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Frank J. Peryea

Two multiyear field studies were conducted to compare the phytoavailability and effectiveness of a variety of commercial foliar B fertilizer sprays applied at the pink flowering stage to 'Fuji'/EMLA.26 apple trees grown under irrigated semi-arid conditions. Treatments included products that differed by initial chemical form of B, physical state, and presence of additives of varying composition. Additional treatments were polymeric urea added to one B product and soil application of one B product. Boron application rates varied from 0.56 to 1.68 kg·ha–1·yr–1. All of the B sprays increased flower cluster B concentration in all years. The B sprays at the lower rate sometimes but not always increased leaf B concentration. Increasing the B rate substantially increased plant tissue B concentrations. In general, there was little substantive difference between the tested products/product mixtures on plant tissue B concentrations. Flower cluster B in the ground-applied B treatment was similar to the water control; however, leaf B concentration corresponded to the B spray treatments, indicating effective uptake of B from the soil during the early summer. Sodium polyborate-based products increased flower cluster Na concentration but not leaf Na concentration. The amount of Na contributed by Na polyborate-based products applied at commercial rates apparently was too small to be of horticultural concern. Fruit quality was excellent and was not affected by the experimental treatments in any year. Flower cluster and leaf B concentrations returned to near or at control levels in the season following the last spray application, validating the recommendation for annual B fertilizer applications to maintain adequate tree B status.

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Carl J. Rosen, Peter M. Bierman, Adriana Telias, and Emily E. Hoover

Application of calcium (Ca) sprays is a recommended practice to reduce the incidence of Ca-related disorders such as bitter pit in apple (Malus ×domestica), but effectiveness of sprays to increase Ca concentrations in the fruit is not always consistent. Strontium (Sr) has been used as a Ca analog to evaluate Ca transport processes and distribution in plants. A field study was conducted using foliar- and fruit-applied Sr as a tracer for Ca transport in 20-year-old `Honeycrisp' apple trees on Malling.26 (M.26) rootstock. The objectives of this study were to 1) measure the amount of Sr translocation from leaves to fruit, 2) determine the effectiveness of eight sprays applied over the growing season vs. four late-season sprays on increasing Sr concentrations in leaves and fruit, and 3) evaluate the effect of an experimental adjuvant consisting of alkyl-polysaccharides and monosaccharides on spray efficacy. Seven treatments were tested, which included a control and six Sr treatments applied in various combinations with or without an adjuvant. Trees were sprayed four or eight times during the growing season, either directly to leaves and fruit or to leaves only (fruit covered during application). Spray treatments did not significantly affect total fruit fresh or dry weight. Although some discrimination between Ca and Sr was detected, the similar distribution of Ca and Sr in fruit tissue of control treatments suggested that Sr is a suitable tracer for Ca. Based on the covered vs. uncovered fruit treatments, about 11% to 17% of the Sr in the fruit came from Sr applied directly to the leaves. Eight spray applications over the growing season more than doubled both the concentration and content of fruit Sr compared with four late season sprays. The tested adjuvant doubled Sr absorption by and translocation to fruit compared with not using an adjuvant. Assuming similar transport for Ca and Sr, and adjusting for the atomic weight of Ca relative to Sr, the maximum increase in fruit Ca concentration at harvest from foliar and fruit applications (eight sprays with adjuvant and uncovered fruit) would have been as follows: core = 78 mg·kg–1; flesh = 35 mg·kg–1; peel = 195 mg·kg–1; entire fruit = 67 mg·kg–1. In addition to being an underused tool for studying Ca transport patterns, the results also suggest that use of Sr may be a novel technique for testing the efficacy of various adjuvants used to enhance uptake and transport of Ca in leaves and fruit.

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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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Marianne Andresen and Nina Cedergreen

Various plant extracts are being marketed claiming to enhance both crop yield and quality and being environmentally friendly. However, these claims are rarely documented by scientific data. In this study, we investigate the growth regulatory effect of Tea Seed Powder (TSP), a saponin-rich waste product from tea seed (Camellia sp.) oil production. The product was tested in various concentrations on Lemna growth and as a soil and spray application on growth of pot grown beet, mustard, oat, and barley. Finally, two treatments, 0.2 g TSP/L dry soil and weekly sprays with TSP solutions corresponding to 1.5 g TSP/m2, were tested for effects on strawberry yield. The results showed significant growth-enhancing effects on the sterile Lemna of ≈20% above control, demonstrating that the growth increase was a plant physiological response to TSP rather than an indirect effect of TSP affecting pests and diseases or improving nutrient uptake. Soil-treated, pot-grown beet, oat, and barley plants showed significant biomass increases in the range of 27% to 41% above control at concentrations of ≈0.3 g TSP/L dry soil, whereas increases of 14% to 26% were observed in plants sprayed with 0.15 to 1.5 g TSP/m2. Sprayed strawberries had a 38% higher berry yield compared with control plants in 2008, whereas no difference in leaf number and area, number of runners, and inflorescences were detected. In 2009, there were no significant observable differences between sprayed plants and controls. Soil-treated strawberry plants, however, showed a decrease in leaf number in 2008 and in strawberry yield in 2009. The study concludes that TSP has pronounced and direct physiological effects on plants, which can both increase and decrease growth and yield depending on the applied dose. The growth-enhancing effect could be used commercially to improve crop yield; however, because TSP is also known to be very harmful to earthworms, possible environmental effects of the use of TSP in agriculture and horticulture must be considered before use.

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Emily A. Clough, Arthur C. Cameron, Royal D. Heins, and William H. Carlson

Influences of vernalization duration, photoperiod, forcing temperature, and plant growth regulators (PGRs) on growth and development of Oenothera fruticosa L. `Youngii-lapsley' (`Youngii-lapsley' sundrops) were determined. Young plants were vernalized at 5 °C for 0, 3, 6, 9, 12, or 15 weeks under a 9-hour photoperiod and subsequently forced in a 20 °C greenhouse under a 16-hour photoperiod. Only one plant in 2 years flowered without vernalization, while all plants flowered after receiving a vernalization treatment, regardless of its duration. Thus, O. fruticosa had a nearly obligate vernalization requirement. Time to visible bud and flower decreased by ≈1 week as vernalization duration increased from 3 to 15 weeks. All plants flowered under 10-, 12-, 13-, 14-, 16-, or 24-hour photoperiods or a 4-hour night interruption (NI) in a 20 °C greenhouse following 15-weeks vernalization at 5 °C. Time to flower decreased by ≈2 weeks, flower number decreased, and plant height increased as photoperiod increased from 10 to 16 hours. Days to flower, number of new nodes, and flower number under 24 hour and NI were similar to that of plants grown under a 16-hour photoperiod. In a separate study, plants were vernalized for 15 weeks and then forced under a 16-h photoperiod at 15.2, 18.2, 20.6, 23.8, 26.8, or 29.8 °C (average daily temperatures). Plants flowered 35 days faster at 29.8 °C but were 18 cm shorter than those grown at 15.2 °C. In addition, plants grown at 29.8 °C produced only one-sixth the number of flowers (with diameters that were 3.0 cm smaller) than plants grown at 15.2 °C. Days to visible bud and flowering were converted to rates, and base temperature (Tb) and thermal time to flowering (degree-days) were calculated as 4.4 °C and 606 °days, respectively. Effects of foliar applications of ancymidol (100 mg·L-1), chlormequat (1500 mg·L-1), paclobutrazol (30 mg·L-1), daminozide (5000 mg·L-1), and uniconazole (15 mg·L-1) were determined on plants vernalized for 19 weeks and then forced at 20 °C under a 16-h photoperiod. Three spray applications of uniconazole reduced plant height at first flower by 31% compared with that of nontreated controls. All other PGRs did not affect plant growth. Chemical names used: α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); (2-chloroethyl) trimethylammonium chloride (chlormequat); butanedioic acid mono-(2,2-dimethyl hydrazide) (daminozide); (2R,3R+2S,3S)-1-(4-chlorophenyl-4,4-dimethyl-2-[1,2,4-triazol-1-yl]) (paclobutrazol); (E)-(S)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ene-3-ol (uniconazole).

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Mara Grossman, John Freeborn, Holly Scoggins, and Joyce Latimer

Foliar spray applications of plant growth regulators (PGRs) benzyladenine (BA) and dikegulac sodium (DS) on herbaceous perennial liners and transplants were evaluated to determine effects on branching and quality. PGRs were applied three times (main plot): liner (24 h after removal from mist), post-transplant (5 to 7 days after transplant), or both (applications at liner and post-transplant). PGRs (subplots) were applied at concentrations of 400, 800, or 1600 mg·L−1 DS; 600 mg·L−1 BA; or a combination of 400 mg·L−1 DS and 600 mg·L−1 BA (DS/BA). All studies included an untreated control. Sedum spectabile ‘Autumn Joy’ treated with PGRs at both application times had a 100% increase in branching compared with either single application time. Applied post-transplant, 800 mg·L−1 DS, BA, or DS/BA increased branching. Applied at both times, all DS concentrations or BA tripled the number of lateral branches per plant, whereas DS/BA resulted in a 4-fold increase in number of branches. Sedum treated with 1600 mg·L−1 DS at liner, post-transplant, or both application times was shorter than controls; plants sprayed with 1600 mg·L−1 DS at both application times were stunted. Phytotoxicity (yellow, narrow leaves) was present in finished plants treated with 800 or 1600 mg·L−1 DS or DS/BA post-transplant or with 1600 mg·L−1 DS applied both times. Gaillardia aristata ‘Gallo Red’ treated with PGRs at both application times had increased branching compared with plants subjected to a single application. Number of branches was increased by liner application of 400 mg·L−1 DS, post-transplant applications of DS/BA, or applications both times of BA or DS/BA, whereas applications both times of 1600 mg·L−1 DS decreased branching and caused stunting and chlorotic foliage. In application as liners or at both times, all PGRs except 400 mg·L−1 DS caused 16- to 33-day delays in flowering. Branching of Phlox paniculata ‘Bright Eyes’ was unaffected by application time. Only Phlox treated with BA or 1600 mg·L−1 DS at both application times had increased branches, although plants treated with 1600 mg·L−1 DS were shorter than controls and had phytotoxicity in the form of narrow, yellow leaves. Nepeta racemosa ‘Walker’s Low’ treated with PGRs post-transplant or both application times had more branches than plants treated with PGRs once as liners. Number of branches was increased with BA or 800 mg·L−1 DS applied post-transplant or 1600 mg·L−1 DS, BA, or DS/BA applied both times, but the plants treated with 1600 mg·L−1 DS were stunted and had yellow leaves. Neither BA nor DS affected branching in Delosperma ‘Table Mountain’. Application time did not affect branching in Achillea ‘Moonshine’; only both applications of BA increased the number of branches in Achillea, whereas either single application of 1600 mg·L−1 DS or both applications of 800 or 1600 mg·L−1 DS caused phytotoxicity and stunting. Chemical names used: N-(phenylmethyl)-1H-purine-6-amine [benzyladenine (BA)], sodium 2,3:4,6-bis-O-(1-methylethylidene)-α-L-xylo-2-hexulofuranosonate (DS)

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Fernando Ramírez, Thomas L. Davenport, Gerhard Fischer, and Julio Cesar Augusto Pinzón

that if apical shoot initiation occurred in a set of trees after a particular spray application or if a maximum of four non-responsive sprays was recorded, the set was to be retired from further treatment and observation and the next numbered set was to

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Duane W. Greene

of these were devoted to mulching, irrigation, pruning, pollination, and harvest. Although spray application and the use of plant bioregulators (PBRs) have been mentioned in previous books and reviews, in Blueberries all of Chapter 7 was devoted to

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Nicole L. Waterland, Craig A. Campbell, John J. Finer, and Michelle L. Jones

sprays (volume of ≈28 mL) at the rate of 0 or 500 mg·L −1 s-ABA with the addition of 0.05% CapSil® (Aquatrols Corporation of America, Inc., Cherry Hill, NJ). Spray applications were applied with a Regulator Bak-pak® sprayer (H.D. Hudson Manufacturing

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Kent E. Cushman, William B. Evans, David M. Ingram, Patrick D. Gerard, R. Allen Straw, Craig H. Canaday, Jim E. Wyatt, and Michael M. Kenty

foliar nitrogen [CoRoN 25–0–0 (25N–0P–0K); Helena Chemical Co.]. Spray treatments consisted of a control, defined as a spray application of tap water, and six combinations of azoxystrobin/chlorothalonil alone or with various combinations of the previously