Evaluation of the parasitoids, Copidosoma koehleri (Blanchard) and Orgillus lepidus Muesebeck for biological control of Phthorimaea operculella (Zeller) in Nepal

The potato tuber moth Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) is a major pest of potato in field and stored house. To manage this pest, for the first time, as the means of classical biological control strategy, the life table of egg parasitoid Copidosoma koehleri (Blanchard) and larval parasitoid Orgilus lepidus Muesebeck were studied in its host potato tuber moth, Phthorimaea opercullela at laboratory condition of Entomology Division, NARC, Khumaltar while parasitization efficacy was determined in field, glasshouse and store house in 2013/14.  The life table study showed that the average premaginal development, fecundity, longevity and replacement rate of C. koehleri was found to 21.1 days, 8.4 per female, 5.5 days, 166, respectively. While average premaginal development, fecundity, longevity and replacement rate of O. lepidus was found 20.3 days, 19 per female, 7 days and 12, respectively. The efficacy study of both parasitoids in field and store house revealed that the average parasitization in plant foliage and storage tuber for C. koehleri was 11.19 and 4.59 percent, respectively which was lesser than that of O. lepidus i.e. 21.37 and 23.45 percent indicating establishment of parasitoids was successful in farmers field and storage condition in Kavreplanchowk district. The efficacy of C. koehleri was found higher (18.7%) in glasshouse condition of Khumaltar, Lalitpur than O. lepidus (7.3 percent). The parasitoids population was build up in successive days of release and more frequently in field condition than storage. Hence, The present study illustrated that  both the parasitoids are potential to suppress the potato tuber moth population and its introduction in Nepal was successful, although an integrated control program would be required to further increase their effectiveness.

Key words: Potato tuber moth, parasitoids, classical bio-control, life table