Surveillance on corynespora leaf fall disease: Incidence and severity on natural rubber (Hevea brasiliensis) in certain hot spots areas in Kerala

Transcription

1 Surveillance on corynespora leaf fall : Incidence and on natural rubber (Hevea brasiliensis) in certain hot spots areas in Kerala Sadanand K. Mushrif and Jacob Mathew Rubber Research Institute of India, Kottayam , Kerala, India. Introduction Corynespora leaf fall (CLF) of rubber is prevalent in almost all rubber growing regions of the world. Noticed during the refoliation period in the rubber plantations. High humidity, a temperature range of 28 to 30 C, humid air and cloudy weather are congenial to development. Caused extensive damage during the past two decades and may become a potential limiting factor in rubber yield in Asia. Malaysia More prominent and widely distributed since Sri Lanka Clone RRIC 103 was totally uprooted India minor in 60 s. Later, sporadic incidences were noticed in Kerala. But in late nineties, it assumed severe form in Dakshina Kannada. 1

2 KARNATAKA STATE KERALA STATE CLF affected areas in South Karnataka and North Kerala states CLF affected areas in Central Kerala state 2

3 Objective: To assess the incidence, spread and of CLF in hot spots areas in Kerala MATERIALS AND METHODS Survey in two localities viz., Thodupuzha and Kothamangalam regions The survey was conducted for 2 years from 2011 to 2012 A total of 128 and 181 units were surveyed in the years 2011 and 2012 Totally 25 plants of the existing clone were assessed in a plot (Manju, et al., 2001) Disease was assessed on a 0 5scale no very light (up to five spots) light (5 10 spots and leaf fall) moderate (> 10 spots and leaf fall) severe (large lesions and leaf fall) and very severe (large lesions and > 75 leaf fall). The per cent intensity (PDI) was calculated using the formula of McKinney (1923). CLF survey 2011 RESULTS AND DISCUSSION Area wise distribution of Corynespora leaf fall 2011 Place Village No. of units visited No. of units infected Percentage of infected units Thodupuzha Nalpathu acre, Neyassery Thommankuthu Mullappuram Mission kunnu Vannapuram Kothamangalam Pinavoorkudy Kadavoor Neriamangalam Varapetty Kanjiravelli

4 Area wise distribution of Corynespora leaf fall 2011 Corynespora leaf fall progress 2011 Place Village Per cent in different months January February March April Nalpathu acre, Neyassery Thodupu zha Thommankuthu Mullappuram Mission Kunnu Vannapuram Pinavoorkudy Kothama ngalam Kadavoor Neriamangalam Varapetty Kanjiravelli

5 Fig. Corynespora leaf fall progress 2011 Clone wise Corynespora leaf fall 2011 Disease in immature and mature crop Clone Immature (1 7 years) Mature (8 years and above) RRII RRII RRII PB

6 Thommankuthu Mulappuram Public utility buildings Nalpathu Acre Forest RRII 105 (Mature) Other clones RRII 105 (Immature) Neyasserry CLF affected immature phase of RRII 105 Fig. Map showing CLF affected region of Nalpathu Acre Area wise distribution of Corynespora leaf fall 2012 Place Village No. of units visited No. of units infected infected Thodupuzha Nalpathu acre, Neyassery Thommankuthu Mullappuram Mission Kunnu Vannapuram Kothamangalam Pinavoorkudy Kadavoor Neriamangalam Varapetty Kanjiravelli

7 Fig. Area wise distribution of Corynespora leaf fall 2012 Corynespora leaf fall progress 2012 Place Thodupuzha Village Per cent in different months January February March April Nalpathu acre, Neyassery Thommankuthu Mullappuram Mission Kunnu Vannapuram Kothamangalam Pinavoorkudy Kadavoor Neriamangalam Varapetty Kanjiravelli

8 25 Nalpathu acre Thodupuzha 20 Mullappuram Disease Mission Kunnu Vannapuram Pinavoorkudy 5 Kadavoor 0 January February March April Months Neriamangalam Varapetty Kanjiravelli Fig. Corynespora leaf fall progress 2012 Clone wise Corynespora leaf fall 2012 Clone Disease in immature and mature crop Immature (1 7years) Mature (8 years and above) RRII RRII RRII PB

9 Conclusion In the present study, the was noticed to be prominent in a few pockets of Idukki and Ernakulam districts of Kerala state. These pockets were surrounded by forest. The was severe in Nalpathu Acre of Neyassery village and Pinavoorkuty in Kothamangalam region The was severe in February/March and thereafter declined. The incidence was on increase as reflected by more no. of units infected in 2012 The was severe in 2011 and it was declined in 2012 probably due to seasonal variation/immediate plant protection measures taken up by the growers. The immature phase of the popular clone RRII 105 was highly susceptible to the than the mature phase. The clones the clones RRII 414, RRII 430 had negligible infection while the clone PB 260 was free from the. 9