Guanfacine and Clonidine Reduce Defoliation and Phytotoxicity Associated with Abscission Agents

Guanfacine and clonidine were combined with ethephon or metsulfuron-methyl in the spray tank and applied as foliar sprays to Citrus sinensis L. Osb. `Valencia', Citrus madurensis Loureiro (calamondin), and Prunus persica `Elberta' to determine their effects on leaf loss, fruit detachment force (FDF), immature fruit loss, and twig dieback. In `Valencia' orange, `Elberta' peach and calamondin, guanfacine and clonidine effectively reduced ethephon-induced defoliation in all three tree species, whereas only guanfacine was effective with metsulfuron-methyl applications in `Valencia'. The ability of ethephon to reduce FDF in `Valencia' was only minimally impaired by guanfacine but not impaired by clonidine. Both guanfacine and clonidine diminished the capacity of metsulfuron-methyl to reduce FDF. Guanfacine reduced immature fruit loss of `Valencia' caused by metsulfuron-methyl and reduced twig-dieback. Leaf loss was reduced whether guanfacine or clonidine were applied with ethephon, or 24 hours or 17 days before ethephon application. Guanfacine and clonidine reduced leaf loss induced by continuous exposure of potted calamondin trees to ethylene, and leaf loss was similar with guanfacine and 1-methylcyclopropene (1-MCP) treatments. In separate experiments, guanfacine and clonidine were unable to block ethylene perception in Arabidopsis seedlings and petunia flowers but promoted rooting in coleus and tomato vegetative cuttings, suggesting that these compounds have auxin-like activity. The results demonstrate the potential to enhance selectivity of abscission agents with guanfacine and clonidine. Chemical names used: 2-[(2,6-dichlorophenyl)amino]-2-imidazoline, clonidine; 5-chloro-3-methyl-4-nitro-pyrazole, CMN-P; [(2,6-dichlorophenyl)acetyl]guanidine, guanfacine; [(2-chloroethyl)phosphonic acid, ethephon; indole-3-butyric acid, IBA; 1-methylcyclopropene, 1-MCP.

Download Full-text

Fruit Abscission and Leaf Drop in Citrus Cultivars Treated with Metsulfuron-methyl

HortTechnology ◽

10.21273/horttech.9.3.412 ◽

1999 ◽

Vol 9 (3) ◽

pp. 412-416 ◽

Cited By ~ 1

Author(s):

Walter J. Kender ◽

Ulrich Hartmond ◽

Jacqueline K. Burns

Keyword(s):

Active Ingredient ◽

Citrus Sinensis ◽

Citrus Fruit ◽

Fruit Abscission ◽

Metsulfuron Methyl ◽

Fruit Drop ◽

Valencia Orange ◽

Leaf Drop

Fruit of 11 citrus cultivars were evaluated for their response to the experimental abscission material metsulfuron-methyl at 2 mg·L-1 (ppm) active ingredient as an aid to mechanical or hand harvest. Cultivars evaluated included `Ambersweet', `Glen Navel', `Hamlin', and `Valencia' oranges [Citrus sinensis (L.) Osb.], `Robinson' tangerine (Clementine × Orlando, C. reticulata Blanco), `Sunburst' tangerine [`Robinson' × `Osceola', C. reticulata × (C. paradisi Macf. × C. reticulata)], `Murcott' and `Temple' tangor (C. reticulata × C. sinensis), `Orlando' tangelo (C. reticulata × C. paradisi), `Ray Ruby', and `Marsh' grapefruit (C. paradisi). Six of the 11 cultivars were effectively loosened by sprays of metsulfuron-methyl (`Hamlin', `Valencia', `Orlando', `Murcott', `Temple', and `Ray Ruby'). Addition of an adjuvant (Kinetic, 0.125%) was necessary for abscission activity in fruit and leaves. Trees sprayed with metsulfuron-methyl in combination with an adjuvant had higher percent cumulative fruit drop, higher internal ethylene, and lower fruit detachment forces (FDF) than trees sprayed with metsulfuron-methyl alone. `Sunburst' tangerine responded poorly to the abscission material in the presence or absence of Kinetic. Leaf loss was greatest in trees sprayed with metsulfuron-methyl and adjuvant, intermediate in trees sprayed with metsulfuron-methyl alone, and least in control trees. Twig dieback was observed in trees of `Valencia' orange and `Marsh' grapefruit sprayed with metsulfuron-methyl. The peel of some cultivars had irregular coloration and developed pitted areas after harvest. Although metsulfuron-methyl is an effective abscission agent for mature citrus fruit, further work is needed to more accurately define conditions for its safe and dependable use.

Download Full-text

Seasonal Variation in the Response of `Valencia' Orange to Two Abscission Compounds

HortScience ◽

10.21273/hortsci.35.2.226 ◽

2000 ◽

Vol 35 (2) ◽

pp. 226-229 ◽

Cited By ~ 7

Author(s):

U. Hartmond ◽

J.D. Whitney ◽

J.K. Burns ◽

W.J. Kender

Keyword(s):

Seasonal Variation ◽

Active Ingredient ◽

Citrus Sinensis ◽

Field Studies ◽

Separate Experiment ◽

Fruit Removal ◽

Metsulfuron Methyl ◽

Valencia Orange ◽

Leaf Drop ◽

Before And After

Two field studies were conducted to evaluate the effect of metsulfuron-methyl and 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMN-pyrazole) on abscission of `Valencia' orange [Citrus sinensis (L.) Osbeck] during the 3-month harvest season. Solutions of metsulfuron-methyl at 0.5, 1, and 2 mg·L-1 active ingredient (a.i.) were applied at 10-day intervals beginning on 13 Feb. and ending 18 May 1998. Early in the harvest season, 1 or 2 mg·L-1 metsulfuron-methyl significantly reduced fruit detachment force (FDF) 14 days after application. Metsulfuron-methyl was less effective during a 4- to 6-week period following bloom (“less-responsive period”). After this period, metsulfuron-methyl regained the ability to loosen fruit. Applications of 2 mg·L-1 a.i. were more effective than 1 mg·L-1 in reducing FDF and causing leaf drop, but 0.5 mg·L-1 a.i. had little or no effect on FDF. Flowers and leaflets on developing shoots and young fruit completely abscised with 1 and 2 mg·L-1 a.i. Defoliation and twig dieback was extensive at all concentrations and spray dates, eliminating metsulfuron-methyl as a commercially viable abscission agent for citrus. In a separate experiment CMN-pyrazole at 50 and 100 mg·L-1 a.i. and metsulfuronmethyl at 0.5 mg·L-1 a.i. were applied to `Valencia' trees to determine fruit removal with a trunk shake and catch harvesting system. Application of both abscission materials before and after the “less-responsive period” resulted in a 10% to 12% increase in fruit removal when compared to control trees. Less than a 35% reduction in FDF was sufficient to significantly increase fruit removal. Only 100 mg·L-1 a.i. CMN-pyrazole significantly increased fruit removal when applied during the “less-responsive period.” Chemical names used: Methyl-2-(((((4-Methoxy-6-Methyl-1,3,5-Triazin-2-yl)-Amino)Carbonyl) Amino)Sulfonyl)Benzene (Metsulfuron-methyl); 5-Chloro-3-methyl-4-nitro-1-H-pyrazole (CMN-pyrazole).

Download Full-text

Late-season `Valencia' Orange Mechanical Harvesting with an Abscission Agent and Low-frequency Harvesting

HortScience ◽

10.21273/hortsci.41.3.660 ◽

2006 ◽

Vol 41 (3) ◽

pp. 660-663 ◽

Cited By ~ 8

Author(s):

Jacqueline K. Burns ◽

Fritz M. Roka ◽

Kuo-Tan Li ◽

Luis Pozo ◽

Richard S. Buker

Keyword(s):

Citrus Sinensis ◽

Low Frequency ◽

Mature Fruit ◽

Fruit Removal ◽

Immature Fruit ◽

Late Season ◽

Valencia Orange ◽

Significant Difference ◽

Orange Trees

An abscission agent (5-chloro-3-methyl-4-nitro-1H-pyrazole [CMNP]) at 300 mg·L–1 in a volume of 2810 L·ha–1 was applied to Valencia orange trees [Citrus sinensis (L.) Osb.] on 22 May 2004. At this time, immature and mature fruit were present on the tree simultaneously. Three days after application, fruit were mechanically harvested using a trunk-shake-and-catch system. The power to the shaker head was operated at full- or half-throttle (FT or HT, respectively), and the duration of trunk shaking was 2 seconds at FT or 4 seconds at FT and HT. Mature fruit removal percentage and number of immature fruit removed, and fruitlet weight and diameter were determined. Mature fruit removal percentage with 2 seconds at FT or 4 seconds at FT harvesting ±CMNP, or 4 seconds at HT + CMNP was not significantly different and ranged between 89% to 97%. Harvesting at 4 seconds HT without CMNP removed significantly less mature fruit than any treatment. CMNP did not affect immature fruit removal by the trunk shaker. Harvesting at 4 seconds at HT removed significantly less immature fruit than 2 seconds at FT or 4 seconds at FT. No significant difference in fruitlet weight or diameter was measured between any trunk shaker harvest operation and CMNP treatment. Trunk shaking frequency was estimated to be 4.8 and 8.0 Hz at HT and FT, respectively. Yield in 2005 was determined on the same trees used for harvest treatments in 2004. CMNP did not impact yield. No significant difference in yield was seen between the hand-picked control and 4 seconds at HT, whereas yield in the remaining treatments was lower. The results demonstrate that CMNP application combined with low frequency trunk shaker harvesting can achieve high percentage of mature fruit removal with no significant impact on return yield of the following crop.

Download Full-text

Geometric Modeling of the Valencia Orange (Citrus sinensis L.) by Applying Bézier Curves and an Image-Based CAD Approach

Agriculture ◽

10.3390/agriculture10080313 ◽

2020 ◽

Vol 10 (8) ◽

pp. 313

Author(s):

Hector A. Tinoco ◽

Daniel R. Barco ◽

Olga Ocampo ◽

Jaime Buitrago-Osorio

Keyword(s):

Computer Aided Design ◽

Citrus Sinensis ◽

Geometric Modeling ◽

Prediction Models ◽

Two Dimensions ◽

Radius Of Curvature ◽

Computer Design ◽

Bezier Curves ◽

Bézier Curves ◽

Valencia Orange

The computer-aided design of fruits are used for different purposes, e.g., to determine mechanical properties by applying engineering simulations, to design postharvest equipment, and to study the natural changes related to the topology. This paper developed a methodology to model Valencia orange (Citrus sinensis), applying Bézier curves and an image-based CAD approach; the orange geometry was designed for different ripening stages. In the modeling process, a 3D construction was carried out using third-order Bézier curves, adjusted to the images taken in orthogonal planes. Four control points defined each profile to compose the geometric pattern of the orange, with geometric errors lower than 3%. Two prediction models were proposed to relate the orthogonal dimensions with a factor size; this means that two dimensions out of three can be predicted. The results showed that the shape ratios kept constant in any ripening stage; however, the radius of curvature evidenced differences in the analyzed shape profiles. The methodological framework presented in the paper might be used to draw other types of citrus fruits. This contribution is a tool to model fruits in 3D, instead of using expensive technological equipment, since it is only necessary to apply computer design tools.

Download Full-text

Seasonal changes in endogenous ABA and IAA and the influence of applied ABA and auxin in relation to shoot growth and abscission in Valencia Orange (Citrus sinensis (L.) Osbeck)

Plant Growth Regulation ◽

10.1007/bf00024960 ◽

1991 ◽

Vol 10 (2) ◽

pp. 139-151 ◽

Cited By ~ 6

Author(s):

Julie A. Plummer ◽

Michael G. Mullins ◽

John H. Vine

Keyword(s):

Seasonal Changes ◽

Citrus Sinensis ◽

Shoot Growth ◽

Valencia Orange ◽

Endogenous Aba

Download Full-text

Turfgrass-Applied Metsulfuron-Methyl Induces Specific Symptomology on Non-Target Tree Species

cftm ◽

10.2134/cftm2019.01.0006 ◽

2019 ◽

Vol 5 (1) ◽

pp. 190006

Author(s):

Clebson G. Gonçalves ◽

J. Scott McElroy ◽

J.M. Peppers ◽

Suma Basak ◽

Glenn B. Fain ◽

...

Keyword(s):

Tree Species ◽

Metsulfuron Methyl

Download Full-text

Activity of ribulose-1,5-bisphosphate carboxylase in the leaf tissues of blight-affected ‘Valencia’ orange trees (Citrus sinensis (L.) Osbeck)

Environmental and Experimental Botany ◽

10.1016/0098-8472(87)90055-4 ◽

1987 ◽

Vol 27 (1) ◽

pp. 45-51 ◽

Cited By ~ 1

Author(s):

J.C.V. Vu ◽

M.G. Bausher ◽

G. Yelenosky

Keyword(s):

Citrus Sinensis ◽

Bisphosphate Carboxylase ◽

Valencia Orange ◽

Leaf Tissues ◽

Orange Trees

Download Full-text

Long-term effects of saline irrigation water on 'Valencia' orange trees: relationships between growth and yield, and salt levels in soil and leaves

Australian Journal of Agricultural Research ◽

10.1071/ar06199 ◽

2007 ◽

Vol 58 (4) ◽

pp. 349 ◽

Cited By ~ 26

Author(s):

L. D. Prior ◽

A. M. Grieve ◽

K. B. Bevington ◽

P. G. Slavich

Keyword(s):

Soil Salinity ◽

Irrigation Water ◽

Citrus Sinensis ◽

Irrigation Management ◽

Growth And Yield ◽

Balance Model ◽

Salt Treatment ◽

Saline Irrigation ◽

Valencia Orange ◽

Eastern Australia

This study documents changes in yield, growth, soil salinity (ECe) and leaf sodium (Na) and chlorine (Cl) concentrations in mature Valencia orange [Citrus sinensis (L.Osbeck)] trees on sweet orange (Citrus sinensis) rootstock in response to increased levels of Na and Cl in irrigation water. Four levels of salt, ranging from the river-water control (0.44 dS/m) to 2.50 dS/m, were applied over a 9-year period through an under-tree microsprinkler system to trees in the Sunraysia area of the Murray Valley in south-eastern Australia. A salt-balance model showed that evapotranspiration was reduced by salinity, whereas leaching fractions increased from an average 24% in the control to 51% in the most saline treatment. The high leaching fractions were achieved as a result of freely draining soils and good irrigation management, and allowed us to maintain low to moderate levels of soil salinity throughout the trial and minimised the effect of salt treatment on fruit yield. Soil salinity increased almost linearly in response to irrigation-water salinity during the first year, and fluctuated seasonally thereafter; however, very few readings exceeded 3 dS/m, even in the highest treatments. By contrast, leaf Na and Cl concentrations in the highest salt treatment continued to increase over the first 4 years. The relationship between yield and soil salinity was extremely weak, but yield did decrease as foliar concentrations of Na and Cl increased: in Year 9, leaf Na in the highest treatment relative to the control was associated with a predicted reduction of 17% in yield and 59% in annual trunk-diameter growth.

Download Full-text