~ 224 ~ Journal of Entomology and Zoology Studies 2017; 5(1): 224-228 E-ISSN: 2320-7078 P-ISSN: 2349-6800 JEZS 2017; 5(1): 224-228 © 2017 JEZS Received: 06-11-2016 Accepted: 07-12-2016 Shiva Shankar Bhattarai Department of Horticulture and Plant Protection, Tribhuvan University, Institute of Agriculture and Animal Sciences, Nepal Correspondence Shiva Shankar Bhattarai Department of Horticulture and Plant Protection, Tribhuvan University, Institute of Agriculture and Animal Sciences, Nepal The lignin effect to the inactivation curve of Phthorimaea operculella Granulovirus ( Phop GV) from different bioassays in laboratory condition Shiva Shankar Bhattarai Abstract Laboratory experiment was conducted in completely randomised design to determine the inactivation curve that consisted of five different virus concentrations (20, 3.33, 0.55, 0.0925 and 0.015432 LE/l) of purified and raw type of viruses which were added with lignin (1%) to play UV (ultraviolet) protectant role and without mixing lignin were also prepared and again the solutions were applied to potato and egg bioassay. These solutions were subjected to artificial UV radiation through UV lamp for different time i.e., 0, 2, 4, 8, 16, 32 and 64 minutes. PhopGV larvas were harvested from different bioassays: purified PhopGV in egg, raw PhopGV in egg, purified PhopGV in potato and raw PhopGV in potato. Hiatt modelling gave the common intercept between the lignin treated and non-treated i.e., -1.53288 which indicated that there was no difference in the effect of lignin on the activity of different type of virus, i.e. raw and purified virus. The parameters of egg and potato bioassay i.e., intercepts, inactivation coefficients (k1, k2) and proportion of virus particles against increased resistance (log ) had the same value i.e., -1.53288, k1= 0.538571, k2= 0, 0.065673 and log  = -1.67081 respectively. This pointed out that these bioassays had no differences in the inactivation curves. Half inactivation speed with lignin was 4.58 days compared to 0.559 days without lignin in lab condition. The decrease in inactivation speed in case of lignin applied in lab condition proved the reduction of potato tuber moth with virus combined with lignin through the use of low dosage. Keywords: Raw, purified, PhopGV, lignin, egg, potato 1. Introduction Among more than 40 insect species that have been found to be associated with potato crops in Nepal, the potato tuber moth (PTM), Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae) is one of the most important insect pests of potato [18] . Its infestation starts right from the field during the plant growth [11] . During control of the pest, misuse of pesticides causes harmful effects on human beings and the environment [26] . Naturally occurring granulovirus Phthorimaea operculella infecting Granulovirus (PhopGV, Baculoviridae) has been standing out as one prime candidate of microbial bio-control, which is effective in controlling PTM and can play a significant role in integrated management of this pest in stored tubers and in field crops as well [14, 15] . Granulosis viruses are effective for the control of Lepidopteran order and the host range in the order includes closely related species [20] . PhopGV was first isolated in Sri Lanka [24] and later in other countries [27] . In Australia, the isolation of virus was confirmed in 1964 [21] , in South Africa, it was isolated in 1974 [5] and in Peru in 1988 [20] . However, it has been proved from numerous findings that granulosis virus if deposited on foliage are inactivated by direct sunlight and the main reason for this is ultraviolet (UV) radiation as the main factor which reduces the activity of virus [10] . Griego et al. (1985) and Davidson et al. (1969) have found that pathogen use in the field is limited by its rapid inactivation due to Ultraviolet (UV) radiation. The identification of effective adjuvant for field application of PhopGV is of interest for commercial viability and utility of this technology. Lignin based formulation mixed with CpGV provided significant UV protectant compared to CpGV alone due to its ability to absorb UV wavelength of light thus reducing virus degradation [2] . The lignin effect towards purified SeMNPV (Spodoptera exigua multiple embedded nucleopolyhedrovirus) was found as a good absorber for both UVB and UVA radiation [7] . The capacity of lignin as UV protectants would vary upon different factors such as diet, media upon larva is reared and type of virus [8] . This research of lignin towards different media (egg and potato) and type of virus (raw and purified) is the prospects for finding out the most appropriate conditions.