Red firespike (Odontonema strictum) is an ornamental shrub with potential for use as a flowering potted plant due to its dark green foliage and attractive red flower spikes. To stimulate branching and improve quality of red firespike, foliar spray applications of dikegulac sodium (DS) and benzyladenine (BA) and hand pinching were evaluated across two seasons (Spring and Summer 2014). There were three pinching treatments: one, two, or three pinches. Plant growth regulators (PGRs) were applied at 400, 800, 1600, or 2400 ppm DS or 600, 1000, 1250, or 1750 ppm BA. Both studies included an untreated control. Red firespike treated with all concentrations of BA and 1600 and 2400 ppm DS had increased branching compared with the control, except 1000 ppm BA in Expt. 1. Pinching did not affect the number of branches. Dikegulac sodium at 1600 and 2400 ppm and all concentrations of BA resulted in shorter plants than the control. Phytotoxicity was observed in plants treated with 1600 or 2400 ppm DS. In both experiments, DS at 1600 and 2400 ppm had the least plant dry weight compared with the control. Treatment with BA at 1750 ppm resulted in greatest leaf area compared with control. Dikegulac sodium at 800 ppm increased the number of flowers compared with control. Pinching and BA did not affect number of inflorescences. All concentrations of BA and DS delayed flowering, except 1000 ppm BA. Plants treated with 800, 1600, and 2400 ppm DS had shorter inflorescences compared with control plants. Benzyladenine decreased the length of the inflorescence at high concentrations, 1250 and 1750 ppm. Pinching treatments did not affect inflorescence length.
Amir Rezazadeh, Richard L. Harkess, and Guihong Bi
Christopher S. Cramer, Neel Kamal, and Narinder Singh
Iris yellow spot (IYS) disease, caused by Iris yellow spot virus (IYSV), results in irregular and diamond-shaped, chlorotic, and necrotic lesions on the leaves and seedstalks of onions (Allium cepa L.). These lesions reduce leaf photosynthetic area and ultimately reduce onion bulb size and yield from larger bulb classes. IYSV is vectored by onion thrips (Thrips tabaci L.) that are difficult to control under certain environmental conditions. Currently, no onion cultivar is resistant to the disease symptoms, virus, and/or thrips. Twenty-one cultivars and 17 germplasm lines were evaluated in the field for IYS disease severity and thrips densities at multiple times during the season as well as leaf color, waxiness, and axil openness of these entries. Plants were grown under conditions that favored thrips populations (high temperatures, low moisture, and no insecticidal spray applications), IYSV presence and distribution, and IYS development. Plants of New Mexico State University (NMSU) 07-10-1 had fewer thrips than several entries later in the season in both 2009 and 2010. Several entries exhibited a lower number of thrips per plant early or later in the season; however, these results were not consistent across years and were not associated with a particular foliage characteristic. Lighter leaf color and/or a lesser amount of epicuticular wax did not always result in the fewest number of thrips per plant as has been reported in the literature. Plants of NMSU 09-58 tended to exhibit fewer and less severe IYS symptoms early in the season as compared with plants of other entries.
A.A. Csizinszky and D.J. Schuster
The impact of two insecticide spray application schedules (weekly or on demand), three N and K rates [1x, 1.5x, and 2x; 1x = (kg·ha-1) 130N-149K], and two transplant container cell sizes [small, 21 mm wide × 51 mm deep (7.5 cm 3), and large, 38 mm wide × 70 mm deep (33.7 cm”)] on `Market Prize' cabbage (Brassica oleracea L. Capitata group) yield was investigated in Fall and Winter 1982-83 and Spring 1983. Fenvalerate was sprayed at 0.112 kg·ha-1. For the weekly schedule, 10 sprays were applied in fall and winter and nine in spring; for the on-demand schedule, two sprays were applied in both seasons. There were more insect-damaged heads in both seasons in the plots sprayed on demand than in those sprayed weekly. In fall and winter, the combination of a weekly schedule with 1.5x and 2x N and K rates increased marketable yields over those of the on-demand schedule. Marketable yields at the 1.5x and 2x N and K rates were similar for plants in small or large transplant container cells, but the lx N and K rate applied to plants in small cells reduced yields. In spring, both application schedules produced similar yields, but yield increased with increasing N and K rates and large transplant container cells. Insecticide application schedule and cell size did not affect leaf nutrient concentration significantly, but increasing N and K rates resulted in higher N, P, and K leaf concentrations. Concentrations of N and K in the soil at 42 days after transplanting (DAT) were higher with increasing N and K rates. At harvest (86 DAT), only K concentrations had increased with N and K rates. Chemical name used: cyano (3-phenoxyphenyl) methyl 1-4 chloro-alpha-(1-methylethyl benzeneacetate) (fenvalerate).
Larry Kuhns and Tracey Harpster
Though glyphosate is considered to be a nonselective herbicide, conifer growers have long known that under certain conditions, they could contact the lower branches of their trees with the herbicide Roundup without injuring them. Species, time of application, rate of application, surfactant, method of application, and pruning wounds are all factors affecting conifer tolerance to glyphosate. Because Roundup was widely used by conifer growers, they were very concerned when the formulation of Roundup was changed to contain a more active surfactant. The new product was marketed under the name Roundup Pro. This change increased its herbicidal activity and raised the possibility that it could damage trees if applied in the same way as Roundup. To determine the tolerance of conifers grown in the northeast to a variety of glyphosate formulations, and sulfosate, a set of studies was established. Roundup, Roundup Pro, Glyfos, Accord, and Sulfosate were all applied to field grown hemlock, white fir, Canaan fir, fraser fir, douglas fir, Colorado spruce, and eastern white pine. Rates of 1 to 3 lb active ingredient/A were applied in the fall after new growth was hardened off. In general, it was found that the risk of injuring trees with Roundup Pro is greater than with the old formulation of Roundup. However, in all cases in which Roundup Pro caused more injury than Roundup, the Roundup Pro was applied at 3 lb active ingredient/A. This rate is double the rate recommended for this use. In calibrated, directed spray applications at 1.5 lb active ingredient/A or less, Roundup Pro should be safe for use around the species tested after their growth has fully hardened in the fall.
Jamie R. Stieg, S. Alan Walters, Jason P. Bond, and Mohammad Babadoost
Management strategies for Phytophthora blight (caused by Phytophthora capsici) in bell pepper production are limited and there is no single method that will consistently provide adequate control. Twelve bell pepper cultivars (including four marketed as resistant/tolerant to P. capsici) were transplanted into a P. capsici-infested field and were managed with or without fungicide applications. The fungicide applications consisted of: i) Mefenoxam (Ridomil Gold EC, 1.2 L/ha) at transplant; and ii) a spray application of Dimethomorph (Acrobat, 0.45 kg/ha) + Copper (Tenn-Cop, 3.6 L/ha) alternated with Manganese ethylenebisdithiocarbamate (Maneb, 2.8 kg/ha) + Copper (Tenn-Cop; 3.6 L/ha) at 10- to 14-day intervals. Regardless of cultivar, the standard fungicide program reduced the incidence of Phytophthora blight and resulted in greater yields and farm-gate revenues when compared to the no fungicide program. Across all cultivars, total farm-gate revenues per hectare were $6,773 and $3,674 for the standard fungicide program and the no fungicide program, respectively. For P. capsici-tolerant cultivars, farm-gate revenues improved with the use of the standard fungicide program by $1,316, $4,427, and $5,447 per hectare for `Aristotle X3R', `Revolution', and `Alliance', respectively, compared to no fungicide applications. Furthermore, farm-gate revenue for P. capsici-resistant `Paladin' was improved by $3,240 per hectare when a standard fungicide program was used. Results indicate that although plant resistance is an important component of a P. capsici bell pepper management program, the use of recommended fungicides could improve disease control and increase farm-gate revenues.
Brent Rowell, Sue Nokes, Annete Meyer, Ric Bessin, and William Nesmith
Farmers' field trials conducted in western Kentucky counties in 1995 and 1996 showed that dramatic reductions in insecticide usage are possible using scouting and action thresholds. Five-acre plots were scouted and treated according to action thresholds while adjacent 5-acre plots were treated weekly with insecticides. Seven out of 10 insecticide sprays were eliminated, saving $65/acre for the 1995 season. There were no differences in yield, insect damage, or fruit quality between the scouted plots and the plots that were treated weekly. Assuming similar low pest populations in all 885 acres of the company's contracted fields, savings could have amounted to nearly $31,000 for 1995 after deducting scouting costs. There were no yield or quality differences from three test plots treated according to regularly scheduled applications and three plots treated according to action thresholds for insect pests and according to Tomcast predictions for fungal disease control in 1996. We have demonstrated the value of using Tomcast as an aid in making fungicide spray scheduling decisions for processing tomatoes in Kentucky. Although we were able to greatly simplify the Tomcast-CR10 datalogger interface program in 1996, there were still difficulties in getting information from the university-based computer to the company making spray applications. The company will be able to access the datalogger and obtain the information directly in 1997. The further analyses of “Skybit” satellite data collected in 1996 should also tell us whether this type of information might be used instead of a remote datalogger thus simplifying the process even further. We plan to build on the quick adoption of the Tomcast system and to make it sustainable by transferring “ownership” to the growers and processing company in 1997.
Kent E. Chushman and Theodore W. Tibbitts
The role of tehylene in the development of constant-light injury of potato (Solanum tuberosum L.) and tomato (Lycopersicon esculentum Mill.) was investigated. In one study, silver thiosulfate (STS) was applied to the foliage of four potato cultivars growing under constant light. Leaf area and shoot dry mass of `Kennebec' and `Superior', cultivars normally injured by constant light, were greater (P<0.05) than those of control plantsgiven foliar applications of distilled water. Examination of STS-treated `Kennebec' leaflets revealed significantly less injury (necrotic spotting and reduced starch content) than the water-treated controls. `Norland' and `Denali', cultivars tolerant of constant light, exhibited no differences in growth between treatments. In a second study, injury (necrotic spotting and reduced starch content) was induced in leaflets of `Denali' when exposed to spray applications of 0.5 mmol·L-1 ethephon or air containing 0.5 to 0.8 μL·L-1 ethylene. In a third study, three genotypes of `Ailsa Craig' tomato were grown under constant light. Leaves of the normal `Ailsa Craig' exhibited epinasty, reduced chlorophyll concentration, and reduced starch content. Leaves of a mutant `Ailsa Craig', containing the Never ripe mutation, did not exhibit epinasty but exhibited the same amount of reduced chlorophyll concentration and starch content as normal plants. Leaves of a transgenic `Ailsa Craig', containing an antisense gene of 1-aminocyclopropane 1-carboxylate (ACC) oxidase, were epinastic, but chlorophyll concentration and starch content were greater than in leaves of normal and mutant plants. These results suggest that transgenic plants were more tolerant of constant light than the other genotypes. Evidence from these studies indicates that ethylene, combined with constant light, has an important role in the development of constant-light injury.
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.
Jeffrey G. Williamson, Gerard Krewer, Brian E. Maust, and E. Paul Miller
Experiments were conducted in north Florida and south Georgia to determine the effects of H2CN2 sprays on vegetative and reproductive growth of blueberry. In Florida, mature, field-grown `Misty' southern highbush (Vaccinium corymbosum L. hybrid) blueberry plants were sprayed to drip with 0, 10.2, or 20.4 g·L-1 of H2CN2 [hereafter referred to as 0%, 1.0%, and 2.0% (v/v) H2CN2] on 20 Dec. 1996 and 7 Jan. 1997. During the following winter, mature `Misty' southern highbush and `Climax' rabbiteye (V. ashei Reade) plants were sprayed to drip with 0, 7.6, or 15.3 g·L-1 of H2CN2 [hereafter referred to as 0%, 0.75%, and 1.5% (v/v) H2CN2] on 17 Dec. 1997 and 6 Jan. 1998. For all experiments, plants were dormant and leafless, with slightly swollen flower buds, at the time of spray applications. Generally, H2CN2 sprays increased the extent and earliness of vegetative budbreak and canopy establishment and advanced flowering slightly. The number of vegetative budbreaks usually increased linearly with increasing spray concentrations. In Florida, H2CN2 [0.75% to 1.0% (v/v)] sprays increased mean fruit fresh weight and yield, and shortened the fruit development period (FDP) compared to controls. However, H2CN2 sprays ranging in concentration from 1.5% to 2.0% (v/v) resulted in significant flower bud injury and reduced total fruit yield compared to controls. In south Georgia, 27 of 37 field trials conducted between 1991 and 1998 on several rabbiteye and southern highbush cultivars indicated that leaf development was significantly enhanced by H2CN2. H2CN2 shows potential for increasing early fruit maturity, fruit size, and yield of southern highbush and rabbiteye blueberry cultivars with poor leaf development characteristics in low-chill production regions. Chemical name used: hydrogen cyanamide (H2CN2).
Stephen C. Myers, Amy T. Savelle, D. Stuart Tustin, and Ross E. Byers
Partial thinning of peach (Prunus persica L. Batsch) during bloom to 50% of the necessary level by hand, and followed by adjustment hand thinning at 42 days after full bloom (DAFB) was compared to a similar degree of thinning accomplished entirely at 42 DAFB by hand. Partial flower thinning altered the distribution of fruit by diameter, increasing the percentage of large diameter (≥62.0 mm) fruit harvested compared to unthinned trees or trees thinned entirely at 42 DAFB. Although shoot number per limb was not altered by thinning time, the distribution of shoots by length was affected, increasing the percentage of long shoots (≥20.0 cm). Compared to unthinned trees and trees thinned at 42 DAFB, partial flower thinning increased the subsequent development of flower buds per shoot and the number of flower buds per node. Number of flower buds on the proximal five nodes of shoots 15.0-30.0 cm in length was increased, although not on shoots 5.0-7.0 cm in length. Additional trials established that airblast spray application of AMADS was effective in achieving a similar level of thinning as that accomplished by partial flower thinning by hand in previous experiments. The degree of flower removal exhibited a linear response to chemical concentration. Fruit diameter on chemically flower-thinned trees was greater at adjustment thinning time, when compared to trees thinned by hand at 42 DAFB only. Distribution of fruit at harvest indicated a larger percentage of fruit >65.0 mm in trees which received partial flower thinning in comparison to trees thinned at 42 DAFB only. As a result, overall crop value was increased, based on the commercial processing peach price structure at the time of harvest. Chemical name used: 1-aminomethanamide dihydrogen tetraoxosulfate (AMADS)