International Journal of Tropical Insect Science

Research Paper

Effect of pH, rearing temperature and sunlight on infectivity of Malaysian isolate of nucleopolyhedrovirus to larvae of Spodoptera litura (Lepidoptera: Noctuidae)

A.S. Sajapa1 c1, M.A. Bakira1, H.A. Kadira2 and N.A. Samada3

a1 Department of Forest Management, Universiti Putra Malaysia, 43400, UPM, Serdang, Selangor, Malaysia

a2 Malaysian Agricultural Research Development Institute, PO Box 12341, Kuala Lumpur, Malaysia

a3 Department of Biochemistry, Universiti Putra Malaysia, 43400, UPM, Serdang, Selangor, Malaysia

Abstract

The effects of pH, sunlight and rearing temperature on infectivity of nucleopolyhedrovirus (SpltNPV) were investigated against larvae of Spodoptera litura (Fabricius). The infectivity of virus increased with increased larval rearing temperature. The LT50 values were significantly reduced from 24 to 6 days when rearing temperature was increased from 20 to 35 °C. The pH of the substrate significantly affected the infectivity of the virus. The LT50 values increased to about fourfold when the pH of suspension was raised from 7 to 11. Infectivity of the virus was more adversely affected in alkaline than in acidic suspension. Sunlight also deleteriously affected infectivity of the virus. The LT50 values increased with the increase in the period of sunlight exposure. A complete viral inactivation occurred after 12 h of direct sunlight exposure.

(Accepted April 27 2007)

Correspondence

c1 E-mail: ahsaid@putra.upm.edu.my

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