Impact of climatic factors on leaf roll-inducing mite, Floracarus perrepae (Acari: Eriophyidae) feeding on the Old World climbing fern, Lygodium microphyllum (Pteridophyta: Lygodiaceae)

Abstract

ABSTRACT The Old World climbing fern Lygodium microphyllum is native to Asia but has become a category I weed in the Everglades ecosystem of Florida, USA. The eriophyid mite Floracarus perrepae induces leaf rolls on the subpinnae of L. microphyllum through its feeding and has been found throughout the year in the host plant, with varying prevalence. The impact of weather parameters such as temperature, rainfall, and relative humidity on the phenology of leaf rolls and mite density has been studied under natural conditions at two locations: Thomaiyarpuram (Nagercoil, Tamil Nadu, India) and Ithikkara (Quilon, Kerala, India). The trend of % leaf roll at both the sites was high during the months of August, September, October, and December in both study years. The density of mites per leaf roll varied considerably during the study, peaking in August 2003 (44.2 and 33.1 mites per roll at Nagercoil and Quilon, respectively). Statistical analysis revealed that there was no significant interaction or impact between weather variables and the % leaf roll (Nagercoil, r = 0.077 and Quilon, r = 0.025) but in Quilon the rainfall played a role in reducing the mite population. However, a significant positive correlation was found between mite density and abiotic factors (Nagercoil r = 0.6457; Quilon r = 0.9514), i.e. all the abiotic factors such as temperature, rainfall and relative humidity can influence mite density.