Role of Climatic Factors on Population Fluctuation of Aphids (Brevicoryne Brassicae, Myzus persicae and Lipaphis erysimi) on Canola (Brassica napus) in Punjab, Pakistan

A field study was carried out to determine the role of weather factors on canola aphids population. Aim of this study was to investigate, how meteorological factors play a role in fluctuating aphid population. The experiment was conducted on canola crop grown under three farming systems i.e., synthetic fertilizer, farm yard manure and untreated control. Aphid population was recorded from 1st week of February to 2nd week of March during 2009 and 2010 and weather data was collected from metrological observatory during the same period. The results revealed that a peak aphid population was recorded during the beginning of 2nd week of March in both years of the study. Aphid density was positively associated with maximum as well as minimum temperature while it showed a negative correlation with relative humidity. The rainfall during 2009 showed significant and negative correlation with aphid population while during 2nd year of studies (2010) it showed non significant correlation. On division of aphid infestation period into different phases of infestation, it was observed that during the establishment phase, the rainfall and relative humidity were negatively correlated, whereas, temperature was positively correlated while, during the declining phase temperature had negative relationship with aphid population build up.