Ecological engineering-based bhendi designer seeds enhanced biocontrol services of coccinellids on aphid, Aphis gossypii

Abstract

The ecologically-engineered bhendi seeds were developed with biologicals like azadirachtin 1%, Beauveria bassiana, B bassiana + Azospirillum, B bassiana + Azotobacter, humic acid, gibberellic acid, amino acid mixture, Kappaphycus alvarezii and Sargassum wightii and evaluated in the field with imidacloprid 600 FS-based designer seeds and conventional seeds on the biocontrol services of predatory coccinellids on aphids in RBD with three replications. Mean population of all coccinellids in all the treatments varied from 1.93 to 5.75 per plant. There was a remarkable increase in coccinellid population (5.75/plant) (Cheilomenes sexmaculatus F, Coccinella transversalis F, Illeis cincta F, Propylea dissecta M, Brumoides suturalis F and Oenopia billieti M) with an occurrence ratio (OR) of 2.99 due to designer seed plants treated with combination of B bassiana (10 g/kg of seeds) and Azospirillum (200 g/kg of seeds) which influenced for the maximum coccinellid population to 66.50 per cent when compared with control along with minimum population of aphids (1.70 per leaf) with preference ratio (PR) of 0.25. Designer seeds developed with seaweed extracts of S wightii (10%) and K alvarezii (7%) also influenced for higher coccinellid population of 59.97 and 56.18 per cent with OR of 2.50 and 2.28 and lesser population of aphids (3.10 and 3.05/plant) with PR of 0.46 and 0.46 respectively. However imidacloprid 600 FS-based designer seeds contributed for 38.39 per cent coccinellid population and 1.62 OR along with 4.39 aphids per plant with PR of 0.66 when compared to untreated bhendi plants (1.93 coccinellids/plant and 6.69 aphids/leaf). The behavioural bioassay by olfactometer showed that designer seed plants treated with combination of B bassiana (10 g/kg of seeds) and Azospirillum (200 g/kg of seeds) attracted more number of coccinellids (3.18) when compared to untreated bhendi seeds (0.83). The significance of designer seeds with biologicals in pest management is discussed.