PLANT PATHOLOGY SERIES TIMELY INFORMATION Agriculture & Natural Resources Quash Fungicide Now Available for Foliar and Soil Control on Peanut A. K. Hagan Professor and Extension Plant Pathologist Newly available for the peanut market, Quash 50WDG, which is a product of Valent Ag. Products is a broad spectrum triazole (Group 3) fungicide containing the new active ingredient metconazole. Like propiconazole and tebuconazole, metconazole works by inhibiting demethylation and other processes in sterol synthesis in target fungi. Like these fungicides, metconazole is quickly absorbed into the plant tissues and is move systemically upward through the plant. Early and late leaf spot fungi with reduced sensitivity to tebuconazole may also display tolerance to metconazole. In areas where reduced tebuconazole efficacy has been seen, Quash 50WDG should be tank mixed with 0.75 to 1.0 pints of Bravo Weather Stik or an equivalent rate of a generic chlorothalonil fungicide. Quash 50WDG is generally active at lower rates compared with most triazole fungicides. For the control of early and late leaf spot as well as rust, the suggested application rate ranges from 2.5 to 4.0 ounces/a for a four block application program. First of the four consecutive applications of Quash 50WDG should be scheduled approximately 60 days after planting. Repeat applications at no longer than 2-week intervals. Bracket the block of four sequential Quash 50WDG applications with two early and one late application of Bravo Weather Stik or an equivalent generic chlorothalonil fungicide. For optimal control of leaf spot diseases, add a recommended rate of a non-ionic surfactant to the fungicide tank mixture. While 2.5 ounce/a of Quash 50WDG will control leaf spot and rust, for consistent white mold (stem rot) control, increase the Quash 50WDG application rate to 4.0 ounce/a. The last Quash 50WDG application can be made up until 14 days prior to the expected digging date. The approximate cost for Quash 50WDG ranges from $9.50/A for the 2.5 ounce/a rate/application to $15/A for the 4 ounce/a rate/application. When the three Bravo Weather Stik applications needed to complete a 7-applicaton calendar fungicide program are added to the mix, total cost for a Quash 50WDG program should range from about $68/A for the 2.5 ounce/a to $90/A for the 4 ounce/a program. A $10/A savings would be realized by replacing the Bravo Weather Stik with generic chlorothalonil. Methods - Efficacy of Quash 50WDG for the control of foliar and soil diseases of peanut was evaluated at the Wiregrass and Gulf Coast Research and Extension Centers in 2005 and 2006 on the leaf spot and white mold-susceptible peanut cultivar Carver. While the study site at the Gulf Coast Research and Extension Center (GCREC) was cropped to peanut after two years of cotton, peanut were cropped behind one year of cotton at the Wiregrass Research and Extension Center (WGREC). Weed control and soil fertility recommendations were followed. The study site was irrigated as needed at WGREC but not the GCREC. Fungicide treatments were applied on with a tractor mounted sprayer. Early and late leaf spot (LS) were rated together before digging using the 1-10 Florida peanut leaf spot scoring system where 1 = no disease, 2 = very few leaf spots in canopy, 3 = few leaf spots in lower and upper canopy, 4 = some leaf spotting and < 10% defoliation, 5 = leaf spots noticeable and < 25% defoliation, 6 = leaf spots numerous and < 50% defoliation, 7 = leaf spots very numerous and < 75% defoliation, 8 = numerous leaf spots on few remaining leaves and <90% defoliation, 9 = very few remaining leaves covered with leaf spots and < 95% defoliation, and 10 = plants defoliated or dead. White mold hit counts (1 hit was equivalent to < 1 ft of consecutive diseased plants per row) were made immediately after digging. s are reported at 10% moisture. ALABAMA A&M AND AUBURN UNIVERSITIES, AND TUSKEGEE UNIVERSITY, COUNTY GOVERNING BODIES AND USDA COOPERATING The Alabama Cooperative Extension System offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, sex, age, veteran status, or disability.
Results - In the 2005 WGREC study, the season-long Bravo 720 6F standard, as well as the Abound 2SC and Moncut 70DF + Bravo 720 6F but not the Folicur 3.6F programs gave significantly better leaf spot control than all but one of the Quash 50WDG programs, which was as effective against leaf spot as the three former fungicide programs (Table 1). Without the non-ionic surfactant (NIS), application rate had no impact on leaf spot control with Quash 50WDG. A significant improvement in leaf spot control with the addition of the NIS was seen with the 4.0 but not the 3.42 or 2.56 ounce/a rates of Quash 50WDG. With the exception of Quash 50WDG at 4.0 ounces + NIS, this fungicide and Folicur 3.6F with and without NIS were less effective in controlling leaf spot diseases on peanut. Quash 50WDG at the 4.0 ounce/a rate + NIS proved as effective as the Moncut 70DF + Bravo 720 6F program in reducing white mold incidence. The latter fungicide programs gave better white mold control compared with three of the remaining nine fungicide programs. At the 4 ounce/a but not the lower rates, control of white mold with Quash 50WDG was improved with the addition of the NIS. Equally high yields were obtained with the Abound 2SC, Moncut 70DF + Bravo 720 6F, Bravo 720 6F standard, as well as the 2.56 and the 4 ounce/a Quash 50WDG + NIS programs. As reflected in significantly better leaf spot and white mold control, superior yield response was obtained with the 4 ounce/a rate of Quash 50WDG with the addition of the NIS but not with the two lower rates of this fungicide. s for both of the Folicur 3.6F programs were lower than the 4 ounce/a Quash 50WDG + NIS but not the other rates of Quash 50WDG. Table 1. Rates of Quash 50WDG compared with recommended fungicides for the control leaf spot diseases and white mold as well as yield response on Carver peanut, WGREC 2005. timing Leaf spot z White mold y Lb/A 1-7 4.9 b x 6.5 bc 3251 abcd Quash 50WDG 2.56 oz Quash 50WDG 2.56 oz + NIS 0.125% v/v Quash 50WDG 3.42 oz Quash 50WDG 3.42 oz + NIS 0.125% v/v Quash 50WDG 4.0 oz Quash 4.0 50WDG oz + NIS 0.125% v/v + NIS 0.125% v/v 6.7 a 8.8 abc 2686 bcd 6.2 a 8.2 abc 3283 abc 6.6 a 10.2 ab 2598 d 6.1 a 9.0 abc 2976 bcd 6.6 a 9.7 ab 2622 d 5.3 b 5.3 c 3888 a 6.5 a 8.8 abc 2815 bcd 6.5 a 10.7 a 2735 cd 4.9 b 8.0 abc 3465 ab Moncut 70DF 1.1 lb + 4.6 b 5.2 c 3436 ab y White mold severity is expressed as the number of hits per 60 ft of row. At the GCREC in 2005, late leaf spot and rust were the primary diseases noted on the Carver peanut. A significant improvement in late leaf spot control was noted at three of four rates of Quash 50WDG when the NIS was added (Table 2). In addition, the level of 2
late leaf spot control obtained at all rates of Quash 50WDG plus the NIS was similar to the season-long Bravo 720 6F standard as well as the Abound 2SC and Moncut 70DF + Bravo 720 6F programs. Poorest late leaf spot control was obtained with the recommended Folicur 3.6F program. When applied without the NIS, Quash 50WDG proved significantly less effective in controlling rust than the season-long Bravo 720 6F standard. In contrast, all rates of Quash 50WDG when tank mixed with the NIS controlled rust as effectively as the season-long Bravo 720 6F standard as well as the Abound 2SC and Moncut 70DF + Bravo 720 6F programs. Rust ratings for all rates of Quash 50WDG + NIS were similar. Overall, the level of rust control obtained with Quash 50WDG without the NIS, regardless of application rate, was poorer compared with the Bravo 720 6F standard. for all of the Quash 50WDG programs with and without the NIS were statistically similar and did not differ from the season-long Bravo 720 6F standard. The Quash 50WDG + NIS program also had higher yields compared with the Folicur 3.6F + NIS and Abound 2SC programs. Table 2. Rates of Quash 50WDG compared with recommended fungicides for the control late leaf spot and rust as well as yield response of Carver peanut, GCREC 2005. timing Leaf spot z Rust y Lb/A 1-7 3.6 e x 3.8 d 5666 ab Quash 50WDG 2.56 oz (0.08 lb ai/a) 4.3 bc 5.2 abc 5552 ab Quash 50WDG 2.56 fl oz + NIS 0.125% v/v Quash 50WDG 3.42 oz Quash 50WDG 3.42 oz + NIS 0.125% v/v Quash 50WDG 4.0 oz Quash 50WDG 5.0 oz Quash 50WDG 5.0 oz + NIS 0.125% v/v + NIS 0.125% v/v 3 3.8 de 4.0 cd 5689 ab 4.1 cd 5.3 ab 5559 ab 3.9 cde 4.5 abcd 5437 ab 4.3 bc 5.7 a 5437 ab 4.0 de 4.3 bcd 5873 a 4.7 ab 5.5 ab 5207 b 3.7 de 4.5 abcd 5651 ab 4.8 a 5.3 ab 5383 ab 4.6 ab 4.8 abcd 5156 b 3.7 de 4.8 abcd 5284 b Moncut 70DF 1.1 lb + 3.9 cde 4.5 abcd 5896 a y Rust was rated using the ICRISAT 1-9 rating scale (1 = no disease to 9 = plants severely affected, 80-100 percent leaves withering). For the 2006 WGREC study, the 3 and 4 ounce/a rates of Quash 50WDG were less effective in controlling leaf spot diseases compared with the season-long Bravo 720 standard as well as the recommended Headline 2.09EC, Abound 2SC, and Moncut 70DF + Bravo 720 programs (Table 3). Leaf spot ratings for both of the Quash 50WDG and Folicur 3.6F programs were similar. When compared with the Bravo 720 standard, no reduction in the incidence of white mold was noted with either rate of Quash 50WDG along with the Headline 2.09E and Abound 2SC programs. White mold incidence was lower with the Folicur 3.6F + NIS and the
Moncut 70DF + Bravo 720 programs compared with the low but not high rate of Quash 50WDG. With the exception of the Abound 2SC program, yield responses with both rates of Quash 50WDG were similar to the other fungicide programs. Table 3. response and disease control with Quash 50WDG and recommended fungicide programs compared at WGREC in 2006 on Carver peanut. timing Leaf spot z White mold y Lb/A 1-7 3.1 b x 6.5 a 4074 ab Quash 50WDG 3.0 oz + NIS 0.125% v/v Headline 2.09EC 9 fl oz + NIS 0.125% v/v 4.3 a 6.2 a 3888 b 4.2 a 4.7 ab 4195 ab 2.7 b 6.5 a 4114 ab 4.2 a 5.3 ab 4332 ab 4.0 a 3.3 b 4187 ab 3.0 b 4.3 ab 4542 a 2.9 b 3.5 b 4187 ab Moncut 70DF 1.1 lb + y White mold severity is expressed as the number of hits per 60 ft of row. At GCREC in 2006, both rates of Quash 50WDG did not control late leaf spot and rust as effectively as the season-long Bravo 720 6F standard as well as the recommended Headline 2.09EC, Abound 2SC, and Moncut 70DF 1.1 lb + Bravo 720 6F programs, which gave similar control of both diseases (Table 4). Late leaf spot and rust ratings for both rates of Quash 50WDG and Folicur 3.6F programs were similar. Addition of the NIS did not improve the effectiveness of Folicur 3.6F against late leaf spot and rust. Incidence of white mold for both rates of Quash 50WDG were similar to all other fungicide programs except for Moncut 70DF 1.1 lb + Bravo 720 6F, which gave better control. response with the Moncut 70DF 1.1 lb + Bravo 720 6F and Abound 2SC programs was higher compared with both rates of Quash 50WDG, the Bravo 70 6F standard, Folicur 3.6F alone, and Headline 2.09EC programs, all of which had similar yields. 4
Table 4. Rates of Quash 50WDG compared with recommended fungicides for the control late leaf spot, rust, and white mold as well as yield response of Carver peanut, GCREC 2006. timing Leaf spot z Rust y White mold x lb/a 1-7 2.9 c w 3.8 b 5.8 a 4802 b Quash 50WDG 3.0 oz + NIS 0.125% v/v Headline 2.09EC 9 fl oz + NIS 0.125% v/v 3.4 a 4.5 a 5.3 a 4886 b 3.5 a 4.8 a 4.3 a 4519 b 2.9 c 3.8 b 5.5 a 4772 b 3.3 ab 4.7 a 4.5 ab 4871 b 3.3 ab 4.3 ab 4.0 ab 5024 ab 2.9 c 3.8 b 4.3 ab 5506 a 3.1 bc 3.7 b 2.5 b 5536 a Moncut 70DF 1.1 lb + y Rust was rated using the ICRISAT 1-9 rating scale (1 = no disease to 9 = plants severely affected, 80-100 percent leaves withering). x White mold severity is expressed as the number of hits per 60 ft of row. w Means in each column that are followed by the same letter are not significantly different according to analysis of variance and least Summary When tank mixed with a non-ionic surfactant (NIS), Quash 50WDG at the 4 ounce/a rate proved in 2005 not only to be as effective in controlling leaf spot diseases and rust as the current industry standards such as Bravo 720 6F season-long and Abound 2SC but better than Folicur 3.6F when applied alone or when tank mixed with a NIS. Without the NIS (non-ionic surfactant), Quash 50WDG was unimpressive against leaf spot diseases and rust. So the addition of a NIS is critical to obtaining optimal leaf spot, rust, and white mold control with Quash 50WDG. In 2006, performance of this fungicide at both locations against leaf spot diseases and rust was equal to that of Folicur 3.6F and less effective controlling both diseases when compared with the Bravo 720 6F standard and Headline 2.09EC programs. Since the metconazole a.i. in Quash 50WDG and tebuconazole have the same mode of action, the possibility of cross tolerance in leaf spot fungi to both of these fungicides is a major concern, particularly in areas where tolerancerelated control failures with the latter fungicide have already occurred. Additional field trials will be needed to determine whether a chlorothalonil tank-mix partner will be required with Quash 50WDG in order to maintain effective leaf spot control on peanut, particularly in the traditional peanut production counties in the Wiregrass region of Alabama. While application rate appeared to have little impact on leaf spot and rust control with Quash 50WDG, results in 2005 suggest that the higher 4.0 ounce/a rate may be critical to controlling white mold on peanut. Also, yield response with better with the 4.0 ounce/a rate compared with lower rates of Quash 50WDG and several fungicide standard programs, particularly in 2005. So, results support the use of the Quash 50 WDG at the highest rate, even in situations where white mold pressure is relatively light. 5