Maximizing Economic Returns and Minimizing Stem Rot Incidence with Optimum Plant Stands of Peanut in Nicaragua

Abstract

Peanut growers in Nicaragua use high seeding rates, often greatly in excess of the 19.7 seeds/m recommended for growers in Georgia. Significant yield loss to peanut stem rot (caused by Sclerotium rolfsii) often occurs because of rapid disease spread in high density plant stands. It was hypothesized that lower seeding rates would be beneficial, and field experiments were conducted from 2005 to 2006 in Nicaragua to determine the optimum plant stands for stem rot management, peanut yield, and maximum economic returns. The cultivar Georgia Green was planted in twin rows at seven locations with final stands of 4 to 30 plants/m. Paired plots were either treated or not treated with flutolanil to control stem rot. Stem rot incidence consistently increased with higher peanut plant populations in fields with significant levels (.5%) of stem rot. In fields with more than 5% stem rot incidence, peanut yield and gross income adjusted for seed cost were maximized at within row populations of 12 to 13 and 11 plants/ m, respectively, when treated with flutolanil to reduce stem rot. When flutolanil was not applied, yield and gross income adjusted for seed cost were maximized at 10 to 11 and 8 to 10 plants/m, respectively. In locations with low stem rot incidence (,5%), maximum yield and gross income adjusted for seed cost were attained at within row populations of 13 and 12 plants/m, respectively. Nicaraguan growers may maximize their economic return by utilizing seeding rates to obtain final stand counts of 8 to 11 plants/m in fields with severe stem rot and 12 plants/m with low disease pressure.

Implications of fungicide application timing and post-spray irrigation on disease control and peanut yield

“…Although stem rot often occurs in rainfed peanut (Watkins, 1961), irrigation can exacerbate the problem (Davis et al, 1996). High soil moisture promotes infection and fungal mycelial spread between and within plants, especially in dense stands resulting from use of high seeding rates (Punja, 1985;Sconyers et al, 2005;Augusto et al, 2010). Infection of S. rolfsii is limited to basal stems, roots, pegs and pods, and colonization of the tissues coincides with beginning peg and beginning pod [R2 and R3 as defined by Boote (1982)] when peanut branches spread rapidly across the soil (Augusto et al, 2010a).…”

Plant Population and Replant Method Effects on Peanut Seeded in Single Rows

“…Similarly, Sconyers et al (2007) reported increased stem rot in plots seeded at 22.6 seeds/m when compared to those seeded at 12.5 and 17.4 seeds/m, respectively. Augusto et al (2010) reported consistent increases in stem rot at increased plant populations in areas with significant levels of the pathogen.…”

“…In this study, the high-risk model of the Peanut Disease Risk Index (Kemerait et al, 2011) was used at all siteyears resulting in a robust fungicide program for preventative maintenance of incidence and spread of disease, and overall stem rot pressure was low. Augusto et al (2010) reported that a greater number of plants/m of row are allowable without increasing stem rot incidence in areas of low pressure. While they described low incidence as 3% and below, average incidence of 4% in our study was only slightly above that level.…”

“…The University of Georgia's recommendation for peanut seeding rate in single-row peanuts is 19.7 seeds/m of row in an effort to obtain a final stand of 13.1 plants/m (Beasley et al, 1997). While 13.1 plants/m is the standard by which recommendations have been made, research has shown that in some cases, yield potential can be maintained at reduced plant stands (Augusto et al, 2010;Bell et al, 1987;Tewolde et al, 2002).…”

Fungicides and Application Timing for Control of Early Leafspot, Southern Blight, andSclerotiniaBlight of Peanut

“…Southern blight often is an issue due to moist conditions brought on by irrigation or rainfall [33,34]. High soil moisture promotes infection and fungal mycelial spread between and within plants, especially in dense stands resulting from the use of high seeding rates such as used in these studies (approximately 16 seed/m) [35][36][37]. Southern blight infection is limited to basal stems, roots, pegs, and pods, and colonization of the tissues coincides with beginning peg and pod formation (R2 and R3) as defined by Boote [38] when peanut branches spread rapidly across the soil [37].…”