Blast of rice caused by Pyricularia oryzae Cav. (Magnaporthe grisea Sacc.) is one of the most destructive disease (Ou, 1985) and it accounts for 30 to 100% yield losses in all rice growing areas of the country (Padmanabhan, 1965). In South Gujarat (Ahwa-Dangs and in hilly area of Dharmpur and Vansada), it is a major disease of rice and occurs every year on high yielding improved susceptible varieties during kharif (Anonymous, 1984-2007).

 

The blast of rice causes huge losses of quality and quantity of harvest. The various chemicals, antagonists and botanicals were recommended in different area to control the blast. Hence, the present investigation was undertaken.

An experiment was conducted at two locations using Randomized Block Design (RBD) with three replication in Kharif 2007 - 2008 at Krishi Vigyan Kendra, Waghai Rajendrapur and Hill Millet Research Station, Rambhas farm (Ahwa-Dangs) of Navsari Agricultural University, Waghai, on highly susceptible cv. Pankhali. It was transplanted in 2.00 x 2.25 m net plots with 20 x 15 cm spacing. The fertilizers and other recommended cultivation practices were followed to raise good crop.  The fungicides viz., tricyclazole (Beam 75WP 1 g lit^-1), iprobenfos (Kitazin 48EC 1 ml lit^-1), mancozeb (Dithane M-45 75WP 2.5 g lit^-1), bio-agent Pseudomonas fluorescens (Sudocel 0.5WP 2 x 10⁸ cfu g^-1) and botanicals viz., neem and tulsi leaves extracts (10%) were sprayed after appearance of disease, two spray at boot leaf stage  and third at flowering stage. The incidence of leaf and neck blast were recorded from 30 hills/plot randomly selected and labelled. These labelled plants were observed for disease intensity using Standard Evaluation System for Rice, IRRI (1988) at 10 days interval till harvest. The percent disease intensity was worked out by using the formula:

 

 

The grain and straw yield/plot and 1000 grain weight were record and statistically analyzed.

All the treatments had significantly reduced the percent leaf and neck blast as compared to control at both the locations (Table 1). The bio-efficacy of all the fungicides were all most same in controlling the disease at both the locations and location pooled analysis. Tricyclazole (beam) was found significantly superior than the rest of treatments and recorded minimum (9.56%) leaf blast intensity. The next effective treatment was Pseudomonas fluorescens (15.12%) which was statistically at par with iprobenfos (kitazin) (16.17%), followed by mancozeb (dithane M-45) (21.11%), neem leaf extract (27.16%) and tulsi leaf extract (59.99%).

 

The similar trend was observed in case of controlling neck blast. The tricyclazole recorded significantly lowest (24.25%) neck blast intensity than the rest of treatments. The next best treatment was P. fluorescens (37.46%) which was statistically at par with iprobenfos (39.44%), followed by mancozeb (44.56%), neem leaf extract (47.15%) and tulsi leaf extract (59.99%) in location pooled analysis.

 

 

The results of grain and straw yield were significant at both location and in location pool analysis (Table 2). Here also trend of yield production was similar due to different treatment was almost same. Significantly highest grain yield (3197 kg/ha) was harvested in tricyclazole which was at par with P. fluorescens (3044 kg/ha) and iprobenfos (2805 kg/ha). Grain yield performance of mancozeb (2580 kg/ha) and neem leaf extract (2300 kg/ha) were also superior over control treatment (1805 kg/ha). Treatment of tulsi leaf extract gave numerically higher grain yield (2014 kg/ha) as compared to untreated control but was at par with control treatment in grain yield performance. 

 

The straw yield performance was similar to that of grain yield due to different treatments at both location and in pool analysis. The straw yield was significantly highest (5900 kg/ha) in tricyclazole which was at par with P. fluorescens (5583 kg/ha) and iprobenfos (5472 kg/ha). Straw yield performance of mancozeb (5300 kg/ha) and neem leaf extract (5027 kg/ha) were also superior over control treatment (4178 kg/ha). Incase of 1000 grain wt., the effect of treatment was similar to earlier parameters. The tricyclazole was found significantly superior over the rest of treatments as highest (24.52 g) 1000 grain wt. was recorded. The next best was P. fluorescens (22.43 g) which was at par with iprobenfos (21.70 g) and mancozeb (20.60 g). Treatment of neem and tulsi leaf extract gave numerically higher 1000 grain wt. 18.55 and 17.48 g, respectively, as compared to untreated control (16.58 g) but was at par with control treatment in their performance.

 

 

In the present study, tricyclazole was found significantly superior over rest of the treatments for all the attributes viz., leaf blast, neck blast, grain yield, straw yield and 1000 grain wt. at both the location and in pooled data. This may be due to tricyclazole, a melanin biosynthesis inhibiting fungitoxicant, which provide an effective control of rice blast (P. oryzae Cav.) by preventing pathogen from entering through the host epidermis and also prevents melanization of appressoria and subsequent formation of infection peg apparatus. The next effective treatment was P. fluorescens which was at par with iprobenfos. It may be due to P. fluorescens suppress rice blast through salicylic acid accumulation and induction of systemic resistance. While, iprobenfos act as a chitin inhibitor in rice blast pathogen, P. oryzae Cav.

 

The results of our studies are similar to earlier of several workers. Singh and Prasad (2007) reported tricyclazole (beam) as most effective fungicide for the control of rice blast and increase the yield. Similar result was also reported by Prajapati et al. (2004). Effectiveness of iprobenfos (kitazin) in controlling rice blast and increasing grain yield has also been reported by Sharma and Kumar (1992). While, Vidhyasekaran et al. (1997) who reported that when P. fluorescens applied as foliar spray, it suppress rice blast in field condition.

The authors have not declared any conflict of interest.

The authors are grateful to the N.A.R.P., (Rice) and K.V.K., Waghai, N.A.U., Navsari for providing facilities, materials and helped in conducting the field experiments.