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James P. Gilreath, Carlene A. Chase and Salvadore J. Locascio

Drift from pesticides can kill or damage nontarget organisms. In these studies, the effects of sublethal rates of the herbicide glyphosate applied prebloom, at bloom, and postbloom of the first flower cluster were evaluated in tomato (Lycopersicon esculentum Mill.). As rates increased from 1 to 100 g·ha-1, foliar injury and flower and fruit number per plant varied with the stage of development at the time of exposure and the time of evaluation after treatment. Plants treated with 60 and 100 g·ha-1 glyphosate prebloom and at bloom had developed moderate to severe foliar injury by 14 days after treatment, but phytotoxicity to plants treated postbloom was only mild to moderate. Blooms abscised from plants treated with 60 and 100 g·ha-1 glyphosate for several weeks after application and fruit set was reduced. Greatest yield losses occurred following treatment prebloom (just prior to bloom) and at bloom. Plants treated before emergence of flower buds, and more mature plants exposed when first cluster fruit were sizing, yielded better than did those treated just prior to bloom and at bloom. Chemical name used: N-(phosphonomethyl)glycine (glyphosate).

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James P. Gilreath, Carlene A. Chase and Salvadore J. Locascio

Cucumber (Cucumis sativus L.) growth and yield in response to application of sublethal rates of 2,4-D at several developmental stages were evaluated in field studies during two seasons. In Expt. 1, prebloom applications of 2,4-D amine reduced plant vigor and increased foliar epinasty as rates increased from 0 to 112 g·ha-1. Early and total fruit yields also declined linearly as 2,4-D rates increased; 112 g·ha-1 2,4-D reduced early yield by 25% and total yield by 20%. In Expt. 2, plant vigor declined with increasing rates of 2,4-D applied at all four stages of development from first true leaf to early fruit enlargement; however, response at stage 1 differed with time after application. Epinasty increased with 2,4-D rate when applied at all developmental stages; however the severity of the response varied with time after application for stages 1, 2, and 3, but not for stage 4. Averaged over all developmental stages, vine length, fresh weight, and yield decreased linearly as rates increased. Early and total yields with 112 g·ha-1 were 22% and 19% lower than those of nontreated plants, respectively. Growth inhibition and yield decline, pooled across 2,4-D rates, were greater when exposure occurred at the earlier stages of development. Chemical name used: (2,4-dichlorophenoxy)acetic acid (2,4-D).

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James P. Gilreath, Carlene A. Chase and Salvadore J. Locascio

Sublethal rates of 2,4-D and dicamba were applied to pepper to evaluate the possible effects of single or multiple exposures to drift from these herbicides. Dicamba induced more foliar injury than did 2,4-D and reduced vigor more as herbicide rates increased. Postbloom applications reduced vigor less than did earlier applications. Epinastic response was affected by stage of development at application and time after treatment. Postbloom applications did not affect yield, but dicamba and 2,4-D applied at earlier stages of development resulted in linear reduction of marketable and total yields as rates increased to 112 g·ha-1. Reductions in plant vigor with increased rates were greater and foliar epinasty was more pronounced with two sequential applications of 2,4-D or dicamba than with single applications. Marketable yields were unaffected by single prebloom applications but declined linearly with two applications. Cull and total yields were not affected by the number of applications. With prebloom and bloom applications of 2,4-D, flower abscission increased and fruit set decreased as rate increased. Chemical names used: 3,6-dichloro-2-methoxybenzoic acid (dicamba); 2,4-dichlorophenoxy)acetic acid (2,4-D).

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H. John Elgar, Nagin Lallu and Christopher B. Watkins

fruit harvesting and determining crop load factors, Sally Roughan for mineral analyses, and Melissa Miller and Marcus Davy for statistical analyses. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal

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Harlene Hatterman-Valenti, Greg Endres, Brian Jenks, Michael Ostlie, Theresa Reinhardt, Andrew Robinson, John Stenger and Richard Zollinger

-target injury to broadleaf and horticultural crops ( Johnson et al., 2012 ). Several studies have reported injury from simulated glyphosate drift on specialty crops such as onion [ Allium cepa ( Felix et al., 2012 )], potato ( Felix et al., 2011 ; Hatterman

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Michele Renee Warmund, Patrick Guinan and Gina Fernandez

, freezing, and tissue damage will actually occur within the plant. “Critical temperatures” for injury at a specific stage of such crops as grapes, blueberries, and strawberries have been published on various web sites ( Michigan State University Extension

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Katie J. Kammler, S. Alan Walters and Bryan G. Young

Weed control is a major issue in jack-o-lantern pumpkin production as a result of the limited number of registered herbicides ( Walters et al., 2008 ). Many of the herbicides currently registered for pumpkins have potential crop injury risks, high

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Charles L. Webber III, Merritt J. Taylor and James W. Shrefler

control is expected ( Webber et al., 2012a ). A potential solution to this would be to increase weed control efficacy on larger weeds and decrease crop injury by using multiple or sequential postdirected herbicide applications (herbicides postdirected

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Charles L. Webber III, Merritt J. Taylor and James W. Shrefler

reduced from 100 to 40 gal/acre in postdirected applications in spring transplanted onion ( Allium cepa ) and maintain good weed control with PA applied at 5, 10, and 15 lb/acre . Unfortunately, crop injury and significant reduction in onion yields were

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Martin M. Williams II, Loyd M. Wax, Jerald K. Pataky and Michael D. Meyer

metabolic inactivation compared with homozygous-tolerant hybrids, resulting in greater levels of injury and more variable responses under different conditions. Severity of crop injury is the result of a combination of genotypic and other factors affecting