Efficacy of Bioagents, Plant Extracts and Fungicides against Chilli Powdery Mildew Incited by Leveillula taurica

1Department of Plant Pathology, College of Agriculture, University of Agricultural and Horticultural Sciences, Shivamogga 577 225, India. 2Agricultural and Horticultural Resserch Station, Bavikere, University of Agriculturla and Horticultural Sciences, Shivamogga 577 144, India. 3Organic Farming Research Centre, University of Agricultural and Horticultural Sciences, Shivamogga 577 225, India.

Chilli (Capsicum annum L.), is an important commercial vegetable cum spice crop in India.India is a major producer, consumer and exporter of chilli and the crop is being grown in almost all the states.In addition to its domestic importance, chilli has tremendous export potential as a spice crop.Chilli suffers from many diseases caused by fungi, bacteria, viruses, nematodes and also abiotic stresses.Among the fungal diseases, powdery mildew, leaf spot and anthracnose or fruit rot are the most prevalent ones.
The powdery mildew caused by Leveillula taurica (Lev.)Arn. is a major constraint in chilli production in India causing heavy yield loss ranging from 14 to 20%, due to severe defoliation and reduction in photosynthesis, size and number of fruits per plant (Mathur et al., 1972;Sivaprakasam et al., 1976;Gohokar and Peshney, 1981;Sharmila et al., 2004).Many systemic and non-systemic fungicides were reported to manage the powdery mildew and anthracnose of chilli.The information on the efficacy of new fungicides, bioagents and plant extracts against powdery mildew is insufficient.Hence, there is a need to evaluate new fungicides, bioagents and plant extracts against Leveillula taurica.By considering the the seriousness of disease and the economic damage caused by the disease, the present investigation was carried out by using different fungicides, bioagents and plant extracts for its efficacy against powdery mildew of chilli under field condition.

MATERIALS AND METHODS
A field experiment was conducted during kharif and rabi 2015-16 at College of Agriculture, University of Agricultural and Horticultural Sciences, Shivamogga.The experiment was laid out in Randomized Block Design with three replications and twelve treatments.Chilli local variety Byadagi kaddi seeds were sown in small beds and the nursery was raised.The seedlings of twenty five days old were transplanted at a spacing of 75×45 cm in plot size of 3.0×2.0m with the recommended intercultural practices.All the foliar sprays were given as per their doses.Treatments includes two bioagents, viz., Trichoderma harzianum (6×10 7 cfu/ml of water-1%) and Pseudomonas fluorescens (6×10 7 cfu/ml of water-1%), five plant extracts, viz., Azardiracta indica (10%), Allium sativa (5%), Agave americana (5%), Tagetes indica (5%) and Eichhornia crassipes (5%) and four fungicides, viz, Wettable sulphur (0.3%) Triadimefon (0.1%), Myclobutanil (0.1%) and Hexaconazole (0.1%) with one untreated control were evaluated for their efficacy on management of powdery mildew disease.The first spray of the fungicides, biagents and plant extracts was done soon after the first appearance of disease.The same concentration were followed for second and third sprays at 12 days interval.The severity of the disease was scored at 10 days interval after each spray.The per cent disease index (PDI) was recorded on 10 plants and 10 leaves on lower, middle and upper leaves by using 0-9 scale (Mayee and Datar, 1986) and per cent disease reduction over control (PDC) was calculated and angular transformed data were analyzed statistically.Finally the dry chilli yield was recorded from each treatment.The cost: benefit ratio was worked out based on the cost of fungicides, bioagents and plant extracts spray cost, yield and the market value of chilli during 2015-16.PDC = Per cent disease index over control PDIC = PDI in control PDIT = PDI in treatment

RESULTS AND DISCUSSION
During kharif 2015, the percent disease index (PDI) was to the tune of 88.24 percent.Proportionately different fungicides, bioagents and plant extracts controlled the disease effectively.Among the different fungicides, the percent disease index was significantly less (PDI 17.37) in Myclobutanil sprayed plots followed by Triadimefon (PDI 20.70) and Hexaconazole (PDI 23.75) and Wettable Sulphur (PDI 45.37).Whereas, the other treatments like Pseudomonas fluorescens, neem leaf extract, garlic bulb extract and Trichoderma harzianum were statistically on par with each other with PDI of 61.14, 62.56, 63.54 and 63.79 respectively and they were significantly superior over untreated control (Table 1).
Chemicals are the most common and practical method for the management of powdery mildew disease.The strobilurin fungicides, viz., azoxystrobin (Quadris), trifloxystrobin (Flint) and pyraclostrobin (Cabrio) have recently been labeled for the management of powdery mildew on chilli, but only preliminary reports are available on the efficacy of these fungicides against the severe form of the disease (Alexander and Waldenmaier, 2002).The strobilurin fungicides represent important class of chemicals for the management of a broad range of fungal diseases in agricultural production systems.
The highest per cent disease reduction of 80.31 per cent was recorded in Myclobutanil followed by Triadimefon (76.55) and Hexaconazole (73.08).Treatments like Wettable Sulphur, Pseudomonas fluorescens and neem leaf extract recorded considerably more per cent disease reduction (48.59, 30.71 and 29.10) respectively.Lowest per cent reduction of 6.56, 7.12 and 8.67 was recorded in marigold leaf extract, water hyacinth leaf extract and agave leaf extracts treatments respectively.Whereas, the other treatments which showed considerable per cent disease reduction over control were garlic bulb extract (28.0) and Trichoderma harzianum (27.71) respectively.These findings are in conformity with  Sharmila et al. (2004) showed that control of chilli powdery mildew was achieved with the application of Penconazole followed by Propiconazole.Ekbote (2006) reported that Anvil 5SC (Hexaconazole) at 0.15 per cent was found best and recorded the lowest per cent disease index.Sudheendra Astaputre et al. (2007) reported that all Triozole fungicides (Penconazole followed by Triademefon, Propiconazole, Hexaconazole and Difenconazole) were found effective in reducing powdery mildew of chilli.Surwase et al. (2009) reported that Hexaconazole, Penconazole, botanical NSKE (5%) and Trichoderma harzianum (0.5%) were found highly effective and economical for controlling powdery mildew of pea.
The dry chilli yield was significantly superior in all the treatments as compared to untreated control.The highest yield was recorded in Myclobutanil treated plots (12.72 q/ha) which was significantly superior over all other treatments followed by Triadimefon (12.27 q/ha) and Hexaconazole (11.77 q/ha).The least yield of 6.45 q/ha was recorded in untreated control.This management effect was mainly due to translaminar and systemic movement of myclobutanil, triadimefon and hexaconazole, inside the tissues and it is widely distributed from the application side by diffusion.The results were supported by (Ahiladevi and Prakasam, 2014) who reported that effective management of powdery mildew disease of chilli by using azoxystrobin 25% SC.Alharbi et al. (2014) revealed that spraying with Topaz 200 EW significantly reduced the disease severity (3.5%) and increased the fruit yield of pepper (244.5 g/plant).Azit et al., 2014, reported that combifungicide UPF-509 (Azoxystrobin 8.3% + Mancozeb 66.7%) 75% WG at 1200, 1500 and 1800 g/ha along with recommended fungicides found effective in reducing the powdery mildew diseases in chilli and recorded maximum fruit yield of 22.28 q/ha.
Further, the results revealed that highest cost benefit ratio was obtained in Myclobutanil treated plots (1:2.43)followed by Triadimefon (1:2.39) and Hexaconazole (1:2.37).Among plant extracts and bioagents, garlic bulb extract recorded highest B:C ratio of 1:1.20 followed by Neem leaf extract (1:1.36),Trichoderma harzianum (1:1.28),Pseudomonas fluorescens (1:1.34)sprayed plots respectively.The plots sprayed with plant extracts like marigold leaf, agave leaf and water hyacinth leaf extracts were found to be less effective with low cost benefit ratio.This clearly indicated that three sprays of Myclobutanil (0.1%) are more useful not only in reducing the cost of protection but also gave higher benefits as compared to other treatments and can be recommended for the management of chilli powdery mildew.This is followed by Triadimefon and Hexaconazole applications.Similar types of findings were reported by many workers (Sharmila et al., 2004 andAlharbi et al. 2014).
In the present study, the fungicide myclobutanil and tridimefon were found superior in reducing the chilli powdery mildew disease severity which remain on par with each other and thus helped for getting highest dry chilli fruit yield and B:C ratio.Alternatively the bioagent, P. fluorescens and plant extract, neem leaf extract can also be employed in the integrated management of chilli powdery mildew.

Table 1 .
Efficacy of bioagents, plant extracts and fungicides against powdery mildew of chilli under field conditions during 2015-16