EVALUATION OF FIVE BIO-RATIONAL PESTICIDES AGAINST Bactrocera cucurbitae (COQUILLETT) IN BITTER GOURD FIELD AND THEIR RESIDUAL EFFECT ON Coccinella septempunctata (L.) IN LABORATORY CONDITIONS

Abstract

The cucurbit fruit fly (Bactrocera cucurbitae Coquillett) is one of the most important and devastating insect pests for several cucurbits. Biopesticides are an ecofriendly manner to minimize the infestation caused by insect pests. To evaluate the efficacy of five selected biopesticides viz. Ecomec 1.8 EC (Abamectin), Sunmectin 1.8 EC (Abamectin), Lumectin 10 WDG (Emamectin benzoate and Lufenuron), Tracer 45 SC (Spinosad), Green Meta (Metarhizium anisopliae) and control against cucurbit fruit fly on bitter gourd were studied from January to June 2023 with consecutive three sprays. The experiment was designed with Randomized Complete Block Design (RCBD) and replicated thrice. The data on the number and weight of healthy and infested fruits and the number of maggots inside the infested fruits were collected. Residual effects on Coccinella septempunctata in the laboratory conditions was also performed. The result showed that all the treatments had different levels of infestation reduction and significantly differed from control. The lowest percent of fruit infestation (16.20%, 10.44% and 10.44%) and the highest percent infestation reduction over control (68.75%, 84.39% and 85.33%) were found when applied Tracer 45 SC (Spinosad) after 7 days of 1st, 2nd and 3rd spray, respectively. Spinosad also showed the highest weight of healthy fruits (0.0426, 0.621 and 0.776 kg plot-1) and the lowest percent infestation by weight (11.12, 6.15 and 5.66%) in all the 3 consecutive picking after 1st, 2nd and 3rd spray. The cumulative yield was found the highest (1.832 kg plot-1) with 3.62 times increase over the control when applied Tracer 45 SC (Spinosad). The number of maggots inside the infested fruits was also found the lowest (2.33) in Tracer 45 SC treated plot and the highest (6.67) in the control plot. In the case of residual effect on C. septempunctata in the laboratory conditions, Sunmectin 1.8 EC (Abamectin) had the longest residual effect on adults of C. septempunctata causing 20% mortality at 7 days after treatment (DAT), but low toxicity against fruit fly. However, Green Meta (M. anisopliae) (0.00%) had the shortest residual effect on adults of C. septempunctata followed by Tracer 45 SC (Spinosad) at 3 DAT. Therefore, Tracer 45 SC (Spinosad) and Green Meta (M. anisopliae) can be used for the management of cucurbit fruit flies for their higher efficacy against fruit fly and lower residual activity against C. septempunctata.