Population Dynamics of Mexican Beetle, Zygogramma bicolorata Pallister

Mean population counts revealed that maximum population (121 adults/plant) of Zygogramma bicolorata was observed during September 2005 followed by 97 adults/plant in May 2005 as against low population during rest of the period. Thus, population build up of Z. bicolorata was positively correlated with temperature and relative humidity. Interestingly, adults were observed on all the locations in Delhi during January 2006. Beetles were found active continuously from January 2005 to June 2006. Larval population was recorded at all the four sites and ranged from 1 - 152/plant depending on period and weather conditions. Egg density of Z. bicolorata was highest (242 eggs/plant) during April and August 2005 and May 2006. Lowest egg density was noticed during both the years 2005 and 2006 especially in December-January (cooler months) and June-July (hotter months). The eggs, grubs and mating pairs of the beetle were regularly seen on Parthenium hysterophorus.