International Journal of Agriculture Sciences ISSN: 0975-3710 & E-ISSN: 0975-9107, Volume 10, Issue 10, 2018, pp.-6096-6099. Available online at https://www.bioinfopublication.org/jouarchive.php?opt=&jouid=BPJ0000217

Research Article SURVEY FOR THE OCCURRENCE OF RICE LEAF BLAST IN PRAKASAM AND SRI POTTI SREERAMULU DISTRICT OF

RAO VARAPRASADA*1 AND ANIL KUMAR P.2 1ICAR-Krishi Vigyan Kendra, Darsi, Prakasam, 523247, Acharya N. G. Ranga Agricultural University, Lam, , 522034, Andhra Pradesh, 2Department of Plant Pathology, Agricultural College, Bapatla, 522101, Acharya N. G. Ranga Agricultural University, Lam, Guntur, 522034, Andhra Pradesh, India *Corresponding Author: Email - [email protected]

Received: May 14, 2018; Revised: May 24, 2018; Accepted: May 25, 2018; Published: May 30, 2018

Abstract: A roving survey was conducted for the occurrence and percent disease severity of rice leaf blast caused by Pyriculariagrisea Sacc. in Prakasam and Sri Potti Sreeramulu Nellore (SPSR) districts of Andhra Pradesh during Kharif 2010-2011 and 2011-2012 and Rabi 2010-2011 and 2011-2012. In Prakasam district32.2% mean disease severity was recorded during Kharif 2010-2011 and 2011-2012 and 34.9% mean percent disease severity (PDS) was recorded during Rabi 2010-2011 and 2011-2012. Highest mean PDS (34.1%) was recorded in Chimakurthy mandal and least mean PDS (27.1%) was recorded in Kandukuru mandal. During Rabi 2010- 2011 and 2011-2012, Darsi mandal recorded highest mean disease severity (41.1%) and least mean PDS (35.8%) was recorded in Kandukuru mandal. During Kharif 2010-2011 and Kharif 2011-2012 in SPSR recorded 34.0% of mean disease severity. Among the different mandals surveyed, Kavali mandal had highest PDS (34.2%) and Podalakuru mandal recorded least mean PDS (27.4%). During Rabi 2010-2011 and Rabi 2011-2012 in SPSR Nellore district, Kavali mandal had highest mean disease severity and Podalakuru mandal recorded least disease severity. The transplanting and tillering stages were highly susceptible for blast when mean values were compared for their progression from one stage to the other. Keywords: Leaf blast, Percent disease severity, Pyricularia grisea Citation: Rao Varaprasada and Anil Kumar P. (2018) Survey for the Occurrence of Rice leaf Blast in Prakasam and Sri Potti Sreeramulu Nellore District of Andhra Pradesh. International Journal of Agriculture Sciences, ISSN: 0975-3710 & E-ISSN: 0975-9107, Volume 10, Issue 10, pp.- 6096-6099. Copyright: Rao Varaprasada and Anil Kumar P. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.

Introduction Rice (Oryza sativa L.) is the staple food for more than 60 per cent of the world’s Sum of individual ratings 100 PDS = × population and more than 90 per cent of the rice produced in the world is No. of leaves assessed Maximum disease grade value consumed in the Asian countries. Globally, during 2011-12 rice crop occupied an area of about 159.22 million hectares with 465.81 million tonnes of production and Results and Discussion productivity of 4.36 metric tonnes per hectare [1]. The crop is attacked by number Survey conducted during Kharif 2010-11 and 2011-12 indicated prevalence of rice of pathogens which include fungi, bacteria, viruses and nematodes besides non- blast in all the rice growing areas of Prakasam District at all stages of crop growth parasitic disorders. Among them, fungi alone account for more than thirty diseases [Table-1]. The pooled data of 2010-2011 and 2011-2012 Kharif seasons indicated of which rice blast caused by Pyriculariagrisea Sacc. is one of devastative and 32.2% disease severity (PDS) in Prakasam District. The mean PDS at different destructive diseases of rice worldwide, causing yield losses to the extent of 70- stages of crop growth indicated 3.4, 19.0, 29.4 and 32.2 % at transplanting, 80% in various rice ecosystems [2]. In recent times, rice blast has become one of tillering, panicle initiation and grain filling stages respectively. This indicated a the prevalent and mojor disease on rice in Prakasam and Sri Potti Sreeramulu progressive increase in the PDS from transplanting to grain filling stages. Among Nellore districts of Andhra Pradesh, causing heavy losses to the rice growing the mandals surveyed, Kandukuru mandal had least PDS of 27.1 and 36.0 % farmers. respectively during 2010-2011 and 2011-2012 Kharif. In other mandals surveyed in Prakasam district, PDS ranged from 32.3 to 34.0 % Material and Methods during 2010-2011 Kharif and 37.2 to 41.1% during 2011-2012 Kharif. Further, Roving survey for the disease severity of rice blast was conducted in different rice during Kharif2010-11, Chimakurthy mandal had higher PDS among the different ecosystems, viz., irrigated, rainfed, tank fed, bore wells, low lying and upland mandals at all stages of crop growth i.e., 5.2, 28.0, 38.0 and 38.4 % PDS ecosystems during Kharif and Rabi seasons of 2010-11 and 2011-12 in Prakasam respectively at transplanting, tillering, panicle initiation and grain filling stages and SPSR Nellore Districts. In each district four mandals and in each mandal except in Giddaluru mandal where in PDS was higher during panicle initiation three villages were selected. In each village, two fields were selected for the study. (38.9%) and grain filling (40.3%) stages compared to Chimakurthy mandal. Least The observations recorded by selecting hundred plants randomly in each field by PDS was recorded at all stages of crop growth in Kandukuru mandal. walking diagonally starting from South west corner. The percent disease severity Among the different villages surveyed, Pallamalli of Chimakurthy mandal had was recorded at transplanting, tillering, panicle initiation and grain filling stages. maximum PDS (5.4, 26.0, 34.3 and 37.1 %) at all stages of crop growth whereas The percent disease severity of blast in a locality was recorded by using the Palukuru of Kandukurumandal had least PDS (2.8, 7.5, 17.8 and 22.8%) at all formula stages of crop growth.

International Journal of Agriculture Sciences ISSN: 0975-3710&E-ISSN: 0975-9107, Volume 10, Issue 10, 2018 || Bioinfo Publications || 6096 Survey for the Occurrence of Rice leaf Blast in Prakasam and Sri Potti Sreeramulu Nellore District of Andhra Pradesh

Table-1 Occurrence of rice blast in Prakasam District of Andhra Pradesh during Kharif, 2010-11 and 2011-12

Per cent Disease Severity (PDS)

Mandal Villages Transplanting stage Tillering stage Panicle Initiation stage Grain Filling stage 2010-11 2011-12 Mean 2010-11 2011-12 Mean 2010-11 2011-12 Mean 2010-11 2011-12 Mean Reddynagar 5.3 2.7 4.0 25.4 18.5 21.9 27.5 22.6 25.1 29.7 28.5 29.1 Darsi Pulipadu 2.5 3.8 3.2 18.8 21.0 19.9 30.6 30.5 30.5 32.3 33.5 32.9 Darsi 4.5 2.0 3.2 21.6 24.5 23.0 34.3 31.9 33.1 36.4 33.3 34.9 Mandal Mean 4.1 2.8 3.5 21.9 21.3 21.6 30.8 28.4 29.6 32.8 31.8 32.3 Manchikalapadu 4.1 4.4 4.2 24.6 20.3 22.4 37.8 31.1 34.4 39.5 33.8 36.7 Chimakurthi Pallamalli 6.5 4.3 5.4 29.8 22.0 26.0 35.9 32.8 34.3 38.2 36.0 37.1 Bhusarapalli 4.9 1.6 3.2 29.5 21.2 25.3 39.8 25.3 32.6 37.4 28.9 33.2 Mandal Mean 5.2 3.4 4.3 27.9 21.2 24.6 37.8 29.8 33.8 38.4 29.8 34.1 Giddaluru 3.9 1.9 2.9 27.8 12.2 20.0 35.5 23.6 29.6 36.7 25.9 31.3 Giddaluru Adimurthipalli 5.7 2.5 4.1 20.3 17.2 18.7 38.4 27.8 33.1 39.9 28.8 34.4 Ambavaram 3.7 2.3 3.0 22.3 15.7 19.0 42.8 26.5 34.7 44.2 27.6 35.9 Mandal Mean 4.4 2.2 3.3 23.5 15.0 19.3 38.9 26.0 32.5 40.3 27.5 33.9 Mopadu 1.6 2.7 2.1 12.1 16.8 14.5 31.1 24.8 28.0 38.7 26.3 32.5 Kandukuru Palukuru 2.9 2.7 2.8 12.3 2.7 7.5 28.3 7.4 17.8 33.3 12.2 22.8 Oguru 1.6 3.4 2.5 10.0 9.6 9.8 23.5 15.9 19.7 28.6 23.5 26.0 Mandal Mean 2..0 2.9 2.5 11.5 9.7 10.6 27.6 16.1 21.9 33.5 20.7 27.1 Over all Mean 3.9 2.8 3.4 21.2 16.8 19.0 33.8 25.0 29.4 36.3 28.2 32.2

Table-2 Occurrence of rice blast in Prakasam District of Andhra Pradesh during Rabi 2010-11 and 2011-12

Per cent Disease Severity (PDS)

Mandal Villages Transplanting stage Tillering stage Panicle Initiation stage Grain Filling stage 2010-11 2011-12 Mean 2010-11 2011-12 Mean 2010-11 2011-12 Mean 2010-11 2011-12 Mean Rajampalli 11.3 10.5 10.9 27.6 24.6 26.1 31.7 33.4 32.6 38.3 37.8 38.0 Darsi Samanthapudi 12.4 6.1 9.2 24.8 30.1 27.5 42.3 40.0 41.1 43.1 41.9 42.5 Veerayapalem 10.4 13.2 11.8 23.0 29.5 26.2 36.5 40.5 38.5 39.4 46.1 42.7 Mandal Mean 11.3 9.9 10.6 25.1 28.1 26.6 36.9 38.0 37.5 40.3 41.9 41.1 Devarapalem 11.3 10.0 10.7 31.1 27.5 29.3 45.4 38.2 41.8 47.7 40.9 44.3 Chimakurthi Nippatlapadu 11.7 9.1 10.4 30.1 25.0 27.5 41.0 32.6 36.8 42.9 36.0 39.5 Pulikonda 7.9 8.3 8.1 20.5 25.5 23.0 31.1 29.1 30.1 36.5 31.0 33.8 Mandal Mean 5.2 9.1 7.2 27.9 26.0 27.0 37.8 33.3 35.6 38.4 36.0 37.2 Brahmanapalli 10.1 7.0 8.6 27.7 21.3 24.5 37.7 25.2 31.4 40.7 30.7 35.7 Giddaluru Kongalavedu 9.8 8.9 9.4 30.5 25.5 28.0 39.3 31.8 35.5 42.0 36.4 39.2 Mundlapadu 10.4 8.5 9.5 29.2 16.0 22.6 32.6 30.2 31.4 34.1 37.3 35.7 Mandal Mean 4.4 8.2 6.3 23.5 20.9 22.2 38.9 29.1 34.0 40.3 34.8 37.6 Kandukuru 1.6 11.1 6.3 12.1 20.1 16.1 31.1 32.6 31.8 38.7 40.9 39.8 Kandukuru Machavaram 2.9 8.1 5.5 12.3 22.9 17.6 28.3 31.3 29.8 33.3 38.3 35.8 Mahadeva puram 1.6 12.4 7.0 10.0 20.8 15.4 23.5 29.0 26.2 28.6 35.0 31.8 Mandal Mean 2.0 10.5 6.3 11.5 21.2 16.4 27.6 30.9 29.3 33.5 38.0 35.8 Over all Mean 6.4 11.5 8.9 18.8 22.7 20.7 27.6 31.2 29.4 33.4 36.4 34.9

Comparison of mean values over all the villages surveyed indicated relatively 35.8% during Rabi 2010-2011 and 2011-2012. Further, Darsi mandal had higher higher PDS values in 2010-2011 Kharif (36.3 % PDS at grain filling stage) disease at all stages of crop growth i.e., 10.6, 26.6, 37.5 and 41.7 % disease compared to 2011-2012 Kharif (28.2 % PDS at grain filling stage). severity at transplanting, tillering, panicle initiation and grain filling stages respectively. At tillering stage Chimakurthy mandal recorded higher PDS of 27.9% Survey of the disease severity in Rabi 2010-11 and 2011-12 in Prakasam compared to Darsi mandal (26.6% PDS). Among the villages Devarapalem of district Chimakurthy mandal showed higher PDS of 47.7% during Rabi 2010-11 and The results of survey conducted during Rabi 2010-11 and 2011-12 also indicated Veerayapalem of Darsi mandal showed highest PDS of 46.0% during Rabi 2011- prevalence of rice blast at all the rice growing fields of Prakasam district at all 2012. Comparison of mean values across villages surveyed indicated relatively stages of crop growth [Table-2]. The pooled data on blast severity during 2010- higher PDS values in 2011-2012 Rabi (36.4 % PDS at grain filling stage) 2011 and 2011-12 Rabi seasons revealed that 34.9% PDS in Prakasam district. compared to 2010-2011 Rabi (33.4% PDS at grain filling stage). Mean PDS at different stages of crop growth indicated 8.9, 20.7, 29.4, and 34.9% PDS at transplanting, tillering, panicle initiation and grain filling stages. As Survey of the disease severity in Kharif 2010-11 and 2011-12 in SPSR Nellore observed in Kharif season, survey in Rabi season also indicated progressive district increase in PDS from transplanting to grain filling stage. However, contrary to Survey conducted during 2010-11 and 2011-12 Kharif indicated prevalence of rice Kharif where in 2010-2011 recorded maximum percent disease severity compared blast in all the rice growing fields of SPSR Nellore District at all stages of crop to 2011-12, during Rabi higher PDS was recorded in 2011-2012 compared to growth [Table-3]. The pooled data of 2010-2011 and 2011-2012 Kharif seasons 2010-11. Among the mandals surveyed Kandukuru mandal had least PDS of indicated 34.0% of disease severity (PDS) in SPSR Nellore District.

International Journal of Agriculture Sciences ISSN: 0975-3710&E-ISSN: 0975-9107, Volume 10, Issue 10, 2018 || Bioinfo Publications || 6097 Rao Varaprasada and Anil Kumar P.

Table-3 Occurrence of rice blast in Sri Potti Sreeramulu Nellore District of Andhra Pradesh during Kharif, 2010-11 and 2011-12

Mandal Villages Per cent Disease Severity (PDS) Transplanting stage Tillering stage Panicle Initiation stage Grain Filling stage 2010-11 2011-12 Mean 2010-11 2011-12 Mean 2010-11 2011-12 Mean 2010-11 2011-12 Mean Atmakuru 4.0 2.0 3.0 25.4 16.3 20.9 28.4 19.7 24.1 29.9 21.2 25.5 Atmakuru Aravedu 2.3 2.1 2.2 21.1 23.5 22.3 31.1 26.8 28.9 33.0 31.9 32.4 Bandarupalli 4.4 1.7 3.1 27.4 18.6 23.0 32.2 22.4 27.3 34.7 27.7 31.2 Mandal Mean 3.6 1.9 2.8 24.7 19.4 22.1 30.5 23.0 26.8 32.5 26.9 29.7 Podalakuru 3.6 1.9 2.8 24.7 19.4 22.1 30.5 23.0 26.8 32.5 26.9 29.7 Podalakuru Thatiparthi 7.2 3.1 5.2 27.4 6.8 17.1 34.5 10.7 22.6 35.1 11.8 23.5

Mahendrapuram 7.7 1.6 4.6 32.3 7.6 19.9 39.1 10.6 24.9 42.4 12.9 27.7 Mandal Mean 6.7 2.5 4.6 31.2 6.8 19.0 39.0 10.4 24.7 40.9 13.5 27.4 Kavali 5.4 2.9 4.1 34.0 5.9 20.0 43.4 9.8 26.6 45.3 15.9 30.6 Kavali Anemadugu 6.7 2.5 4.6 31.2 6.8 19.0 39.0 10.4 24.7 40.9 13.5 27.2 Musunuru 3.9 4.1 4.0 29.4 30.4 29.9 33.8 34.2 34.0 36.9 37.8 37.4 Mandal Mean 3.2 3.1 3.2 27.4 28.5 28.0 31.5 33.2 32.4 33.6 34.8 34.2 Kovuru 1.8 1.8 1.8 28.9 29.4 29.1 30.0 33.8 31.9 31.6 32.8 32.2 Kovuru Padugupadu 3.9 3.5 3.7 24.1 25.7 24.9 30.8 31.5 31.1 32.4 33.8 33.1 Pothireddypalem 3.2 3.1 3.2 27.4 28.5 28.0 31.5 33.2 32.4 33.6 34.8 34.2 Mandal Mean 2.0 2.2 2.1 18.3 19.9 19.1 29.5 30.8 30.2 34.2 33.7 34.0 Over all Mean 1.2 1.8 1.5 16.2 18.2 17.2 30.1 31.8 31.0 33.1 35.3 34.2

Table-4 Occurrence of rice blast in Sri Potti Sreeramulu Nellore District of Andhra Pradesh during Rabi, 2010-11 and 2011-12

Disease Severity (%)* Mandal Villages Transplanting stage Tillering stage Panicle Initiation stage Grain Filling stage 2010-11 2011-12 Mean 2010-11 2011-12 Mean 2010-11 2011-12 Mean 2010-11 2011-12 Mean Vasali 10.0 5.6 7.8 25.4 23.3 24.4 38.2 30.3 34.2 40.4 33.0 36.7 Atmakuru Battepadu 9.9 5.0 7.5 26.9 20.6 23.8 43.1 36.9 40.0 45.8 40.2 43.0 Yadavalli 11.1 6.0 8.5 27.6 29.8 28.7 37.1 38.0 37.6 40.1 38.4 39.2 Mandal Mean 10.3 5.5 7.9 26.7 24.6 25.7 39.4 35.1 37.3 42.1 37.2 39.7 Mogalluru 10.9 4.2 7.5 35.2 21.7 28.5 47.9 26.6 37.2 51.8 36.8 44.3 Podalakuru Sangam 10.9 4.7 7.8 33.0 21.0 27.0 45.6 25.5 35.6 49.9 27.6 38.8 Chejerla 9.2 4.9 7.0 22.4 19.3 20.9 33.9 20.6 27.3 34.2 22.9 28.6 Mandal Mean 10.3 4.6 7.5 30.2 20.7 25.5 42.4 24.3 33.4 45.3 29.1 37.2 Kavali Bitragunta 10.3 6.0 8.1 35.0 29.8 32.4 42.5 35.8 39.1 43.3 38.8 41.0 Bhogolu 10.4 9.8 10.1 40 30.1 35.0 42.5 35.0 38.8 42.8 40.3 41.5 Jaladanki 7.4 7.5 7.4 36.3 40.4 38.4 42.0 46.4 44.2 45.5 51.1 48.3 Mandal Mean 9.3 7.8 8.6 37.1 33.4 35.3 42.3 39.1 40.7 43.9 43.4 43.7 Rajupalem 7.2 10.7 8.9 30.0 42.9 36.5 31.6 47.1 39.4 32.9 52.4 42.6 Kovuru Inamadugu 9.5 11.1 10.3 25.0 42.8 33.9 30.6 47.1 38.8 31.7 57.0 44.4 Gangavaram 8.4 9.5 9.0 27.1 43.3 35.2 30.0 46.2 38.1 32.8 50.8 41.8 Mandal Mean 8.4 10.4 9.4 27.4 43.0 35.2 30.7 46.8 38.8 32.5 53.7 43.1 Over all mean 9.2 7.6 8.4 26.3 33.3 29.8 34.1 38.3 36.2 36.6 41.9 39 .3

Table-5 Progression in the amount of mean leaf blast severity over years in Kharif Table-6 Progression in the amount of mean leaf blast severity over years in Rabi 2010-2011 and 2011-2012 2010-2011 and 2011-2012 Kharif 2010-2011 Kharif 2011-12 Stages of crop Rabi 2010-2011 Rabi2011-12 Stages of crop Mean PDS Progression Mean PDS (%) Progression Mean Progression Mean PDS Progression (%) (%) (%) PDS (%) (%) (%) (%) Transplanting 3.9* -- 2.8 -- Transplanting 6.4* -- 11.5 --- Tillering 21.2 17.3 16.8 14 Tillering 18.8 12.4 22.7 11.2 Panicle initiation 27.6 8.8 31.2 8.5 Panicle initiation 33.8 12.6 25 8.2 Grain filling 33.4 5.8 36.4 5.2 Grain filling 36.3 2.5 28.2 3.2 *Figures are mean PDS values over all the villages and mandals surveyed *Figures are mean PDS values over all the villages and mandals surveyed In other mandals surveyed in SPSR Nellore district, PDS ranged from 34.2 to 40.9 % during 2010-2011 Kharif and 29.7 to 34.2% during 2011-2012 Kharif. Further The mean PDS at different stages of crop growth indicated 1.51, 17.2, 31.0 and during Kharif 2010-11, Kavali mandal had higher PDS among the different 34.2 PDS at transplanting, tillering, panicle initiation and grain filling stages mandals at all stages of crop growth, i.e., 3.2, 28.0, 32.4 and 34.2% PDS respectively. This indicated a progressive increase in the PDS from transplanting respectively at transplanting, tillering, panicle initiation and grain filling stages. In to grain filling stages. Among the mandals surveyed, Atmakurumandal had least Podalakuru mandal, PDS was higher only during transplanting stage (4.6% PDS) PDS of 32.5 during 2010-2011 Kharif and Podalakuru mandal had 13.5 PDS compared to (3.2% PDS) in Kavali mandal. during 2011-2012 Kharif respectively.

International Journal of Agriculture Sciences ISSN: 0975-3710&E-ISSN: 0975-9107, Volume 10, Issue 10, 2018 || Bioinfo Publications || 6098 Survey for the Occurrence of Rice leaf Blast in Prakasam and Sri Potti Sreeramulu Nellore District of Andhra Pradesh

Except at transplanting stage, Podalakuru mandal had lesser PDS. Among the rice is growing in large area. The two districts Prakasam and Sri Potti Sreeramulu villages, Musunuru of Kavalimandal had maximum PDS (4.0, 29.2, 32.4 and 34.2 Nellore districts are facing severe rice blast problem in every year. In view of this %) at all the stages of crop growth in both 2010-2011 Kharif and 2011-12 Kharif survey was conducting to formulate good disease management practices. whereas Thatiparthi of Podalakurumandal had least PDS (5.2, 17.1, 22.6 and 23.5%) at all stages of crop growth during Kharif 2010-2011 and Anemadugu of Research Category: Leaf blast, roving survey Kavali mandal (4.6, 19.0, 24.6 and 27.2%) during Kharif 2011-2012. Comparison of mean values across villages surveyed indicated higher PDS values in 2011-12 Abbreviations: Kharif (36.6 % PDS at grain filling stage) compared to Kharif 2010-11 (33.1% PDS PDS: Percent disease severity at grain filling stage). Acknowledgement / Funding: Author thankful to ICAR-Krishi Vigyan Kendra, Survey of the disease severity in Rabi 2010-11 and 2011-12 in SPSR Nellore Darsi, Prakasam, 523247, Acharya N. G. Ranga Agricultural University, Lam, district Guntur, 522034, Andhra Pradesh, India for providing the opportunity to conduct The results of survey conducted during Rabi 2010-11 and 2011-12 also indicated the work. prevalence of rice blast at all the rice growing fields of SPSR Nellore district at all stages of crop growth [Table-4]. The pooled data on blast severity during Rabi *Research Guide or Chairperson of research: Professor P. Anil Kumar 2010-2011 and 2011-12 revealed that 39.3 % PDS in SPSR Nellore district. Mean University: Acharya N. G. Ranga Agricultural University, Lam, Guntur, 522034, PDS at different stages of crop growth indicated 8.4, 29.8, 36.2, and 39.3% PDS Andhra Pradesh, India at transplanting to and grain filling stages. As observed in Kharif, survey in Rabi Research project name or number: ‘Studies of blast disease of rice caused by also indicated progressive increase in PDS from transplanting to grain filling Pyricularia grisea Pers. EX (Fr) Grove’ stages. Among the mandals surveyed Podalakuru mandal had least PDS of 37.2% during Rabi 2010-2011 and Rabi 2011-2012. Further Kavali mandal had Author Contributions: All author equally contributed higher disease at all stages of crop growth i.e., 8.6, 35.3, 40.7 and 43.7 PDS respectively. However, Kovuru mandal had recorded higher PDS of 9.4 % Author statement: All authors read, reviewed, agree and approved the final compared to Kavali mandal (8.6% PDS). Among the villages, Mogalluru of manuscript Podalakuru mandal showed higher PDS of 51.8 during Rabi 2010-11 and Inamadugu of Kovuru mandal showed highest PDS of 57.0 during Rabi 2011- Conflict of Interest: None declared 2012. Comparison of mean values across villages surveyed indicated higher PDS values in 2011-2012 Rabi (41.9 % PDS at grain filling stage) compared to 2010- Ethical approval: This article does not contain any studies with human 2011 Rabi (35.5 % PDS at grain filling stage). The results indicated that participants or animals performed by any of the authors. transplanting and tillering stages were highly susceptible for blast when mean values were compared for their progression from one stage to the other [Table-5] References and [Table-6]. Higher disease progression from transplanting to that of tillering [1] United States Department of Agriculture Circular Series (2013) stage may be due to more vegetative growth compared to that of tillering to [2] Ratna Madhavi K., Srinivas Prasad N., Laha G.S., Madan Mohan K., panicle initiation stages and no further vegetative growth from panicle initiation Seshu Madhav M. and Viraktamath B.C. (2011) Indian Journal of Plant stage to grain filling stage It is well known that various factors such as host, Protection, 39(2), 124-129. pathogen and environments are involved in the occurrence of a plant disease in [3] Van der Plank J.E. (1968) Academic Press,New York, 20, 6. nature [3]. The absence or low frequency of any component may result in low [4] Puri K.D., Shrestha S.M., Joshi K.D. and Chhetri G.K.B. (2006) incidence of a disease. The differences in blast severity in different years, in Journal of Institutional Agricultural and Animal Sciences, 27, 37-44 different locations and at different stages of the crop may be because of [5] Dar M.S., Hussain S., Nabi G.H. and Masood M. (2010) International differences in the varieties grown, agronomic practices, environmental factors and journal of pharma and bio sciences,1,1-4. the possible variability in the pathogen. Differences in the incidence and severity [6] Hossain M.M. and Kulakarni S. (2001) Journal of Maharashtra of rice blast in different geographical locations, in different seasons and at different Agricultural University, 26(2), 151-153. crop stages were reported by earlier workers in their surveys. Puri, et al., (2006) [7] Ali Anwar, Teli M.A., Bhat G.N., Parry G.A. and Wani S.A. (2009) reported the highest disease severity at dough stage (30.45%) followed by booting SAARC Journal of Agriculture, 7(2),25-37 stage (29.77%) and tillering stage (15.4%) in low land rice growing areas [4]. Dar, et al., (2010) recorded prevalence and distribution of blast in Kupwara district of Jammu and Kashmir and reported 25 % disease incidence and 15% [5]. However, the present investigation indicated transplanting to panicle initiation stage is more vulnerable for leaf blast occurrence in the areas surveyed. Hossain and Kulakarni, (2001) conducted survey for rice blast during Kharif 1999 in different villages of Dharwad, Belgaum and Uttara Kannada districts of Karnataka and reported maximum disease incidence in Haliyal (61.66%) and Mundagod (54.00%) talukas of North Karnataka [6]. Ali Anwar, et al., (2009) surveyed temperate districts of Kashmir for the severity of rice blast [7]. They reported that the leaf blast severity ranged from 3.7 to 41.3 % where as highest nodal blast was found in Kulgam (7.3%) followed by Khudwani (5.4%) and Larnoo (3.8%) zones of Anantanag district. The most destructive phase of neck blast severity was found in every district with an average range of 0.3-4.9%. Present investigation is the first comprehensive survey in the districts of Prakasam and PSPR Nellore districts of Andhra Pradesh which revealed prevalence of rice blast in both Kharif and Rabi seasons.

Application of research: Rice blast is a major disease in Andhra Pradesh where

International Journal of Agriculture Sciences ISSN: 0975-3710&E-ISSN: 0975-9107, Volume 10, Issue 10, 2018 || Bioinfo Publications || 6099