Mancha de ramulária afeta a produtividade e qualidade da fibra em algodoeiro submetido à aplicação de fungicidas

A mancha de ramulária (MR) é a principal doença do algodoeiro no Brasil e uma das principais causas de redução na produtividade da cultura. A doença causa desfolha, reduz a capacidade fotossintética e provoca abertura precoce de capulhos. Devido a importância da doença para o algodão e da carência de publicações nessa área, neste se avaliou a eficiência de fungicidas no controle da MR em algodoeiro e mensurou os danos causados sobre a produtividade e a qualidade da fibra. Foram conduzidos três experimentos de nas safras 2014/15 e 2016/17, em Planaltina/DF e Cristalina/GO, seguindo o delineamento de blocos casualizados e os tratamentos foram compostos pelos fungicidas, além de uma testemunha. As aplicações foram iniciadas preventivamente e repetidas a cada 14 dias (6 pulverizações). As variáveis mensuradas foram a severidade da MR, com a qual foi calculada a área abaixo da curva de progresso da MR (AACPR), a produtividade e a qualidade da fibra do algodão. Os fungicidas avaliados reduziram significativamente a AACPR em relação à testemunha e obtiveram maior produtividade de algodão em caroço. As estrobilurinas (azoxistrobina, piraclostrobina e picoxistrobina) mostraram baixa efetividade no controle da doença. Os triazóis (difenoconazol, epoxiconazol, tetraconazol e metconazol) apresentaram desempenho superior às estrobilurinas. Maior eficiência de controle foi obtida pela aplicação de piraclostrobina + fluxapiroxade, piraclostrobina + epoxiconazol + fluxapiroxade e hidróxido de fentina. A MR reduziu a produtividade do algodoeiro e induziu danos de 14,8 a 31,7%, reduzindo a qualidade da fibra, impactando negativamente o micronaire, comprimento, resistência e uniformidade da fibra.Ramularia leaf spot (RLS) is the major cotton disease in Brazil and one of the main causes of crop yield reduction. The disease causes defoliation reduces photosynthetic capacity and causes premature opening of bolls. Due to the impact of RLS on the production of Brazilian cotton and the lack of scientific publications investigating the disease, the present work aims to evaluate the efficiency of fungicides in controlling disease and their impact on yield and fiber quality. Three field experiments were carried out during the 2014/2015 and 2016/2017 seasons in Planaltina, Federal District and Cristalina, Goiás. Experiments followed a randomized complete block design (4 blocks) and treatments consisted of the application of fungicides, plus a non-treated plot. The fungicide applications began preventively and were repeated every 14 days until six sprays had been completed. Severity of RLS was assessed and used to calculate the area under disease progress curve (AUDPC). Yield and cotton fiber quality were also evaluated. All fungicides had reduced AUDPC and obtained higher cotton yields in relation to the non-treated plot. Strobilurin-group fungicides (azoxystrobin, pyraclostrobin and picoxystrobin) showed low effectiveness when sprayed alone. The demethylation inhibitor fungicides (difenoconazole, epoxiconazol, tetraconazol and metconazole) were more effective than the strobilurins. The highest efficiency rates were achieved by application of pyraclostrobin + fluxapyroxad, pyraclostrobin + epoxiconazole + fluxapyroxad and fentin hydroxide. Disease severity affected cotton yield, causing losses from 14.8% to 31.7%. Resultant reductions in cotton fiber quality negatively affect the micronaire composition, altering the length, strength and uniformity of fibers

Reaction of soybean genotypes to cercospora leaf blight

Foram realizados dois experimentos em um delineamento em blocos ao acaso com três repetições, em Cristalina (GO), na sa¬fra de 2005/2006, para avaliar a reação de genótipos de soja convencional e transgênica (RR) ao crestamento foliar causado por Cercospora kikuchii. No experimento 1, foram avaliados 86 genótipos de soja convencional e no experimento 2, 30 genó¬tipos de soja convencional e transgênica quanto à reação ao crestamento foliar. Como padrões de genótipos convencionais foram usados Emgopa 313 e Msoy 8001 e como genótipos transgênicos Msoy 8585 RR e Msoy 8787 RR. Os genótipos com menor incidência (<1%) da doença no experimento 1 foram: GT04-7229, GT04-8987, GT04-8902, GT04-7991, GT04-8218, GT04-9501, GT04-7020, GT04-7505 e GT04-7439. No experimento 2, os menos afetados foram: GT04-7437 RR, GT04-9192 RR, GT04-8091 RR, GT04-8203, GT04-9265 RR e GT04-9085 RR. Não houve diferença na intensidade de doença entre genótipos transgênicos e convencionais. A intensidade do crestamento nos experimentos foi baixa (área foliar lesionada de 0 a 1,5% e incidência de 0 a 20%).This study evaluated the reaction of soybean genotypes (conventional and transgenic) to cercospora leaf blight (Cercospora kikuchii). Two experiments in a completely randomized block design with three replications were carried out (Cristalina GO and Brasília DF, Brazil) during the crop period of 2005/2006. In the experiment 1, 86 non-transgenic genotypes were evalu¬ated, while in the experiment 2, 30 transgenic (RR) and non-transgenic genotypes were tested. For comparisons purposes the following genotypes were used: conventional Emgopa 313 and Msoy 8001, and transgenic Msoy 8585 RR and Msoy 8787 RR. The genotypes with lower levels of disease incidence (<1%) were: experiment 1 - GT04-7229, GT04-8987, GT04-8902, GT04-7991, GT04-8218, GT04-9501, GT04-7020, GT04-7505 and GT04-7439; experiment 2 - GT04-7437 RR, GT04-9192 RR, GT04-8091 RR, GT04-8203, GT04-9265 RR and GT04-9085 RR. There was no significant difference in disease intensity between transgenic and non-transgenic genotypes and the Cercospora leaf blight intensity reported in this study was low when considering lesions on leaf area (< 1.5%) and disease incidence (< 20%)

Patterns of urediniospores release and development of rose apple rust

O objetivo deste trabalho foi avaliar padrões epidemiológicos de campo do fungo (Puccinia psidii Winter) que causa a ferrugem em jambeiro (Syzygium jambos). Entre 29/3 e 31/12/1988, levantou-se a incidência da doença e a população aérea de urediniósporos, na Universidade de Brasília, DF. Avaliaram-se dez plantas, sendo que, entre duas delas, instalou-se uma armadilha Burkard caça-esporos de sete dias. A maior quantidade de urediniósporos capturada foi de 23 de junho a 6 de julho. A principal carga de esporos ocorreu de maio a julho, entre as 10h e as 13 horas. Os maiores números de brotos de jambeiro com pústulas esporulantes ocorreram entre 28 de abril e 20 de julho. O número de brotos terminais infectados foi positivamente correlacionado com a quantidade de esporos. A temperatura (às 12h) foi negativamente correlacionada com a quantidade de urediniósporos dispersos no ar. O número de dias com umidade relativa (UR) do ar (às 24h) ³80% foi positivamente correlacionado com a quantidade de brotos deformados. A quantidade de urediniósporos foi positivamente correlacionada com o número de dias com temperatura £20oC e UR(24h) ³80%. Ao maior pico de urediniósporos capturados precedeu um período sem precipitação, porém com vários dias de UR(24h) ³80% e temperatura £20oC. Estes dados mostraram que a doença foi favorecida por temperaturas £20oC e por UR noturna ³80%.This research was conducted to evaluate some epidemiological features of the rose apple (Syzygium jambos) rust (Puccinia psidii Winter) under field conditions at the Universidade de Brasília, Brasília, DF, Brazil, from March 29 through December 31, 1988. Data for the amount of airborne urediniospores were collected in ten plants, using a Burkard's seven-day volumetric spore trap set between two rose apple trees. Most of the airborne urediniospores were collected between June 23 and July 6, from 10 a.m. to 1 p.m. The major quantity of S. jambos affected shoots occurred between April 28 and July 20. There was a positive correlation between the amount of trapped urediniospores and infected young shoots. A negative correlation was shown between temperature (12h) and number of airborne urediniospores. The number of days with relative humidity (RH) ³80% was positively correlated to the amount of deformed shoots. Also, the amount of urediniospores and infected young shoots were positively correlated to the number of days with night (24h) temperature £20oC or night RH³80%. These data show that this disease was favored by low temperatures (£20oC), high night RH (³80%) and high levels of airborne urediniospores

Row spacing, cultivar and fungicide application affect the incidence of soybean stem blight

Brazil is a major soybean production country and cultivate yearly more than 36 million hectares. Several factors have been reported reducing soybean production and occurrence of diseases is one of the most important. Some diseases such as the pod and stem blight (Diaporthe phaseolorum var. sojae) can limit soybean yield by shortening plant cycle and reducing seed quality. Field experiments were conducted aiming to evaluate the effect of row spacing, soybean cultivar and fungicide application on the incidence of pod and stem blight on soybean. The trial was carried out twice, with planting date at 11/15/2012 and 12/15/2012, in Planaltina-DF, Brazil. Treatments were arranged in a split-split plot scheme obeying the randomized block design. The factors evaluated were row spacing (42, 60 and 75 cm), soybean cultivars (“Syn1180RR” and “Syn1080RR”) and spray or not the fungicide Boscalid (500 g a.i./ha) at R1 and R3 soybean growth stages. Disease incidence was assessed on stems at the harvest time and on seeds after harvest and yield was estimated. Results obtained show that broader row spacing increased disease incidence on stems and seed, cultivar “Syn1180RR” was more susceptible than “Syn1080RR” and fungicide application reduced disease incidence. Pod and stem blight significantly reduced soybean yield

Pós-secos de kudzu, mucuna e casca de pinus adicionados ao solo aumentam a população microbiana e diminuem a murcha por esclerócio em soja

Southern blight (Sclerotium rolfsii) of soybean (Glycine max) is an important disease throughout the world. Some soil amendments can reduce disease levels by improving soil microbial activity. The main goals of this study were to investigate the effects of soil amendments such as dried powders of kudzu (Pueraria lobata), velvetbean (Mucuna deeringiana), and pine bark (Pinus taeda), on soil microbial population and disease caused by S. rolfsii on soybean. Pine bark, velvetbean (mucuna) and kudzu (25 g kg-1) added to soil were effective in reducing disease incidence [non-amended (NA) ~ 39%; amended (A) ~ 2 to 11%)]. Bacillus megaterium was the bacteria most frequently isolated in soils with velvetbean or kudzu (NA ~ log 5.7 CFU g-1 of dried soil; A ~ log 6.2). Soils with velvetbean and kudzu stimulated increase in population of Enterobacter aerogenes (NA ~ log 3; A ~ log 5.1-5.8). Pseudomonas putida population was higher in A than in NA (NA ~ log 4; A ~ log 5.5), and was negatively correlated (r = -0.83, P = 1%) to disease incidence. Soil amended with kudzu and pine bark stimulated increases in populations of Trichoderma koningii (NA ~ log 1.6; A ~ log 2.9) and Penicillium citreonigrum (NA ~ log 1.3; A ~ log 2.6), respectively. Penicillium herquei soil population increased with addition of kudzu (NA ~ log 1.2; A, ~ log 2.5). These microorganisms are antagonists of soil-borne pathogens. Powders of velvetbean, kudzu, and pine bark can increase antagonistic population in soil and reduce disease

Efeitos de resíduos orgânicos no solo na germinação de esclerócios, no crescimento micelial e na ocorrência de doenças induzidas por Sclerotium rolfsii

The addition of organic residues to soil is an option to control some soil-borne diseases. Benzaldehyde and powders of kudzu (Pueraria lobata), velvetbean (Mucuna deeringiana), and pine-bark (Pinus elliottii and P. taeda) added to soil could reduce certain soil-borne diseases. This study evaluated the effects of benzaldehyde and the dried powders of kudzu, velvetbean, and pine-bark as soil amendments on germination and formation of sclerotia, on mycelial growth of Sclerotium rolfsii, on plant survival, and disease incidence. The data showed that high amounts of benzaldehyde (0.4 ml kg-1 of soil) and velvetbean (100 g kg-1) inhibited S. rolfsii mycelial growth and sclerotium germination. However, low amounts of benzaldehyde (0.1 ml kg-1), kudzu (25 g kg-1), and pine-bark (25 g kg-1) stimulated mycelial growth and sclerotium germination. Kudzu (25-100 g kg-1) and velvetbean (25-100 g kg-1) inhibited the formation of sclerotia. Nevertheless, benzaldehyde at 0.2 and 0.4 ml kg-1 stimulated the formation of sclerotia. Kudzu (50 and 100 g kg-1) and pine-bark (50 g kg-1) favored the colonization of sclerotia by Trichoderma sp. The numbers of soybean (Glycine max) plants were higher and diseased plants were lower than the non-amend soil in the following treatments: kudzu (50 and 100 g kg-1), velvetbean (50 and 100 g kg-1), and pine-bark (50 g kg-1). Disease severity on tomato (Lycopersicon esculentum) plants was low in soil treated with kudzu or velvetbean (30 and 35 g kg-1) and pine-bark (35 g kg-1). Dried powders of kudzu, velvetbean, or pine-bark added to soil can reduce disease by reducing pathogen inoculum.The addition of organic residues to soil is an option to control some soil-borne diseases. Benzaldehyde and powders of kudzu (Pueraria lobata), velvetbean (Mucuna deeringiana), and pine-bark (Pinus elliottii and P. taeda) added to soil could reduce certain soil-borne diseases. This study evaluated the effects of benzaldehyde and the dried powders of kudzu, velvetbean, and pine-bark as soil amendments on germination and formation of sclerotia, on mycelial growth of Sclerotium rolfsii, on plant survival, and disease incidence. The data showed that high amounts of benzaldehyde (0.4 ml kg-1 of soil) and velvetbean (100 g kg-1) inhibited S. rolfsii mycelial growth and sclerotium germination. However, low amounts of benzaldehyde (0.1 ml kg-1), kudzu (25 g kg-1), and pine-bark (25 g kg-1) stimulated mycelial growth and sclerotium germination. Kudzu (25-100 g kg-1) and velvetbean (25-100 g kg-1) inhibited the formation of sclerotia. Nevertheless, benzaldehyde at 0.2 and 0.4 ml kg-1 stimulated the formation of sclerotia. Kudzu (50 and 100 g kg-1) and pine-bark (50 g kg-1) favored the colonization of sclerotia by Trichoderma sp. The numbers of soybean (Glycine max) plants were higher and diseased plants were lower than the non-amend soil in the following treatments: kudzu (50 and 100 g kg-1), velvetbean (50 and 100 g kg-1), and pine-bark (50 g kg-1). Disease severity on tomato (Lycopersicon esculentum) plants was low in soil treated with kudzu or velvetbean (30 and 35 g kg-1) and pine-bark (35 g kg-1). Dried powders of kudzu, velvetbean, or pine-bark added to soil can reduce disease by reducing pathogen inoculum

Aerobiology of Cercospora kikuchii

Neste estudo, foram quantificados os conídios de Cercospora kikuchii [crestamento foliar em soja (Glycine max)]presentes no ar, sua relação com a intensidade da doença e com os fatores ambientais [temperatura, umidade relativa do ar (UR), precipitação e molhamento foliar] no período de novembro a março de 2006/07 e 2007/08 em Brasília, DF. Para tanto, foi instalada uma armadilha volumétrica captaesporos ‘Burkard’ de sete dias em campo experimental com soja. Houve maior captura de conídios no período diurno, com mais de 60% dos esporos coletados entre 8h e 15h. Os dados climáticos variaram de acordo com a safra, mas, de modo geral, em ambos os experimentos, o período de maior captura de esporos ocorreu quando houve redução da precipitação e do molhamento foliar. A UR acima de 80% e temperatura entre 20 e 24ºC foram mais favoráveis para a captura de conídios e a intensidade do crestamento foliar. Nos dois anos de avaliação, a maior quantidade de esporo capturado ocorreu quando a soja se apresentava no estádio R6-R7, assim como a intensidade da doença foi maior após o início do estágio reprodutivo da cultura. Apesar da quantidade de conídio capturado em 2006/07 ter sido maior que em 2007/08, o padrão da flutuação aérea de conídios foi semelhante. _________________________________________________________________________________ ABSTRACTThe objective of this study was to evaluate the relation of airborne released conidia of Cercospora kikuchii [cercospora leaf blight of soybean (Glycine max)] with the disease intensity and some environmental factors [temperature, relative humidity (RH), precipitation and leaf wetness period) under experimental field conditions in Brasília, DF, Brazil. The evaluation was from November to March of 2006/07 and 2007/08. Data for the amount of airborne conidia were collected using a Burkard’s seven-day volumetric spore trap set in a field with soybean. Most of the conidia were collected during the day, with over 60% of the spores collected between 8h and 15h. Climatic data varied according to the crop period, but for both periods the highest amount of spores occurred with reduction of precipitation and leaf wetness period. RH above 80% and temperature from 20 to 24ºC were more favorable to capture of conidia and disease intensity. For both crop period of evaluation the major amount of spores were collected when plant stage was R6-R7, as well as, disease intensity increased after beginning of reproductive stage of soybean. Although the number of captured conidia in the 2006/07 crop period was higher than in 2007/08, the variation of fluctuation of airborne spores occurred similarly

Use of phosphites in postharvest to control anthracnose of yellow passionfruit

Brazil is the largest producer of yellow passionfruit (Passiflora edulis f. flavicarpa) and one of its production problems is the anthracnose (Colletotrichum spp.). The use of fungicides on control of postharvest diseases is a method that protects the fruits during storage. However, precautions must be taken due to fungicide toxicity. The restriction to the use of fungicides in post-harvest led a demand for alternative methods of disease control, and, the phosphite application is one of these methods. Therefore, this work aimed to evaluate the effects of fruit immersion in phosphite on postharvest control of anthracnose. Two tests were developed in vitro to assess the effect on the fungus: phosphite Mg2 (40%P2O5+6%Mg), Zn (40%P2O5+10%Zn), Ca1 (30%P2O5+7%Ca) and K1 (40%P2O5+20%K2O). For the in vivo tests, passionfruit (Gigante Amarelo), were wounded and inoculated (50mL; 106conidia mL-1). Two tests were done with: Cu (25%P2O5+5%Cu), 2.5mL L-1; Zn, 2.5mL L-1; K1, 2.5mL L-1; Mg1 (30%P2O5+4%Mg), 3mL L-1; Ca1, 3mL L-1; Ca2 (10%P2O5+6%Ca), 4mL L-1; K2 (40%P2O5+20%K2O), 1.5mL L-1; Mg2 (40%P2O5+6%Mg), 1.5mL L-1; K3 (20%P2O5+20%K2O) 1.75 mL L-1; K4 (30%P2O5+20%K2O), 1.75mL L-1. Other two tests with phosphites Mg2, Ca1, Zn and K1 were with CaCl2 (2%) was developed. In addition, phosphites were tested at 25, 50, 100 and 200% of the dose: K2 (100%; 1.5mL L-1) and Ca1 (100%; 3 mL L-1). The phosphites Mg2, Ca1, K1 and Zn in vitro have reduced mycelial growth and fungus conidia production. The phosphites K1, K2, Ca1 and Zn were the ones that most reduced the size of the anthracnose lesion. There were no differences among treatments, concerning the physico-chemical fruit properties analyzed (% fresh mass loss, total soluble solids, pH and titratable acidity)

Pós secos de mucuna e casca de pinus adicionados ao solo reduzem a doença causada por Rhizoctonia solani em soja

As doenças em soja (Glycine max) causadas por Rhizoctonia solani são um sério problema ao redor do mundo. A incorporação ao solo de resíduos orgânicos é uma alternativa para o controle destas doenças. Neste estudo, benzaldeido e pós-secos de kudzu (Pueraria lobata), mucuna (Mucuna deeringiana) e casca de pinus (Pinus spp.) foram usados com o objetivo de melhorar o crescimento de plantas de soja e de diminuir a doença causada por R. solani (AG-4). Benzaldehyde (0,1-0,4 mL/kg de solo) e mucuna (25-100 g/kg) reduziram significativamente (P < 0.05) o crescimento micelial de R. solani em experimentos de laboratório. Em experimentos conduzidos em casa de vegetação a porcentagem de plantas sobreviventes foi maior em solo com casca de pinus e mucuna (50-100 g/kg). Em solo tratado com kudzu (r²=0,91) ou mucuna (r²=0,94), houve tendência significativa em aumentar a massa fresca das plantas de soja. Em microparcelas de campo solos com mucuna (r²=0,85) ou com casca de pinus (r²=0,61) reduziram significativamente a quantidade de doença. A quantidade de Bacillus megaterium (r²=0,87) e Trichoderma hamatum (r²=0,92) e a hidrólise de diacetato fluoresceina (r²=0,91) foram maiores em solo com doses crescentes de mucuna, indicando uma maior atividade microbiana. Neste estudo conclui-se que pós-secos de mucuna e casca de pinus, incorporados ao solo, podem reduzir a doença causada por R. solani em soja.Diseases induced by Rhizoctonia solani, like damping-off and root and stem rot on soybean (Glycine max), are a serious problem around the world. The addition of some organic material to soil is an alternative control for these diseases. In this study, benzaldehyde and dried powders of kudzu (Pueraria lobata), velvetbean or mucuna (Mucuna deeringiana), and pine bark (Pinus spp.) were used in an attempt to improve soybean plant growth and to reduce the disease R. solani (AG-4) causes on soybean. Benzaldehyde (0.1-0.4 mL/kg of soil) and velvetbean (25-100 g/kg) significantly (P < 0.05) reduced mycelial growth of R. solani in laboratory tests. In greenhouse experiments, the percentage of non-diseased plants was higher in treatments with pine bark and velvetbean (50-100 g/kg). In soil treated with kudzu (r²=0.91) or velvetbean (r²=0.94), increasing rates of these amendments tended to increase plant fresh mass. In microplot field conditions, soil amended with velvetbean (r²=0.85) and pine-bark (r²=0.61) significantly reduced disease on soybean. Numbers of Bacillus megaterium (r²=0.87) and Trichoderma hamatum (r²=0.92) and hydrolysis of fluorescein diacetate (r²=0.91) were higher in soil amended with increasing rates of velvetbean, indicating an increase in microbial activity. From this study it is concluded that dried powders of velvetbean and pine bark added to soil can reduce Rhizoctonia-induced disease on soybean

Efeitos da pulverização pré-colheita com thidiazuron sobre a qualidade e a maturação de frutos em macieiras

ABSTRACTApple trees, cultivars Gala and Fuji, were sprayed at full bloom with thidiazuron (TDZ) at the doses of 0, 5, 10, or 20 g (a.i.) ha-1 and fruit were assessed for quality and maturity. In both cultivars, the increase of TDZ dose had detrimental effects on fruit quality, causing a reduction of fruit red surface and an increase of percentage of fruit that was asymmetrical and with calyx-end rot. TDZ caused an increment of calyx-end aperture that might have increased calyx-end rot. TDZ increased density and the length : diameter (L : D) ratio of the fruit. The number of viable seeds was not affected by TDZ. TDZ resulted in a substantial delay of fruit maturity in ‘Gala’ but not in ‘Fuji’. TDZ also reduced soluble solids content (SSC) in ‘Gala’ and reduced titratable acidity in both cultivars. ______________________________________________________________________________ RESUMOMacieiras, cultivares Gala e Fuji, foram pulverizadas em plena floração com thidiazuron (TDZ), nas doses de 0; 5; 10 e 20 g (i.a.) ha-1, e os frutos avaliados em termos de qualidade e maturação. Em ambas as cultivares, o TDZ apresentou efeitos negativos na qualidade dos frutos, com redução na percentagem de cor vermelha na casca e aumento na percentagem de frutos assimétricos e com podridão carpelar. O TDZ causou aumento na abertura carpelar, o que pode ter ocasionado aumento de incidência de podridão carpelar. O TDZ aumentou a densidade e a relação comprimento : diâmetro (C : D) dos frutos. O número de sementes viáveis não foi afetado pelo TDZ. O TDZ retardou substancialmente a maturação dos frutos na cultivar Gala, mas não na cultivar Fuji. O TDZ reduziu os teores de sólidos solúveis totais na cultivar Gala e reduziu a acidez titulável em ambas as cultivares