Influence of important weather parameters on population fluctuation on major insect pest of mandarin orange (Citrus reticulata Blanco) at Darjeeling district of West Bengal (India)

摘要

Multiple correlation studies were carried out to assess the influence of important weather factors on tile population fluctuation of insect pests of mandarin orange (Citrus reticulata Blanco) at Pedong, West Bengal during 1996 and 1997. The incidence of citrus brown aphid (Toxoptera citricidus (Kirk.) had a significant positive association with rainfall. Similarly, back fly (Aleurocanthus woglumi (Ashby)) population significantly increased with tilt increase in R.H. and rainfall. Abundance of helmet scale (Saissetia coffeae coffeae (Walker)) showed positive association with maximum temperature, R.H. and rainfall, but an inverse relation was observed with minimum temperature. In the case of soft brown scale (Coccus hesperidium Linnaeus), an identical relationship existed only with maximum and minimum temperatures. The infestation of citrus dog (Papilio demoleus Linnaeus) increased significantly with the increase iii maximum temperature and R.H., but leaf folder (Psorosticha zizyphi Staint.) showed a significant negative association with rainfall and positive correlatiou with R.H. However, individual weather parameter had no such influence on tile other frequently observed insect species of mandarin orange.