Plant response to ethephon treatment was tested on 27 cultivars of vegetative annuals that have spreading and trailing growth habits. A control treatment was compared to 500 and 1000 mg·L-1 (ppm) foliar spray treatments of ethephon. Plant height and/or width index were significantly reduced for 81% of the cultivars tested. Responsive cultivars were alternanthera (Alternanthera dentata), brachyscome (Brachyscome iberidifolia) `Toucan Tango'; calibrachoa (Calibrachoa hybrids) `Colorburst Red', `Million Bells Cherry Pink', and `Trailing Pink'; diascia (Diascia × hybrida) `Sunchimes Rose' and `Red Ace'; double impatiens (Impatiens wallerana) `Tioga Red' and `Tioga White'; sweetpotato vine (Ipomoea batatas) `Sweet Caroline Bronze'; lantana (Lantana camara) `Patriot Cherry' and `Samantha'; nemesia (Nemesia × hybrida) `Aromatica Dark Lavender', `Blue Bird', and `Blueberry Sachet'; nolana (Nolana paradoxa) `Blue Eyes'; ivy geranium (Pelargonium hybrida) `King of Balcon'; petunia (Petunia × hybrida) `Cascadia Pink', `Mini Bright Pink', and `Supertunia Mini Purple'; bacopa (Sutera cordata) `Bridal Showers'; and vinca vine (Vinca minor) `Illumination'. Ethephon was not effective on monopsis (Monopsis unidentata) `Royal Flush', persicaria (Persicaria microcephala) `Red Dragon', or calibrachoa `Liricashower Rose'. Different cultivars of petunia showed varied responses to ethephon treatments as did trailing snapdragon (Antirrhinum majus) `Chandelier Yellow' and `Luminaire Yellow'. Flower number was reduced in 55% of the cultivars due to a delay in flowering. The experiment finds efficacy of ethephon for most cultivars treated at rates greater than or equal to that used commercially, however more research is needed to determine optimum concentrations for the specific cultivars. Chemical name used: ethephon [(2-chloroethyl) phosphonic acid].
Terri W. Starman, Melissa C. Robinson and Kristen L. Eixmann
T. L. Robinson, W. C Stiles and A. N. Lakso
In two field studies with `Redchief Delicious'/MM.106, 'Empire'/M.9/MM.106 and 'Mutsu'/M.9/MM. 106 trees on fertile silt loam soils, trickle irrigation increased vegetative growth during the first three years and resulted in a 16%-20% increase in cumulative yield over the first five years. When fertilizer was injected into the irrigation water weekly from mid-April until the end of June, tree growth was further increased and cumulative yield was improved an additional 11%-15% for a total of 27%-35% greater yield than the non-irrigated trees. In these studies, ground fertilization did not improve growth or yield unless trickle irrigation was also applied. However, ground fertilization was not as effective as fertigation.
Irrigation and fertigation increased the dry weight of roots by 23% and that of shoots by 36% in the first year resulting in a 10% reduction in the root/shoot ratio. Total tree dry weight was increased by 30% if trees were planted early (April 14) but only 14% if trees were planted late (June 10).
Early planting resulted in 17% greater cumulative yield than trees planted late. Initial tree caliper also had a significant effect on early growth and yield with large caliper trees yielding 12% more than the small caliper trees. The interaction of planting date, tree caliper and fertigation resulted in a 50%-70% increase in yield during the first five years.
Warren C. Stiles, Terence L. Robinson and W. Shaw Reid
Experiments conducted since 1986 indicate that multi-nutrient fertigation may be effective in improving early growth and yield of new orchards. However, the early studies did not provide information concerning the contributions of individual nutrient elements to these responses. Experiments were established in 1993 and 1994 to compare effectiveness of alternative sources, rates, and methods of applying K, Zn, and Cu through drip irrigation compared with annual soil surface applications to `McIntosh'/M.9 and `Empire'/M.9 trees. After 3 years, leaf K, cumulative shoot growth, and first crop year yields were increased by application of K. Differences between sources, rates, times, or methods of application generally were not significant when relatively high rates were applied. However, early results from a rate study indicate a significant K source by rate interaction. Soil surface application of K plus drip irrigation appears to be comparable to fertigation in supplying this element. After 2 years, applying EDTA chelates of Zn and Cu through fertigation increased leaf Zn and Cu, respectively, but high rates required are considered to be uneconomical when compared with foliar sprays of these elements.
Warren C. Stiles, Terence L. Robinson and W. Shaw Reid
Fertilizer treatments were applied by spreading over an herbicide-treated in-row strip, with or without irrigation using single-drip emitters per tree, or through drip irrigation. Distribution of nutrients in soils was evaluated by analysis of soil samples collected at various depths and distances from the irrigation emitters at the end of the 8-year experimental period. NO3-N was increased in the 0- to 40-cm depth by soil surface application but below 40 cm with fertigation. Fertigation increased P in the wetted zone within the 0- to 40-cm depths. Surface application of K increased levels primarily in the 0- to 20-cm zone, while fertigation increased K to depths of 80 cm. Zinc and Cu concentrations were increased by fertigation to 80-cm depth. In general, nutrients applied to the soil surface were less readily moved into the soil profile, while fertigation resulted in greater movement of nutrients to greater depths within the wetted zone of soil.
A.W. Fleener, C.W. Robinson, J.D. Williams and M. Kraska
Children's gardens have recently been shown to increase life skills. The purpose of this study was to assess the effects that gardening/plant activities from the Junior Master Gardener curriculum, Literature in the Garden, have on children's life skills. The life skills examined were leadership, teamwork, self-understanding, decision-making skills, and communication skills. About 130 third-grade students from a Lee County, AL, school participated in the study. Students were equally divided into control and experimental groups, and each student was given the youth life skills inventory (YLSI) as a pre- and posttest. The experimental group participated in eight gardening/plant activities after the pretest, whereas the control group did not complete the activities. No significant differences were found between pretests and posttests for teamwork, self-understanding, decision making, communication, and overall life skills. Significant decreases from pretest to posttest were found on leadership skills for the experimental group. Several trends were observed with students who read more for fun, read more each week, and read more garden books generally increasing in life skills.
D.A. Rosenberger, T.L. Robinson, J.R. Schupp, C.A. Engle-Ahlers and F.W. Meyer
Effects of three sterol-demethylation inhibiting (DMI) fungicides and a contact fungicide were compared over two years at each of two locations to determine if fungicide treatments had differential effects on productivity, fruit size and shape, or gross returns for `Empire' apples (Malus ×domestica Borkh.). Treatments were applied four to five times per year during the primary apple scab season. Effects of treatments were assessed by comparing fruit set efficiencies, number of fruit per tree, total harvested fruit weight, and fruit length: diameter ratios at harvest. No significant differences were noted among individual treatments in any of the four trials. However, when treatments were contrasted by grouping individual treatments, significantly larger fruit size was noted for triflumizole treatments vs. combined fenarimol and myclobutanil treatments in one of the four trials and for captan or mancozeb compared to fenarimol and myclobutanil treatments in two trials. None of the DMI fungicides compared in these trials had any consistent adverse affect on fruit size, total yield, or estimated gross return per hectare. We conclude that the plant growth regulator effects of DMI fungicides are inconsistent and are unlikely to have significant economic impact on commercial apple production.
Jianjun Chen, R.W. Henley, R.J. Henny, C.A. Robinson and R.D. Caldwell
Aglaonema is among the most popular tropical ornamental foliage plants used indoors because of its bright foliar variegation, low light and humidity tolerance, and few pests. Aglaonema, however, has been labeled as one of the most chilling-sensitive foliage plants. The dark, greasy-appearing patches on leaves injured by chilling can result in completely unsalable plants. With recent breeding activity, more and more Aglaonema cultivars have been developed and released. How new cultivars respond to chilling temperatures is, however, mostly unclear. This study was undertaken to evaluate cultivar chilling responses to identify chilling-resistant cultivars. Twenty cultivars were chilled at 1.7, 4.4, 7.2, 10, and 12.7 °C for 24 h using a detached single-leaf method and also whole-plant assay. Results indicate that great genetic variation exists among the cultivars, ranging from no injury at 1.7 °C to severe injury at 12.7 °C. A popular cultivar, Silver Queen, is the most sensitive, while the cultivar Stars is the most resistant. There was also a chilling response difference based on leaf maturity. Young leaves showed less injury than did either mature or old leaves. In addition, there was a significant correlation between the single-leaf and whole-plant assay for chilling resistance in Aglaonema'; the single leaf assay could be particularly useful for a quick test.
B.I. Reisch, R.M. Pool, W.B. Robinson, T. Henick-Kling, B.K. Gavitt, J.P. Watson, M.H. Martens, R.S. Luce and H.C. Barrett
Alan N. Lakso, Terence L. Robinson, Eddie W. Stover, Warren C. Stiles, Stephen Hoying, Kevin Iungerman, Craig Telgheder, Chris Watkins and Kenneth Silsby
Many chemical, environmental, and physiological factors have been reported to be important to apple chemical thinning, so we have been developing a multi-site and multi-year database of chemical thinning results and potentially important factors. For 3 years, we have conducted replicated thinning trials in `Empire' and `McIntosh' apple orchards at six or seven sites around New York state in different climatic regions. Different concentrations of NAA and Accel (primarily benzyladenine), NAA/carbaryl and Accel/carbaryl combinations and unthinned controls were tested with treatments applied at the 10-mm king fruit stage by airblast sprayers. Flower cluster counts, set counts, yields, fruit sizes, and other factors thought important to thinning response (orchard condition/history, weather, application conditions, etc.) were measured or estimated in each trial. Analysis of factor importance is continuing, but some general results have come from the thinning trials so far. Thinning effectiveness varied among years from poor to adequate. There have not been consistent thinner concentration responses. Commercial NAA and Accel concentrations have not thinned adequately. NAA/carbaryl and Accel/carbaryl have thinned the most. For the same crop load, trees thinned with Accel or the carbaryl combination have had better fruit size than when thinned with NAA.