Field studies were performed on established carpetgrass (Axonopus affinis Chase) in 1994 and 1995 to evaluate plant growth regulators (PGRs) and application rates. Trinexapac-ethyl (0.48 kg·ha-1) improved turf quality and reduced cumulative vegetative growth (CVG) of unmowed and mowed plots by 38% and 46%, respectively, in 1995, and suppressed seedhead height in unmowed turf by >31% 6 weeks after treatment (WAT) both years. Mefluidide (0.14 and 0.28 kg·ha-1) had little effect on carpetgrass. Sulfometuron resulted in unacceptable phytotoxicity (>20%) 2 WAT in 1994 and 18% phytotoxicity in 1995. In 1995, sulfometuron reduced mowed carpetgrass CVG 21%, seedhead number 47%, seedhead height 36%, clipping yield 24%, and reduced the number of mowings required. It also improved unmowed carpetgrass quality at 6 WAT. Sethoxydim (0.11 kg·ha-1) suppressed seedhead formation by 60% and seedhead height by 20%, and caused moderate phytotoxicity (13%) in 1995. Sethoxydim (0.22 kg·ha-1) was unacceptably phytotoxic (38%) in 1994, but only slightly phytotoxic (7%) in 1995, reduced clipping yields (>24%), and increased quality of mowed carpetgrass both years. Fluazasulfuron (0.027 and 0.054 kg·ha-1) phytotoxicity ratings were unacceptable at 2 WAT in 1994, but not in 1995. Fluazasulfuron (0.054 kg·ha-1) reduced seedhead height by 23% to 26% in both years. Early seedhead formation was suppressed >70% when applied 2 WAT in 1994, and 43% when applied 6 WAT in 1995. The effects of the chemicals varied with mowing treatment and evaluation year. Chemical names used: 4-(cyclopropyl-x-hydroxy-methylene)-3,5 dioxo-cyclohexane-carboxylic acid ethyl ester (trinexapac-ethyl); N-2,4-dimethyl-5-[[(trifluoro-methyl)sulfonyl]amino]phenyl]acetamide] (mefluidide); [methyl 2-[[[[(4,6-dimethyl-2-pyrimidinyl) amino]carbonyl] amino] sulfonyl]benzoate)] (sulfometuron); (2-[1-(ethoxyimino)butyl-5-[(2-ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one) (sethoxydim); 1-(4,6-dimethoxypyrimidin-2yl)-3-[(3-trifluoromethyl-pyridin 2-yl) sulphonyl] urea (fluazasulfuron).
combination of damaged floral tissue and reduced photosynthesis due to leaf injury. In some experiments, ATS caused unacceptable leaf phytotoxicity ( Byers, 1997 ; Embree and Foster, 1999 ), which resulted in reduced fruit growth ( Wertheim, 2000
on Promalin ® , with no differences between MaxCel ® sprayed–trees and control trees. Phytotoxicity was very low with all the treatments except trees sprayed with Tiberon™ SC which had higher amounts of phytotoxicity. On those trees, high
al. 1975 ). One study found that pomegranate grown in the sandy soil of Florida showed unacceptable phytotoxicity (e.g., leaf burning, leaf drop, and tree death) at the labeled rate of diuron ( Castle et al. 2011 ). Another study suggests that diuron can
. 93 512 518 Holb, I.J. Schnabel, G. 2005 Effect of fungicide treatments and sanitation practices on brown rot blossom blight incidence, phytotoxicity, and yield for organic sour cherry production Plant Dis. 89
, halosulfuron, has provided reduced phytotoxicity on pepper when compared with rimsulfuron ( Stall 1999 ). The objective of this research was to determine if POST applications of several ALS-inhibiting herbicides would provide selective broadleaf weed control in
Abstract
The effect of daminozide as a plant growth retardant to protect potato seedlings from metribuzin injury was investigated. Plants of 6 potato cultivars were sprayed 42 days after planting with daminozide at 0, 2500, 5000 ppm concentrations. Four days after daminozide treatment, metribuzin at 0.56 kg/ha was applied. Within 3 days after metribuzin treatment, differences between potato cultivars in metribuzin tolerance was observed. Seven days after metribuzin application 25.2% to 42% of the control plants had more than 20% necrosis, and of this percentage, 0% to 13.9% plants were dead. Only 2.3% to 10.7% of the plants exhibited more than 20% metribuzin injury when pretreated with 2500 ppm daminozide. Potato plants treated with 5000 ppm daminozide were not damaged. The soluble solids of stem sap increased with daminozide rate. Protection from metribuzin injury in potato was associated with the increase in soluble solids in daminozide treated plants. Chemical name used: butanedioic acid mono (2, 2-dimethylhydrazide) (daminozide).
Hot water immersion of citrus fruit is a potential postharvest quarantine treatment for insect disinfestation. Little is known about fruit injury in the temp. ranges/exposure times required to control surface insects. We immersed lemons in water at 25, 50, 52.5 or 55C for 5, 7.5 or 10 min. Fruits were held overnight at 20, 25 or 30C before hot water immersion. Fruits were stored at 10C for 4 wk after treatment. We compared (1) fresh-picked late-season (July-Aug.) coastal “silver” maturity lemons with (2) fresh-picked ripe but green-colored early/mid-season (Oct.) desert lemons and (3) similar desert lemons commercially degreened 7 days with ethylene to attain desirable yellow color prior to heat treatment. Heat injury symptoms were small-large light-dark brown necrotic lesions or discoloration which developed on peel surface within 2-3 wk after treatment. Order of sensitivity to heat was: most sensitive = coastal silver (≥ 90% of fruit injured at 55C/10 min) > degreened desert > green (≥ 34% of fruit injured at 55C/10 min) desert lemons. Up to 50C/5 min could be used on coastal and 52.5C/5 min on desert lemons without appreciable injury. There were no differences between fruit cured overnight at 20, 25 or 30C before heat treatments.
This study evaluated the influence of insecticides on gas exchange, chlorophyll content, vegetative and floral development, and plant quality of gerbera (Gerbera jamesonii Bolus `Festival Salmon'). Insecticides from five chemical classes were applied weekly at 1× or 4× their respective recommended concentration. The insecticides used were abamectin (Avid), acephate (Orthene), bifenthrin (Talstar), clarified hydrophobic extract of neem oil (Triact), and spinosad (Conserve). Photosynthesis and stomatal conductance were reduced in plants treated with neem oil. Plants treated with neem oil flowered later—and at 4× the recommended label concentration had reduced growth, based on lower vegetative dry mass (DM) and total aboveground DM, reduced leaf area, thicker leaves (lower specific leaf area), higher chlorophyll content (basal leaves), and reduced flower production. Plants treated with acephate at 4× the recommended label concentration were of the lowest quality due to extensive phytotoxicity (leaf chlorosis). Plants treated with 1× or 4× abamectin or spinosad were of the highest quality due to no phytotoxicity and no thrips damage (thrips naturally migrated into the greenhouse). The control plants and plants treated with 1× bifenthrin had reduced quality because of thrips feeding damage; however gas exchange was not negatively affected.
This article reports on the physiological effects and horticultural benefits of chemical blossom thinners on 9-year-old and 12-year-old `Bing'/`Gisela®5′ sweet cherry trees in 2004 and 2005, respectively. Chemical thinning agents were applied at 20% and 80% full bloom (FB) by air-blast sprayer and were comprised of: 2% ammonium thiosulphate (ATS), 4% vegetable oil emulsion (VOE), 2% fish oil + 2.5% lime sulfur (FOLS), 1% tergitol, and an untreated control. Leaf gas exchange, leaf SPAD meter readings, chlorophyll fluorescence parameters, fruit yield, and fruit quality were evaluated. FOLS, tergitol, VOE, and ATS suppressed leaf net CO2 exchange rate (NCER) by 33%, 30%, 28%, and 18%, respectively, over a variable length recovery period directly after 80% FB treatment. Leaf NCER recovered fully from every thinning treatment. Reductions in leaf NCER were unrelated to gS. VOE reduced estimated leaf chlorophyll content the greatest, suppressing overall levels by 11% for 23 days after treatment. All blossom thinners reduced constant fluorescence (Fo). No thinning agent reduced fruit set or yield in 2004. ATS, FOLS, and tergitol reduced fruit set in 2005. VOE was ineffective as a thinner yet exhibited significant leaf phytotoxicity. Among thinners, there was no relationship between inhibition of leaf NCER and thinning efficacy.