Aphid (Aphididae: homoptera) vectors of papaya ringspot virus (prsv) disease and their management

Abstract

A. gossypii, A. craccivora and M. persicae are the dominant aphid species in yellow funnel traps. Among these, A. gossypii was observed to be the pre-dominant species in terms of number in yellow funnel trap catches compared to A. craccivora and M. persicae. A number of A. gossypii trapped in yellow funnel trap was higher between March and April and from December to Second fortnight of February. Fresh PRSV infection was higher in April-May. Fresh incidence of PRSV (%) coincided with alates caught in yellow funnel traps in the fourth previous week suggesting the strong relationship between aphid number and PRSV incidence. Multiple regression models point to total number of alates caught in traps, maximum and minimum temperature in influencing the PRSV incidence. The model developed for 2004-5, when validated for 2005-6 explained 80%(R2=0.80) variation by a combination of three factors (total of three species of aphid vectors, maximum temperature and minimum temperature) which indicates the strength of the model developed. The cropping pattern also has bearing on higher trap catches. In south Karnataka, cultivation of cucurbits has an influence on PRSV epidemiology. Alate production of A. gossypii is dependent on the density of apterous forms and age of the plant. A gossypii a dominant vector in terms of number is also an efficient vector and can inoculate PRSV to a number of plants (at least four) once acquired the PRSV. Leaf – disc assay is the first of its kind to use for PRSV vector efficiency of aphids and opens a window of opportunity for studying virus-vector relationship. Time of infection was observed to influence total yield. Avoiding early PRSV infection was crucial to enhance yield. The plants which were infected prior to flowering (9 months after planting) yielded very less fruits compared to plants infected later.