Proceedings of the Sixty-first Annual Meeting of the Northeastern ...
Proceedings of the Sixty-first Annual Meeting of the Northeastern ... Proceedings of the Sixty-first Annual Meeting of the Northeastern ...
104 USE OF TRICLOPYR TO REDUCE ANTICHROMATIC EFFECTS OF MESOTRIONE IN TURFGRASS. J.B. Willis and S.D. Askew, Virginia Tech, Blacksburg. ABSTRACT Chromatic is defined as all colors other than white, black, and pure gray. When p- hydroxyphenylpyruvate dioxygenase inhibitors (HPPD) are applied to susceptible plants, leaves turn white. This response can be described as antichromatic. Mesotrione is an HPPD inhibitor that is currently being evaluated for use in turfgrass. Many turfgrass managers have indicated that their clientele will be unpleased with discoloration caused by mesotrione. Previous research at Virginia Tech evaluated all combinations of mesotrione, triclopyr, and fenoxaprop-P for common bermudagrass control. An interesting result was that plots treated with combinations of mesotrione and triclopyr had higher turf color than plots treated with mesotrione alone. Therefore, we speculate that triclopyr is an effective tank-mix partner for reducing antichromatic effects of mesotrione and improving efficacy towards perennial broadleaf weeds. Our objective is to evaluate mesotrione plus triclopyr for effects on turfgrass and weed color and control. Studies were conducted at two low-maintenance lawn locations and used a 2 by 4 factorial treatment arrangement. The first factor was single or sequential treatment and the second factor was the following herbicide treatment combinations: mesotrione at 0.125 lb ai/A, triclopyr at 1 lb ai/A, mesotrione + triclopyr, and an industry standard for broadleaf weeds, SpeedZone ® at 4 pt/A. Fenoxaprop-P at 0.12 lb ai/A applied twice and a nontreated check were included as comparison treatments. Sequential applications were made at 3-wk intervals. Turf color was visually estimated (9 = ideal green; 1 = no green) based on an assessment of both desirable turfgrass and weeds. Tank-mixing mesotrione and triclopyr improves turf color compared to mesotrione alone. Turf color was reduced by mesotrione alone mostly due to whitened nimblewill (NW) and white clover, the predominant weed species accounting for 40-60% of initial ground cover. Results from previous research with mesotrione indicate that single applications do not effectively control NW, and adding triclopyr in the current trial did not improve NW control with single applications. However, triclopyr does not decrease NW control by mesotrione although it greatly increase turf color by eliminating antichromatic effects of mesotrione on NW. NW control 60 DAT was equivalent between sequential applications of mesotrione alone and mesotrione plus triclopyr and averaged 65% at one location and 78% at another location while no other treatment controlled NW. Sequential applications of mesotrione and single applications of triclopyr effectively control ground ivy. Tank mixing mesotrione and triclopyr with one application improved ground ivy control to 97% compared to 0 and 70% control by single applications of mesotrione and triclopyr, respectively with similar effects on broadleaf plantain. PowerZone ® controlled broadleaf plantain and not ground ivy. Mesotrione controlled white clover only when mixed with triclopyr. The combination of mesotrione and triclopyr both reduces the antichromatic response of susceptible species and adds control of perennial broadleaf weeds that mesotrione alone does not control. Ongoing research is evaluating mesotrione plus triclopyr compared to each product alone for injury to Kentucky bluegrass, perennial ryegrass, bermudagrass, tall fescue, and fine fescue. 86
105 METHODS TO ASSESS ENVIRONMENTAL INFLUENCE ON TURFGRASS RESPONSE TO MESOTRIONE. S.D. Askew, M.J. Goddard and J.B. Willis, Virginia Tech, Blacksburg. Mesotrione is expected to be available for turfgrass markets Spring 2008. Of several turfgrass species known to tolerate mesotrione treatment, perennial ryegrass (PRG)(Lolium perenne) and fine fescue (Festuca spp.) are among the most sensitive. The visual manifestation of turfgrass injury from mesotrione is striking and ranges from a dull yellow to bright white. It is hard to predict when turfgrass will be discolored by mesotrione. In several field trials since 2001, we have observed turfgrass responses to mesotrione 4 SC at 0.14 to 0.28 kg ai/ha range from no effect to completely white foliage. Studies were conducted in 2006 at three field locations and in growth chambers in Blacksburg, VA to evaluate the influence of various environmental conditions on PRG and hard fescue (Festuca longifolia) response to mesotrione. In growth chamber studies, mesotrione was applied at 0, 0.14, 0.21, and 0.28 kg ai/ha to PRG maintained at daytime and nighttime temperatures of 13 and 7, 18 and 13, 24 and 18, and 30 and 24 C, respectively. PRG was placed in 15 cm x 15 cm pots and maintained at 2.5 cm in height. Chlorophyll b and a + b levels decreased by 750 µg g -1 fresh weight and 2970 µg g -1 fresh weight, respectively, for each 100g increase in herbicide rate. Carotenoid levels were strongly temperature dependent and followed a quadratic response with peak carotenoid production (820 µg g -1 fresh weight) occurring near 25 C, the plants growth optimum. In field trials, weather stations (Spectrum Technologies) were installed at each site to monitor soil moisture, soil temperature, air temperature, dew period, solar radiation, and photosynthetically active radiation every 30 minutes. Mesotrione was applied at 0.14 kg ai/ha each week between March 8, 2006 and September 4, 2006. A sample of leaf tissue was collected just prior to treatments, 5 days after treatment (DAT) and 10 DAT. At each evaluation timing, leaf tissue was assayed for cuticle wax weight, carotenoids, and chlorophyll a and b. Plots were also evaluated for color both visually and with digital image analysis. Principle component analysis (PCA) techniques and regressions were used to determine correlations between measured environmental conditions and observed treatment responses. The PCA analysis indicates some correlation between carotenoids and several environmental conditions. However, correlation between visual injury responses due to mesotrione and environmental conditions will likely be complicated. As with other carotenoid synthesis inhibitors, the greatest amount of white tissue occurs during maximum plant growth, as white tissue is typically evident on new leaves. Several factors, however, can influence plant growth including a combination of abiotic factors or even biotic factors such as disease. Thus, turfgrass injury response will be difficult to predict based on environmental conditions before and after treatment. Turfgrass growth rate will likely be the best predictor of injury responses, with increase growth resulting in increased chances for white foliage. Preliminary studies also indicate that conditions that promote foliar absorption of mesotrione, such as high humidity, will also contribute to turfgrass injury. Our future work will evaluate absorption as a contributing factor. 87
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104<br />
USE OF TRICLOPYR TO REDUCE ANTICHROMATIC EFFECTS OF MESOTRIONE IN<br />
TURFGRASS. J.B. Willis and S.D. Askew, Virginia Tech, Blacksburg.<br />
ABSTRACT<br />
Chromatic is defined as all colors o<strong>the</strong>r than white, black, and pure gray. When p-<br />
hydroxyphenylpyruvate dioxygenase inhibitors (HPPD) are applied to susceptible plants,<br />
leaves turn white. This response can be described as antichromatic. Mesotrione is an<br />
HPPD inhibitor that is currently being evaluated for use in turfgrass. Many turfgrass<br />
managers have indicated that <strong>the</strong>ir clientele will be unpleased with discoloration caused<br />
by mesotrione. Previous research at Virginia Tech evaluated all combinations <strong>of</strong><br />
mesotrione, triclopyr, and fenoxaprop-P for common bermudagrass control. An<br />
interesting result was that plots treated with combinations <strong>of</strong> mesotrione and triclopyr had<br />
higher turf color than plots treated with mesotrione alone. Therefore, we speculate that<br />
triclopyr is an effective tank-mix partner for reducing antichromatic effects <strong>of</strong> mesotrione<br />
and improving efficacy towards perennial broadleaf weeds. Our objective is to evaluate<br />
mesotrione plus triclopyr for effects on turfgrass and weed color and control.<br />
Studies were conducted at two low-maintenance lawn locations and used a 2 by 4<br />
factorial treatment arrangement. The <strong>first</strong> factor was single or sequential treatment and<br />
<strong>the</strong> second factor was <strong>the</strong> following herbicide treatment combinations: mesotrione at<br />
0.125 lb ai/A, triclopyr at 1 lb ai/A, mesotrione + triclopyr, and an industry standard for<br />
broadleaf weeds, SpeedZone ® at 4 pt/A. Fenoxaprop-P at 0.12 lb ai/A applied twice and<br />
a nontreated check were included as comparison treatments. Sequential applications<br />
were made at 3-wk intervals. Turf color was visually estimated (9 = ideal green; 1 = no<br />
green) based on an assessment <strong>of</strong> both desirable turfgrass and weeds.<br />
Tank-mixing mesotrione and triclopyr improves turf color compared to mesotrione<br />
alone. Turf color was reduced by mesotrione alone mostly due to whitened nimblewill<br />
(NW) and white clover, <strong>the</strong> predominant weed species accounting for 40-60% <strong>of</strong> initial<br />
ground cover. Results from previous research with mesotrione indicate that single<br />
applications do not effectively control NW, and adding triclopyr in <strong>the</strong> current trial did not<br />
improve NW control with single applications. However, triclopyr does not decrease NW<br />
control by mesotrione although it greatly increase turf color by eliminating antichromatic<br />
effects <strong>of</strong> mesotrione on NW. NW control 60 DAT was equivalent between sequential<br />
applications <strong>of</strong> mesotrione alone and mesotrione plus triclopyr and averaged 65% at one<br />
location and 78% at ano<strong>the</strong>r location while no o<strong>the</strong>r treatment controlled NW. Sequential<br />
applications <strong>of</strong> mesotrione and single applications <strong>of</strong> triclopyr effectively control ground<br />
ivy. Tank mixing mesotrione and triclopyr with one application improved ground ivy<br />
control to 97% compared to 0 and 70% control by single applications <strong>of</strong> mesotrione and<br />
triclopyr, respectively with similar effects on broadleaf plantain. PowerZone ® controlled<br />
broadleaf plantain and not ground ivy. Mesotrione controlled white clover only when<br />
mixed with triclopyr. The combination <strong>of</strong> mesotrione and triclopyr both reduces <strong>the</strong><br />
antichromatic response <strong>of</strong> susceptible species and adds control <strong>of</strong> perennial broadleaf<br />
weeds that mesotrione alone does not control. Ongoing research is evaluating<br />
mesotrione plus triclopyr compared to each product alone for injury to Kentucky<br />
bluegrass, perennial ryegrass, bermudagrass, tall fescue, and fine fescue.<br />
86