1 or higher rates, applied at about 75% to 85% bloom, reduced fruit set without russeting peach fruit. Peach fruit size was often increased by Tergitol-TMN-6 treatment. Applications of Tergitol at 20 mL·L–1 or 30 mL·L–1 excessively thinned peaches. Tergitol-TMN-6 at all rates burned foliage, but the symptoms disappeared after a few weeks without any adverse effects on tree productivity. Tergitol-TMN-6 at 7.5 mL·L–1 or 10 mL·L–1, applied either once at about 80% to 85% bloom or twice at 35% bloom and again at 80% to 85% bloom, reduced fruit set without any fruit russeting in nectarine. Tergitol-TMN-6 at 7.5 mL·L–1 to 12.5 mL·L–1 reduced fruit set in `Empress' plum. CFO at 30 mL·L–1 was effective in blossom thinning of some peach cultivars. A combination of lime sulfur and CFO was not effective in blossom thinning of nectarine. Considering results from several orchards in different locations in the Pacific Northwest over 3 years, Tergitol-TMN-6 is an excellent blossom thinner for peach, nectarine, and plum at rates of 7.5 to 12.5 mL·L–1, sprayed at a spray volume of 1870.8 L·ha–1 when about 75% to 85% blooms are open.