Population dynamics of whitefly Bemisia tabaci (Gennadius 1889) and characterization of their natural enemy community in transgenic Bt and non-Bt cotton

Abstract

Whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a major sucking pest of agricultural and horticultural crops. It causes economic damage directly by feeding plant foliage and indirectly serves as a vector for deadly plant viruses. We studied the population dynamics of B. tabaci and the associated natural enemies in the Bt and non-Bt cotton ecosystems. Through three years of investigation, the population of B. tabaci appeared and remained for 23 weeks both in Bt and non-Bt cotton. The population of adults and nymphs of B. tabaci were higher during the last week of July (30th week; 13.47 ± 8.03 adults leaf–1) and mid of August (33rd week; 91.16 ± 82.67 nymphs leaf–1), respectively in Bt cotton. In non-Bt cotton, the higher population of adults and nymphs was found during the last week of July (30th week; 7.73 ± 3.64 adults leaf–1) and the last week of August (34th week; 35.66 ± 33.37 nymphs leaf–1), respectively. We recorded, 25 species of natural enemies (NEs) of B. tabaci, of which 23 were predators and one species of parasitoid and the entomopathogenic fungi in Bt and non-Bt cotton. The aphelinid parasitoid Encarsia lutea (Masi) was more abundant (71.29%) NEs, followed by coccinellid Serangium parcesetosum Sicard (7.76%). We found no significant difference in the abundance of the NEs observed between the Bt and non-Bt cotton. In general, climatic variables such as maximum and minimum relative humidity, temperature and rainfall influenced the build upof B. tabaci population and NEs abundance both in Bt and non-Bt cotton. Our study recorded higher population of B. tabaci in Bt cotton than the non-Bt cotton and the pest population was regulated by NEs and the prevailing climatic conditions of the region. Thus, the NEs community and population dynamics of B. tabaci need to be taken into consideration for the development of IPM. Further conservation of these wide arrays of NEs could help in the management of this pest for sustainable cotton production.