Publications by CPCRI Staff

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Browsing Publications by CPCRI Staff by Subject "Abiotic factors"

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    Microbial pathogens of the coconut pest Oryctes rhinoceros: influence of weather factors on their infectivity and study of their coincidental ecology in Kerala, India
    (2007-02) Murali Gopal; Nair, C.P.R.; Sathiamma, B.; Alka Gupta
    The rhinoceros beetle, Oryctes rhinoceros L., is an economically important pest of the coconut palm. Management of this pest has been accomplished using microbial agents viz., Oryctes virus (OrV) and an entomofungal pathogen Metarhizium anisopliae. Recently an opportunistic bacterial pathogen Pseudomonas alcaligenes has also been noticed to cause septicaemia in the grubs when under stress. To upravel the influence of abiotic weather factors and the interactions amongst these microbial pathogens, a 3 year study was conducted from September 1996 to August 1999 in three of the southern districts of Kerala, India. Of the 6627 grubs and 307 adults collected from various breeding sites of the pest, 5% of the grubs and 22% of the adults had natural virus infection, 3% larvae died of M. anisopliae mycosis and 20% larvae succumbed to bacterial septicaemia. Oryctes virus infection in grubs and adults was negatively correlated to minimum temperature (correlation co-efficient, r = —0.4, and -0.6 respectively, sample size, n =10). Increase in relative humidity increased the fungal activity (r = 0.8) whereas, maximum temperature had a negative impact (r = -0.7). Occurrence of virus infection in grubs and adults was positively correlated (r = 0.6), supporting the contention of active transmission of the virus pathogen between these two stages. The bacterial septicaemia in the grubs was marginally correlated with virus infection and P. alcaligenes undermined the efficiency of the virus pathogen.
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    Seasonal abundance of Cardiastethus exiguus Pop pius, a potential anthocorid predator of Opisina arenosella Walker in Karnataka
    (2005) Sujatha, A.
    A field surveillance was carried out during 1996-97 in coastal and interior Karnataka, to study the seasonal abundance of Cardiastethus exiguus Poppius an important anthocorid egg predator of coconut leaf eating caterpillar, Opisina arenosella Walker. Data on seasonal variation in the population of C. exiguus revealed peaks during summer and post-monsoon seasons in coastal and interior areas, respectively on all ages of palms namely, seedlings, young and adult palms. The density of C. exiguus showed significant positive correlation with early larval population of 0. arenosella, in both zones of Karnataka. Seasonal fluctuations in the population was dependent more on biotic factors than abiotic.