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Maria Victoria Huitrón, Manuel Diaz, Fernando Diánez, Francisco Camacho, and Antonio Valverde

acid (GA 3 ) in grape ( Retamales et al., 1995 ); CPPU in kiwi ( Antognozzi et al., 1996 ; Lewis et al., 1996 ); naphthalene acetic acid (NAA) and phenothiol in loquat ( Amoros et al., 2004 ); and CPPU, 2,4-dichlorophenoxyacetic acid (2,4-D), and

Open access

M. Lenny Wells, Eric P. Prostko, and O. Wendell Carter

genetically modified crops, including cotton, field corn, soybean, and canola with resistance to dicamba and 2,4-D herbicides has been developed to address the problem of glyphosate-resistant weeds ( Behrens et al., 2007 ; Wright et al., 2010 ). In the few

Open access

Donnie K. Miller, Thomas M. Batts, Josh T. Copes, and David C. Blouin

herbicides and using plant genetic modification to combat such populations. Two new technologies have been commercialized that allow application of 2,4-D choline (in combination with glyphosate) or diglycolamine (DGA)/N,N-Bis(3-aminopropyl) methylamine (BAPMA

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Ockert P.J. Stander, Karen I. Theron, and Paul J.R. Cronjé

Bower 1997 ; Rabe et al., 1990 ). Control strategies have focused on the use of plant growth regulators and nutrients as foliar treatments. Foliar application of 2,4-D has been shown to reduce fruit splitting in ‘Nova’ mandarin and various sweet orange

Open access

Larissa Larocca de Souza and Marcelo L. Moretti

sucker control are 2,4-D and glufosinate, a systemic and a contact herbicide, respectively. Carrier volumes greater than 94 L·ha −1 have been recommended for best performance with 2,4-D. According to Creech et al. (2015) , droplet size did not influence

Open access

Brian Dintelmann, David Trinklein, and Kevin Bradley

combat herbicide-resistant weeds, agrochemical companies have developed soybean and cotton that are resistant to 2,4-dichlorophenoxyacetic acid (2,4-D) and dicamba ( Behrens et al., 2007 ; Wright et al., 2010 ). Recent deregulation of dicamba and 2,4-D

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John N. Sacalis

It has previously been demonstrated that exceedingly high concentrations of 2,4-D, when taken up by cut carnations, inhibit petal senescence, while application of low concentrations of this synthetic auxin promote petal senescence. The mode of action of such high concentrations of 2,4-D has not been elucidated.

In previous work, it was observed that significant amounts of volatiles always emanated from those flowers treated with high 2,4-D, and which displayed inhibition of ethylene synthesis as well as petal senescence. In the present work, the headspace of treated flowers was therefore tested by gas chromatography after enclosure for a short period of time. Two of the major constituents of the volatiles produced by the treated flowers were found to be ethanol and acetaldehyde.

Since ethanol has formerly been shown to delay senescence in carnation flowers, and since 2,4-D has been shown to induce alcohol dehydrogenase, it is suggested that the mode of action of 2,4-D in this case is by means of the ethanol produced as a result of the 2,4-D treatment.

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Harlene Hatterman-Valenti and Paul Mayland

Greenhouse experiments were conducted to compare visible injury from sublethal rates of 2,4-D, dicamba, and a premixed product of 2,4-D + mecoprop + dicamba for eight annual flowers and to describe herbicide injury symptoms for these annual species. Herbicides were applied at rates 0.05×, 0.1×, and 0.2× of their highest labeled rate for turfgrass to simulate spray drift conditions. Visible injury varied between species, herbicide rate, and time after herbicide application. Alyssum (Lobularia maritima Desv.) showed the greatest initial injury and ageratum (Ageratum houstonianum Mill.) showed the greatest injury at 4 weeks after treatment. Symptom severity increased as herbicide rate increased, with the greatest injury from the premixed product, followed by 2,4-D, and then dicamba. The eight species varied in their degree of visible injury and flower production to dicamba, 2,4-D, and the premixed product. Reduced flowering was most obvious for prolific flowering species such as alyssum. Impatiens (Impatiens wallerana L.), salvia (Salvia splendens Sello), and snapdragon (Antirrhinum majus L.) produced more flowers in response to sublethal dicamba rates compared to the untreated plant. All rates of 2,4-D generally reduced flowering compared to untreated plants, except the lowest rate of 2,4-D for geranium (Pelargonium xhortorum Bailey) and snapdragon. Dahlia (Dahlia hortensis Cav.) sprayed with dicamba at the highest rate produced three times as many stems as plants untreated or those sprayed with 2,4-D. Overall order of species susceptibility to sublethal rates of dicamba, 2,4-D, or the premixed product from most susceptible to least susceptible was ageratum > alyssum > marigold (Tagetes erecta L.) > dahlia > geranium = salvia = snapdragon = impatiens. Differences in overall susceptibility to the plant growth regulator herbicides evaluated should provide useful information to horticulturalists designing annual flower beds and borders and lawn care applicators.

Open access

Lavesta C. Hand, Kayla M. Eason, Taylor M. Randell, Timothy L. Grey, John S. Richburg, Timothy W. Coolong, and A. Stanley Culpepper

holes of the plastic mulch from previous crops or areas of natural degradation of the plastic. Mixtures of 2,4-D with glyphosate or paraquat could benefit growers if applied before planting cole crops and leafy greens because of its ability to control

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Ann M. Chanon and R. Daniel Lineberger

The genus Betula contains many important forest and ornamental species and a method of rapid clonal propagation of superior genotypes is needed. Thidiazuron (TDZ) is a potent synthetic plant growth regulator with cytokinin-like activity. TDZ was used to differentiate shoots after long term exposure to dichlorophenoxyacetic acid (2.4-D) as part of a larger study on clonal fidelity. Birch calli were cultured on Woody Plant Medium supplemented with 10-5 M 2,4-D for up to 30 weeks. The calli were transferred to media containing TDZ at concentrations of 10-6 to 10-9M. Most of the tissue which had not been exposed to 2.4-D differentiated shoots five weeks after being exposed to 10-6M TDZ. Increasing the of time exposure to 2.4-D or decreasing the concentration of TDZ delayed differentiation. Calli exposed to 2.4-D for more than 18 weeks rarely differentiated shoots regardless of the concentration of TDZ used.