Maximum Disease Intensity Research Articles

Biorational Approaches for Purple Blotch Disease of Garlic (Allium sativum L.) Incited by Alternaria porri (Ellis) Cif

Garlic (Allium sativum L.) is the second most important bulb crop after onion. It is a major spice crop. Garlic is attacked by many diseases, one of which is Purple blotch. This study was aimed to determine the effect of botanicals and bio-agent on purple blotch disease of garlic caused by Alternaria porri. The research work was undertaken at Central Research Farm (CRF) Sam Higginbottom University of Agriculture, Technology and Sciences, SHUATS, Naini, Prayagraj during Rabi in 2022-23. A randomized block design with eight treatments was employed including T0 (Control - untreated) , T1 ( Azoxystrobin @0.1% as treated check), T2 (Trichoderma harzianum @10g/litre) , T3 (Lantana camara leaf extract @10%), T4 (Azadirachta indica leaf extract @10%), T5 (Henna leaf extract @2% + Licorice root extract @2% + Rosemary leaf extract @2% ), T6 (Licorice root extract @10%) and T7 (Neem cake @50g/m2). The treatments led to significant decrease in purple blotch severity in garlic.The results revealed that among the treatments, T7 showed minimum disease intensity (4.33, 18.74 and 26.35%) at 30, 60 and 90 days after sowing (DAS) respectively; while maximum disease intensity was recorded in T0 (10.42, 25.52 and 34.68%). T7 also recorded maximum plant height (24.02, 34.01 and 45.71cm) at 30, 60 and 90 DAS, respectively and highest yield of 4.46t/ha. Maximum number of leaves were recorded with T3 (5.53, 7.5 and 9.4) at 30, 60 and 90 DAS respectively. Fungicide usage is increasing day by day that can lead to negative effect on human and soil health in the long run, so there is need to find effective and economic alternatives preferably some bio-agents and botanicals.

Cardamom agro-environmental interrelationships analysis in Indian cardamom hills

The rainfall pattern seen in the Indian Cardamom Hills (ICH) has been extremely variable and complicated, with El Niño-Southern Oscillation (ENSO) playing a crucial role in shaping this pattern. In light of this, more investigation is required through improved statistical analysis. During the study period, there was greater variability in rainfall and the frequency of rainy days. About 2,730 mm of rainfall was reported in 2018, while the lowest amount (1168.3 mm) was registered for 2016. The largest decrease in decadal rainfall (>65 mm) was given by the decade 1960–1969, followed by 1980–1989 (>40 mm) and 2010–2019 (>10 mm). In the last 60 years of study, there has been a reduction of rainy days by 5 days in the last decade (2000–2009), but in the following decade (2010–2019), it registered an increasing trend, which is only slightly <2 days. The highest increase in decadal rainy days was observed for the 1970–1979 period. The smallest decadal increase was reported for the last decade (2010–2019). Total sunshine hours were the highest (1527.47) for the lowest rainfall year of 2016, while the lowest value (1,279) was recorded for the highest rainfall year (2021). The rainfall characteristics of ICH are highly influenced by the global ENSO phenomenon, both positively and negatively, depending on the global El Nino and La Nina conditions. Correspondingly, below and above-average rainfall was recorded consecutively for 1963–1973, 2003–2016, and 1970–2002. Higher bright forenoon sun hours occurred only during SWM months, which also reported maximum disease intensity on cardamom. The year 2016 was regarded as a poorly distributed year, with the lowest rainfall and the highest bright afternoon sun hours during the winter and summer months (January-May). Over the last three decades, the production and productivity of cardamom have shown a steady increase along with the ongoing local climatic change. Many of our statistical tests resulted in important information in support of temporal climatic change and variability. Maintaining shade levels is essential to address the adverse effects of increasing surface air temperature coupled with the downward trend of the number of rainy days and elevated soil temperature levels.

Efficacy of Bio-agents and Neem Oil against Alternaria porri (Ellis) in Onion (Allium cepa L.)

Onion (Allium cepa L.) is one of the important cultivated vegetable crops and can be grown in temperate, tropical and sub-tropical climates. It is the important vegetable and spice crop and known as “Queen of the kitchen”. Area, Production and Productivity on onion in India (2020-21) was 16.54 million ha, 26.92 million Tones and 19.40 t/ha. There are many diseases and pests affecting onion. Among the diseases, majorly purple blotch, downy mildew, Stemphylium blight and basal rot attacks the onion and among the pests, onion thrips, red spider mite, onion fly attacks the onion. Among them, purple blotch of onion is one of the most severe diseases, which is caused by Alternaria porri which causes heavy losses in the onion. The treatments viz., Trichoderma viride, Pseudomonas fluorescens, Bacillus subtilis and neem oil were tested under field conditions against Alternaria porri during Zaid for their efficacy against the growth and disease parameters and an untreated plot will serve as control. At desired interval of days (45,60,75 DAT) readings were taken for growth parameters and disease intensity. Based on single trail, it was observed that among all treatments, seedling treatment with Trichoderma viride + Pseudomonas fluorescens + neem oil @ 5% showed the most significant results with maximum growth parameters and minimum disease intensity results followed by Trichoderma viride + Bacillus subtilis + neem oil @ 5% and the minimum growth parameters and maximum disease intensity was shown in untreated (control) plot.

Occurrence of early leaf spot disease (Cercospora arachidicola Hori.) of groundnut (Arachis hypogaea L.) in Bikaner region of Rajasthan

Groundnut (Arachis hypogaea L.) is the major oil seed legume crop in the world. The production and productivity of groundnut is highly affected by collar rot, early leaf spot, Late leaf spot, rust and stem rot diseases. Among the foliar fungal diseases, early leaf spot (ELS) caused by Cercospora arachidicola Hori is one of the most destructive disease in Rajasthan. The early leaf spot infected leaves of groundnut was found to produce typical symptoms, such as presence of light brown to black circular to irregular lesions with chlorotic hallow on the upper surface of the leaves. A proper investigation needs a perfect scrutiny. So, the survey was carried out during Kharif-2019 in the three major groundnut growing tehsils (Nokha, Lunkaransar and Shri Dungargarh) of Bikaner district revealed that none of the locations were free from the disease. However, maximum disease intensity of early leaf spot was observed in Shri Dungargarh tehsil (25.87%) followed by Lunkaransar tehsil (19.32%) at the crop age 45-60 days after sowing.

Downy Mildew Disease Severity on Different Dates of Sowing Under Variable Weather Conditions in Different Varieties of Isabgol

The downy mildew incited by Peronospora plantaginis Underwood is one of the economically important diseases of Isabgol. It is important to study and understand the role of different dates of sowing on the development of diseases and their eco-friendly management. The downy mildew symptoms appeared in four different varieties viz. GI-2, Niharika, H1-5, and HI-2009 sown on 28th October (1st DOS) on 74-76 DAS whereas it was 52-54 days when sown on 12th November (2nd DOS) and 51-52 days on the crop sown on 28th November (3rd DOS). The maximum disease intensity of 62.77% was observed during the second date of sowing and the least disease intensity was recorded on the third date of sowing (27.77%). The maximum average disease progression (7.50 cm) was observed on the first date of sowing and a minimum of 6.49 cm on the third date of sowing. As the disease intensity increased AUDPC values also increased and these values were almost similar for all four varieties with the date of sowing. The apparent infection rate increased to a greater extent from the first date of sowing to the second date of sowing thereafter, decreased during the third date of sowing.

Evaluation of Bush Type Common Bean (Phaseolus vulgaris L.) Genotypes for Morphological Characters and Anthracnose under Cold Arid Ladakh Conditions

In the present study 25 bush type common bean genotypes were evaluated for their adaptability, performance of yield, maturity and anthracnose disease. Among 25 genotypes, ten were red in colour, five were brown in colour, four genotypes were white, two purple and one each was black, pink, yellow and chocolate in colour. For seed shape, 16 genotypes were kidney shaped, 3 were oval, cylindrical and cuboidal. For seed coat pattern, 19 genotypes were plain and 6 were mottled. Seed size revealed that out of 25 genotypes, 6 were large, 17 were medium and two were small. Out of 25 genotypes, 14 were having green colour pods, 10 were yellow and one light green in colour. The pod curvature revealed that 15 genotypes were having medium pod curvature, 7 were curved and 3 genotypes were having straight pod curvature. WB-185 was earliest to flower, whereas WB-956 was earliest to maturity. Highest pod length was recorded in WB-185where as lowest was recorded in local Ladakh and WB-257. Maximum seeds per pod were recorded in genotype WB-185 whereas minimum seeds per pods were recorded in WB-956. Highest plant height was recorded in genotype WB-1690. Highest value for 100 seed weight was recorded in WB-966 and lowest value was recorded in WB-6. Highest yield per plant was recorded in WB-185 and lowest yield per plant was recorded in WB-1129. Analysis of variance revealed that the genotypes exhibited significant variability for all the traits. Screening of genotypes against anthracnose revealed that maximum disease incidence was shown by WB-1690 followed by WB-257, WB-1643, WB-956 and WB-1129. Maximum disease intensity was shown by WB-1690 while lowest disease intensity was recorded in WB-719.

Management leaf spot of field bean (Lablab purpureus L.) caused by Alternaria alternata (Fr.) Keissler

In present studies, 18 genotypes of field bean were screened under natural epiphytotic conditions in field against Alternaria leaf spot at Dapoli (M.S) location revealed that, disease intensity was less in DPLW-2010-7-4-1-31 (25.24 %). Maximum disease intensity was observed in DPLW-2010-6-1-1-8 (32.76 %). Remaining germplasm entries recorded the intensity in range of 26.93 % to 31.72 %. All the germplasm lines screened against Alternaria leaf spot were moderately susceptible. Among the fungicides evaluated in vitro, propiconazole 25 % EC @ (0.05 %) recorded complete inhibition of growth of the test fungus. Thiophanate methyl 70 % WP (0.1 %) was found to be less effective and it recorded mean colony diameter of 47.2 mm and also lowest per cent reduction over control (47.55 %). Field evaluation of different fungicides revealed that, propiconazole 25 % EC (0.05 %) was found most effective with least terminal disease intensity (12.57 %) and maximum yield of 11.11 q ha-1. It was followed by difenconazole 25 % EC @ 0.05 % (13.94 %).

Evaluation of fungicides management of powdery mildew (Erysiphe Polygoni DC) disease of field pea (Pisum Sativum L.) in Eastern U.P.

The experiment was conducted to find out the efficacy of some new fungicides against powdery mildew (Erysiphe polygoni DC.) in the experimental field of experiment was laid out during rabi 2018-19 at supervision of Asha Bhagwan Bax Singh P.G. College Ayodhya, in the 7 farmer's field of Ayodhya and Ambedkarnager district of Uttar Pradesh. The experiment consisted of nine treatments viz. T1- Flusilazole 12.5% @ 1.0 ml/l., T2- Azoxystrobin 18.2 % w/w % @ 1.0 ml/l., T3- Tricyclazole 18 % @ 1.5 g/letter, T4- Propiconazole @ 1.0 ml/l., T5- Trifloxystrobin 25% @ 1.0 g/l, T6- Difenoconazole 11.4 % w/w SC @ 1.0 ml/l., T7- Mancozeb 50% @ 1.5 g/l., T8- Hexaconazole 4%WP @ 1.5 g/l.and T9- Untreated control (Spray of plain water), were applied the recommended dose of each product, were applied at the onset of disease. Minimum disease severity was recorded in propiconazole (8.58 % and 10.12 % at 10 and 20 days after spray respectively) followed by Azoxystrobin 18.2 % w/w (9.33 % and 11.17 % at 10 and 20 days after spray respectively) and significantly maximum disease intensity was observed in mancozeb (26.28 % and 29.13 % at 10 and 20 days after spray respectively) as compare to control (31.10 & 38.80%). The maximum pod yield of treated with propiconazole 11.13 t/ha increase over control 114.03% followed by Azoxystrobin 18.2 % w/w 10.18t/ha respectively.

Evaluation of different fungicides and antagonists In vitro and In vivo condition against Alternaria blight of pigeonpea

Efficacy of bio agents and systemic and non-systemic fungicides @ 50, 100, 200, 250 and 500 ppm were evaluated In vitro against Alternaria tenuissima causing Alternaria blight of pigeonpea. The relative efficacy of bio agents were studied in dual culture plate method showed that Hypocrea rufa was found most effective antagonist against test pathogen followed by T. harzianum. Efficacy of six fungicides was tested in poisoned food technique. Among the six fungicides tested, mancozeb was found most effective against test pathogen followed by Chlorothalonil and Iprodione. Propineb was least effective against mycelial growth of test pathogen. Raise in concentration of fungicides was more effective in inhibiting the mycelial growth of the pathogen. Field condition studies were found out to be the effect of seed treatment, foliar spray, seed treatment+ foliar spray with six fungicides and two bio agents and their combination used as against pathogen. Artificial inoculation of mass culture of A. tenuissima was done in the inoculated seed treatment and after foliar spray on the plants sixty DAS. Amongst them twenty five treatments, combination of Mancozeb with H. rufa was found most effective in reducing the disease intensity and disease control followed by Mancozeb with T. harzianum and Mancozeb alone, respectively. While, T. harzianum alone was least effective and maximum disease intensity recorded as a compared to control followed by T. harzianum with double dose and T. harzianum and H. rufa combination treatment, respectively. In case of both seed treatment and foliar spray of Mancozeb with H. rufa was found most effective in reducing the disease intensity and disease control followed by combination of Mancozeb with T. harzianum and Mancozeb alone, respectively. Whereas, least effective and maximum disease intensity and disease control were observed T. harzianum alone as compared to control.

Relationship of Bacterial Leaf Blight Disease of Cotton with Different Weather Parameters Under South Gujarat Condition of India

Abstract Cotton is a soft, fluffy staple fiber that grows in a boll, around the seeds of the cotton plants of the genus Gossypium in the family Malvaceae. Bacterial blight of cotton, also know as angular leaf spot, boll rot, and black leg, is a potentially destructive bacterial disease of cotton production. The disease caused by Xanthomonas campestris pv. malvacearum (Smith) Dye (synonyms Xanthomonas malvacearum (E.F. Sm) Dowson) is one of the most important and serious disease in cotton crop. Main objective of present research is to study the progress of the bacterial blight disease of cotton (BLB), caused by Xanthomonas campestris pv. malvacearum (Smith) Dye, with relation to the environmental parameters. This is a common disease affecting the growth, development and yield of cotton. A field trial was conducted to determine the influence of environmental factors, viz. rainfall periods, temperature, sun shine hours and humidity on the development of disease. Bacterial blight disease was recorded with its appearance and subsequently at weekly interval till it prevailed on G. Cot. Hy.12 (Non Bt). The incidence of bacterial blight disease (BLB) was noticed during 28 to 49th standard week with the maximum disease intensity in third week of September (23.5% PDI). None of the abiotic factors had significant influence on bacterial blight disease progress and development.

Role of weather factors in development of late leaf spot (Phaeoisariopsis personata) on groundnut (Arachis hypogaea)

The field experiment was conducted during Kharif 2012 and 2013 to find out the influence of weather parameters viz., temperature, relative humidity, rainfall, rainy days and wind velocity on the intensity of late leaf spot disease and defoliation in four groundnut cultivars viz., JL-24, LGN-1, TAG-24 and TG-26. The prevailing weather condition viz., average temperatures of 30.92 °C (max.) and 22.31 °C (min.), average RH of 89.67 % (morning) and 64.25 % (evening), well distributed average rainfall of 50.33 mm, average rainy days of 2.67 and average wind velocity of 4.24 km/hr were found to be conducive for the initiation, development and spread of late leaf spot disease in susceptible groundnut Cv. JL-24, TAG-24 and tolerant Cv. LGN-1, TG-26. As a result, overall average maximum disease intensity of 33.97 (21.96 to 46.37 %) per cent and 29.06 (18.62 to 39.01 %) per cent, were recorded in JL-24 and TAG-24, respectively. Groundnut Cv. JL-24 and TAG-24 (susceptible) exhibited comparatively maximum average defoliation in the range of 6.65 to 14.05 (Av. 10.29 %) and 5.64 to 11.82 per cent (Av. 8.80 %), respectively. The correlation coefficient between weather variables and disease intensity in both the years indicated that maximum temperature had negative and non significant effect in all the groundnut cultivars; whereas, minimum temperature had positive and significant effect on the disease intensity in all the groundnut cultivars. Relative humidity (morning and evening) played significant positive role on the disease intensity in all the groundnut cultivars.

Effect of fungicides on the mycelial growth of Alternaria alternata causing leaf spot disease in ashwagandha

A Leaf spot disease was caused by Alternaria alternata ten isolates were collected from the ashwagandha growing different regions of Tamil Nadu. The virulence of the isolates were tested based on the Per cent Disease Index (PDI) and symptom expressed on the foliar surface. The maximum disease intensity of 65.13 PDI was recorded in Chempatti (I 6 ) isolate. The minimum disease intensity was recorded in I 10 from Cumbum (36.83 PDI). Seven fungicides viz., carbendazim(0.05%), mancozeb (0.2%) copper oxy chloride (1%), chlorothalanil (0.2%), fosetyl (0.1%), Ridomil MZ (0.05%) and dithane M 45(0.05%) were tested against A. alternata. Among the fungicides, the minimum diameter of mycelial growth of A. alternata (0.75cm) and maximum percentage of inhibition (91.34%) were recorded in mancozeb (0.2%). How to view point the article : Kalieswari, N., Raja, I. Yesu and Devi, M. (2016). Effect of fungicides on the mycelial growth of Alternaria alternata causing leaf spot disease in ashwagandha. Internat. J. Plant Protec., 9(1) : 153-157.

Preliminary Studies on Fungal Species Associated with Guava Fruit Drop Disease and Possible Management

Four phytopathogenic fungi i.e., Alternaria alternata, Lasiodiplodia theobromae, Fusarium semitectum and Pestalotiapsidii, were isolated from the dropped guava fruits collected from different orchards located at Beheira Governorate during 2013 and 2014 growing seasons. Disease incidence recorded higher percentages during 2013 than that of 2014 season. Pathogenicity of the isolated fungi was carried out on apparently healthy guava fruits, attached to its branches, collected from 15-year-old trees. Data show that maximum disease intensity was occurred on either petioles and/or fruits inoculated with mixture of fungal pathogens. These results indict that guava fruit drop might be a fungal disease complex when caused by certain phytopathogenic fungi. Four fungicides, i.e. Kemazed, Homai, Vacomil plus and Topas,were in vitro evaluated for their efficacies against the isolated pathogenic fungi. Moreover, the efficacy of four compounds i.e., hydrogen peroxide, potassium sorbate, potassium bicarbonate and calcium chelate, was in vitro evaluated as alternative control means against the growth of tested pathogenic fungi. In this concern, hydrogen peroxide and potassium bicarbonate recorded the highest performance against the tested fungi.Under natural field infection, chemical control trails cleared that the efficiency of Homai 80% WP and Kemazed 50% WP reached 69.0 and 78.8%, respectively, as compared to the check treatment. It is worth to note that the concerned disease could be controlled by applying either of Homai 80% or Kemazed 50% at the rate of 70 g/100 l water.

Effect of bioagents and fungicide against earlyblight disease of tomato (Lycopersicon esculentum L.)

An experiment was conducted to evaluate the effect of bio agents (Trichoderma harzianum and Pseudomonas fluorescens) and fungicides (mancozeb) against earlyblight of tomato caused by Alternaria solani (Ell. and Mart.) at the experimental field of Department of Plant Protection, Sam Higginbottom Institute of Agriculture, Technology and Sciences, Allahabad during Rabi Season (2013-2014). Seven treatments including control with three replications were taken up using RBD. The treatments comprised of seed treatment and foliar spray (once and twice) of bio-agents Trichoderma harzianum and Pseudomonas fluorescens while fungicide taken up was mancozeband Control (spray of plain water) was applied. Observation for percent disease intensity was recorded at 70, 90 and 105 days after transplanting. Minimum disease intensity was recorded in mancozeb with twofoliar spray (15.43%, 17.90% and 20.47%, respectively) as compared to control which recorded maximum disease intensity (25.50%, 33.47%, and 48.73%, respectively).The bio agents Trichoderma harzianum and Pseudomonas fluorescens (seed treatment + two foliar spray) were also effective in reducing the disease intensity.

Relationship between ascochyta blight on field pea (Pisum sativum) and spore release patterns of Didymella pinodes and other causal agents of ascochyta blight

Ascochyta blight of field pea, caused by Didymella pinodes, Phoma medicaginis var. pinodella, Phoma koolunga and Didymella pisi, is controlled through manipulating sowing dates to avoid ascospores of D. pinodes, and by field selection and foliar fungicides. This study investigated the relationship between number of ascospores of D. pinodes at sowing and disease intensity at crop maturity. Field pea stubble infested with ascochyta blight from one site was exposed to ambient conditions at two sites, repeated in 2 years. Three batches of stubble with varying degrees of infection were exposed at one site, repeated in 3 years. Every 2 weeks, stubble samples were retrieved, wetted and placed in a wind tunnel and up to 2500 ascospores g−1 h−1 were released. Secondary inoculum, monitored using seedling field peas as trap plants in canopies arising from three sowing dates and external to field pea canopies, was greatest in early sown crops. A model was developed to calculate the effective number of ascospores using predictions from G1 blackspot manager (Salam et al., 2011b; Australasian Plant Pathology, 40, 621–31), distance from infested stubble (Salam et al., 2011a; Australasian Plant Pathology, 40, 640–7) and winter rainfall. Maximum disease intensity was predicted based on the calculated number of effective ascospores, soilborne inoculum and spring rainfall over two seasons. Predictions were validated in the third season with data from field trials and commercial crops. A threshold amount of ascospores of D. pinodes, 294 g−1 stubble h−1, was identified, above which disease did not increase. Below this threshold there was a linear relationship between ascospore number and maximum disease intensity.

Effect of hail protection nets on apple scab in ‘Royal Gala’ and ‘Fuji’ apple cultivars

In commercial apple orchards in Southern Brazil, it is common to avoid hail damage by covering the trees with nets. However, this technology can affect the epidemiology of some apple diseases, specially the apple scab (AS). This study was carried out to assess the effects of both black and white hail netting on the temporal dynamics of AS disease in a commercial ‘Royal Gala’ and ‘Fuji’ apple orchard in a high-altitude region of Southern Brazil during two growing seasons. Apple trees on M9 rootstock, trained to a slender spindles and with a spacing of 3.5 m × 0.8 m, were left uncovered (control condition) or covered with black or white hail netting. The incidence and severity of AS were quantified biweekly from October to February by evaluating 100 leaves distributed randomly on four medium-height branches per plant with 12 replications. Disease progress curves were constructed and the epidemics were compared by four epidemiological measures: the beginning of symptom appearance (BSA), the time to reach the maximum disease intensity (TRMDI), the maximum value of disease severity (Ymax), and the area under the disease progress curve (AUDPC). The highest intensity of AS was observed in the plants under the black hail netting. Reductions in BSA and TRMDI and increases in Ymax and AUDPC by the hail net were found in both ‘Royal Gala’ and ‘Fuji’ cultivars and growing seasons. Differences between white hail netting and control condition on BSA and TRMDI for AS were found in both cultivars and growing seasons. However, no differences between white hail netting and control condition on AUDPC for AS were found in both cultivars and growing seasons, except for ‘Fuji’ cultivar in 2004/05 growing season. The results of the study showed that the hail protection system using black hail netting is susceptible to increase the intensity of apple scab more than white hail netting.

The effect of hail protection nets on Glomerella leaf spot in ‘royal Gala’ apple

In commercial apple orchards in southern Brazil, it is common to avoid hail damage by covering the trees with nets. This study was carried out to assess the effects of both black and white hail netting on the temporal dynamics of Glomerella Leaf Spot disease (GLS) in a commercial ‘Royal Gala’ apple orchard in a high-altitude region of southern Brazil during two growing seasons (2003/2004 and 2004/2005). Apple trees on M9 rootstock, trained to a slender spindle and with a spacing of 5.5 m × 3 m, were left uncovered (control) or covered with black or white hail netting. The incidence and severity of GLS were quantified biweekly from October to February by evaluating 100 leaves distributed randomly on four medium-height branches per plant on each 12 replications per treatment. Disease progress curves were constructed from the data and the epidemics were compared by using four epidemiological measures: the beginning of symptom appearance (BSA), the time to reach the maximum disease intensity (TRMDI), the maximum value of disease severity ( Y max), and the area under the disease progress curve (AUDPC). The highest intensity of GLS was observed in the plants under the black hail netting. Significant reductions in BSA and TRMDI and significant increases in Y max and AUDPC were found among treatments in both growing seasons. However, no significant differences of GLS were found between the white hail netting and the control in either growing season.

Dinâmica temporal da mancha foliar da 'Gala' em macieiras conduzidas sob os sistemas de produção convencional e orgânico

Este trabalho objetivou avaliar a dinâmica temporal da Mancha Foliar da 'Gala' em macieira nos sistemas convencional e orgânico de produção, em condições edafo-climáticas do Planalto Catarinense. A incidência e severidade foram quantificadas quinzenalmente, em 100 folhas, distribuídas em quatro ramos da cultivar 'Royal Gala' com 12 repetições, gerando 16 mapas em cada sistema de produção. A severidade foi avaliada de acordo com escala diagramática específica. Com os dados obtidos, foram plotadas curvas de progresso da doença, e as epidemias foram comparadas em relação à a) início do aparecimento dos sintomas (IAS); b) tempo para atingir a máxima incidência e severidade da doença (TAMID e TAMSD); c) valor máximo de incidência e severidade da doença (Imax e Smax); e d) área abaixo da curva de progresso da incidência e severidade da doença (AACPID e AACPSD). Os dados de incidência e severidade foram analisados por meio de análise de regressão linear simples, sendo ajustados para três modelos empíricos, Logístico, Monomolecular e Gompertz. A cultivar 'Royal Gala' foi suscetível ao Colletotrichum sp., e as maiores intensidades de doença foram registradas no sistema de produção orgânico. O modelo mais apropriado para descrever o progresso da doença foi o Logístico e, por meio do uso da incidência, não foram detectadas diferenças significativas entre os sistemas de produção, porém a taxa de progresso da severidade da doença foi significativamente maior no sistema de produção orgânico do que no convencional.

Quantitative Modeling of the Effects of Temperature and Inoculum Density of Fusarium oxysporum f. sp. ciceris Races 0 and 5 on Development of Fusarium Wilt in Chickpea Cultivars

ABSTRACT Races 0 (Foc-0) and 5 (Foc-5) of Fusarium oxysporum f. sp. ciceris differ in virulence and induce yellowing or wilting syndrome, respectively, in chickpea. We modeled the combined effects of soil temperature and inoculum density of Foc-0 and Foc-5 on disease developed in chickpea cvs. P-2245 and PV-61 differing in susceptibility to those races, using quantitative nonlinear models. Disease development over time in the temperature range of 10 to 30 degrees C and inoculum densities between 6 and 8,000 chlamydospores g(1) of soil was described by the Weibull function. Four response variables (the reciprocal incubation period, the final disease intensity, the standardized area under the disease progress curve, and the intrinsic rate of disease development) characterized the disease development. Response surface models that expressed the combined effect of inoculum density and temperature were developed by substituting the intrinsic rate of disease development in the Weibull or exponential functions with a beta function describing the relationship of response variables to temperature. The models estimated 22 to 26 degrees C as the most favorable soil temperature for infection of cvs. P-2245 and PV-61 by Foc-5, and 24 to 28 degrees C for infection of cv. P-2245 by Foc-0. At 10 degrees C, no disease developed except in cv. P-2245 inoculated with Foc-5. At optimum soil temperature, maximum disease intensity developed with Foc-5 and Foc-0 at 6 and 50 chlamydospores g(1) of soil respectively, in cv. P-2245, and with Foc-5 at 1,000 chlamydospores g(1) of soil in cv. PV-61. The models were used to construct risk threshold charts that can be used to estimate the potential risk of Fusarium wilt epidemics in a geographical area based on soil temperature, the race and inoculum density in soil, and the level of susceptibility of the chickpea cultivar.

Análise temporal da sarna da macieira nas cultivares Royal Gala e Fuji sob os sistemas convencional e orgânico de produção

A sarna da macieira, causada por Venturia inaequalis, é uma das principais doenças da cultura. Devido à grande preocupação com os riscos de contaminação ambiental e intoxicação humana, o cultivo orgânico surge como uma alternativa, buscando preservar a qualidade do produto final em relação ao sistema convencional. Com o objetivo de avaliar a epidemiologia da sarna da macieira nos sistemas convencional e orgânico de produção, foi empregada a técnica de análise da dinâmica temporal, nas cultivares Royal Gala e Fuji, nas condições edafo-climáticas do Sul do Brasil. A incidência foi quantificada semanalmente, gerando 16 mapas em cada sistema de produção e quinzenalmente, a severidade da doença foi avaliada em 100 folhas, distribuídas em quatro ramos, de acordo com escala diagramática específica, com 12 repetições. Foram plotadas curvas de progresso da doença e as epidemias comparadas em relação a) início do aparecimento dos sintomas (IAS); b) tempo para atingir a máxima intensidade da doença (TAMID); c) valor máximo de severidade da doença (y max) e d) área abaixo da curva de progresso da doença (AACPD). Os dados de incidência foram analisados por meio de análise de regressão linear simples, ajustados para três modelos empíricos, Logístico, Monomolecular e Gompertz. As cultivares avaliadas foram suscetíveis à V. inaequalis, com diferenças significativas entre as cultivares e entre os sistemas de produção. Houve maiores níveis de intensidade de doença e taxa de progresso da doença (r) no sistema orgânico que no sistema convencional de produção, sendo que o modelo mais apropriado para descrever a curva de progresso da doença foi o Logístico.