Ecology of aphid vectors of citrus tristeza virus

Abstract

A field survey was conducted to study the incidence of citrus tristeza virus (CTV) and newlineits aphid vectors, in different citrus growing locations of Assam and Nagaland. 190 samples newlinewere collected from four districts of Assam (Jorhat, Tinsukia, Sivasagar and Golaghat) and two newlinedistricts of Nagaland (Mokokchung and Wokha). Citrus leaf samples were used for detection of newlineCTV infection by double antibody sandwich-enzyme linked immuno-sorbent assay (DASELISA) newlineand Reverse Transcriptase Polymerase Chain Reaction (RT-PCR). According to the newlineresults, 75 per cent CTV disease incidence was detected in surveyed areas of Assam and 24.55 newlineper cent CTV disease incidence was detected in Nagaland. District wise, the highest CTV newlinedisease incidence (96.67 %) was detected in Tinsukia district of Assam and the lowest (21.43 newline%) was detected in Mokokchung district of Nagaland. RT-PCR confirmed the results of DASELISA. newlineThe survey result also indicated the presence of the vector Toxoptera citricida in all the newlinelocations. The elevations of the different location surveyed ranged from 79-1130 m AMSL. newlineThe study on population dynamics of T. citricida, revealed that the aphid reached its newlinehighest peak population of 416.68 on the 4th of June, during 2017 and 431.28 on 15th May, newlineduring 2018. T. citricida was observed to have two population peaks per year. The minimum newlinetemperature was the most dominant factor which showed positive and significant correlation, newlinefor mean population of T. citricida. 15 species of coccinellid predators and one species of newlinesyrphid were observed in the field plot of Assam Lemon and Micraspis discolor, Cheilomenes newlinesexmaculata, Coelophora bisellata and Coelophora saucia, were the most abundant and they newlinewere found actively feeding on T. citricida. The population of T. citricida, showed positive and newlinesignificant correlation, with all four coccinellid beetles, indicating that the populations of the newlinepredators, increased or decreased with the abundance or scarcity of T. citricida..