Fungicide Combinations Research Articles

The effect of biological agent and botanical fungicides on maize downy mildew

Abstract. Prasetyo J, Ginting C, Akin HM, Suharjo R, Niswati A, Afandi A, Adiwijaya R, Sudiono, Nurdin M. 2021. The effect of biological agent and botanical fungicides on maize downy mildew. Biodiversitas 22: 1652-1657. This study was conducted to evaluate the effect of the combination of Trichoderma asperellum and mycorrhizae with botanical fungicides made from betel leaf extract or turmeric extract against maize downy mildew. The study used a randomized complete block (RCB) design with three replications. The treatments applied were: single applications of T. asperellum (Ta); arbuscular mycorrhizal fungi (AMF); turmeric extract (T); betel extract (B); the combination of T. asperellum and AMF (TaM); turmeric extract and T. asperellum (TTa); turmeric extract and AMF (TM); turmeric extract + T. asperellum + AMF (TTaM); betel extract + T. asperellum (BTa); betel extract + AMF (BM); betel + T. asperellum + AMF (BTaM); and Control (C). The observed variables were disease incidence, incubation period, and shoot dry weight. The data were analyzed using ANOVA. Differences between treatments were tested by the LSD test at 5% significance level. The results showed that the combination of botanical fungicides with biological agents could reduce the incidence of downy mildew, extend the incubation period, and increase the dry weight of corn shoots. The best combination treatment was achieved from the combination of T. asperellum with betel extract. There was a synergistic effect between botanical fungicides and biological agents in reducing the disease incidence.

Management of Alternaria Leaf Blight in Pigeonpea through Host Plant Resistance and Micronutrient Application

Background: Pigeonpea [Cajanus cajan (L.) Millsp] is one of the primary grain legume crops grown in India for its high quality vegetable protein, animal feed and fodder. It is affected by various fungal and viral diseases. Among these, leaf blight caused by Alternaria alternata is one of the most destructive diseases and recently the disease of minor importance becomes major one in Tamil Nadu. Use of resistant cultivar is the most effective, economically viable and eco-friendly tool for combating the plant diseases. The micronutrients play a key role in many physiological and biochemical functions of the plants which influences plant pathogenic interaction. The micronutrients viz., Zn.Mn,Cu and Fe found to have greater impact on reducing the plant disease severity. Developing integrated disease management strategy involving disease resistant variety, micronutrient and fungicide application would be the best sustainable method for controlling the pigeonpea leaf blightMethods: Twenty four pigeonpea genotypes along with two local varieties viz., CO5 and CO6 were evaluated in the field for their resistance against Alternaria alternata leaf blight disease, consecutively for three years from 2015-16 to 2017-18 using the disease resistance scale ranging from 0 to 9. Field experiments were also conducted for three consecutive Kharif season from 2015 to 2018 to evaluate the efficacy of the foliar application of different micronutrients and combination fungicide viz., carbendazim 12% + mancozeb 63% on the incidence of leaf blight disease. Result: A total of 24 pigeonpea genotypes were screened for their resistance against leaf blight under field condition. Among these, four genotypes viz., BDN2, IPA 8F, IPA 15F and MA6 were found resistance and nine genotypes were moderately resistant and remaining 11 genotypes showed susceptible reaction to leaf blight. The results of the field experiment on micronutrient and fungicide application revealed that foliar spraying of MnSO 4 @0.2% on 30 days after sowing and carbendazim 12%+ mancozeb 63%@ 1g / lit on 45 days after sowing recorded the lowest leaf blight incidence of 8.1 PDI (Per cent Disease Index) with the highest disease reduction of 76.9% as against 35 PDI in the untreated control plot. The above treatments also recorded the highest grain yield of 905 kg/ ha as against 703 kg/ in the untreated control.

Evaluation of Inducing Agents and Synthetic Fungicide Combinations for Management of Foliar Pathogens of Urban Trees

Unmanaged, foliar pathogens of urban trees can be detrimental to tree health and aesthetics. Overreliance on synthetic fungicides increasingly means alternative means of pathogen management are now required. The purpose of these studies was to investigate the efficacy of 3 commercially available agents, harpin protein, salicylic acid derivative, and liquid chitosan, which can initiate induced resistance (IR) in plants. IR agents were applied independently and in combination with a synthetic fungicide (boscalid + pyraclostrobin) against 2 foliar pathogens (Venturia pirina and Guignardia aesculi) under field conditions with Pyrus communis ‘Williams’ Bon Chrétien’ and horse chestnut (Aesculus hippocastanum) acting as tree hosts. These agents were tested over 3 consecutive years. In 4 of 5 field studies, the use of an IR agent alone reduced pathogen symptom severity, increased fruit/seed yield, and enhanced leaf chlorophyll content. In virtually all studies, application of boscalid + pyraclostrobin at 2/3 strength plus an IR agent provided the same degree of pathogen control as boscalid + pyraclostrobin at full strength. Application of boscalid + pyraclostrobin at 1/3 strength plus an IR agent provided a reasonable degree of foliar pathogen control. Results showed that a combined mix of an IR agent with a 1/3 reduced dose of boscalid + pyraclostrobin was as effective at reducing symptom severity of 2 foliar pathogens as boscalid + pyraclostrobin applied at full strength, provided at least 4 sprays were applied during a growing season.

Effects of combined fungicide in stingless bees Scaptotrigona bipunctata

Locker is a fungicide used in different crops for biological control, affecting both insect pests and pollinators, such as bees. This study aimed to evaluate toxicity and establish the lethal concentration (LC50) of the fungicide Locker in stingless bees Scaptotrigona bipunctata, investigating changes in brain cells chromatin structure and in midgut morphology. This agrochemical is a combined fungicide that contains three active ingredients: benzimidazole, triazole and strobilurin. Adult forage bees were orally exposed to the following concentrations: 1.7 mg a.i./L; 2.55 mg a.i./L; 3.4 mg a.i./L and 4.25 mg a.i./L of fungicide, and submitted to histochemical and morphological analysis 24, 48 and 72 hours after ingestion. The analysis of S. bipunctata brain cells showed changes in chromatin condensation in all treatments. There were also several morphological changes in the midgut at all concentrations and exposure times. Thus, the fungicide Locker significantly affected bee survival, inducing changes in their internal morphology, which can lead to alterations in their activities, directly interfering in their foraging behavior and survival.

Combining Miconazole and Domiphen Bromide Results in Excess of Reactive Oxygen Species and Killing of Biofilm Cells.

Fungal biofilm-related infections are increasingly occurring. We previously identified a fungicidal antibiofilm combination, consisting of miconazole (MCZ) and the quaternary ammonium compound domiphen bromide (DB). DB eliminates tolerance rather than altering the susceptibility to MCZ of various Candida spp. Here we studied the mode of action of the MCZ-DB combination in more detail. We found that DB's action increases the permeability of the plasma membrane as well as that of the vacuolar membrane of Candida spp. Furthermore, the addition of DB affects the intracellular azole distribution. MCZ is a fungicidal azole that, apart from its well-known inhibition of ergosterol biosynthesis, also induces accumulation of reactive oxygen species (ROS). Interestingly, the MCZ-DB combination induced significantly more ROS in C. albicans biofilms as compared to single compound treatment. Co-administration of the antioxidant ascorbic acid resulted in abolishment of the ROS generated by MCZ-DB combination as well as its fungicidal action. In conclusion, increased intracellular MCZ availability due to DB's action results in excess of ROS and enhanced fungal cell killing.

Effect of fungicides on the symbiosis between Bradyrhizobium strains and peanut

ABSTRACT Seed treatment with fungicides is an important practice for the control of phytopathogens in peanut crops. However, these products can harm rhizobacteria (Bradyrhizobium) and inhibit processes such as biological nitrogen fixation. This study aimed to verify the effects of the treatment of peanut seeds cv. BR1 inoculated with Bradyrhizobium spp. with fungicides. The experiment was conducted in a greenhouse, using two combinations of fungicides [C1: carboxin (200 g L-1) + tiram (200 g L-1); C2: pyraclostrobin (25 g L-1) + thiophanate methyl (225 g L-1) + fipronil (250 g L-1)] and one control without fungicide; two inoculants based on Bradyrhizobium spp. (SEMIA 6144 and ESA 123) and one control with a nitrogen chemical source (ammonium nitrate). The experimental design was completely randomized, in a 3 (2 with fungicide and 1 without fungicide) x 4 (2 inoculations based on rhizobia, 1 N mineral source and 1 without N) x 2 (1 or 2 inoculants applications) factorial scheme, with 5 replications. The root and shoot dry mass, plant height, nodulation and leaf nitrogen accumulation were evaluated. The application of both combinations reduced the number of nodules on plant roots, mainly for C1. The vegetative growth and nitrogen in the leaves were affected by C1, whereas, for C2, there were increments higher than for the control without fungicides. ESA 123 was more tolerant to the effects of fungicides on nodulation. Regarding the number of inoculations, there was an increase in the nitrogen rate with two inoculations. C2, despite affecting the nodulation, was less toxic to the inoculants SEMIA 6144 and ESA 123.

In-vitro evaluation of fungicides against Cylindrocladium spp causing defoliation and die-back in Cashew

Among all the 10 fungicides/ fungicide combinations under study, complete inhibition of the mycelial growth occurred in mancozeb (0.00mm) and metalaxyl in combination with mancozeb. They were followed by zineb plus hexaconazole (12mm), Chlorothalonil (12.33mm), carbendazim (15.67mm), Zineb (17.33mm), Hexaconazole (17.67mm), thiophenate methyl (18.00mm), copper oxy-chloride (26.00mm) and copper hydroxide (27.00mm) respectively. Maximum growth (90.00 mm) was recorded in control.

Effect of seed coating on seed storability and longevity in rice (Oryza sativa L.)

The experiment was conducted to identify an effective seed coating treatment and evaluate the effect of seed coating on seed longevity in rice. The experimental material consisted of seeds of rice variety HPR-1068, which were given nine different coating treatments comprising of polymer polykote, fungicide, insecticide, polymer-fungicide and polymer-insecticide combinations along with untreated control. The seeds were stored for thirty six months in three replicates after packing in HDPE (high density polyethylene) interwoven non-laminated bags. The seed quality parameters were evaluated at bimonthly intervals for twelve months. Irrespective of coating, seed showed deterioration and the seed vigour declined, probably due to increased fungal infection and seed aging. Amongst various treatments, seeds coated with polymer polykote @ 3 ml per kg of seed + vitavax 200 @ 2 g per kg of seed (T6) and polymer @ 3 ml per kg of seed + fowable thiram @ 2.4 ml per kg of seed (T4) were found signifcantly superior for all seed quality parameters viz., germination (75.33 and 75.00%), feld emergence (66.00 and 65.33%), seedling length (8.07 and 7.83 cm), seedling dry weight (0.048 and 0.046 g), speed of germination (9.00 and 8.83), seedling vigour index (608 and 588), lowest electrical conductivity (0.266 and 0.265 m mho/cm/g) and lowest seed (7.33 and 7.67%) infection, respectively, at the end of 36 months of storage over untreated control (T1).

POSSIBILITIES OF COMPLEX CONTROL OF PATHOGENS AND PEST ON TOMATO CROPS UNDER HIGH PLASTIC TUNNELS

The experiment was carried out in 2020, under high plastic tunnels conditions, using the tomato hybrid Prekos F1 and aimed to evaluate the efficacy of different combinations of fungicides with insecticides for complex control of pathogens Alternaria solani (early blight), Fulvia fulva (leaf mold) and pests Tuta absoluta (tomato leaf miner) and Helicoverpa armigera (cotton bollworm). The experimental variants were: 1. Cabrio Top 0.2% + Coragen 0.0175%; 2. Cabrio Top 0.2% + Voliam Targo 0.08%; 3. Dagonis 0.1% + Coragen 0.0175%; 4. Dagonis 0.1% + Voliam Targo 0.08%; 5. Cidely Top 0.1% + Coragen 0.0175%; 6. Cidely Top 0.1% + Voliam Targo 0.08%; 7. Ortiva Top 0.1% + Coragen 0.0175%; 8. Ortiva Top 0.1% + Voliam Targo 0.08%; 9. Untreated control. Six foliar treatments were applied at 10- days intervals. The efficacy of these combinations of fungicides with insecticides was assessed according to the degree of attack (%) for Alternaria solani, Fulvia fulva and Tuta absoluta or according to the frequency of the attacked fruits (%) for Helicoverpa armigera and was between 85.0% and 90.7%. The highest yields were registered in variants 1 (Cabrio Top 0.2% + Coragen 0.0175% - 5,535 kg/m2), 3 (Dagonis 0.1% + Coragen 0.0175% - 5,440 kg/m2) and 2 (Cabrio Top 0.2% + Voliam Targo 0.08% - 5,362 kg/m2) as compared to 4,490 kg/m2 in the untreated control variant. The differences of yield, obtained in addition to the untreated control variant, were very significant in all cases.

Identification and Prevention of Microbial Contamination in Tissue Culture of Catharanthus roseus - An Important Medicinal Herb

The explants of two varities rosea and alba of Catharanthus roseus used for in vitro propagation and found to be more than 50% of the cultures became contaminated. The most common bacterial contaminants were Bacillus licheniformis, Micrococcus, Panibacillus and fungal contaminants were Fusarium, Alternaria, Cladosporium and Aspergillus. Combinations of different antibiotics (Penicillin, norfloxacin, tobramycin, gatifloxacin, ofloxacin) and fungicides (Bavastin, captan, fluconazole and trichoderma) were used to control the growth of the contaminants. Gatifloxacin and ofloxacin inhibited 100% growth of bacteria whereas, bavastin and captan appeared to be the most effective fungicides. Combination of gatifloxacin, ofloxacin with bavastin and captan inhibited the growth of contaminants at their minimum phytotoxic concentration (MIC). The observed minimum phytotoxic concentration (MPC) of ofloxacin, gatifloxacin, bavastin and captan was 15, 9, 6 and 5% at their respective MIC. More than 90% of the cultures responded for callus formation in the combination of gatifloxacin (4%) + bavastin (1%). While the combination of gatifloxacin and captan was highly toxic that reduces the growth of the culture.
 Plant Tissue Cult. & Biotech. 30(2): 297-305, 2020 (December)

Synergistic Action of Commercially Available Fungicides for Protecting Wheat from Common Root Rot Caused by Bipolaris sorokiniana in China.

Wheat (Triticum aestivum) common root rot (CRR) caused by predominant fungal pathogen Bipolaris sorokiniana occurs in all wheat-growing regions worldwide and is difficult to control. In this study, the efficacy of eight fungicides against Bipolaris sorokiniana was examined in in vitro assays, and we determined that the combined application of two fungicides significantly inhibits the growth of fungal mycelium. Half of the maximal effective concentration of a mixture containing fludioxonil and difenoconazole in the ratio 1:4 was 0.0372 mg/liter, and the cotoxicity coefficient was 160.14. Under an environmentally controlled pot assay, seed treatment with the mixture of fludioxonil and difenoconazole in the 1:4 ratio demonstrated the best control efficiency at seedling and adult stages, respectively. The best synergistic mixture on seed treatment was assessed in a 2-year field experiment at Hebei, China. The best control efficacy achieved at the seedling and adult stages was 82.65% and 68.48%, respectively. Overall, the in vitro mycelial growth inhibition assay and controlled-environment and field studies indicated that the synergistic action of a mixture of fludioxonil and difenoconazole provides effective control against wheat CRR. These findings highlight the potential application of the fungicide combination for controlling CRR and reducing the selection pressure on fungal pathogens by lessening the use of various fungicides in the field.

Efficiency and profitability of fungicides in controlling Bipolaris diseases and enhancing grain yield in cultivated wild rice (Zizania palustris)

The integrated disease management program for Bipolaris spp. in cultivated wild rice (Zizania palustris) paddies includes the use of one or two fungicide sprays within the growing season, but their effectiveness was questioned due to recent epidemics. To test the efficacy of fungicide applications, on-farm trials were conducted in four Minnesota locations from 2016 to 2018 using five fungicide combinations: QuiltXcel (a.i. propiconazole and azoxystrobin) followed by Quadris (a.i. azoxystrobin) (QX/Q), one early application of QuiltXcel (QX/-), early application of Quadris followed by Quadris (Q/Q), one early Quadris application (Q/-), and one late Quadris application (-/Q). A control treatment without fungicide (-/-) was used. Although there was variation by years and locations, overall, disease severity was reduced and grain yield enhanced in some of the fungicide treated plots compared to the non-treated control. Further, a meta-analysis found that the average disease severity in fungicide treated plants was significantly reduced (p–value = 0.0016) compared to the control. Grain yield of treated plots were also superior to the control (p-value = 0.0061). Grain yield for QX/Q, QX/-, and Q/Q applications were statistically differently from the control with overall grain increases of 200 kg/ha (SEM = 46.7), 123 kg/ha (SEM = 50.2), and 179 kg/ha (SEM = 46.0), respectively. The probability of offsetting fungicide costs for the overall treatments was 85.5% but it differed by treatment from 57% (Q/-) to 87% (QX/Q). Together, these results indicate that the fungicides used within the current disease management program reduce disease and often enhance grain yield in cultivated wild rice paddies.

Chitosan primes plant defence mechanisms against Botrytis cinerea, including expression of Avr9/Cf-9 rapidly elicited genes.

Current crop protection strategies against the fungal pathogen Botrytis cinerea rely on a combination of conventional fungicides and host genetic resistance. However, due to pathogen evolution and legislation in the use of fungicides, these strategies are not sufficient to protect plants against this pathogen. Defence elicitors can stimulate plant defence mechanisms through a phenomenon known as defence priming. Priming results in a faster and/or stronger expression of resistance upon pathogen recognition by the host. This work aims to study defence priming by a commercial formulation of the elicitor chitosan. Treatments with chitosan result in induced resistance (IR) in solanaceous and brassicaceous plants. In tomato plants, enhanced resistance has been linked with priming of callose deposition and accumulation of the plant hormone jasmonic acid (JA). Large‐scale transcriptomic analysis revealed that chitosan primes gene expression at early time‐points after infection. In addition, two novel tomato genes with a characteristic priming profile were identified, Avr9/Cf‐9 rapidly elicited protein 75 (ACRE75) and 180 (ACRE180). Transient and stable over‐expression of ACRE75, ACRE180 and their Nicotiana benthamiana homologs, revealed that they are positive regulators of plant resistance against B. cinerea. This provides valuable information in the search for strategies to protect Solanaceae plants against B. cinerea.

Unconventional Yeasts Are Tolerant to Common Antifungals, and Aureobasidium pullulans Has Low Baseline Sensitivity to Captan, Cyprodinil, and Difenoconazole.

Many yeasts have demonstrated intrinsic insensitivity to certain antifungal agents. Unlike the fungicide resistance of medically relevant yeasts, which is highly undesirable, intrinsic insensitivity to fungicides in antagonistic yeasts intended for use as biocontrol agents may be of great value. Understanding how frequently tolerance exists in naturally occurring yeasts and their underlying molecular mechanisms is important for exploring the potential of biocontrol yeasts and fungicide combinations for plant protection. Here, yeasts were isolated from various environmental samples in the presence of different fungicides (or without fungicide as a control) and identified by sequencing the internal transcribed spacer (ITS) region or through matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Among 376 isolates, 47 taxa were identified, and Aureobasidium pullulans was the most frequently isolated yeast. The baseline sensitivity of this yeast was established for 30 isolates from different environmental samples in vitro to captan, cyprodinil, and difenoconazole. For these isolates, the baseline minimum inhibitory concentration (MIC50) values for all the fungicides were higher than the concentrations used for the control of plant pathogenic fungi. For some isolates, there was no growth inhibition at concentrations as high as 300 µg/mL for captan and 128 µg/mL for cyprodinil. This information provides insight into the presence of resistance among naturally occurring yeasts and allows the choice of strains for further mechanistic analyses and the assessment of A. pullulans for novel applications in combination with chemical agents and as part of integrated plant-protection strategies.

Efficacy of modern combination fungicide molecules against sheath blight of rice

Sheath blight of rice is one of the most damaging diseases of rice worldwide causing serious yield losses. Several fungicide molecules with different mode of actions are available in the market. The present study was undertaken to find the best and most economical combination of fungicides in managing this disease. Hence, an experiment was conducted to evaluate the efficacy and economics of flusilazole 12.5% + carbendazim 25% SC, difenoconazole 11.4% + azoxystrobin 18.2% SC, tebuconazole 18.3% + azoxystrobin 11% SC, tricyclazole 18% + mancozeb 62% WP, zineb 68% + hexaconazole 4% WP, trifloxystrobin 25% + tebuconazole 50% WG, mancozeb 50% + carbendazim 25% WS and epoxiconazole 62.5 g/l + fluxapyroxad 62.5 g/l EC against sheath blight of rice under the field conditions. Results of the present study revealed that, out of the different fungicidal combinations, two foliar sprays of difenoconazole 11.4% + azoxystrobin 18.2% SC @ 1 ml/lit was found to be most economic that provided best incremental net benefit ratio of 6.17:1.00. It was followed by two foliar sprays of epoxiconazole 62.5 g/l + fluxapyroxad 62.5 g/l EC @ 1.5 ml/l, tebuconazole 18.3% w/w + azoxystrobin 11% SC, zineb 68% + hexaconazole 4% WP and trifloxystrobin 25% + tebuconazole 50% WG.

English

Asian soybean rust, if not well managed, can reduce grain yield up to 90%. Due to the severe damage caused by the disease, especially in Brazil, it is important to evaluate management strategies combined with fungicides, to minimize the losses. The aim of the work was to evaluate the effect of adopting different combined management strategies on the severity of soybean rust and its impact on the performance of the crop. Research was carried out at 2016/2017 and 2017/2018 growing seasons. Soybean cultivar NA 5909 RG® (susceptible to Asian rust), LG 60163 IPRO® (highly tolerant) and TMG 7062 IPRO® INOX® (resistant) were evaluated with different combinations of fungicide, copper and potassium phosphites foliar fertilizers applications, in two development stages, R1 (early flowering) and R5.1 (early grain filling). Disease severity assessments were performed at R1 and repeated every 14 days (up to R5 + 14 days) to determine the area under the Disease Progress Curve (AUDPC). The genetics of resistance to Asian soybean rust contributed to the less progress of the disease in plants. Even with differential responses between cultivars and treatments applied to the severity of Asian soybean rust, the disease did not compromise grain yield in both growing seasons. Key words: Phakopsora pachyrhizi, fungicide, foliar fertilizers, genetic resistance.

Management of safflower aphid (Uroleucon compositae) through newer insecticides

A field experiment was conducted for three years during rabi 2013-14 to 2015-16 to evaluate the efficacy and compatibility of insecticides, fungicides and bio-agents for the management of the insect pest, aphid (Uroleuconcompositae) and the diseases like Alternaria leafspot and Fusarium wilt in safflower. The pooled data of three years showed significant reduction in aphid infestation in terms of number of aphids per 5 cm apical twig in all thetreatments in comparison with the absolute control. The extent of aphid control in different treatments ranged from 70.2 to 88.0% after first spray and from 81.6 to 91.4% after second spray. Thus, all the treatments were capable of keeping the aphid population below the ETL level (35-40/5cm apical twig). There was no notable buildup of Alternaria leaf spot as the crop was sown during the normal recommended time. The Fusarium wilt incidence was also less which ranged from 1.2 to 7.6%. All the treatments recorded significant improvement in yield over the absolute control but they were at par with each other. However, the highest average seed yield of 907 kg/ha was recorded by T5 (Spray of thiamethoxam @ 0.25 g/l). The seed yield in other treatments ranged from 801 to 875 kg/ha as against only 292 kg/ha in the absolute control. The benefit-cost analysis of the treatments showed that the treatment T5 recorded the highest B:C ratio of 2.06 followed by T6 (1.94), T7 (1.89), T4 (1.62), T2 (1.44), T1 (1.40) and T3 (1.39). There was no phytotoxic effect on safflower crop in any of the treatments involving combination of different insecticides, fungicides and bio-agents. Therefore, seed treatment with T. asperellum TaDOR 7316 @ 10 g/kg and tank mixing of insecticides and fungicides together for need-based pest and disease management in safflower is recommended.

In vitro evaluation of fungicides against Alternaria leaf spot of cotton

Cotton (Gossypium hirsutum L.) is the one of the most important commercial crops of the world, which belongs to the family Malvaceae. India is the largest cotton growing country in the world with an area of around 12.35 M ha followed by United States and China with production of 36.1 M bales and productivity of 524 kg lint/ha. Cotton crop is known to suffer from number of fungal, bacterial and viral diseases. Cotton is under constant threat of foliar diseases viz., grey mildew, Alternaria leaf spot, Myrothecium leaf spot, bacterial leaf blight, rust etc. Among them, Alternaria leaf spot caused by Alternaria spp. is predominant in causing economic losses to the cotton crop in the country. Evaluation of systemic, non-systemic and combined fungicides under in vitro conditions revealed that the among eight fungicides evaluated against Alternaria macrospora (N2A isolate), Propiconazole, Hexaconazole and Tebuconazole @ 500 and 1000 ppm recorded maximum inhibition with 100 per cent inhibition and no radial growth of mycelium was observed. Pyraclostrobin and Azoxystrobin @1000 ppm showed 91.0 and 87.2 per cent inhibition respectively. Carbendazim+Mancozeb (SAAF) @ 1500 ppm and 2000 ppm showed 96.1 and 96.9 per cent inhibition respectively.

Microbiome-guided evaluation of Bacillus subtilis BIOUFLA2 application to reduce mycotoxins in maize kernels

Fungal diseases are aggravating globally in crop cultivation despite of growing inputs of chemical fungicides. Ear rot and fumonisin contamination of kernels caused by Fusarium verticillioides lead to qualitative and quantitative reductions in maize production. In tropical agriculture, high yielding maize currently can only be assured through foliar protection using fungicides due to the high pathogen pressure. However, the use of chemical fungicides alone does not guarantee the protection of kernels. Recently, a tandem application of fungicides with the Bacillus subtilis strain BIOUFLA2 was identified as a promising strategy to control F. verticillioides-caused diseases. We have employed an integrative approach to assess changes in the microbiome of maize subjected to a combination of chemical and biological fungicides and contrasted it to conventional treatments. This was complemented with molecular and analytical monitoring of the pathogen and mycotoxin levels. Two sampling times were included (10 days after application of treatments and upon harvesting) and two maize fields to account for regional differences. A comparative analysis indicated a treatment-specific enrichment of bacterial and fungal OTUs (Operational Taxonomic Units) that were not detectable in the maize microbiome of untreated plants. Both, the chemical and the tandem application of a chemical and biological pesticide resulted in the occurrence of unique OTUs. Samples subjected to these treatments harbored up to 22 additional OTUs. The lowest fumonisin concentration was observed in the treatment that encompassed BIOUFLA2 (field 1 = 0.29 ppm and field 2 = 0.77 ppm), while the conventional fungicide application resulted in the highest mycotoxin concentrations (field 1 = 3.84 ppm and field 2 = 10.02 ppm). Our study provided strong evidence that conventional treatments of maize with fungicides can promote mycotoxin levels in grains and that partial replacement with biologicals can increase the treatment efficiency.

Effective scheduling of fungicide and insecticide combination for the management of Rice Sheath rot caused by Sarocladium oryzae (Sawada) W. Gams & D. Hawksw

Sheath rot caused by Sarocladium oryzae was recorded in more than 65% locations surveyed in the North coastal zone of Andhra Pradesh. A field trail was conducted at Agricultural Research Station, Ragolu during 2010-13 to study efficacy of fungicide (carbendazim and propiconazole) and insecticide (Profenofos, Cartap hydrochloride) combinations for the management of sheath rot and stem borer in paddy. Scheduled prophylactic spray with propiconazole @ 1 ml/l + cartap hydrochloride (2 g/l) for two times i.e., first spray at 50% of panicle initiation and II spray at 50% flowering resulted in significant reduction of sheath rot (10.6% incidence) in comparison to 29.7% disease recorded in untreated control. Profenofos + propiconazole/ carbendazim treatment combinations were also found effective, but keeping in view the environmental risks posed by Profenofos, scheduled prophylactic foliar spray with propiconazole + cartap hydrochloride could be an effective means in managing stem borer and sheath rot in paddy.