During 2017-19, 30 replicated yield trials were conducted to determine relative tomato spotted wilt (TSW) incidence and general field performance among 19 runner and virginia market type peanut (Arachis hypogaea L.) cultivars. Four different input production practices were compared across three Georgia locations (Tifton, Plains, and Midville). Two early-planted (April) field tests were conducted at Tifton and Plains each year. One early-planted trial involved maximum-input practices of recommended pesticides with irrigation, and the other early-planted field trial did not receive any fungicides, insecticides, or irrigation. Early-planted maximum-input production practices with irrigation resulted in the highest percentage of mid-season TSW and late-season total disease incidences while also producing the highest pod yields and dollar values. Two other optimum-planted (May) maximum-input field tests were conducted at Tifton, Plains, and Midville, GA as part of the official statewide variety trials (OVT). These OVT utilized maximum-input production practices of pesticides both with and without irrigation. In the OVT, midseason TSW incidence showed no difference between irrigated and non-irrigated; however, the end-of-season total disease percentages which were predominantly TSW did show significantly higher disease percentage, produced the highest pod yields and dollar values within the irrigated field tests compared to the non-irrigated tests. In the overall four tests comparison, disease results showed significantly lower TSW incidence in the early-planted tests without fungicides and insecticides input production practices and no-irrigation; whereas, both optimum planted OVT(s) had the lowest total disease incidence. Overall average field performance for pod yields and dollar values were significantly highest in the optimum-planted tests with maximum-inputs including irrigation. Significant differences were also found among the 19 peanut cultivars. ‘Georgia-06G’, ‘Georgia-12Y’, and ‘Georgia-18RU’ had the lowest relative TSW incidence compared to the other runner-type cultivars. ‘Georgia-19HP’ had the lowest TSW incidence and total disease incidence among the virginia-type cultivars. Among the runner cultivars, Georgia-12Y had the lowest total disease incidence at the end of the season. The highest pod yields were found with Georgia-06G and ‘Georgia-16HO’; whereas, Georgia-18RU and Georgia-06G had the highest dollar values among the runner-type peanut cultivars. Georgia-19HP had the highest pod yield and dollar value among the virginia-type cultivars.

ABSTRACT In peanut ( Arachis hypogaea L.), most agronomically important traits such as yield, disease resistance, and pod and kernel characteristics are quantitatively inherited. Phenotypic selection of these traits in peanut breeding programs can be augmented by marker-assisted selection. However, reliable associations between unambiguous genetic markers and phenotypic traits have to be established by genetic mapping prior to early generation marker-assisted selection. Previously, a nested association mapping (NAM) population of 16 recombinant inbred line populations (RILs) consisting 4870 lines was established. In order to facilitate effective mapping of such a large genetic resource, the first objective of the current study was to phenotype the parental lines for yield, pod traits, field maturity, germination, plant morphology, salt tolerance and resistance to tomato spotted wilt virus (TSWV) and late leaf spot (LLS). For most measured traits, more than one parental combination demonstrated statistically significant variation which can be further quantified and mapped in the respective RIL populations. The second objective of this study was to genotype the parental lines using the Arachis Axiom SNP arrays to reveal the marker density of the mapping populations. The Version 1 array identified 1,000 to 4,000 SNPs among the population parents and the number of SNPs doubled on the Version 2 array. Further phenotyping and genotyping of the NAM populations will allow the construction of high density genetic maps containing quantitative trait loci.

ABSTRACT In 2003, 2004, and 2005 standard and reduced input fungicide programs were evaluated throughout the peanut production region of Georgia for control of early leaf spot ( Cercospora arachidicola ), late leaf spot ( Cercosporidium personatum ), and southern stem rot ( Sclerotium rolfsii ). Disease risk was determined for each field based on the cultural practices implemented and ranged from low to high. Six to eight fungicide applications were made in the standard programs, versus three to six applications in reduced programs. Leaf spot ratings were higher for the reduced programs in five of the fourteen trials with substantial defoliation occurring in one trial. Overall, southern stem rot control for the reduced programs was equal to or better than that for the standard program, which could be attributed to the differences in fungicide selection or timing. Pod yields for the reduced programs were equal to or greater than the standard programs in all but one trial. Net returns were higher for the reduced programs in half of the trials; however, the reduced program resulted in lower net returns in one trial in 2004. Our results indicate that reduced input fungicide programs can be used to adequately manage fungal diseases of peanut without compromising yield or profitability, and that the use of cultivars with moderate levels of disease resistance may enhance disease control.

Identification and utilization of peanut cultivars with resistance to Cylindrocladium black rot (CBR) is a desirable approach to manage this disease. The objectives of this study were to improve greenhouse and field screening techniques for resistance to CBR, and to evaluate the reaction of selected runner-type peanut genotypes. Georgia-02C (moderately resistant to CBR) and C-99R (CBR-susceptible) were used in comparing the effectiveness of different inoculation methods in the greenhouse. Disease development was affected by both size and density of microsclerotia in soil. Use of microsclerotia at a size of ≥150 to <250 µm and a density of 1 to 5 microsclerotia/g soil provided the best separation the CBR-resistant cultivar Georgia-02C and the susceptible C-99R based on root rot severity. Genotypes with varying resistance to CBR were evaluated by growth in a naturally infested field, and by inoculating plants in the field and greenhouse. Disease incidence and severity at harvest were the most effective parameters for evaluating CBR resistance in the field and greenhouse, respectively. The cultivars Georgia-02C and Georganic had the lowest disease incidence, whereas C-99R and DP-1 had the highest disease incidence in a naturally infested field in 2005 and 2006. Incidence of CBR was moderate for Georgia-01R in both years, but was inconsistent for C34-24-85. Georgia-02C and Georganic also showed partial resistance to CBR in greenhouse tests. Inoculated plants in the field had similar reaction with Georgia-02C and Georganic showing higher CBR resistance than C-99R and DP-1 in both 2006 and 2007. The root rot severities for genotypes Georgia-02C and Georganic were lower than those for C-99R and DP-1. Incidence of CBR in the naturally infested field was significantly correlated with CBR incidence in the inoculated plants in the field (r = 0.84, P ≤ 0.01), but neither was correlated with disease ratings for greenhouse experiments. Peanut genotypes are most reliably screened by inoculating plants in the field or using uniformly infested fields. Further study is needed to improve greenhouse screening procedures.

Field experiments were conducted in Tifton and Plains, GA in 2001–2007 to determine the efficacy of prothioconazole on early leaf spot ( Cercospora arachidicola ) and late leaf spot ( Cercosporidium personatum ) of peanut ( Arachis hypogaea ). In five of six experiments, application of one or both rates (0.18 and 0.20 kg ai/ha) of prothioconazole in sprays 3–6 (chlorothalonil at 1.26 kg ai/ha in sprays 1, 2, and 7) provided leaf spot control superior to tebuconazole (0.23 kg ai/ha) in a similar regime, and superior to chlorothalonil at 1.26 kg ai/ha applied full season (seven times) in four of six experiments. In a similar series of six experiments, application of 0.085 kg ai/ha of prothioconazole + 0.17 kg ai/ha of tebuconazole provided better leaf spot control than tebuconazole (0.23 kg ai/ha) applied in regimes similar to those described above. Leaf spot control with prothioconazole + tebuconazole was similar to chlorothalonil applied at 1.26 kg ai/ha full season in five of eight experiments, but was less effective in the remaining three experiments. Fungicide effects on yield were inconsistent, but in all experiments, yield response with either rate of prothioconazole was similar to or greater than that obtained with 0.23 kg ai/ha tebuconazole on the same schedule. In a third series of four experiments, full-season (seven sprays) application of mixtures of prothioconazole at 0.063 kg ai/ha with trifloxystrobin at 0.063 kg ai/ha gave similar or better leaf spot control than chlorothalonil full season.

This study assessed components of resistance for three runner-type peanut cultivars to infection by Cercospora arachidicola ( Ca ) and Cercosporidium personatum ( Cp ), the causal organisms of early leaf spot and late leaf spot, respectively. Resistance components were compared to disease resistance observed in the field. A field study monitored the progression of leaf spot incidence and severity in peanut cultivars Georgia Green, Georganic, and DP-1. Time of disease onset (TDO) and temporal epidemic rate (rate) were estimated for incidence with the logistic model, and for severity with the linear model. Early leaf spot was the predominant disease in the field. Estimates of TDO were 9 d later for DP-1 than for Georgia Green, based on incidence models, and 6 and 7 d later for Georganic and DP-1 than for Georgia Green, respectively, based on severity models. Incidence progression rate was highest for Georganic in 2002 and Georgia Green in 2003, while severity progression rate was highest for Georgia Green across years. A detached leaf assay was used to determine components of resistance for these genotypes to infections by Ca and Cp . Infection frequency 30 d after inoculation, lesion diameter, and percent necrotic area were greatest for Georgia Green for both pathogens. Besides a 2-d longer latent period for resistant genotypes, no Ca reproduction differences were detected. For Cp , latent period was shorter for Georganic than DP-1, and sporulation per unit lesion area was greatest for Georganic. Enhanced field resistance to early and late leaf spots reported for DP-1 and Georganic is in part due to lower infection frequencies, smaller lesions, and for DP-1, longer latent periods.

Interest in organic peanut ( Arachis hypogaea L.) production is increasing in the United States. Disease and insect resistant cultivars will be needed to meet the challenge of producing peanuts without conventional pesticides. No-fungicide and no-insecticide field trials were conducted under irrigation four consecutive years (2003–06) at the University of Georgia, Coastal Plain Experiment Station to evaluate peanut genotypes for pest resistance. The most important foliar peanut diseases in the southeast are tomato spotted wilt (TSW) caused by Tomato spotted wilt virus and both early and late leafspots caused by Cercospora arachidicola Hori and Cercosporidium personatum (Berk. & Curt.) Deighton, respectively. Two of the most important insect pests on peanut are tobacco thrips ( Frankliniella fusca Hinds) and potato leafhopper ( Empoasca fabae Harris). Results from these no-fungicide and no-insecticide field trials showed significant differences (P ≤ 0.05) in pest resistance among advanced Georgia breeding lines and cultivars. Two Georgia cultivars ‘Georgia-01R’ and ‘Georgia-05E’ consistently produced the highest yields and had high levels of resistance to TSW, leafhoppers, and leafspots each year. Georgia-01R is a multiple-pest-resistant, mid-oleic, runner-type cultivar; whereas, Georgia-05E is a multiple-pest-resistant, high-oleic, virginia-type cultivar. Both cultivars should be considered as good candidates for potential use in organic peanut production.

Tomato spotted wilt, caused by Tomato spotted wilt tospovirus (TSWV) is a major problem in peanut ( Arachis hypogaea L.) producing areas of the southeastern U.S. The integrated program used to manage spotted wilt relies heavily on cultivars with field resistance to TSWV, and finding new sources and greater levels of resistance to TSWV is highly desirable. Field tests were conducted in 2003 and 2004 in Marianna, FL and Tifton, GA to compare three peanut breeding lines, F NC94022-1-2-1-1-b3-B, C 11-2-39, and C 11-186 to that of standard moderately resistant cultivar Georgia Green for field response to TSWV. F NC94022-1-2-1-1-b3-B was of particular interest because it was developed from a cross between lines of A. hypogaea subsp. hypogaea var. hirsuta Köhler and A. hypogaea subsp. hypogaea var. hypogaea . In all tests, final spotted wilt ratings for breeding lines F NC94022-1-2-1-1-b3-B, C 11-2-39, and C 11-186 were lower and pod yields were higher than for Georgia Green. In three tests, final spotted wilt intensity ratings did not differ among F NC94022-1-2-1-1-b3-B, C 11-2-39, and C 11-186. At Marianna in 2004, spotted wilt intensity ratings were lower and pod yields were higher in F NC94022-1-2-1-1-b3-B than in any other entry. The high level of field resistance to TSWV in F NC94022-1-2-1-1-b3-B is presumably derived from its hirsuta type parent, PI 576638.

Tomato spotted wilt virus (TSWV) resistant, runner-type peanut ( Arachis hypogaea L.) cultivars are the most important defense to control spotted wilt disease in southeast U.S. peanut production. The objective of this 3-yr (1999–01) study was to evaluate six TSWV-resistant, runner-type cultivars (Southern Runner, Florida MDR 98, C-99R, ViruGard, Georgia Green, and Georgia-OIR) at three different seeding rates (3, 5, and 7 seed/30.5 cm) in single conventional row patterns for possible genotype (GE) × seeding rate (SR) interaction at the Univ. of Georgia, Coastal Plain Experiment Station. The combined split-plot analyses of variance resulted in highly significant (P ≤ 0.01) GE × SR interaction, which indicates that not all six runner-type cultivars performed the same at each of these three seeding rates. A good example was the TSWV-resistant, runner-type peanut cultivar Georgia Green. It performed subpar at the below normal or lowest seeding rate; whereas at the highest seeding rate, Georgia Green and Georgia-OIR produced the highest pod yields and dollar value returns per hectare among all of these runner-type cultivars. TSWV disease incidence was also significantly lower for the TSWV-resistant Georgia Green cultivar at each of the two higher seeding rates compared to the lowest seeding rate.

Tomato spotted wilt virus (TSWV) (family: Bunyaviridae) is a continuing threat to several crops in the Southeastern U.S. Acibenzolar-S-methyl is a plant immune-response activator which has been shown to suppress TSWV in tobacco. The following treatments were evaluated for TSWV and thrips suppression: untreated, phorate in-furrow, acibenzolar-S-methyl applied in-furrow, acibenzolar-S-methyl in-furrow + foliar, and acibenzolar-S-methyl in-furrow + phorate in-furrow. Although in-furrow applications of acibenzolar-S-methyl alone and in combination with phorate led to numerical reductions of TSWV during each year of the study, differences were significant only during 1997. Foliar applications of acibenzolar-S-methyl did not provide enough disease suppression during 1997 to warrant additional sprays. However, Acibenzolar-S-methyl also may reduce populations of thrips larvae and suppresses feeding damageby thrips up to 30 d after planting. Acibenzolar-S-methyl applied in-furrow was comparable with in-furrow applications of phorate in its effect on TSWV of peanut; however, acibenzolar-S-methyl does not provide enough benefit alone to justify its use in peanut management at this time.

A field survey to determine the incidence of Impatiens necrotic spot virus (INSV) in Georgia peanut ( Arachis hypogaea L.) was conducted during the 1999 and 2000 growing seasons. Confirmation of INSV infection was made by enzyme-linked immunosorbent assay (ELISA). During August 1999, a total of 504 symptomatic peanut plants were sampled from 42 fields representing 15 counties. Peanut plants showing symptoms of spotted wilt from 14, 15, and 15 counties were sampled during the early (June), mid (July), and late (August/September) periods of the 2000 growing season, respectively. During 2000, a total of 1433 peanut plants were sampled over the course of the survey. The 1999 survey yielded no INSV-positive peanut plants, while 87% of the plants sampled tested positive for TSWV. During the 2000 survey, INSV was detected from 2.0% of all peanut plants sampled, while TSWV was detected in 97.8% of all plants. All plants that tested positive for INSV also tested positive for TSWV. TSWV was detected from plants in each field. INSV was only detected from seven fields in four counties. Additionally, 90 peanut plants were tested for INSV in a Coffee County field in which that virus was detected in July 2000. TSWV was detected in 94% of those plants, while INSV was detected in 20% of the plants. Double infections were detected in 17% of the plants from the field in Coffee County. The natural incidence of another Tospovirus in peanut could have important management implications for peanut production systems.

Field tests were conducted in 1997 and 1998 in Georgia and Florida to compare the effects of 10 and 12 peanut ( Arachis hypogaea L.) cultivars, respectively, on epidemics of spotted wilt caused by tomato spotted wilt Tospovirus. Epidemics of spotted wilt were suppressed for the moderately resistant standard Georgia Green, and in Southern Runner, Florida MDR 98, ViruGard, and NC-V11. The reponse of these five cultivars to spotted wilt were similar and resulted in lower final disease intensity and areas under the disease progress curves than in the susceptible standard Georgia Runner, and in SunOleic 97R and Tamrun 96. Southern Runner and Florida MDR-98 consistently had higher yields than the TSWV-susceptible Georgia Runner. Georgia Green and NC-V11 had higher yields than Georgia Runner in three of the four tests. No consistent differences were found among the cultivars for numbers of adult tobacco thrips ( Frankliniella fusca ) or western flower thrips ( F. occidentalis ). Differences among cultivars for numbers of larvae of Frankliniella spp. also were few and inconsistent. There was no indication that differences in thrips populations were responsible for differences in severity of spotted wilt in the field.

The major peanut ( Arachis hypogaea L.) producing regions in the U.S. are currently faced with an increasing tomato spotted wilt tospovirus (TSWV) problem, and the most effective control is the use of resistant cultivars. This study was conducted to compare the field performance and TSWV disease intensity among different seed sizes of two runner-type cultivars. For three consecutive years, 1995–97, the effect of continuous seed size selection on yield, grade, and TSWV intensity among the two runner cultivars Georgia Green and Florunner was evaluated at the Univ. of Georgia Coastal Plain Exp. Sta. Sound mature kernels from both cultivars were divided into four seed sizes (jumbo, medium, No. 1, and the combined mill run check). Seed size selection pressure was applied to both cultivars each year. Seed stock for planting each year was obtained from the corresponding seed size produced the previous year. The results showed that the Georgia Green cultivar significantly out-performed the Florunner cultivar in yield, grade, dollar value, and had significantly less TSWV. Georgia Green had a similar percentage of jumbo seed, more medium seed, and fewer No. 1 seed than Florunner. Both runner-type cultivars responded similarly to continuous selection pressure with small but significant changes in seed size distribution over a relatively short 3-yr period.

The influences of bahiagrass, corn, and cotton in rotation with peanut and treatments with aldicarb, flutolanil, and aldicarb plus flutolanil on nematodes, thrips, diseases caused by soilborne fungal pathogens, and yield of peanut were studied for 3 yr. Peanut yields following either 1 or 2 yr of bahiagrass, corn, or cotton were higher than those of continuous peanut. Peanut yield was greatest in the aldicarb plus flutolanil treated plots (5270 kg/ha), intermediate where aldicarb (4060 kg/ha), or flutolanil (4597 kg/ha) was used without aldicarb, and least in untreated (3690 kg/ha) plots. Yield increases in response to cropping sequences and pesticide treatments resulted primarily from suppression of crop damage by Meloidogyne arenaria, Sclerotium rolfsii, Rhizoctonia solani , and Frankliniella spp. The data document the pest management benefits and yield response associated with using two widely grown agronomic crops (corn and cotton), an improved bahiagrass cultivar, and pesticide treatments in peanut production.

The localization of tomato spotted wilt virus (TSWV, genus Tospovirus , family Bunyaviridae ) in peanut pods was determined by enzyme-linked immunosorbent assay (ELISA) using TSWV specific antibodies. Pods were collected from symptomatic and asymptomatic fieldgrown plants. All the plants were tested by ELISA for presence or absence of TSWV infection. Normal and abnormal looking pods from symptomatic plants were assayed by ELISA. Each pod was divided into shell, testa, and cotyledons. All of the shell and testa samples of both normal and abnormal pods from symptomatic plants were positive for TSWV, whereas TSWV could not be detected in the cotyledons. Similar results were observed by polymerase chain reaction, except that the cotyledons occasionally had a TSWV-specific sequence. No virus could be detected in any part of the pod collected from asymptomatic, virus-free plants. In growout tests of seed from both symptomatic and asymptomatic plants, none of the plants showed TSWV infection when assayed by ELISA. Results demonstrated the preferential accumulation of the virus in the shell and testa.

Epidemics of tomato spotted wilt, caused by tomato spotted wilt Tospovirus (TSWV), were monitored in field plots of runner-type peanut ( Arachis hypogaea L.) cultivars Georgia Green and Georgia Runner and numerous breeding lines from four different breeding programs as part of efforts toward characterizing breeding lines with potential for release as cultivars. Breeding lines were divided into early, medium and late maturity groups. The tests were conducted near Attapulgus, GA and Marianna, FL in 1997 and in Tifton, GA and Marianna, FL in 1998. Epidemics in some early and medium maturing breeding lines, including some genotypes with high oleic acid oil chemistry, were comparable to those in Georgia Green, the cultivar most frequently used in the southeastern U.S. for suppression of spotted wilt epidemics. No early maturing breeding lines had lower spotted wilt final intensity ratings or higher yields than Georgia Green. However, spotted wilt intensity ratings in some late maturing lines and a smaller number of medium maturing lines were significantly lower than those of Georgia Green. Several of those lines also produced greater pod yields than Georgia Green. Results from these experiments indicated that there is potential for improving management of spotted wilt though development of cultivars that suppress spotted wilt epidemics more than currently available cultivars. There was no indication that differences in spotted wilt ratings corresponded to differences in numbers of thrips adults or larvae.

Spotted wilt, caused by tomato spotted wilt tospovirus (TSWV), has become a major problem in peanut- ( Arachis hypogaea L.) producing areas of the southern U.S. Development of cultivars with resistance to TSWV appears to be among the most promising methods for managing this disease. As part of efforts toward characterizing breeding lines with potential for release as cultivars, epidemics of spotted wilt were monitored in field plots of runner-type peanut cultivars Southern Runner and Florunner and advanced breeding lines: 79/4-6-2-1-1-Z16- b2 -B (virginia-type), F 84/23-11-1-1-1- b2 -B (runner-type), and F 84/28-5-5-2-2-1- b2 -B (runner-type), F 84/28-5-4-2-2- b3 -B (runner-type). The tests were conducted near Attapulgus, GA and Marianna, FL in 1995 and 1996. In 1996, the tests also included the runner-type cultivar AT-108. Epidemics of spotted wilt were suppressed in F 79/4-6-2-1-1-Z16- b2 -B, F 84/23-11-1-1-1- b2 -B, F 84/28-5-5-2-2-1- b2 -B, and Southern Runner in comparison to those in Florunner. Final disease incidence and/or final disease intensity ratings in F 79/4-6-2-1-1-Z16- b2 -B and F 84/23-11-1-1-1- b2 -B were similar to those of Southern Runner. In 1996, final spotted wilt intensity ratings in F 84/28-5-4-2-2- b3 -B and AT-108 did not differ from those of Florunner. Yields of F 79/4-6-2-1-1-Z16- b2 -B and F 84/23-11-1-1-1- b2 -B were superior to those of Florunner in three of the four tests. No differences were found among the genotypes in numbers of adults of tobacco thrips ( Frankliniella fusca ) or western flower thrips ( F. occidentalis ), and differences in numbers of larvae of Frankliniella spp. were few and not consistent. There was no evidence that differences in final disease incidence or disease intensity ratings were due to differential preference by thrips or to suitability for thrips reproduction. F 79/4-6-2-1-1-Z16- b2 -B and F 84/23-11-1-1-1- b2 -B represent potential tools for management of spotted wilt in peanut production areas of the southeastern U.S.

Tomato spotted wilt virus (TSWV) is among the greatest yield-reducing viruses affecting peanut ( Arachis hypogae a L.). The best known method of control of TSWV is through the use of resistant cultivars. Unfortunately, only a few peanut genotypes with moderate levels of resistance are known. The objectives of this study were to identify additional sources of resistance to TSWV and to determine whether plant descriptor information is associated with reaction to TSWV in the field. Peanut plant introductions from a core collection were evaluated for resistance to TSWV in field trials from 1991 to 1993. Great variability was found among PIs for reaction to natural TSWV epidemics at Attapulgus, GA. Accessions which exhibited potential resistance in 1991 or 1992 were reevaluated in subsequent years. Disease pressure was high in 1993 and 27 accessions exhibited significantly greater resistance than Florunner, and one (PI 262049) had lower disease incidence than Southern Runner. Only minor relationships existed between TSWV incidence and plant descriptor traits (growth habit and maturity) using the stepwise multiple regression procedure. Peanut accessions with resistance to TSWV were found among all maturity levels and growth habits. These accessions provide additional parents and may provide additional genes for resistance that may be useful in developing resistant cultivars.

In the past, genetic resistance to both early and late leaf spots [ Cercospora arachidicola Hori and Cercosporidiumpersonatum (Berk. & Curt.) Deighton] has been found to be negatively or inversely correlated with early maturity in the cultivated peanut ( Arachis hypogaea L.). For example, the late leaf spot resistant cultivar Southern Runner is approximately 2 wk later in maturity than the susceptible Florunner cultivar. Recently, an advanced runner-type breeding line (GA T-2844) has been developed by the Georgia peanut breeding program which combines early maturity and leaf spot tolerance. For the past 3 yr (1991–1993), GA T-2844 has been evaluated in replicated field tests without fungicides. Results show that GA T-2844 has on the average >30% yield advantage and a 30-d earlier maturity than Southern Runner. Leaf spot ratings also showed GA T-2844 to be intermediate between Southern Runner and Florunner. Such a combination of early maturity and leaf spot tolerance could significantly enhance U.S. peanut production by providing an environmentally safer and efficient alternative to costly pesticides not previously available among runner-type cultivars.

Field experiments were conducted in one location in 1993 and two locations in 1994 to determine the effects of propiconazole and chlorothalonil tank mix combinations on severity of early ( Cercospora arachidicola ) and late ( Cercosporidium personatum ) leaf spot diseases of peanut ( Arachis hypogaea L.). In all tests, 10 treatments consisted of 0 and 63 g a.i./ha of propiconazole and 0, 0.315, 0.63, 0.945, and 1.26 kg a.i./ha of chlorothalonil arranged factorially. In 1993, final leaf spot intensity ratings decreased according to nonlinear quadratic functions of chlorothalonil concentrations applied with and without propiconazole. No improvement in leaf spot control was evident with the addition of more than 0.945 kg a.i./ha of chlorothalonil with 63 g a.i./ha of propiconazole. In 1994, conditions were more conducive for leaf spot development. At the Plains location, final leaf spot intensity ratings decreased according to non-linear quadratic functions of chlorothalonil concentrations alone. Leaf spot intensity ratings decreased linearly with increasing rates of chlorothalonil when applied with 63 g a.i./ha of propiconazole. At Tifton, final leaf spot intensity ratings decreased linearly with increasing rates of chlorothalonil with or without propiconazole. Leaf spot intensity ratings were lower on plants treated with tank mixes of chlorothalonil and propiconazole compared to those treated with chlorothalonil alone. Pod yields increased linearly or according to quadratic functions of rates of chlorothalonil with or without propiconazole in both years and all locations. Across all rates of chlorothalonil, yields were higher from plants treated with propiconazole than those treated with the respective rates of chlorothalonil alone.