Ecological engineering cropping methods enhance Coccinellids and suppress aphids Aphis gossypii (Glover) in blackgram

Abstract

Blackgram (cv. VBN 3) was border cropped with cowpea, red gram, lab lab, green gram, cluster bean and French bean separately during 2015 and 2016 to enhance activity of predatory coccinellids and to suppress aphids, Aphis gossypii (Glover). Blackgram + cowpea border cropping system significantly influenced maximum coccinellids on blackgram 3.72/plant) along with highest pest defender ratio (PDR) of 1: 2.4, occurrence ratio (OR) of coccinellids (1.83), minimum A. gossypii (3.63/terminal shoot), preference ratio (PR) of A. gossypii (0.94) and maximum BC ratio (1: 4.35). Blackgram and cluster bean, French bean, lab lab, red gram or green gram border cropping systems also effected for higher population of coccinellids; higher PDR and OR of coccinellids; and minimum A. gossypii and PR; and moderate BC ratios than blackgram alone (1.42 coccinellids/plant; 1: 0.39 PDR; mean of A. gossypii, 5.18/ terminal shoot; and BC ratio of 1: 2.02). Maximum coccinellids was observed on cowpea with highest PDR followed by French bean and lab lab. Cluster bean, red gram and green gram had higher coccinellids. Order of preference of coccinellids towards leaves and flowers was cowpea, French bean, cluster bean, lab lab, red gram and green gram by olfactometer studies.