Peanut Production Systems Research Articles

Effect of Soil pH Variation on Peanut Plant Growth

This research investigates the qualitative effects of soil pH variation on peanut plant growth, aiming to provide insights into the complex interactions between soil properties and plant responses in agricultural ecosystems. Through semi-structured interviews with ten informants, supplemented by insights synthesized from prior research and theoretical frameworks, the study explores perceived relationships, implications for soil health and nutrient availability, challenges, opportunities, and practical implications for peanut production. Key findings highlight the critical influence of soil pH on peanut growth and productivity, with deviations from optimal pH levels affecting nutrient availability, root health, and overall plant vigor. Participants underscore the importance of targeted soil management practices, including lime application, organic matter incorporation, and crop rotation, in optimizing soil pH and supporting resilient peanut production systems. The study identifies challenges in soil pH management, such as limited accessibility of soil testing services and inadequate farmer knowledge, while also highlighting opportunities for innovation and improvement. The insights gleaned from the study contribute to advancing knowledge in agricultural sciences and inform evidence-based soil management practices for sustainable peanut production.

Peanut Smut in Argentina: An Analysis of the Disease, Advances, and Challenges.

Peanut (Arachis hypogaea L.) is a globally high-value food crop, with Argentina ranking third in global peanut exports. However, Argentine peanut production faces a severe threat from a fungal disease, peanut smut, caused by Thecaphora frezzii. This disease is particularly prevalent in the Córdoba Province, where recent surveys have documented a gradual increase in the prevalence and incidence of peanut smut, becoming a significant challenge to peanut production. First identified in Brazil in the 1960s in wild peanut and later in Argentina in 1995 in commercial peanut fields, the disease has rapidly spread owing to its distinctive pathogen characteristics, including the lack of visible symptoms on aerial plant parts, spore spread, and survival, and with a lack of proactive efforts to develop and apply management strategies. This results in the gradual accumulation of teliospores of T. frezzii in soil, further exacerbating the problem in subsequent growing seasons by increasing the intensity of the disease and driving a reduction in crop yield and quality. This review summarizes recent research on peanut smut, focusing on disease assessment, molecular characterization, diagnosis and detection, epidemiology, host range and environmental conditions, and the latest advancements in management approaches, including fungicide spraying, breeding programs, cultural management, and biological control, aimed to enhance understanding and support effective disease management strategies in peanut production systems.

Impact of Variety and At-Planting Insecticides on Thrips (Thysanoptera: Thripidae) Management in Peanut

Tobacco thrips are one of the most prevalent early season insect pests in peanut production systems. Experiments were conducted in 2018 and 2019 in Stoneville Mississippi to evaluate integrated pest management approaches to mitigate negative effects of thrips. Experimental treatments included a normal and late planting date, varieties Georgia-06G and QR-14, and in-furrow insecticide treatments consisting of a non-treated control, phorate, and imidacloprid. Measurements included early and final plant stands, immature and adults thrips counts, and pod yield. In-furrow insecticide had a strong effect on number of thrips per plant with treatment thrips ranking of: phorate < imidacloprid < non-treated control. However, in-furrow insecticide had no interaction with variety or plating date. Although phorate provided greater thrips control than imidacloprid, pod yield for the two treatments was similar, and both in-furrow treatments had greater yield than the non-treated control. The variety QR-14 had greater pod yield than Georgia-06G when planted late. Overall, these results confirm that in-furrow insecticide applications of either imidacloprid or phorate are adequate in protecting against yield loss from thrips within a midsouthern peanut production environment.

Green manure increases peanut production by shaping the rhizosphere bacterial community and regulating soil metabolites under continuous peanut production systems

BackgroundGreen manure (GM) is a crop commonly grown during fallow periods, which has been applied in agriculture as a strategy to regulate nutrient cycling, improve organic matter, and enhance soil microbial biodiversity, but to date, few studies have examined the effects of GM treatments on rhizosphere soil bacterial community and soil metabolites from continuous cropping peanut field. Results: In this study, we found that the abundances of several functionally significant bacterial groups containing Actinobacteria, Acidobacteria, and genus Sphingomonas, which are associated with nitrogen cycling, were dramatically increased in GM-applied soils. Consistent with the bacterial community results, metabolomics analysis revealed a strong perturbation of nitrogen- or carbon-related metabolisms in GM-applied soils. The substantially up-regulated beneficial metabolites including sucrose, adenine, lysophosphatidylcholine (LPC), malic acid, and betaines in GM-applied soils may contribute to overcome continuous cropping obstacle. In contrast to peanut continuous cropping, planting winter wheat and oilseed rape in winter fallow period under continuous spring peanut production systems evidently improved the soil quality, concomitantly with raised peanut pod yield by 32.93% and 25.20%, in the 2020 season, respectively. Conclusions: GMs application is an effective strategy to overcome continuous cropping obstacle under continuous peanut production systems by improving nutrient cycling, soil metabolites, and rhizobacterial properties.

Color contour texture based peanut classification using deep spread spectral features classification model for assortment identification

Agriculture is one of great economic growth in India by producing variety of peanuts for various co products development. Peanut Crop and weed identification is an important step in developing a highly efficient automotive peanut production system. Most of the exiting classification fix the threshold margins to select the inappropriate features cause classification inaccuracy. Deep learning, as a powerful image processing technology, can extract conventional and characteristic features in layers. Spectral information is used as the input of the network, and the output spectral characteristics of the network are directly passed to the subsequent classifiers to achieve pixel-level classification. To resolve the classification categorization problem, we propose a Color contour texture based peanut classification using deep spread spectral features classification model for variety identification. Initial the Cascading subset Feature Filtering (CSFF) is applied to select the shape textures, color gradient rate form histogram equivalence and returns the feature scalar values. Based in CSFF the feature weight is attained to Social Spider Optimization to select the Impact Features Weight (SSO-IFW). The optimal object segmentation war applied based on cross fold object verification to select the shape projection features. Then Ada Boosting classifier generate the type of object structural for identifying type definition to generate pattern to produce peanut characteristic clusters. Based on Image Features recognition clusters, deep spread spectral neural classification is applied to train the features with soft-max logical activation function with Adaptive Convolution Neural Network (ACNN) to categorize the peanuts based on feature characteristics using image recognition, 20 varieties of peanut are collected through scanner type dataset to train the images into deep neural network. This produce high classification accuracy up to 89 %, high precision, recall rate under F-measure with low false rate. This achieves high classification than other existing methods.

X-ray driven peanut trait estimation: computer vision aided agri-system transformation

BackgroundIn India, raw peanuts are obtained by aggregators from smallholder farms in the form of whole pods and the price is based on a manual estimation of basic peanut pod and kernel characteristics. These methods of raw produce evaluation are slow and can result in procurement irregularities. The procurement delays combined with the lack of storage facilities lead to fungal contaminations and pose a serious threat to food safety in many regions. To address this gap, we investigated whether X-ray technology could be used for the rapid assessment of the key peanut qualities that are important for price estimation.ResultsWe generated 1752 individual peanut pod 2D X-ray projections using a computed tomography (CT) system (CTportable160.90). Out of these projections we predicted the kernel weight and shell weight, which are important indicators of the produce price. Two methods for the feature prediction were tested: (i) X-ray image transformation (XRT) and (ii) a trained convolutional neural network (CNN). The prediction power of these methods was tested against the gravimetric measurements of kernel weight and shell weight in diverse peanut pod varieties1. Both methods predicted the kernel mass with R2 > 0.93 (XRT: R2 = 0.93 and mean error estimate (MAE) = 0.17, CNN: R2 = 0.95 and MAE = 0.14). While the shell weight was predicted more accurately by CNN (R2 = 0.91, MAE = 0.09) compared to XRT (R2 = 0.78; MAE = 0.08).ConclusionOur study demonstrated that the X-ray based system is a relevant technology option for the estimation of key peanut produce indicators (Figure 1). The obtained results justify further research to adapt the existing X-ray system for the rapid, accurate and objective peanut procurement process. Fast and accurate estimates of produce value are a necessary pre-requisite to avoid post-harvest losses due to fungal contamination and, at the same time, allow the fair payment to farmers. Additionally, the same technology could also assist crop improvement programs in selecting and developing peanut cultivars with enhanced economic value in a high-throughput manner by skipping the shelling of the pods completely.This study demonstrated the technical feasibility of the approach and is a first step to realize a technology-driven peanut production system transformation of the future.

Frankliniella fusca(Thysanoptera: Thripidae), The Vector ofTomato Spotted Wilt OrthotospovirusInfecting Peanut in the Southeastern United States

AbstractThe tobacco thrips, Frankliniella fusca Hinds, is a phytophagous pest and vector of orthotospoviruses in many crops around the world. F. fusca causes direct feeding injury to peanut plants, resulting in leaf chlorosis and curling, and yield loss. Adults and larvae also transmit the economically important tomato spotted wilt orthotospovirus (TSWV) in all peanut market types grown in the U.S. TSWV infection causes spotted wilt disease, a plant disease characterized by chlorosis, stunting, and death. From 1996 to 2006, spotted wilt disease resulted in an estimated U.S.$140 million in annual peanut production losses in the U.S. At present, a thorough documentation of F. fusca’s impacts on the U.S. peanut production system is not available. Here, we describe the morphology, life cycle, and biology of F. fusca and provide images of immature life stages. Feeding injury characteristics and TSWV transmission in peanuts are also discussed. Currently, F. fusca and TSWV are managed in peanut with a combination of tactics, including prophylactic insecticide applications and TSWV-resistant cultivars. However, standardized scouting protocols and economic thresholds for F. fusca are not yet available. Very few biological control agents have been evaluated for use against F. fusca, and few studies have quantified the contributions of native natural enemies. More research into natural enemies’ contributions to F. fusca management and the mechanisms underlying TSWV-resistance in peanut could help inform and diversify integrated pest management programs.

A Risk Tool and Production Log Created using Microsoft Excel to Manage Pests in Peanut (Arachis hypogaea)

Abstract Peanut (Arachis hypogaea L.) growers and their advisors need to address a wide range of biotic and abiotic stresses to maximize yield and financial return. Mitigating risk to yield and financial investment requires knowledge of interactions among pests and strategies to manage pests, including chemical inputs, crop rotation, cultivar selection, field pest history, planting pattern and population, planting date, and tillage systems. Using Microsoft Excel, a comprehensive peanut risk tool was developed to assist growers and advisors in identifying and selecting production strategies to minimize risk to yield based on empirical data and practical experience while providing cost estimates of production practices. Initially, the risk tool was developed for North Carolina (USA) peanut production. However, the current platform is designed to facilitate the development of similar tools for other USA peanut regions, peanut production systems in other countries, and with the capability to develop risk tools for other crops. This article discusses components of the risk management tool developed for North Carolina peanut production. Benefits of the risk tool to practitioners, extension services, genetics and breeding programs, and formal classroom instruction will be discussed. One goal of this paper is to provide an example of how the Microsoft Excel framework used for peanut in North Carolina can be used for peanut in other regions of the USA and other countries.

Biology and Management of Peanut Burrower Bug (Hemiptera: Cydnidae) in Southeast U.S. Peanut

Abstract Peanut burrower bug, Pangaeus bilineatus (Say), is a piercing-sucking pest of peanut, Arachis hypogaea (L.), that is native to Central and North America. The insect spends most of its life below the soil surface and is not easily detected in the field. Although injury to peanut is sporadic in the Southern USA, the bug has become a serious economic pest for farmers in the region in recent years. During and after peanut seed formation, adult and immature bugs feed directly on seeds through the hull, reducing the quality and value of the crop. The value of peanut is reduced by approximately $209/MT when feeding injury is present on ≥3.5% of kernels by weight. Deep tillage prior to planting and application of granular chlorpyrifos during the growing season are the only tactics currently available for managing P. bilineatus in peanut in the United States. Relatively little research attention has been focused on P. bilineatus, and improved knowledge of the insect’s biology and ecology is needed to develop an integrated pest management (IPM) strategy that significantly reduces financial losses caused by this insect. The purpose of this article is to provide a review of the taxonomic history, biology, pest status, and management of P. bilineatus primarily as it relates to peanut production systems in the Southeast USA.

Supplementing Nitrogen in Combination with Rhizobium Inoculation and Soil Mulch in Peanut (Arachis hypogaea L.) Production System: Part I. Effects on Productivity, Soil Moisture, and Nutrient Dynamics

Peanuts (Arachis hypogaea L.) are the world’s fourth-most important source of edible oil and the third-most valuable source of high-quality vegetable protein; they also contain carbohydrates, fatty acids, vitamins, and minerals essential for good human nutrition. Peanuts area particularly valuable crop in tropical and subtropical regions. While the demand for peanuts is increasing globally, there is a significant gap in nitrogen supply and demand in peanut production systems. To alleviate this, nitrogen fertilizers are often applied indiscriminately; this practice leads to the deterioration of indigenous soil fertility and to a long-term decline in crop productivity. Considering these aspects of soil health, a field study was conducted over two consecutive winter (November–March) seasons in 2015–2016 and 2016–2017 at the research farm of the agricultural university Bidhan Chandra Krishi Viswavidyalaya in West Bengal, India. This study examined supplementing different levels of nitrogen fertilizer with rhizobium and soil mulch in an irrigated peanut crop. The effects of these management interventions were evaluated in terms of crop productivity, nutrient dynamics, soil moisture, and the soil microbial activity. Peanuts grown with the 100% recommended dose of nitrogen, which was applied with rhizobium and grown under polythene mulching, recorded the highest average pod yield (3.87 and 3.96 t ha−1 in 2015–2016 and 2016–2017) and average kernel yield (2.88 and 2.99 t ha−1) in both growing seasons. This treatment also resulted in the greatest accumulation of nitrogen, phosphorous, and potassium by the peanut plants. In contrast, the maximum soil moisture distribution and the greatest total root zone moisture content were observed in the treatment with only rhizobium under the polythene mulch (i.e., no nitrogen was applied). The populations of soil bacteria and rhizobia were highest in the treatment where nitrogen fertilizer was applied to the crop at 75% of the recommended rate combined with rhizobium and under polythene mulch. After two cropping seasons, the peanut crop grown under polythene mulch with rhizobium and with nitrogen fertilizer applied at either the full recommended rate or 75% of this rate performed best in terms of crop productivity, soil nutrient dynamics, and soil moisture.

The Influence of Nozzle Type and Application Speed on Sicklepod Control with Cadre and Butyrac

Sicklepod, also colloquially known as coffeeweed, is one of the most common and troublesome weeds in Georgia peanut production systems. Spray chamber/greenhouse studies were conducted to evaluate the effects of application speed (8 and 12 MPH), nozzle type (XR, TTI, and AIXR), and herbicide treatment on sicklepod control. Earn 0.5 CEUs in Integrated Pest Management by reading the article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/804.

Risk to sustainability of pest management tools in peanut

AbstractA diversity of pests can adversely affect peanut (Arachis hypogaea L.) yield, quality, and financial return. Farmers rely heavily on applied chemicals to suppress many of the economically important pests present in peanut. The effectiveness of this approach to pest management may not be sustainable, however, due to evolved resistance in pests to chemicals, reluctance of basic chemical manufacturers to invest in product development because of the relatively small market for peanut compared with other crops, cost to initially register or re‐register chemicals, and the desire for peanut buyers and processors to capture international markets that may have varying agrochemical residue restrictions for peanut. Heavy reliance on chemical control could leave peanut production systems vulnerable to yield loss; thus, a more concerted research effort is needed to increase the number and availability of nonchemical tools that protect peanut from pests in order to ensure long‐term sustainability of peanut production systems.

Interactive Effects of Cultivation, Insect Control, and Fungal Disease Control in Organic Peanut Production

ABSTRACT During previous organic peanut weed management trials, maintenance pesticides were not applied and it was observed that insect infestations and disease epidemics were not problematic. This was surprising considering that conventional peanut are routinely treated with insecticides and fungicides to control common pests. It was hypothesized that components of the organic peanut production system could be integrated into conventional peanut production to reduce inputs. Structured research trials were conducted from 2012 through 2014 to determine interactions among three levels of weed control, two levels of insect control, and three levels of fungal disease control in organic peanut production using a factorial arrangement of treatments. Weed control treatments were weed-free using handweeding, cultivation with a tine weeder repeated weekly for six weeks, and a non-cultivated (weedy) control. Insect control treatments were two early-season applications of spinosad (Organic Materials Review Institute approved) and a nontreated control. Fungal disease control treatments were applications of cupric oxide plus sulfur (Cu+S) at three-week intervals, the conventional fungicide azoxystrobin at three-week intervals, and a nontreated control. The peanut cultivar Georgia-04S was planted each year of the study. The crop rotation at the research sites was corn grown in alternating years between peanut experiments. There were no interactions among the main effects. Compared to the non-cultivated control, cultivation with a tine weeder consistently reduced weed densities, and yields were equivalent to handweeded peanut two years of three. Intensive cultivation with a tine weeder did not increase disease epidemics or reduce peanut yield, which is contradictory to long-standing peanut production recommendations. Spinosad applications did not affect any of the parameters measured, including incidence of thrips-vectored spotted wilt and peanut yield. Cupric oxide plus sulfur controlled peanut diseases equal to azoxystrobin two years out of three, but peanut yields did not consistently respond to improved disease control from the conventional fungicide. We speculate that ideal crop rotations to reduce disease inoculum and modern peanut cultivars with improved disease tolerance are also factors that allow the use of reduced pest control inputs.

Peanut Yield and Injury from Thrips with Combinations of Acephate, Bradyrhizobium Inoculant, and Prothioconazole Applied in the Seed Furrow at Planting

Core Ideas Acephate and prothioconazole did not adversely impact peanut response to Bradyrhizobium inoculant. Peanut was more responsive to Bradyrhizobium inoculant when planted in fields with no history of peanut production than in fields with recent peanut plantings. Acephate, Bradyrhizobium inoculant, and prothioconazole can be applied simultaneously in the seed furrow without losing effectiveness of individual components. Peanut (Arachis hypogaea L.) growers often apply commercial inoculant in the form of Bradyrhizobium to the seed furrow at planting to promote biological nitrogen fixation. Additionally, disease and injury from thrips (Frankliniella spp.) feeding can be reduced when prothioconazole and acephate, respectively, are applied in the seed furrow. Interactions of these products have not been determined for Virginia market‐type peanut. Six experiments were conducted during 2009 and 2010 to define interactions of acephate, Bradyrhizobium inoculant, and prothioconazole when co‐applied in the seed furrow at planting. Acephate and prothioconazole did not affect peanut yield response to Bradyrhizobium inoculant. Peanut yield increased in two of six experiments when Bradyrhizobium inoculant was applied. The increase in yield was observed in fields that did not have a known history of peanut production. Visible thrips damage was lower when prothioconazole was applied in absence of acephate, although acephate was more effective in minimizing injury from thrips than prothioconazole. Although acephate did not affect peanut yield, prothioconazole increased yield in all experiments regardless of acephate or Bradyrhizobium treatment. Results from these experiments indicate that acephate, inoculant containing Bradyrhizobium, and prothioconazole are compatible in peanut production systems.

Environmental impacts of peanut production system using life cycle assessment methodology

Agricultural activities emit the greenhouse gases and the other environmental contaminants to the atmosphere. Thus, the environmental impacts of agricultural activities have to be examined for identification, assessment and mitigation. In this study, life cycle assessment (LCA) methodology was used to determine the environmental impacts of peanut production system in Guilan province of Iran. These environmental impacts were classified into six impact categories including global warming, acidification, terrestrial eutrophication, depletion of fossil resources, depletion of phosphate and potash resources. Results indicated that the final indices for these six impact categories were calculated as 0.040, 0.216, 0.360, 3.98, 0.291 and 0.026 for one ton peanut production in this region, respectively. The depletion of fossil resources had wider negative effects on the environment. Farms of 0.1–0.5 ha showed the highest amount of global warming potential as well as the depletion of fossil resources. The environmental index and resource depletion index for one ton production of peanut were 0.62 and 4.30, respectively. Also, the final indices of global warming, acidification, terrestrial eutrophication, fossil, phosphate and potash resource depletion were revealed to be 0.0017, 0.0091, 0.0152, 0.168, 0.012 and 0.001 for generating 1000 MJ energy, respectively.

Interactions of agrochemicals applied to peanut; part 1: Effects on herbicides

Numerous agrochemicals are applied in peanut production systems. Field and laboratory experiments were conducted in North Carolina to characterize biological and physicochemical interactions when the herbicides clethodim, imazapic, imazethapyr, lactofen, sethoxydim, and 2,4-DB were applied in combination with adjuvants, fungicides, insecticides, and micronutrients. A wide range of interactions was noted when comparing across herbicides, weed species, and agrochemical combinations. There was little consistency across weed species for a herbicide or across herbicides for a weed species when comparing significant main effects and interactions. In most instances, when compared with the standard herbicide treatment and adjuvant applied alone, herbicide efficacy was not affected in the presence of other agrochemicals. Changes in solution pH and formation of precipitates varied according to the herbicide combinations used. Boron, manganese, and 2,4-DB often caused dramatic changes in solution pH.

Interactions of agrochemicals applied to peanut; part 3: Effects on insecticides and prohexadione calcium

A wide range of agrochemicals can be applied in a peanut production system to control various stresses and manage crop growth and development. Field and laboratory experiments were conducted in North Carolina to define biological and physicochemical interactions when insecticides (fenpropathrin and lambda-cyhalothrin) or plant growth regulator (prohexadione calcium) were applied in combination with other agrochemicals including fungicides, herbicides, and micronutrients. Fenpropathrin or lambda-cyhalothrin combinations did not injure peanut in 2008 and 2009. Two sprays of prohexadione calcium improved row visibility and reduced main stem height compared with one prohexadione calcium spray irrespective of agrochemical combinations. In many instances, applying prohexadione calcium with other agrochemicals resulted in lower main stem height compared to prohexadione calcium alone. In one of the experiments, prohexadione calcium with prothioconazole plus tebuconazole lowered fall army worm population compared with prohexadione calcium alone. Addition of boron, manganese, and 2,4-DB to fenpropathrin, lambda-cyhalothrin, and prohexadione calcium combinations changed solution pH dramatically. Prohexadione calcium had the least effect on pH of the carrier.

Peanut pod, seed, and oil yield for biofuel following conventional and organic production systems

Peanut (Arachis hypogaea L.) is a crop that can enter the human diet in various forms or be used as an alternative feedstock for livestock or industrial applications. Increased use of organic production systems and peanut's potential use as a biodiesel feedstock makes it increasingly necessary to develop organic methods in their production. Corn gluten meal (CGM) and vinegar are materials used in organic weed control. These were used alone, or in conjunction with cultivation, to evaluate their efficacy for weed control in peanut that had followed winter cover crops of red clover (Trifolium pratense L.) or wheat (Triticum vulgaris L.). Comparisons were made to conventional weed control (Dual®, S-metolachlor) and cultivation. Pod and oil yields and seed oil percentages were determined over 2 years in high oil cultivars Olin and Tam Runner. In 2009, cover crop, cultivar, and weed control treatments resulted in significant interactions impacting pod, seed oil yields, and seed oil percentages. Conventional weed control produced greater pod yields with clover (8220kgha−1) and wheat (7800kgha−1) cover crops, compared to all alternative weed control treatments. When averaged across cover crops, the conventional treatment produced greater seed oil yields (295.9Lha−1) and few differences in seed oil percentages. In 2010, the conventional weed control treatment produced superior seed oil yield and oil percentage for both cover crops and cultivars, and greater pod yields when the wheat cover crop was used for both cultivars; and Tam Runner with clover as a cover crop. Application of CGM and vinegar did not produce pod or oil yields at levels produced with conventional weed control, and/or reduced seed oil percentage. Further research should investigate additional alternative weed control systems that would increase weed control efficacy for organic peanut production systems.

Managing early leaf spot and stem rot with reduced fungicide inputs on disease-resistant peanut cultivars

Abstract Fungicide inputs are a costly but critical component of peanut production systems in the southeast U.S. Current strategies for reducing fungicide application numbers that are needed to control diseases on peanut include extending application intervals beyond a 2-wk schedule or implementation of a fungicide advisory, such as AU-Pnuts. In this study, fungicide programs with azoxystrobin, chlorothalonil, and tebuconazole, using different application schedules, were compared for the control of early leaf spot and stem rot. Application schedules were the standard 2-wk calendar interval, extended 3- and 4-wk intervals, and applications were made according to the AU-Pnuts leaf spot advisory. Studies were conducted on the disease resistant cultivars DP-1 in 2003 and C-99R in 2004 and 2005. The numbers of fungicide applications for the 2, 3, and 4-wk schedules were 7, 5, and 4, respectively, in 2003 and 2004, and were 6, 5, and 4, respectively, in 2005. One less fungicide application was scheduled according to AU-Pnuts than with the 2-wk calendar schedule in all three years, yet final early leaf spot levels with these schedules were similar in 2 of 3 years. With one fewer fungicide application, the 3-wk schedule had higher leaf spot levels than the AU-Pnuts advisory in 2003 and 2004. Further, when application intervals were extended from 2 wk to 3 or 4-wk intervals, a significant increase in early leaf spot was noted in two of three years. Despite these differences in early leaf spot severity, application schedule had limited impact on yield in this study. Application interval also had little impact on stem rot incidence, but incidence of this disease was lower with the azoxystrobin than chlorothalonil programs in 2 of 3 years. The azoxystrobin program significantly increased yield in 2 of 3 years compared with the chlorothalonil or tebuconazole programs. Yield was also higher for the tebuconazole compared with chlorothalonil programs in 2 of 3 years. When fungicide product and application costs were calculated, and those and other typical peanut production costs were deducted from estimated returns based on actual yields, the resulting net returns did not significantly differ among fungicide programs or application schedules.

THE ECONOMICS OF PEANUT PRODUCTION IN BULGARIA DURING THE TRANSITION PERIOD

We examined peanut production systems and selected factors affecting the development of commercial peanut enterprises in Bulgaria. A survey of 220 individual farms and farm cooperatives engaged in the cultivation of peanuts was conducted during 2000 and 2002. Poor farm structure, low level of technology, and nonconformity to farm decision making impede the financial and economic development of Bulgarian peanut production and farm growth, thus limiting farm enterprises emergence into competitive economic units financially operative in a freemarket economy. The underlying cost structure, couple with small farms, averaging 0.8 ha in size, prevent farmers from capturing economies of scale, limit farm profitability and hence farm modernization. The lack of owned farm machinery, equipment and storage facilities renders the restructuring and specialization extremely difficult. However, peanut production is still a viable farm enterprise for Bulgarian farmers.