Citrus black spot (CBS) symptom expression on sweet oranges has been reported to be affected by the fruit developmental stage and inoculum concentration in greenhouse conditions. However, there is little information concerning the period in which the fruit is susceptible in commercial orchards. This study assessed the influence of fruit age and inoculum concentration of Phyllosticta citricarpa on CBS intensity and fruit drop in the field. Two field trials were conducted in commercial 'Valencia' orchards in Sao Paulo state, Brazil. Fruit were inoculated from October (petal fall stage) to July (c.6.5 cm diameter), with 10(1), 10(3) and 10(5) pycnidiospores/ml. CBS symptoms and fruit drop were observed in higher levels for fruit inoculated from October to February than from March to July. In both trials, when fruit were inoculated 10 times from October to July or single-inoculated in November or December, high CBS severities of 11%-22% were observed and the proportion of fruit remaining on the tree was 48%-77%; in contrast, noninoculated fruit had severity below 1.1% and 90% remained on the tree. Inoculations in November or December of green fruit with 1.5-3.0 cm diameter using 10(5) pycnidiospores/ml were associated with higher CBS intensity and fruit drop and shorter incubation period than inoculations with lower concentrations. This work provides a better understanding of fruit stages and P. citricarpa inoculum concentrations most related to symptom expression and losses under natural conditions and may be helpful for improvement of CBS management in the Sao Paulo citrus belt.

Citrus black spot (CBS) may cause substantial yield loss in sweet orange orchards. Severity and distribution of CBS symptoms on fruit may be variable and not all affected fruit may fall. However, the relationship between CBS symptoms and yield loss has not yet been investigated. This study aimed to determine CBS characteristics associated with premature fruit drop. A set of fruit was removed from the tree to measure the detachment force and another set of dropped fruit was collected from Pera and Valencia sweet orange orchards in three municipalities in Sao Paulo state, Brazil. CBS severity, distance of the nearest lesion from the peduncle, and fruit peel colour were assessed in both fruit sets. CBS severity was consistently related with the force to remove fruit and hence associated to the premature fruit drop, irrespective of the cultivar and location. The segmented linear regression showed that the fruit detachment force was reduced abruptly, at a rate of 7% for every 1% increase in disease severity up to 4.2 +/- 1.0% CBS severity and, above this breakpoint, the force decreased slightly at a rate of 1.5%. Taking into account all orchards, the proportion of dropped fruit with CBS severity higher than the breakpoint was approximately 90%. This study provides a better understanding of the relationship between CBS severity and premature fruit drop of sweet orange. CBS severity breakpoint may be used as a reference to anticipate harvest and reduce CBS-related yield loss in orchards intended for juice processing.

Background Despite technical improvements in the citrus chain and leadership in orange production achieved in the past decades, premature fruit drop remains a major component of crop loss in Sao Paulo state citrus belt, the largest sweet orange production area in the world. The present study aimed to determine, during five consecutive seasons, the impact of the diseases and pests on premature fruit drop in the orange belt. Results Fruit drop due to the main diseases and pests averaged approximately 11.0%, which corresponded to approximately 63% of the annual fruit drop. The average fruit drop rate due to fruit borer and fruit flies combined was 4.0%, Huanglongbing (HLB) 3.3%, black spot 2.6%, leprosis 1.0% and citrus canker 0.3%. The average amount of fruit drop (million 40.8 kg boxes) and value of crop losses (million US$ dollars), in five seasons, were 12.7 and 66.2 for fruit borer/fruit flies, 11.0 and 57.9 for HLB, 8.1 and 42.2 for black spot, 3.1 and 15.6 for leprosis, and 0.9 and 4.9 for citrus canker, respectively. Conclusion Fruit borer and fruit flies (combined), HLB, black spot, leprosis and citrus canker are, in this order, the main diseases and pests in the orange belt of Sao Paulo state. All of these causes significantly increased the overall fruit drop rate in the evaluated seasons. The results will contribute to the development of the Brazilian citrus industry, while showing to other citrus-growing regions the potential that diseases and pests have to jeopardize production. (c) 2022 Society of Chemical Industry.

Copper is the most efficient pesticide for the control of citrus canker (Xanthomonas citri subsp. citri). To mitigate the environmental impacts and costs, the copper sprays in citrus orchards are being optimized based on the tree row volume (TRV). A previous investigation allowed for significant reductions of the spray volume and copper rates. Nevertheless, the results also indicated the need for additional studies. The aim of this work was to assess whether both the spray volume and the metallic copper rate based on the TRV may be further reduced. A field trial was carried out during two seasons in a 3-year-old commercial orchard of Pera sweet orange located in the municipality of Paranavaí, Paraná, Brazil. The volumes of 20 and 40 ml of spray mixture per m3 of the tree canopy were assessed in combination with the metallic copper rates of 10.5, 21.0, 36.8, or 52.5 mg/m3. Disease was measured as the temporal progress of canker incidence on leaves, cumulative dropped fruit with canker, and incidence of diseased fruit at harvest. The quality of sprays was assessed by measuring the copper deposition and leaf coverage. The treatment with the highest citrus canker control for the lowest use of water and copper was the combination of 40 ml and 36.8 mg/m3. Regression analyses indicated that the minimum threshold deposition of copper was ∼1.5 µg Cu2+/cm2 leaf area. In addition, the lowest spray volume and copper rate necessary to achieve this deposition are 35 ml/m3 and 30 mg/m3. The use of 20 ml/m3 did not efficiently control the disease due to the deficient coverage of treated surfaces. This study demonstrated that it is possible to use even lower amounts of copper and water without interfering with the efficiency of control of citrus canker.

The objective of this work was to assess yield losses due to stalk rot in corn ( Zea mays ) hybrids, as well as to identify the main pathogenic fungi responsible for the disease during the off-season, in the state of Tocantins, Brazil. Two field experiments were carried out, one with five hybrids, in 2015, and another with four, in 2016. Ears of healthy and stalk rot-infected plants were collected from each plot, at harvest. Ear size, grain and ear weights, and grain moisture content were measured. From each diseased plant, a stalk piece with two to three nodes was removed for pathogen identification and quantification. The most common pathogens were: Fusarium graminearum, Stenocarpella maydis, and Macrophomina phaseolina. All yield parameters were significantly lower in stalk rot-infected plants, with average losses of 30.6%, in 2015, and of 34.3% in 2016. The highest yield losses are observed in hybrids with the highest grain/ear weight ratio.

The objective of this work was to assess yield losses due to stalk rot in corn (Zea mays) hybrids, as well as to identify the main pathogenic fungi responsible for the disease during the off-season, in the state of Tocantins, Brazil. Two field experiments were carried out, one with five hybrids, in 2015, and another with four, in 2016. Ears of healthy and stalk rot-infected plants were collected from each plot, at harvest. Ear size, grain and ear weights, and grain moisture content were measured. From each diseased plant, a stalk piece with two to three nodes was removed for pathogen identification and quantification. The most common pathogens were: Fusarium graminearum, Stenocarpella maydis, and Macrophomina phaseolina. All yield parameters were significantly lower in stalk rot-infected plants, with average losses of 30.6%, in 2015, and of 34.3% in 2016. The highest yield losses are observed in hybrids with the highest grain/ear weight ratio.

The copper‐based products widely used for control of citrus canker may lead to the development of Xanthomonas citri subsp. citri ( X. citri ) resistant to copper (Cu R ). However, the study of copper sensitivity of X. citri strains from Paraná state, Brazil, did not reveal the existence of Cu R , but copper tolerant (Cu T ) strains. The aim of this study was to describe for the first time the existence of Cu T X. citri and compare the genetic determinants that differentiate the Cu T strains from the sensitive (Cu S ) and Cu R strains. Cu T strains supported intermediate concentrations of copper in comparison to Cu S and Cu R . Cu T strains lack the gene clusters cop LAB or cop ABCD responsible for copper resistance in Cu R strains and the large plasmids (c. ≥200 kb) that normally carry these genes. The nucleotide sequences of chromosomal homologous genes coh LAB , involved in copper homeostasis, were 100% similar in strains of all phenotypes. Cu T strains differed from Cu S strains by the higher expression of the homologous chromosomal genes cohA and cohB in the presence of copper. Cu T X. citri strains are not precursors of Cu R strains and do not pose a threat to the efficient use of copper‐based bactericides for management of citrus canker in citrus orchards. Copper resistance and tolerance are distinct phenotypes and should not be used as synonyms. The proper characterization of the sensitivity to copper leads to a more confident monitoring of the distribution of copper resistant populations of X. citri and adoption of containment measures only when necessary.

Artificial drying, although costly, ensures a safe storage and preserves post-harvest grain quality. Alternatively, a more cost-effective measure is to delay harvest to promote natural drying, but this management may increase the risk of mycotoxigenic ear rot fungi contamination. The objective was to evaluate the effect of increasing maize harvest delay on fungal disease and fumonisin levels. Three maize hybrids (BRS1035, Attack and DKB390 YG) were sown in the field to study the effect of five harvest delays (15, 30, 45, 60 and 75 days) after the optimum date (18% grain moisture). There was a significant trend of increasing the incidence of kernel rot and total fumonisins in the grains when delaying harvest, but fungal incidence and mycotoxin contamination varied with the hybrid. The main fungi detected in the grain samples were Fusarium verticillioides and Stenocarpella maydis. The hybrid DKB390 YG showed significantly lower incidence of F. verticillioides contamination and lower fumonisin accumulation in the grains than the other hybrids. The hybrid Attack was the least susceptible to kernel rot incidence. Our data shows that delaying harvest for minimizing drying costs may increase the risk of mycotoxin contamination in maize in the tropics of Brazil.

Citrus black spot (CBS), caused by Phyllosticta citricarpa, affects different citrus species worldwide. CBS is mainly expressed as false melanose and hard spot symptoms. There is no consensus in the literature about the period when fruit are susceptible to P. citricarpa infection and the length of the CBS incubation period. Therefore, this study aimed to assess the influence of sweet orange variety, fruit age, and inoculum concentration on the incubation period and the expression of different CBS symptoms. Attached fruit of Hamlin, Pera, and Valencia sweet orange at 1.5, 3.0, 5.0, and 7.0 cm diameter were inoculated with suspensions containing 103 and 105 conidia/ml of P. citricarpa. The percent conidial germination was quantified using scanning electron microscopy. The CBS symptoms on fruit were assessed monthly. The four diameters did not significantly affect conidial germination on the inoculated fruit, although CBS incidences were lower when larger fruit were inoculated. Hard spot symptoms on sweet orange fruit did not develop from the false melanose symptoms and vice versa. The incubation periods for false melanose were shorter than those observed for hard spot. False melanose began to appear 44 days after inoculation, but hard spot only formed at 113 days or later. Incubation periods were shorter and incidences of false melanose were higher following inoculation with higher inoculum concentration and smaller fruit diameter. The incubation period of hard spot varied among varieties and fruit diameters. However, there was no relationship between hard spot incidence and variety. This study provides a better understanding of the factors affecting the variation in the CBS incubation period and disease incidence on fruit.

During the development of a citrus fruit, many cycles of infection by Xanthomonas citri subsp. citri may occur leading to the development of a range of characteristics of citrus canker lesions scattered across the fruit surface. This study aimed to determine whether the size of the lesions, their distance from the peduncle, and the number and time of appearance of the lesions on fruit of sweet orange were associated with premature fruit drop. A multiple linear regression analysis revealed a negative relationship between the fruit detachment force and the lesion diameter, the proximity of the nearest lesion to the peduncle and the number of lesions. A survival analysis demonstrated that these characteristics significantly influenced the probability and the time that a cankered fruit remained attached to the tree. More than 90% of dropped fruit had large lesions (>5 mm) but not all fruit with large lesions dropped before harvest. Approximately 50% of the harvested fruit had lesions >5 mm. On the harvested fruit remaining on the tree, although large, the lesions had a smaller diameter, were located farther from the peduncle, and were less numerous than those observed on dropped fruit. Small canker lesions neither reduced the detachment force nor the survival of fruit in the tree. The earlier a fruit expressed canker symptoms, the higher the probability the fruit developed large lesions near the peduncle and/or developed lesions in greater numbers. This study provides a better understanding on the relationship between the time of appearance of lesions of citrus canker on fruit and premature fruit drop. This information defines the critical period for fruit protection and may be used to improve disease management.

The period of citrus black spot (CBS) control used in South Africa (SA) and Australia, from October to January or February, has not been as effective in São Paulo (SP), Brazil. This study aimed to evaluate different periods of protection and determine the critical period for CBS control in SP. A field trial was carried out for two seasons in a mature Valencia sweet orange orchard located in Mogi Guaçu, SP. Spray programs with a total of 60, 100, 140, 180, and 220 days of fruit protection (DFP) were evaluated. CBS symptoms and fruit drop decreased exponentially as the length of the period of protection increased. The reductions in CBS intensity and crop loss with these programs ranged from 34 to 96 and 50 to 77%, respectively. The programs with 180 and 220 DFP, which protected the fruit from September to March and May, showed the highest cost benefit. The critical period needed for CBS control in SP is longer than that in SA and Australia. The results obtained with the present study are helpful for scheduling a more efficient and rational program for CBS control not only in SP but also in other tropical and subtropical regions with similar weather conditions.

The leaf anthracnose disease in sorghum, caused by Colletotrichum sublineolum (Henn. ex Sacc. & Trotter), is widely distributed throughout its Brazilian cultivation areas. The disease can cause significant losses in grain yield and quality. This study aimed to quantify the effects of leaf anthracnose on grain yield of different sorghum genotypes. Two elite inbred lines of sorghum, BR009 (susceptible) and BR008 (moderately resistant), and the hybrids, BR304 and MR43 (susceptible), BRS310 and DKB599 (moderately resistant) and BRS308 and AG1060 (resistant), were planted in a complete randomized block design with three replicates. The disease severity (DS) was evaluated weekly, starting from the onset of the first foliar symptoms, and yield losses were estimated using linear regression analysis. Leaf anthracnose significantly reduced sorghum yields in the susceptible genotypes. The highest yield loss of 86% was observed in the inbred line BR009, when the disease severity reached 100%. For the hybrids, the grain yield loss varied from 35% (BRS310) to 72% (BRS308). According to the adjusted model, a grain yield reduction of 23.48kg/ha for BR304, 14.57kg/ha for BRS310 and 15.91kg/ha for DKB599 was observed for every 1% increase in disease severity. We demonstrate for the first time the effect of leaf anthracnose disease on grain sorghum yields under Brazilian conditions. The results from this study provide a starting point for developing new strategies for the integrated disease management of sorghum anthracnose.

Toxigenic fungi that infect corn grains are among the major problems in Brazil as they are associated with toxicological implications for both humans and animals. Mechanical-physical methods have been used to separate contaminated grains in lots of corn kernels based on the symptoms caused by fungi. The objective of this study was to assess whether the presence or the type of symptoms were associated with fungal incidence and total fumonisin levels in corn kernel samples from the field. Kernels of two hybrids were separated visually into three groups: 1) asymptomatic or symptomatic exhibiting 2) kernel rot or 3) kernel streak symptoms. A high frequency of Fusarium spp. was observed in asymptomatic (69.5%) and kernel rot (69.9%). Stenocarpella sp. and Penicillium sp. were found in kernel rot (16.0%) and kernel streak (44.1%), respectively. High fumonisin levels (7.24 μg.g- 1 ), above the maximum tolerated limit, were detected only in kernel rot. No association between fumonisin levels and the frequency of Fusarium spp. in kernels was found.

Copper bactericides have been widely studied and used for control of citrus canker caused by Xanthomonas citri subsp. citri. New formulations become available periodically, however, little is known about the relative efficacy of insoluble (ICuF) and soluble (SCuF) copper formulations and the performance of ICuF at the same metallic copper rates. In the present study, we compared three rates of five ICuF (syn. fixed copper) and two SCuF for control of citrus canker during two seasons in a commercial orchard of Valencia' sweet orange located in Paranavai, Parana, Brazil. Control of citrus canker was evaluated as the temporal progress of canker incidence on leaves, cumulative dropped fruit with canker, and incidence of diseased fruit at harvest. All copper formulations and rates reduced the progress of citrus canker incidence on leaves. However, SCuF were not as effective as the ICuF. The incidence of leaves with canker on trees treated with ICuF never exceed 73%. In contrast, incidence of leaf canker on trees treated with SCuF ranged from 9.9 to 44.8%. Fruit drop per tree due to citrus canker for trees treated with ICuF did not exceed 6.2 and 17.3 in seasons 1 and 2, respectively. These losses were significantly lower than 20.4 and 38.6, observed for the untreated trees. Fruit drop was 10.4 and 20.9 for trees treated with SCuF in seasons 1 and 2, respectively. The citrus canker incidence on harvested fruit followed the same trend observed for other variables assessed. A non-linear regression analysis showed that the metallic copper rate accounted for a large proportion of the variation in incidence of citrus canker on leaves, fruit and premature fruit drop up to 1 kg of metallic copper/ha/application. Rates exceeding 1 kg/ha of metallic copper did not consistently improve disease control or reduce the fruit loss. (C) 2017 Elsevier Ltd. All rights reserved.

HomePlant DiseaseVol. 100, No. 5First Report of Fusarium temperatum Causing Maize Seedling Blight and Seed Rot in North America PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Fusarium temperatum Causing Maize Seedling Blight and Seed Rot in North AmericaF. E. Lanza, D. A. Mayfield, and G. P. MunkvoldF. E. Lanza, D. A. Mayfield, and G. P. MunkvoldAffiliationsAuthors and Affiliations F. E. Lanza , CAPES Foundation, Ministry of Education of Brazil, Brasília/DF 70040-020, Brazil D. A. Mayfield G. P. Munkvold , Department of Plant Pathology and Microbiology, Iowa State University, Ames 50010. Published Online:3 Mar 2016https://doi.org/10.1094/PDIS-11-15-1301-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Fusarium subglutinans is an important toxigenic pathogen of maize in temperate regions, causing seedling disease, stalk, and ear rot (Munkvold et al. 2009). Recently, a population of Fusarium strains from maize, morphologically similar and phylogenetically closely related to F. subglutinans, was described as a new species, F. temperatum (Scauflaire et al. 2011). Fusarium temperatum has been reported from European countries, Argentina, China, and South Africa, but little is known about its occurrence and pathogenicity on maize in North America. In this study, EF-1α sequences were analyzed for 46 strains (originally identified as F. subglutinans) collected from maize ears with symptoms of Fusarium ear rot in Iowa (Munkvold et al. 2009). In addition, F. temperatum strains M-7330 and NSM225 were used as reference controls (R. Proctor, personal communication). For all strains, the EF-1α gene was sequenced using primers EF1 and EF2 (Scauflaire et al. 2011). The resulting sequences were compared via GenBank BLAST search. Partial sequences of gene EF-1α of three strains (Accession Nos. ISU93147-S, ISU95163, and ISU95227) showed 100% homology with F. temperatum strains (HM067687 and HM067688) and also with the control strains. Two of the strains (ISU95163 and ISU95227) had previously been identified as F. subglutinans Group 1 according to RFLP analysis (Munkvold et al. 2009). Sequences of all three F. temperatum strains were deposited in GenBank (KT447148, KT447149, and KT447150). Pathogenicity of the F. temperatum strains was confirmed using a modified rolled-towel assay (Ellis et al. 2011). Seeds of hybrid "Silver Queen F1" (Johnny's Seeds Company) were subjected to thermotherapy (55°C/5 min), then soaked in a spore suspension (107 spores/ml) at 25°C on a rotary shaker at 80 RPM for 48 h. Control seeds were subjected to thermotherapy and then kept in sterile distilled water. Inoculated and noninoculated seeds were placed in moist towels in a growth chamber for 7 days at 25°C and 80% humidity. All F. temperatum strains tested were pathogenic on maize. F. temperatum inoculated plants were significantly different from control plants for seedling blight severity (P < 0.05), germination (P < 0.05), shoot and root length and fresh weight (P < 0.05). Symptoms of infected plants occasionally included small brown lesions on the shoot and roots. Fusarium temperatum strain ISU93147-S caused the greatest reductions in germination (87.5%), shoot weight (85.0%), and root weight (82.4%) relative to the noninoculated controls (P < 0.05). F. temperatum strains were aseptically reisolated from inoculated seedlings, but not from the controls. To our knowledge, this is the first report of F. temperatum causing seedling blight and seed rot of maize in North America; however, it is likely that the previously reported cryptic species F. subglutinans Group 1 is synonymous with F. temperatum. If so, F. temperatum may be a common maize pathogen in North America, but previously reported as F. subglutinans. In our collection from Iowa, F. subglutinans was far more common than F. temperatum, but in a previous study (Desjardins et al. 2006), F. subglutinans Group 1 represented more than 50% of F. subglutinans isolates collected from various U.S. states.References:Desjardins, A. E., et al. 2006. J. Agric. Food Chem. 54:7383. https://doi.org/10.1021/jf0612272 Crossref, ISI, Google ScholarEllis, M. L., et al. 2011. Plant Dis. 95:401. https://doi.org/10.1094/PDIS-05-10-0317 Link, ISI, Google ScholarMunkvold, G. P., et al. 2009. Food Addit. Contam. 26:388. https://doi.org/10.1080/02652030802471239 Crossref, Google ScholarScauflaire, J., et al. 2011. Mycologia 103:586. https://doi.org/10.3852/10-135 Crossref, ISI, Google ScholarDetailsFiguresLiterature CitedRelated Vol. 100, No. 5 May 2016SubscribeISSN:0191-2917e-ISSN:1943-7692 Metrics Article History Issue Date: 15 Apr 2016Published: 3 Mar 2016First Look: 29 Dec 2015Accepted: 20 Dec 2015 Pages: 1019-1019 Information© 2016 The American Phytopathological SocietyCited byFirst Report of Fusarium temperatum Causing Fruit Blotch of Capsicum pubescens in Puebla, MéxicoM. A. K. Pérez-Vázquez, L. A. Morales-Mora, O. Romero-Arenas, A. Rivera, G. Landeta-Cortés, and N. Villa-Ruano21 April 2022 | Plant Disease, Vol. 106, No. 6Influence of Endosperm Starch Composition on Maize Response to Fusarium temperatum Scaufl. & Munaut8 March 2022 | Toxins, Vol. 14, No. 3Fusarium temperatumCABI Compendium, Vol. CABI CompendiumEtiology, Epidemiology, and Management of Maize Diseases26 October 2022Effects of water activity and temperature on fusaric and fusarinolic acid production by Fusarium temperatumFood Control, Vol. 114Fumonisin and Beauvericin Chemotypes and Genotypes of the Sister Species Fusarium subglutinans and Fusarium temperatumApplied and Environmental Microbiology, Vol. 86, No. 13Impact of Environmental Conditions and Agronomic Practices on the Prevalence of Fusarium Species Associated with Ear- and Stalk Rot in Maize21 March 2020 | Pathogens, Vol. 9, No. 3Potential of Novel Sequence Type of Burkholderia cenocepacia for Biological Control of Root Rot of Maize (Zea mays L.) Caused by Fusarium temperatum26 February 2019 | International Journal of Molecular Sciences, Vol. 20, No. 5A loop-mediated isothermal amplification (LAMP) assay for the rapid detection of toxigenic Fusarium temperatum in maize stalks and kernelsInternational Journal of Food Microbiology, Vol. 291Aggressiveness and Fumonisins Production of Fusarium Subglutinans and Fusarium Temperatum on Korean Maize Cultivars15 February 2019 | Agronomy, Vol. 9, No. 2Fusarium temperatum isolated from maize in France9 January 2017 | European Journal of Plant Pathology, Vol. 148, No. 4Fusarium Species and Their Associated Mycotoxins7 December 2016First Report of Fusarium temperatum in Diseased Sweet Corn Ears in the Western United StatesM. E. Ridout, G. Newcombe, and B. Godfrey13 September 2016 | Plant Disease, Vol. 100, No. 12

Resumo: O objetivo deste trabalho foi avaliar a eficiência da aplicação foliar de fungicidas na redução da incidência de patógenos fúngicos, de grãos ardidos e de fumonisinas totais em grãos de milho (Zea mays). Foram conduzidos três ensaios: um no município de Luís Eduardo Magalhães, na Bahia, e dois em Sete Lagoas, em Minas Gerais, nas safras 2010/2011 e 2011/2012, com cultivo de diferentes híbridos comerciais. Os seguintes fungicidas foram aplicados zero, uma e duas vezes: picoxistrobina + ciproconazol, piraclostrobina + epoxiconazole, trifloxistrobina + tebuconazole, azoxistrobina + ciproconazol e tiofanato metílico. Em todos os ensaios, foram realizados a quantificação da incidência de grãos ardidos, o teste de patologia de sementes e a quantificação dos teores de fumonisinas totais. Não foi observada diferença significativa para os fatores fungicida e número de aplicações, exceto para rendimento de grãos, em todos os ensaios. Esses resultados são indicativos da ineficiência da aplicação de fungicidas na redução da incidência de patógenos fúngicos, de grãos ardidos e dos teores de fumonisinas totais em grãos de milho.

Anthracnose stalk rot (ASR) disease caused by Colletotrichum graminicola can lead to major corn yield losses in Brazil.Studies on plant resistance and genetic variation in pathogen populations are required towards the development of ASR disease management strategies.However, the lack of adequate methods for C. graminicola inoculation in maize stalk has hindered these efforts.The main objective of the study was to develop a confident and feasible method for C. graminicola inoculation into maize stalk.Three inoculation methods were evaluated: TCMP (toothpick colonized by pathogen mycelium), TICS (toothpicks immersed in conidial suspension), and ICS (injection of conidial suspension).The effect of the internode position, the phenological stage, and the period of time required for maize reactions to ASR infection were also evaluated.The infection severity was assessed by a diagrammatic scale with six levels of severity from 0 (no necrotic spots) to 5 (100 % infection).The TICS was the best method, inoculation in the third internode and assessment of disease severity at tasselling stage (VT) 30 days after inoculation presented the more accurate results.The procedure was validated under field conditions.

ABSTRACT: Adoption of resistant cultivars is the primary measure used to control anthracnose stalk rot. The goal of this study was to identify maize-resistant genotypes to anthracnose stalk rot, which are similar to the hybrid 2B710. Experiments were performed at Embrapa Maize and Sorghum experimental fields in Brazil. The first experimental trial evaluated 234 maize lines as well as two commercials hybrids, BRS1010 (susceptible) and 2B710 (resistant). Artificial inoculations were performed with a strain at the blister (R2) phase, and evaluation of disease severity was performed after 30 days. The second experimental trial evaluated 48 maize lines and hybrids, inoculated with two Colletotrichum graminicola strains. In the first trial, eight resistance groups were formed, and the last lines were more resistant, as was the hybrid 2B710, with values between 11.50% and 23.0% of severity. In the second trial, there was an interaction between the two factors, lines and isolates, and the lines often showed the same reaction features as those obtained in the first trial. However, the disease severity was higher for most lines, even when using other isolates. These lines with effective levels of resistance could be used in future studies of inheritance, in programs to develop hybrids, and to identify molecular markers associated with resistance to anthracnose stalk rot in maize.