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

). Adjuvants can be used to overcome an antagonism between herbicides ( Campbell and Penner, 1982 ). For example, the antagonism of sethoxydim and the sodium salt of bentazon was overcome by the addition of ammonium sulfate and changing the adjuvant from a crop

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Vladimir Orbović, Diann Achor, and James P. Syvertsen

. Despite significant antifungal and antibacterial effects of Cu on different crops ( Reil et al., 1974 ; Teviotdale et al., 1997 ), its use has been occasionally problematic because of phytotoxic effects often attributed to inappropriate adjuvants added to

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W. Carroll Johnson III and Jerry W. Davis

conditions could reduce efficacy of contact herbicides like clove oil. Therefore, studies were initiated in 2010 to determine if herbicide adjuvants improve clove oil efficacy without the need for higher sprayer output volume in organic Vidalia ® sweet onion

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Bruce W. Wood

Of 18 commonly used adjuvants evaluated on pecan [Carya illinoinensis (Wangenh) K. Koch], a few exhibited potential for substantially suppressing net photosynthesis (A) and the conductance of foliage to water vapor (g sw) when used within their recommended concentration range; however, most provided no evidence of adversely influencing A or g sw. Suppression of gas exchange by certain adjuvants persisted at least 14 days after a single application. The recently developed organosilicone-based surfactants generally exhibited the greatest potential for suppression. These data indicate that orchard managers should consider the potential adverse influence of certain adjuvants when developing orchard management strategies.

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Krishna N. Reddy and Megh Singh

A field study was conducted to evaluate the effectiveness of Kinetic and Sylgard 309 organosilicone adjuvants to increase the efficacy of glyphosate for control of Florida pusley (Richardia scabr a L.), southern crabgrass [Digitaria ciliari s (Retz.) Koel], hairy beggarticks (Bidens pilos a L.), camphorweed [Heterotheca subaxillaris (Lam.) Britt. and Rusby], bahiagrass (Paspalum notatu m Fluegge), bermudagrass [Cynodon dactylo n (L.) Pers.], and torpedograss (Panicum repen s L.). Glyphosate, either at 0.5 or 1.0 kg a.i./ha, was applied alone or in combination with Kinetic, Sylgard 309, or X-77 using a tractor-mounted boom sprayer that delivered 187 liters·ha-1 at 207 kPa pressure. Glyphosate applied at 0.5 kg·ha-1 controlled > 94% of Florida pusley, southern crabgrass, hairy beggarticks, and camphorweed. Glyphosate efficacy improved on Florida pusley and southern crabgrass when applied with the adjuvants. Glyphosate, regardless of adjuvant, completely controlled hairy beggarticks and camphorweed. Control of bahiagrass, bermudagrass, and torpedograss with adjuvants was better than without adjuvants. However, glyphosate with Kinetic or Sylgard 309 was more effective in suppressing regrowth of these perennial grasses than glyphosate with X-77. Chemical names used: isopropylamine salt fo N -(phosphonomethyl)glycine with an in-can surfactant (glyphosate); proprietary blend of polyalkyleneoxide-modified polydimethylsiloxane and nonionic organosilicone adjuvant (Kinetic); silicone adjuvant mixture of 2-(3.hydroxypropyl)-heptamethyltrisiloxane, ethyloxylated, acetate EO glycol, -allyl, -acetate (Sylgard 309); mixture of alkylarylpolyoxyethylene glycols, free fatty acids, and isopropanol nonionic adjuvant (X-77).

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Gary L. McDaniel, William E. Klingeman, Willard T. Witte, and Phillip C. Flanagan

One-half (18 g·ha-1 a.i.) and three-fourths (27 g·ha-1 a.i.) rates of halosulfuron (Manage®, MON 12051) were combined with adjuvants and evaluated for effectiveness in controlling purple nutsedge (Cyperus rotundus L.) and for phytotoxic responses exhibited by two kinds of container-grown ornamental plants. Adjuvants included X-77®, Scoil®, Sun-It II®, Action “99”®, and Agri-Dex®. By 8 weeks after treatment (WAT), halosulfuron combined with X-77®, Agri-Dex®, or Action “99”® at the lower halosulfuron rate provided <90% purple nutsedge suppression. In contrast, Sun-It II® provided 100% control when combined with the higher halosulfuron rate. Nutsedge control persisted into the following growing season and halosulfuron combined with either Scoil® or Sun-It II® provided >97% suppression of nutsedge tuber production. Growth of liriope [Liriope muscari (Decne.) Bailey `Big Blue'] was not inhibited by Scoil® or Sun-It II® adjuvants in combination with the low rate of halosulfuron. However, regardless of the rate of halosulfuron or adjuvant used, initial foliar chlorosis was observed in both daylily (Hemerocallis sp. L. `Stella d'Oro') and liriope. All liriope receiving halosulfuron with X-77®, Scoil®, or Sun-It II® adjuvants recovered normal foliage by 8 WAT. By contrast, at 8 WAT some daylily still maintained a degree of foliar discoloration. In addition to chlorosis, all treatments reduced flower number in daylilies. The number of flower scapes produced by liriope was not affected by halosulfuron when in combination with either Sun-It II® or Scoil®. The high rate of halosulfuron combined with X-77® or Action “99”® improved control of purple nutsedge. However, this rate inhibited growth of both species, daylily flower numbers, and scape numbers of liriope, regardless of adjuvant. Chemical names used: halosulfuron (Manage®, MON 12051, methyl 5-{[(4,6-dimethyl-2-pyrimidinyl) amino] carbonyl-aminosulfonyl}-3-chloro-1-methyl-1-H-pyrozole-4-carboxylate); proprietary blends of 100% methylated seed oil (Scoil® and Sun-It II®); proprietary blend of 99% polyalkyleneoxide modified heptamethyl trisiloxane and nonionic surfactants (Action “99”®); alkylarylpolyoxyethylene, alkylpolyoxyethelene, fatty acids, glycols, dimethylpolysiloxane, and isopropanol (X-77®); proprietary blend of 83% paraffin-based petroleum oil, with 17% polyoxyethylate polyol fatty acid ester and polyol fatty ester as nonionic surfactants (Agri-Dex®)

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Frederick S. Davies, Craig A. Campbell, and Matthew W. Fidelibus

It is desirable to mix gibberellic acid (GA3) with other commonly applied materials to reduce application cost. However, applying GA3 with some compounds can reduce its efficacy or cause phytotoxicity. We conducted experiments in 1997-98 and 1998-99 to determine if GA3 (ProGibb) can be tank-mixed with fosetyl-Al (Aliette), or avermectin (Agri-Mek) and oil, without reducing GA3 efficacy. In addition, we compared Silwet and Kinetic adjuvants for enhancement of GA3 efficacy. Five tank mixes were tested along with a nonsprayed control. These included 1) GA3; 2) GA3 and Silwet; 3) GA3 and Kinetic; 4) GA3 Silwet, and fosetyl-Al; and 5) GA3, Silwet, avermectin, and oil. All compounds were applied at recommended concentrations. In September 1997 or October 1998, about 2.5 gal (9.5 L) of each tank mix was applied with a hand sprayer to 14- or 15-year-old `Hamlin' orange (Citrus sinensis) trees on sour orange (Citrus aurantium) rootstock. Peel puncture resistance (PPR), color, and juice yield (% juice weight) were evaluated monthly between December 1997 and March 1998, and December 1998 and January 1999. In both years, fruit of treated trees usually had higher PPR and were less yellow in color than fruit from control trees. There were tank mix effects on juice yield in January of both seasons and February 1998. Gibberellic acid was most effective at enhancing juice yield when applied singly or with avermectin and oil. In both seasons there were dates when GA3 applied singly was superior at enhancing juice yield than a tank mix of GA3, Silwet and fosetyl-Al, indicating that GA3 was incompatible with fosetyl-Al. Neither Kinetic nor Silwet adjuvants consistently enhanced GA3 effects on peel quality or juice yield over GA3 alone.

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E.W. Stover, M.J. Fargione, R.A. Risio, and C.I. Mulvihill

In 1995, effects of adjuvants on fruit thinning with Accel [10:1 ratio of 6-benzyladenenine (BA):GA4&7] at 75 ppm BA were studied. Silwet L-77 was used at 0.027% (v/v). Regulaid and ultrafine spray oil were used at 0.125% (v/v). Treatments also included unthinned controls, NAA (naphthalene acetic acid) at 7.5 ppm plus 600 ppm carbaryl, and Accel plus 600 ppm carbaryl. `Empire' apple trees on M.9/MM.111 rootstock in Milton, N.Y., were used in the 6th leaf. Trees were blocked by number of blossom clusters/cm2 trunk cross sectional area. Applications were made at 1.5x concentration, using tree-row volume to calculate appropriate dilute volume. Each spray treatment was applied near the high temperature on each of three consecutive days around 10-mm king fruitlet diameter. Conditions were as follows: day 1–high temperature of 19°C with moderate drying time, and rain several hours after application; day 2–high temperature of 15.5°C and prolonged drying; and day-3–high temperature of 21.1°C and moderate drying. All treatments significantly thinned and enhanced fruit size compared to unthinned controls. Application conditions (treatment day) did not significantly affect response when compared within any spray treatment. However, in combined analyses, treatment with Accel or Accel with Regulaid resulted in significantly smaller fruit on day 1, when rain followed application, compared to these treatments on other days, or compared to Accel with other adjuvants on day 1. Accel with carbaryl resulted in largest fruit size and cropload reduction, but significantly reduced seed number/fruit. It is postulated that prolonged drying times occurring in cool conditions can compensate for reduced uptake rate at lower temperatures.

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F.S. Davies, M.W. Fidelibus, and C.A. Campbell

An experiment was conducted to determine if gibberellic acid (GA; ProGibb, Abbott Labs) can be mixed with Aliette or Agri-Mek and oil to reduce application costs, without reducing GA efficacy, and if Silwet and Kinetic adjuvants enhance GA efficacy. Five tank mixes were tested along with a nonsprayed control. The tank mixes included: 1) GA, 2) GA + Silwet, 3) GA + Kinetic, 4) GA + Silwet + Aliette, and 5) GA + Silwet + Agri-Mek + oil. All compounds were applied at recommended concentrations. In September, ≈24 L of each tank mix was applied with a hand sprayer to mature `Hamlin' orange trees [Citrus sinensis (L.) Osb.] on sour orange (Citrus aurantium L.) rootstock. Peel puncture resistance (PPR), peel color, and juice yield (percent juice weight) were evaluated monthly between Dec. 1997 and Mar. 1998. On most sampling dates the fruit of treated trees had higher PPR and were less yellow in color than fruit from control trees. However, in Jan., fruit treated with GA + Silwet and GA + Kinetic had greater PPR than other treatments. In Feb., fruit treated with GA + Silwet + Agri-Mek + oil had the lowest PPR. The effect of the different tank mixes on juice yield was usually similar to the effect of the tank mixes on PPR and peel color. On 8 Jan. 1998, fruit from trees treated with GA alone yielded significantly more juice than fruit from control trees. On 24 Feb. 1998, fruit from trees treated with GA alone yielded more juice than fruit from the other treatments. Thus, GA efficacy is generally not reduced by these tank mixes, nor improved by adjuvants.

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Vladimir Orbovic, John L. Jifon, and James P. Syvertsen

Urea solutions, with or without non-ionic (X-77) and organosilicone (L-77) surfactant, were applied to Citrus leaves and isolated cuticles to examine adjuvant effects on urea uptake and leaf net gas exchange. When compared to X-77, L-77 exhibited superior features as a surfactant, resulting in smaller contact angles of droplets deposited on teflon slide. Both L-77 and X-77 had a strong effect on penetration rate of urea within first 20 min of experiment. Effect of L-77 on urea penetration rate decreased quickly within next 20 min, whereas the effect of X-77 was sustained over a 24-h period following application. When compared to solution of urea alone, addition of X-77 to urea resulted in significant increase of the total amount of urea that penetrated the cuticles. The effect of L-77 was smaller, although the total amount of urea that penetrated the cuticles within a 4-day period was similar for both surfactants. Solutions of either urea alone, urea+L-77 and urea+X-77, or L-77 alone, induced a negative effect on net CO2 assimilation (ACO2) for 4 to 24 h after they were sprayed onto leaves. X-77, when applied alone, had no effect on ACO2. Scanning electron microscopy revealed that 1 h after application, leaf surfaces treated with X-77 appeared to be heavily coated, as opposed to those treated with L-77, which appeared similar to untreated control leaves.