Calendar and AU-Pnuts Advisory Programs Compared for Leaf Spot Diseases and Rust Control on Peanut in Southwest Alabama

Abstract

Peanut production acreage has increased substantially in southwest Alabama in the past several years. Since prevailing weather conditions in this newer production area are conducive to peanut diseases, primarily due to frequent rainfall during summer months, a 2-week calendar fungicide treatment schedule is considered essential to controlling leaf spot diseases and rust in order to optimize yields. In 2003, 2004, and 2005, extended calendar application intervals and the AU-Pnuts leaf spot advisory were compared with the recommended 2-week calendar schedule for peanut disease control on partially disease-resistant peanut cultivars (DP-1 in 2003 and Florida C99R in 2004 and 2005). Fungicide programs included recommended rates of azoxystrobin, chlorothalonil, and tebuconazole. Numbers of fungicide applications for the 2-, 3-, and 4-week calendar schedule treatments were 7, 5, and 4, respectively in each year. Fungicide applications made according to AU-Pnuts are based on rain events and resulted in 5 sprays in 2003 and 7 sprays in 2004 and 2005. Fungicide application schedule had a significant impact on leaf spots, rust, southern stem rot and yield in at least two of the three study years. Results indicate that recommendations for the 2-week fungicide application schedule should be maintained in this area. Fungicide program also had a consistent effect on measured variables, with the azoxystrobin program providing better disease control and higher yields. Accepted for publication 16 August 2006. Published 10 November 2006.

Managing early leaf spot and stem rot with reduced fungicide inputs on disease-resistant peanut cultivars

“…When applied on 2-wk intervals, azoxystrobin and tebuconazole programs have often been shown to be equal in terms of peanut disease and yield management (Hagan et al, 2004;Jaks and Grichar, 2004;Phipps and Partridge, 2007;Shew, 2004). As was seen in the current study, reducing the number of applications of tebuconazole in a calendar or advisory schedule below the recommended four did not have a negative impact on leaf spot or stem rot control (Bowen et al, 1997;Brenneman and Culbreath, 1994;Gricher et al, 2005;Hagan et al, 2006;Jaks and Gricher, 2004;Phipps and Partridge, 2007). Previously, Bowen et al (1997) reported that between three and four applications of tebuconazole were best for disease control and maximum yield of Florunner peanut.…”

“…this study builds on our previously published report (Bowen et al, 2006) in which reduced application fungicide programs with azoxystrobin were compared for disease control and yield. Fewer fungicide applications were applied when the AU-Pnuts advisory was implemented for this study, compared to a 2-wk application schedule, and this situation did not occur for our previous study done in southwest Alabama (Hagan et al, 2006). In addition, AU-Pnuts fungicide programs were often as effective for controlling early leaf spot and stem rot, while maintaining peanut yield as were the 2wk application schedules.…”

“…These results are similar to those previously reported by Bowen et al (2006) on the disease resistant cultivars C-99R and DP-1 where lengthening application intervals with azoxystrobin from 2 to 4 wk led to a decline in early leaf spot control, but yield declined in only one of three years. Hagan et al (2006) reported that yields of DP-1 and C-99R declined in two of three years when application intervals with azoxystrobin, tebuconazole, and chlorothalonil programs were extended from 2 to 4 wk. The latter study was done in southwest Alabama, a wetter and more disease conductive environment than the traditional peanut production region in southeast Alabama.…”

“…In south Texas, azoxystrobin, pyraclostrobin, and tebuconazole applied according to AU-Pnuts advisory, gave similar disease control and yield, compared to a 2-wk calendar program with chlorothalonil while reducing application numbers from seven to three (Grichar et al, 2005). In contrast, application numbers for the 2 wk and AU-Pnuts advisory programs were similar in two of three years in Southwest Alabama where almost daily rainfall occurred throughout much of the summer (Hagan et al, 2006).…”

“…The medium-maturing cultivar Georgia-03L (Branch, 2004) also has better disease resistance than the most widely planted cultivar, Georgia Green (Branch and Culbreath, 2008;Hagan et al, 2005;Woodward et al, 2008). When used in combination with a disease resistant cultivar, the fungicide azoxystrobin, which has excellent activity against leaf spot diseases and stem rot (Bowen et al, 2006;Hagan et al, 2006;Monfort et al, 2004) should allow the extension of application intervals beyond 2 wk without yield loss. In this study, we evaluated reduced applications of fungicide programs with azoxystrobin, chlorothalonil, and tebuconazole for the control of early leaf spot and stem rot and yields of the late maturing, disease-resistant cultivars DP-1 and C-99R.…”