Jack E. Bailey

Management of Sclerotinia Blight of Peanut with the Biological Control Agent Coniothyrium minitans

Sclerotinia blight, caused by Sclerotinia minor, is an important disease of peanut in North Carolina. The effectiveness of Coniothyrium minitans, a mycoparasite of sclerotia of Sclerotinia spp., was studied in a 5-year field experiment and in eight short-term experiments in northeastern North Carolina. The 5-year experiment was initiated in November 1999 to evaluate the effectiveness of repeated soil applications of C. minitans (commercial formulation, Contans WG) at 2 and 4 kg ha-1 in reducing Sclerotinia blight. In addition, individual commercial peanut fields were selected in 2001 and 2002 to evaluate a single application of C. minitans at 4 kg ha-1. No differences were found between the 2 and 4 kg ha-1 rates of C. minitans in reducing Sclerotinia blight. In 2002, there was less disease in plots receiving applications of C. minitans for either 1 or 3 years compared with the nontreated control; whereas, in 2003, C. minitans applications for 1, 2, or 3 years reduced disease and the number of sclerotia isolated from soil. A single application of C. minitans reduced sclerotia in only two of the eight short-term experiments. The integration of consecutive years of soil applications of C. minitans at 2 kg ha-1 with moderately resistant cultivars and fungicide applications may aid in the management of Sclerotinia blight in peanut.

Peanut response to cultivar selection, digging date, and tillage intensity

reduced tillage systems often do not exceed those of conventional tillage. Determining the cause of inconsisPeanut (Arachis hypogaea L.) in the United States is generally tent yield response to reduced tillage would be benefigrown in conventionally tilled systems. However, interest in reduced tillage peanut production has increased. Five experiments were concial in determining when reduced tillage systems could ducted in North Carolina to determine if cultivar selection and digging be successfully implemented in peanut production. date affected peanut yield and economic value when peanut was Cultivar selection can have a dramatic effect on crop seeded into conventionally tilled seedbeds compared with strip tillage response to production and pest management practices. into small-grain cover crop or stubble from the crop planted the preCulpepper et al. (1997) reported that peanut cultivars vious summer. In separate experiments, peanut yield and economic responded differently to the plant growth regulator provalue in these tillage systems were compared with peanut strip-tilled hexadione calcium (calcium salt of 3,5-dioxo-4-propiointo beds prepared the previous fall (stale seedbeds). Cultivar selection nylcyclohexanecarboxylic acid). Cultivars also respond and digging date did not affect pod yield or gross value when compardifferently to digging date (Jordan et al., 1998). Disease ing tillage systems. Pod yield in conventional and stale seedbed sysmanagement approaches can be affected by cultivar setems was similar in all five experiments where these systems were compared, and yields in these tillage systems exceeded those of strip lection (Bailey, 2002). Virginia market-type cultivars vary tillage into crop stubble in three of five experiments. Pod yield was considerably in pod size, maturity, and several other agrosimilar among all three tillage systems in the other two experiments. nomic factors (Swann, 2002). Although not well estabIn experiments where only conventional tillage and strip tillage syslished in the literature, pod loss can be severe if peanut tems were compared, pod yield was similar between the two tillage is dug under poor soil conditions (Beam et al., 2002). systems in four experiments, higher in conventional tillage compared It is suspected that pod loss may be greater in reduced with strip tillage in one experiment, and higher for strip tillage comtillage systems than conventional tillage systems bepared with conventional tillage in one experiment. In 16 of 17 comcause the plants may be more difficult to dig. Peanut parisons, pod yield of peanut planted in conventional tillage systems cultivars with larger pods may be more susceptible to equaled or exceeded that of peanut planted into stubble from the digging losses compared with smaller-seeded cultivars previous crop. because they have a greater surface area, which may cause increased exposure to detachment during the digging process. Practitioners indicate that pod loss from P in the United States is typically grown in smaller-seeded runner market types is less than that for conventionally tilled systems (Sholar et al., 1995). large-seeded virginia market types during the digging Peanut response to reduced tillage has been inconsiscomponent of the harvest process. However, these comtent. Research suggests that yields in reduced tillage sysparisons have not been documented in the literature. tems can be lower than (Brandenburg et al., 1998; Cox Determining if pod yield differs among tillage systems and Sholar, 1995; Grichar, 1998; Jordan et al., 2001; for cultivars with different pod sizes may help explain Sholar et al., 1993; Wright and Porter, 1995) or similar inconsistent peanut response to reduced tillage systems. to (Baldwin and Hook, 1998; Dowler et al., 1999; HartStale seedbed crop production has been successful zog et al., 1998; Williams et al., 1998) yields in convenfor a variety of row crops, including soybean [Glycine tional tillage systems. Higher yields in reduced tillage max (L.) Merr.] and cotton (Gossypium hirsutum L.) systems have been associated with lower incidence of (Shaw, 1996). Seedbeds are prepared the previous fall tomato spotted wilt virus (TSWV) (Baldwin and Hook, or during the spring several weeks or months before 1998; Johnson et al., 2001; Wright et al., 2000). In most seeding directly into previously established stale seedexperiments where this disease is not a factor, yields in bed without significant soil disturbance. This approach to peanut production may be a viable alternative to both D.L. Jordan, P.D. Johnson, and A.S. Culpepper, Dep. of Crop Sci., conventional tillage systems and strip tillage directly Box 7620, North Carolina State Univ., Raleigh, NC 27695-7620; J.S. into stubble from the previous crop. Barnes, Peanut Belt Res. Stn., North Carolina Dep. of Agric. and The objectives of this research were to determine if Consumer Serv., Box 220, Lewiston-Woodville, NC 27849; C.R. Bogle, Dep. of Soil Sci., North Carolina State Univ., Upper Coastal Plain peanut response to tillage was associated with cultivar Res. Stn., Box 7619, Raleigh, NC 27695 and North Carolina Dep. of selection and digging date and if peanut yield in stale Agric. and Consumer Serv., Rt. 2 Box 400, Rocky Mount, NC 27801; seedbeds differs from yield in conventional tillage or R.L. Brandenburg, Dep. of Entomol., Box 7613, North Carolina State strip tillage into crop stubble. Univ., Raleigh, NC 27695-7613; and J.E. Bailey, Dep. of Plant Pathol., Box 7616, North Carolina State Univ., Raleigh, NC 27695-7616. ReAbbreviations: CBR, Cylindrocladium black rot; %ELK, percentage ceived 11 Apr. 2002. *Corresponding author (david_jordan@ncsu.edu). of extra large kernels; %TSMK, percentage of total sound mature kernels; TSWV, tomato spotted wilt virus. Published in Agron. J. 95:380–385 (2003).

Compatibility of In-Furrow Application of Acephate, Inoculant, and Tebuconazole in Peanut (Arachis hypogaea L.)

Abstract Research was conducted in North Carolina to compare tobacco thrips (Frankliniella fusca Hinds) control, early season peanut emergence and growth, and pod yield with combinations of the insecticide acephate, inoculant containing Brady rhizobium, and the fungicide tebuconazole applied in the seed furrow during planting. Although interactions among treatment factors were significant, greater control of tobacco thrips damage was noted when acephate was applied and in some cases when tebucanozole was applied. Tebucanzole-treated peanut emerged more slowly than peanut not receiving tebucanazole. Delayed emergence of tebuconazole-treated peanut most likely resulted in emergence when fewer tobacco thrips were present in fields. Peanut pod yield was affected by acephate, inoculant, and tebuconazole independently. Applying acephate and inoulcant increased pod yield in two and three of five experiments, respectively. Pod yield was lower in one of five experiments when tebuconazole was applied. These data su...

Winter Occurance and Spring Migration of Frankliniella fusca (Hinds) (Thysanoptera: Tripidae) in North Carolina Peanut (Arachis hypogaea L.) Fields

Abstract Overwintering of Frankliniella fusca (Hinds), tobacco thrips, in North Carolina and their subsequent spring movement into peanut fields were evaluated using two winter sampling techniques and three spring sampling techniques at the Peanut Belt Res. Sta., Lewiston, NC. In the spring of 1992 and 1993, for 14 d following peanut planting, the aerial movement of tobacco thrips was monitored using cylindrical sticky traps, trap plants, and exclusion cages. Frankliniellafusca were trapped significantly more often at 0.2 m and 0.9 m than at 1.8 m and during the afternoons. Thrips catch was significantly influenced by prevailing wind direction. No thrips were caught on sticky traps on days when maximum temperatures did not exceed 18.7 C. Frankliniella fusca began to colonize emerging peanut plants as they cracked the soil surface on days when there were temperatures above 18.7 C and times when there was no precipitation. Aerial F. fusca movement was monitored with sticky traps for three consecutive winter...