Radical changes in crop production have occurred in the southeastern USA in recent years. Peanut (Arachis hypogaea L.) and cotton (Gossypium hirsutum L.) are now planted in direct rotation, and conservation tillage is commonly used for both crops. Comprehensive data is lacking on crop and pest management recommendations in those systems, so a long‐term study was conducted in Tifton, GA on the effects of tillage systems on crop and pest management in a peanut–cotton rotation. Systems evaluated were conventional, reduced, and minimum tillage. Plots in conventional tillage systems were harrowed, deep‐turned, and planted each year. In reduced tillage systems, plots were harrowed in the fall and planted to rye (Secale cereale L.), and crops were planted into killed rye. In minimum tillage systems, plots were neither tilled nor planted to rye and remained nontilled during the winter, and crops were planted directly into the previous crop stubble. Weed control was based on species present and tillage system. Peanut was either treated with flutolanil [3′‐isopropoxy‐2‐(trifluoromethyl) benzanilide] for soil‐borne disease control or not treated (control). Yields were sustained for 5 yr with no difference in peanut or cotton yields among tillage systems. Flutolanil controlled soil‐borne diseases and increased peanut yields, working equally well in all three tillage systems. Weed densities and species composition changed, causing more intensive and costly weed control in reduced and minimum tillage systems than in conventional tillage systems. Spotted wilt (tomato spotted wilt tospovirus) incidence was 42% lower in reduced and minimum tillage systems than in conventional tillage systems and is now part of the recommended strategy to manage the disease.

Carya illinoinensis (pecan) belongs to the Juglandaceae (walnut family) and is a major economic nut crop in the southern USA. Although evidence suggests that some species in the Juglandaceae are ectomycorrhizal, investigations on their ectomycorrhizal fungal symbionts are quite limited. Here we assessed the ectomycorrhizal fungal diversity in cultivated orchards of C. illinoinensis. Five pecan orchards in southern Georgia, USA, were studied, three of which were known to fruit the native edible truffle species Tuber lyonii. We sequenced rDNA from single ectomycorrhizal root tips sampled from a total of 50 individual trees. Mycorrhizae were identified by ITS and LSU rDNA sequence-based methods. Forty-four distinct ectomycorrhizal taxa were detected. Sequestrate taxa including Tuber and Scleroderma were particularly abundant. The two most abundant sequence types belonged to T. lyonii (17%) and an undescribed Tuber species (~20%). Because of our interest in the ecology of T. lyonii, we also conducted greenhouse studies to determine whether this species would colonize and form ectomycorrhizae on roots of pecan, oak, or pine species endemic to the region. T. lyonii ectomycorrhizae were formed on pecan and oak seedlings, but not pine, when these were inoculated with spores. That oak and pecan seedling roots were receptive to truffle spores indicates that spore slurry inoculation could be a suitable method for commercial use and that, ecologically, T. lyonii may function as a pioneer ectomycorrhizal species for these hosts.

Field experiments were conducted in 2000 and 2001 on Georgia Green, Florida MDR-98, and C-99R peanut (Arachis hypogaea) cultivars in Tifton, GA, to determine the effects of tillage practices on early leaf spot (Cercospora arachidicola) epidemics under standard fungicide regimes and fungicide regimes with fewer applications. Leaf spot epidemics were suppressed in reduced tillage (strip-till) plots compared with conventional tillage plots and were suppressed in MDR-98 and C-99R cultivars compared with the standard runner-type cultivar, Georgia Green. Within tillage and cultivar combinations, leaf spot intensity typically was lower in plots treated with fungicides at standard intervals (seven total applications) than in those treated at extended intervals (four total applications). However, in most cases, leaf spot control in extended interval treatments in the strip-till system was comparable to that in the standard interval treatments in conventional tillage. Based on these results, the number of fungicide applications could be reduced without compromising control of leaf spot when reduced tillage is used, especially if combined with moderately resistant cultivars. Suppression of leaf spot epidemics in the strip-till plots did not coincide with higher yields in either year. In 2001, yields were lower in strip-till plots than in conventional tillage plots. Yields were typically higher in the cultivar C-99R than in Georgia Green, regardless of the tillage treatment.

Field experiments were carried out to evaluate the effects of integrated management of early leaf spot, caused by Cercospora arachidicola, and spotted wilt, caused by Tomato spotted wilt virus (TSWV), on peanut (Arachis hypogaea) using host resistance, two tillage systems, and varying fungicide programs. Effects on pod yield and economic return were assessed. Genotypes C-11-2-39 and Tifrunner demonstrated the best field resistance to TSWV, whereas cvs. DP-1 and GA-01R and line C-28-305 were among the genotypes with the best leaf spot resistance. Epidemics of both diseases were comparable or suppressed in strip-tilled plots compared with conventionally tilled plots. Leaf spot intensity decreased with increased fungicide applications, but to a lesser degree with use of resistance and strip tillage. Yields and net returns were similar between tillage treatments in 2002 and lower in strip tillage in 2003. Genotypes with the greatest yields and returns were C-11-2-39, C-99R, and GA-01R. Returns were comparable among the four-, five-, and seven-spray programs in both years, despite differences in yield. The standard production system, Georgia Green in conventional tillage with seven sprays, resulted in lower returns than half the integrated systems tested in 2002, but had comparable or higher returns than nearly all systems in 2003. When significant, yields and returns were correlated with spotted wilt intensity to a greater degree than leaf spot intensity.

Diseases caused by Rhizoctonia solani lead to significant reductions in peanut yields and quality throughout the world. A subset of accessions from the peanut germ plasm core collection plus the commercial cultivars Florunner, Southern Runner, Georgia Browne, and Georgia Green were evaluated for resistance to limb and seedling hypocotyl infections caused by R. solani. Georgia Green and core accessions 95 (PI 497351), 197 (PI 331326), 208 (PI 274193), 244 (PI 343361), 246 (PI 343398), and 524 (PI 288178) had levels of resistance comparable to Georgia Browne, the only commercial cultivar reported to have partial resistance to Rhizoctonia limb rot. Eleven core accessions, representing the full range of disease expression, and the commercial cultivars were evaluated in growth chambers to quantify their susceptibility to seedling hypocotyl infections and to determine if evaluating seedlings could serve as a primary screening method to identify potential sources of limb rot resistance. The most resistant core accessions to seedling hypocotyl infections were 234 (PI 159664) and 366 (PI 268968), and the most resistant commercial cultivar was Georgia Green. There was not a significant correlation between resistance to limb rot in the field and the severity of hypocotyl infections in growth chambers, indicating that resistance to hypocotyl infections is not a good indicator of resistance to Rhizoctonia limb rot.