P. Sivasankaran ¹, S. Easwaramoorthy ¹, H. David ¹

Affiliations
1 Sugarcane Breeding Institute, Coimbatore 641 007, Tamil Nadu, IN

Abstract

Among the five different temperature conditions tested; radial growth, biomass production and sporulation were greater at 25°C foHowed by 30 and 20De. Similarly susceptibility of third instar shoot borer (Chilo infuscatellus Snellen) larvae to fungal infection was higher when the larvae were held at 25°C after treatment. Among the 5 relative humidity (RH) levels tested at 25°C, the radial growth of the fungus was maximum at 90 per cent RH, whereas biomass production and sporulation were greater at 100 per cent RH. Higher mortality of borer larvae occurred at 100 and 90 per cent RH levels and the susceptibility decreased as the RH increased.

Keywords

Beauveria nr. bassiana, Chilo infuscatellus, Relative Humidity, Temperature.

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P. Sivasankaran ¹, S. Easwaramoorthy ¹, H. David ¹

Affiliations
1 Sugarcane Breeding Institute, Coimbatore - 641 007, IN

Abstract

Second and third Instar larvae of the shoot borer Chilo infuscatellus Snell., were more susceptible (51.47 to 65.2 %) to the fungus, Beauveria nr. bassiana even at a low dosage (10⁵ or 10⁶ spores/ml), At 10⁷ spores/ml, the mortality observed was 68.53-75.93 %. Mortality of the larvae decreased with increase in larval age or decrease in the concentration of the fungus. The fungus took less time to cause mortality in second instar larvae and the incubation period Increased with Increase in the age of the larvae or decrease in the dosage. All the six species of phytophagous insects tested Viz., Chilo sacchariphagus indicus (Kapur), C. partellus Swinhoe, Scirpophaga excerptalis Walker, Sesamia inferens Walker, Heliothis arniigera Hubner and Spodoptera litura Fabricius were susceptible to the fungal Infection. The mean mortailty of third Instar larvae varied from 50.0 to 65.0 per cent in the different species. The fungus was not infective to Sturmiopsis inferens Tns. the principal larval parasite of the shoot borer.

Keywords

Beauveria nr. bassiana, Chilo infuscatellus, Pathogenicity, Host Range.

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