Flurprimidol substrate drenches at 2 mg a.i. per 15.3 cm (6 inch) pot were more effective on `Pacino' pot sunflowers (Helianthus annuus) than flurprimidol foliar sprays of ≥30 mg.L –1 (ppm), but both treatments resulted in significantly smaller plant height and diameter than the control (28,350 mg = 1 oz). Flurprimidol drenches of 2 mg were comparable in controlling plant height and diameter to the commercial drench recommendations of 2 mg paclobutrazol. The commercial recommendation of daminozide foliar sprays at 4000 mg.L –1 had greater efficacy in controlling plant height than the most effective flurprimidol foliar sprays of ≥30 mg.L –1. Daminozide had no effect on plant diameter, while flurprimidol resulted in narrower plants. Flurprimidol and paclobutrazol drenches of 2 mg offer the economic advantage to producers of increased plant density on greenhouse benches, while plants treated with daminozide would require a greater amount of bench area. Producers should evaluate the trade-offs between the added costs of a drench vs. the higher cost-per-square-foot-week of production space required for a daminozide foliar spray. With these options, producers can select a plant growth regulator (PGR) that best fits their production and market requirements.
Brian E. Whipker, Ingram McCall, James L. Gibson, and Todd J. Cavins
Brian E. Whipker and Ingram McCall
Plant growth retardant (PGR) foliar sprays of daminozide at 4,000 or 8,000 mg·L-1 (ppm) and paclobutrazol drenches of 2 or 4 mg a.i. per pot were applied to `Big Smile', `Pacino', `Sundance Kid', `Sunspot', and `Teddy Bear' pot sunflowers (Helianthus annuus L.) to compare their chemical height control. Plant height varied among the cultivars due to genetic variation. The percentage reduction in plant height from the untreated control only was significant at the PGR level, indicating similar responses of all five cultivars to each PGR rate. Paclobutrazol drenches at 2 mg and daminozide foliar sprays at 4,000 or 8,000 mg·L-1 reduced plant height by about 24% when compared to the control. Paclobutrazol drenches at 4 mg produced plants that were 33% shorter than the control. Plant diameter of `Big Smile', `Pacino', or `Sundance Kid' was unaffected by daminozide, whereas `Sunspot' plants were smaller than the controls. Paclobutrazol drenches at 2 or 4 mg decreased plant diameter for all cultivars except `Teddy Bear', with the reduction being greater as paclobutrazol drench rates increased. The number of inflorescence buds increased by ≥18% with the use of daminozide sprays, while paclobutrazol drenches at 2 or 4 mg had no effect when compared to the untreated control. Paclobutrazol drenches of 2 or 4 mg offer the economic advantage to growers of increased plant density on greenhouse benches, while plants treated with daminozide had an increased bud count but would require a greater amount of bench space.
A. Hagiladi and A.A. Watad
Potted Cordyline terminalis L. `Prins Albert', a foliage plant, was treated with foliar sprays or growth medium drenches of paclobutrazol for plant growth control. Paclobutrazol effectively reduced shoot length measured 4 months following application, the drench being more effective than the spray. Application of paclobutrazol at 200 ppm by either method gave a desirable compact and marketable product. Drench applications at 1000 ppm promoted side-shoot formation. Leaf morphology was altered from an elongated to a more oval form as the paclobutrazol concentration increased, but leaf count was not affected by paclobutrazol, except for the highest drench concentration, which reduced leaf count by 10%. Chemical name used: β– [(4-chlorophenyl)methyl] –α– (1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).
H.C. Wien and Y. Zhang
Catfacing of tomato (Lycopersicon esculentum Mill.) fruit describes the enlarged blossom-end scar and ridged, flattened or irregular fruit shape often found on plants subjected to low temperature during ovary development. Experiments were conducted to determine if GA3 foliar sprays could be used as a screening tool for catfacing. Concentrations of 5 to 50 μM of GA3, applied once at transplanting, significantly increased catfacing incidence on the susceptible `Revolution', whereas the resistant `Valerie' was less affected. Two applications 8 days apart extended symptoms to later clusters formed on branches and may be useful for screening cultivars of a wide range of earliness. Plant apex removal may also be possible as a fruit catfacing screening tool. Chemical name used: gibberellic acid (GA3).
A.P. Papadopoulos, U. Saha, X. Hao, and S. Khosla
Encouraging results from previous trials on field vegetables led to the expectation that a kinetin foliar spray from the commercial product KIN-Gro (5000 ppm kinetin) on greenhouse vegetables would positively affect their growth and productivity. Thus, in this study, we evaluated the usefulness of this product on rockwool-grown `Bodega' cucumber (Cucumis sativus), `Rapsodie' tomato (Lycopersicum esculentum), and `4-Ever' and `444' pepper (Capsicum annuum) at the Greenhouse and Processing Crops Research Centre of Agriculture and Agri-Food Canada, Harrow, Ont. Two replicated experiments were conducted to study the effect of kinetin spray on growth and production of all three crops: the first in Spring-Summer 2004 and the second in Fall-Winter 2004. Foliar sprays of kinetin at 2.5, 5, and 10 ppm concentrations were tested against a water spray (control) on each crop. A 2.5-ppm kinetin spray had beneficial effects on the growth of cucumber transplants (taller plants and greater leaf area and fresh weight of leaves and stems). Furthermore, this treatment resulted in higher marketable yield in the Spring-Summer crop and in larger fruit size in the Fall-Winter crop. Regression analysis showed that cucumber marketable yield had an overall quadratic response to kinetin spray concentration in Spring-Summer season maximizing at 5.1 ppm kinetin. Kinetin spray also had beneficial effects on the growth of tomato seedlings, but not on yield. On the other hand, significant beneficial effects were observed on the growth of pepper seedlings and on marketable yield and fruit quality. Regression analysis showed that the response of pepper marketable yield to kinetin spray concentration was positive and linear. It must be noted that, given the rather short-term nature of our experiments, the observed beneficial effects of the kinetin sprays on yield can only be interpreted as beneficial effects on early yield rather than on the total yield. We concluded that under our growing conditions, cucumber production would benefit from a dilute (2.5 ppm) kinetin spray, and pepper production from a high concentration spray (10 ppm); tomato transplant growth will also benefit from a kinetin spray at 2.5 ppm. The results of this study could be of considerable significance to the greenhouse vegetable industry.
Franz J. A. Niederholzer and R. Scott Johnson
Urea foliar sprays may be a more efficient and environmentally sound alternative to soil applied fertilizer N in the postharvest period in tree crop production in California. While tree crop sulfur (S) status can interact with tree N status to affect growth, we know of no study assessing tree crop leaf N and S dynamics following fall (postharvest) foliar urea applications. We conducted a field study to measure temporal dynamics of leaf N and leaf S (% dry weight basis) following postharvest urea sprays on prune (Prunusdomestica) and almond (Prunus dulcis). June-budded nursery stock prune (`French' on Myro 29C) and almond (`Price' on Lovell) trees were sprayed to dripping with 6.5% (w/w) and 10% (w/w) standard urea solutions, respectively. Prunes were sprayed on 1 Oct. 2003 and almonds on 18 Nov. 2003. Leaf samples were taken over a 3-week (almond) or 8-week (prune) period, beginning just before treatment. Foliar urea sprays significantly increased prune (23%) and almond (14%) leaf N compared to untreated control within 8 days of application. This affect was transient, as there were no differences in leaf N concentrations between treated and untreated trees at final leaf sampling. Urea sprays did not affect almond leaf S concentration relative to untreated trees. Prune leaf S was significantly reduced compared to untreated trees 8 days after treatment, but only on that sampling date. Remobilization of S from the leaves of control trees of either species was not apparent.
H.C. Wien and A.D. Turner
The blossom-end scarring of tomato fruit caused by exposure of the plant to cool weather during ovary formation, commonly termed catfacing, can also be induced by GA3 foliar sprays. To determine if GA3 treatment could serve as a cultivar screening tool to identify lines susceptible to the disorder, we compared the catfacing incidence in 14 fresh-market tomato cultivars after GAS sprays and in nontreated controls in two field experiments. In 1 year, removal of the plant's apex was also imposed. GA3 sprays (22 μm twice, applied 1 week apart to tomato seedlings ≈5 weeks old) increased catfacing incidence in both years and accentuated cultivar differences in the disorder. Topping did not increase catfacing significantly. The cultivars Valerie, Sunrise, and Basketvee were least affected by catfacing in the experiments, while `Starfire', `New Yorker', and `Olympic' had the highest percentage of catfaced fruit. The GA3 screening method shows promise for identifying cultivar differences in susceptibility to blossom-end scarring. Chemical name used: gibberellic acid (GA3).
Qinglong Zhang and Patrick H. Brown
In this study, we investigated the effectiveness of several Zn formulations applied at various times of the year in increasing Zn status of pistachio and walnut leaves. Formulations included inorganic and organic forms of Zn. Fall sprays was ineffective at supplying Zn to developing leaves even when very high rates (5000 ppm) were used. Late dormant and budbreak sprays were effective at supplying Zn to developing leaves and nuts only when extremely high rates (5000 ppm) were applied. Spring flush sprays were the most effective, while late spring and summer sprays were ineffective. The majority of the Zn applied remained in the epidermis of the sprayed leaves, which resulted in high Zn content of leaves but poor correction of Zn deficiency and little or no translocation of Zn to other plant parts. Many of the Zn formulations sprayed at spring flush at a rate of 1000 ppm effectively increased leaf Zn values by at least 10 μg–g–1. Addition of an appropriate organic acid to the spray solution and adjustment of pH to ≈4.5 improves leaf uptake and translocation of Zn. Addition of specific surfactants into the spray solution is also recommended. Use of N- and P-containing Zn spray formulations is less effective than sulfur-based sprays (i.e., ZnSO4). Significantly, there is little residual effect of foliar sprays (even at spring flush), indicating that consecutive sprays for several years are needed to maintain productivity in Zn-deficient regions.
Several fungicides, including benomyl, flutolanil, iprodione, metalaxyl, and a mixture of metalaxyl and benomyl that control rhizoctonia stem rot (Rhizoctonia solani Kuhn) of poinsettia (Euphorbia pulcherriman Willd. ex Kl.) were evaluated for inhibition of poinsettia root initials and suppression of root elongation. Fungicides were applied as either foliar sprays to poinsettia cuttings in rooting cubes or as soaks of rooting cubes before sticking of cuttings. Rooting cube soaks of iprodione and benomyl and fungicide sprays of iprodione, benomyl, and chlorothalonil inhibited root initiation as measured by root counts 28 days after sticking cuttings. However, root elongation as measured by root rating was similar for all fungicides and the untreated control at 28 days. Plant height of rooted poinsettia cuttings transplanted to 400-cm3 pots was significantly less (P = 0.05) only for cuttings sprayed initially with iprodione, but not for rooting cubes soaked in iprodione 58 days after transplanting. The inhibitory effect of other fungicides on root initiation did not appear to affect plant growth once plants were transplanted. Chemical names used: methyl 1-(butyl-carbamoyl)-2-benzimidazolecarbamate (benomyl); tetrachloroisophthalonitrile (chlorothalonil); N -[3-(methylethoxy)phenyl]-2-(trifluoromethyl)benzamide (flutolanil); 3-(3,5dichlorophenyl)N -(lmethylethyl)-2,4-dioxo-l-imidazolidinecarboxamide (iprodione); N -(2,6-dimethylphyenyl)N -(methoxyacetyl) alanine methyl ester (metalaxyl).
Christopher J. Currey, Nicholas J. Flax, and Kellie J. Walters
.2 boron, and 0.5 molybdenum. Seven days after planting, nine individual plants of each cultivar were treated with foliar sprays of deionized water, ancymidol [20, 40, or 80 mg·L −1 (Abide; Fine Americas, Walnut Creek, CA)], chlormequat chloride [750, 1500