Effects of Row Pattern, Seeding Rate, and Inoculation Date on Fungicide Efficacy and Development of Peanut Stem Rot

Abstract

Two field studies were conducted in 2000, 2001, and 2002 to determine the effects of row pattern (91.4-cm single or 20.3-cm twin) and seeding rate (single: 12.5, 17.4, or 22.6 seed m-1or twin: 6.2, 8.9, or 11.5 seed m-1) on peanut stem rot (Sclerotium rolfsii) development. The first study was conducted in a naturally infested field and relative efficacy of azoxystrobin (Abound 2.08 F, applied at a rate of 0.3 kg a.i. ha-1 at 60 and 90 days after planting [DAP]) also was evaluated. In this study, stem rot incidence was significantly greater (P < 0.05) in single rows planted at high seeding rates than in twin rows planted at any of the seeding rates. Row pattern did not affect azoxystrobin efficacy, and disease incidence was nearly half as much in twin rows treated with fungicide than incidence in single rows treated with fungicide. In the second field study, individual peanut plants in fumigated plots were inoculated once with S. rolfsii at 50, 70, or 90 DAP. Stem rot incidence at harvest was significantly greater on plants inoculated 50 DAP than plants inoculated 70 or 90 DAP. The incidence of spread to adjacent rows was higher in plots where plants were inoculated at 50 than at 90 DAP. Plants inoculated 90 DAP had less disease at harvest, but often developed more severe symptoms within the first week after inoculation compared with plants inoculated 50 or 70 DAP. Symptoms were more severe in single than in twin rows, and at the higher seeding rates. Data from these studies suggest that the physical spacing between plants is a critical factor in stem rot development both on individual plants and in plant populations.

Row Pattern and Seeding Rate Effects on Agronomic, Disease, and Economic Factors in Large-Seeded Runner Peanut

“…This includes net revenue increases as high as 21% by using twin rows instead of single rows (Table 6). Our results agree with other research findings where yield and/ or a reduction in disease incidence were improved by utilizing the twin row pattern (Baldwin et al, 2001;Brown et al, 2003;Culbreath et al, 2008;Lanier et al, 2004;Nuti et al, 2008;Sconyers et al, 2007;Sorensen et al, 2004;Tillman et al, 2006;Wehtje et al, 1984).…”

“…In this study, higher seeding rates resulted in reduced TSWV incidence in 2008, which would be the expected trend and agrees with previous research (Branch et al, 2003;Wehtje et al,1994). However, several other experiments did not observe a decreased risk to TSWV at higher seeding rates (Black et al, 2001;Sconyers et al, 2007), which is what was observed in our 2009 data. Tillman et al (2006) likewise reported no differences in yield or TSWV at seeding densities equivalent to those in this test, but did observe greater TSWV incidence at a greatly reduced seeding rate (13 seed/m of row).…”

“…Although, as with yield, there was a row pattern 3 seeding rate interaction at P#0.10 (data not shown), in which there were no differences in southern stem rot incidence in twin rows, but there was nearly half as much southern stem rot in single rows at the reduced seeding rate (2.8%) than at the UGA Extension recommended rate (5.4%). Reports of seeding rate's effect on southern stem rot are mixed, with no differences reported at reduced levels of irrigation (Black et al, 2001), nor with fungicide applications of azoxystrobin (Sconyers et al, 2007). However, a greater incidence of southern stem rot has been reported at higher seeding rates when heavily irrigated (Black et al, 2001) and when not treated with azoxystrobin (Sconyers et al, 2007), and also when averaged over several planter-types (Wehtje et al, 1994).…”

“…Reports of seeding rate's effect on southern stem rot are mixed, with no differences reported at reduced levels of irrigation (Black et al, 2001), nor with fungicide applications of azoxystrobin (Sconyers et al, 2007). However, a greater incidence of southern stem rot has been reported at higher seeding rates when heavily irrigated (Black et al, 2001) and when not treated with azoxystrobin (Sconyers et al, 2007), and also when averaged over several planter-types (Wehtje et al, 1994). Yet, the reverse relationship is often the case between plant stand and TSWV.…”

“…Studies have reported a decreased incidence of southern stem rot in twin rows compared to single rows (Minton and Csinos, 1986;Sconyers et al, 2007). Likewise, TSWV occurs less frequently in twin than in single rows (Brown et al, 2003;Culbreath et al, 2008;Tillman et al, 2006).…”