STUDY ON THE BIOLOGY AND DAMAGE ASSESSMENT OF SWEET POTATO WEEVIL, CYLAS FORMICARIUS IN THE LABORATORY

Abstract

Consequently two experiments was conducted in laboratory of the Department of Entomology, Sher-e-Bangla Agricultural University, Dhaka-1207 during the period from July to December, 2017 to damage assessment and study on the biology of sweet potato weevil Cylas formicarius. Different sweet potato such as BARI sweet potato 2 (kamala sunduri), BARI sweet potato 4 and local variety of sweet potato were used as experimental materials. An average incubation period was 4.6±6.188 days under room conditions on BARI sweet potato 2 in laboratory condition. Total 13.60±1.81 and 6.20±1.095 days were required for larval stage and pupal stage respectively. Adult longevity of sweet potato weevil, C. formicarius was 81.40±8.11 days. The length of egg was 0.68 ±0.083 mm and width 0.32±0.083 mm; 1 st , 2 nd and 3 rd instar larval length were 1.6 ±0.38 mm, 3.76 ±0.36 mm and 5.88 ±0.25 mm respectively and larval width were 0.28±0.03 mm, 0.52±0.07 mm and 0.81 ±0.04 mm respectively; Pupal length 6.2 ±0.36 mm and width 1.0 ±0.13 mm; the length of adult was 6.82 ±0.49 mm and width 1.8 ±0.15 mm. At the 1st and 2nd generations on weight basis, % infestation, the highest infestation was recorded from BARI sweet potato-2 (49.15% and 100.00%, respectively), which was statistically different from other sweet potatoes and followed by local variety of sweet potato (41.34 % and 75.05%), whereas, the lowest percent of infestation was recorded in BARI sweet potato 4 (23.37% and 51.68%, respectively). Present study showed positive correlation between weight loss and percent of infestation of all varieties of sweet potato; weight loss increased due to increase of percent of infestation of sweet potato.