The first report of GPS-based mapping of Parthenium beetle (Zygogramma bicolorata Pallister) occurrence, distribution and its impact on Parthenium (Parthenium hysterophorus L.) in Northern Sri Lanka

Abstract

Purpose: Parthenium hysterophorus L. is a globally recognized one of the most invasive noxious weeds. It has invaded more than 17 districts in Sri Lanka, and is listed under weed of national significance for eradication. Biological control using parthenium beetle Zygogramma bicolorata is one of the promising eco-friendly strategies for Parthenium management and is successful in many countries. Research Method: The biennial survey was conducted to explore the potential biocontrol agent Z. bicolarata of the parthenium and its dispersal around Northern Sri Lanka. Preliminary survey data identified sampling sites that were chosen to draw the distribution and density maps of the Parthenium beetle (Z. bicolarata) using GPS tools. The field and greenhouse damage incidence of Z. bicolarata on Parthenium was calculated and subjected to ANOVA using SAS 9.1. Tukey’s HSD multiple comparison tests to identify the best treatment combination at P <0.05. Findings: The results exhibit that the Z. bicolarata distribution is confined to the Jaffna district in Northern Sri Lanka, and occurrence was the first time in Valikamam North in the year 2019/20. The highest density of the Z. bicolorata population was 35-62 per m 2 in the Valikamam North DS division in the years 2019/20 and 2020/21, respectively. The damage incidence varied from <10%-100%, but maximum field damage was 25->50% in Valikamam North whereas in the greenhouse 10 grubs inflicted 75-100% defoliation in 9±0.75 days. Originality/value: This is the first report of the occurrence of Z. bicolorata and a detailed study of its distribution, and damage to Parthenium to decide the biological Parthenium control program.