Competitive Regulation of Dominant Exotic Whiteflies on Coconut Palms as Influenced by Biotic and Abiotic Factors

Abstract

In the recent past, exotic whiteflies viz., Aleurodicus rugioperculatus, Paraleyrodes bondari, Paraleyrodes minei and Aleurotrachelus atratus are infesting coconut plantations in India. Based on the damage potential, the predominant species are the rugose spiralling whitefly, A. rugioperculatus and the Bondars nesting whitefly, P. bondari. A study was undertaken to determine the seasonal incidence and population dynamics of these in the new invasion region at Karungalakudi block of Madurai district from 33rd standard meteorological week (SMW) of 2021 to 32nd SMW of 2022. The results indicated that A. rugioperculatus incidence rose considerably from the first week of April (10.9 adults/ leaflet) to third week of May (8.3 adults/ leaflet; while P. bondari reached maximum during the third week of March (71.99 adults/ leaflet) and extended up to first week of June (67.57 adults/ leaflet) coinciding with summer months with high temperature and limited precipitation. Subsequently, their incidence declined with the onset of north east monsoon coupled with parasitism by Encarsia guadeloupae and predation by chrysopids from third-week of August to fourth-week of December in 2021. The extent of parasitism by E. guadeloupae on A. rugioperculatus nymphs was positively correlated and ranged from 40% (third week of August, 33rd SMW, 2021) to 84% (second week of June 2022, 24th SMW). Chrysopids revealed a highly significant positive correlation with the incidence.