author(s)
P Murali Arthanari, NK Prabhakaran and C Chinnusamy

abstract
Field experiments were conducted at non cropped areas of Coimbatore district, Tamil Nadu, India viz., Arasur, Jageenaickenpalayam, Vedapatty, Vadavalli, Mathampalayam and Devarayapuram blocks, during May – December 2010 and 2011 to study the feeding behavior of Zygogramma bicolorata beetles on Parthenium hysterophorus. Zygogramma biocolorata beetles were released during May months of both the years (2010 and 2011) in heavily Parthenium infested areas of Arasur, Vadavalli, Jageenaickenpalayam, Vedapatty Devarayapuram and Mathampalayam blocks. Adult beetles were released at 400 to 500 numbers / m² per site in about 120m² areas under non-crop situation. Observations on number of eggs, larvae and adult beetles per plant were made at monthly intervals. There was a better multiplication of beetles during September, October and November months of both the years during that period there was fair distribution of rainfall. From mid-November the beetles started evading from the infested blocks and sites. The Parthenium damage ranged between 73.6 to 89.7 percent with an average damage of 81.9 percent during North East Monsoon periods (October to December) than the south west monsoon periods (June to September) wherein damage was in the range of 39.5 to 66.7 percent during first month of observation with an average damage of 48.3 percent.