Control of the banana aphid (Pentalonia nigronervosa) using botanicals and soap

Abstract

Pentalonia nigronervosa is an important aphid in banana production as a vector for the Banana bunchy top virus. Management of the aphid through chemical means has been detested due to its cost, negative impact on humans, animals and environment at large, and possible development of insect resistance. Therefore, the need for eco-friendly and economically sound strategies for controlling the aphid such as biorationals is crucial. Laboratory experiments were conducted in a completely randomized design (CRD) to compare the effect of treatment by selected botanical preparations (neem oil, garlic, fermented garlic, chili pepper, fermented chili pepper, peppermint, fermented peppermint) and soap solutions (bathing soap, laundry bar soap and liquid soap) and some of their mixtures on the mortality of P. nigronervosa. Commercial insecticides i) insecticidal soap, ii) nimbecidine® and iii) a synthetic chemical (aceta-mectin Force®) served as positive control treatments while distilled water served as a negative (water) control treatment. Aphid mortality was observed over a 4-day period. All the tested treatments singly and in mixtures caused aphid mortality; with most of them significantly (P ≤ 0.05) different from the water control. Most importantly, single applications of nimbecidine, garlic, chili pepper and fermented chili pepper botanicals; and insecticidal, bathing and laundry bar soaps at highest concentration caused higher aphid mortalities (31.1% to 87.2%) at 24 hours post spray (HPS). Mixed applications of nimbecidine®, neem oil, garlic, fermented garlic, chili pepper, fermented chili pepper, fermented peppermint with insecticidal soap and nimbecidine® with bar soap (71.0% to 93.8% mortality at 24 HPS) were promising in vitro. Screenhouse experiments based on in vitro promising mixtures with greater than 50% aphid mortality were conducted in a CRD. Of the 12 treatments evaluated, seven caused the greater aphid mortality (proportion of 72.9% to 97.1% after fourth sprays); with three greatly reducing the aphid population abundance to less than 2 (≈ 5 aphids/plant) compared to water control of 5.4 aphid abundance (≈ 140 aphids/plant) at eighth week. Among the seven treatments, mixtures of neem oil, garlic, fermented garlic and fermented chili with insecticidal soap were promising in vivo. These findings revealed the potential use of botanical plant fermentation and botanical mixtures with soap for biorational control of P. nigronervosa. This implies that biorationals can be considered as an eco-friendly and economically alternative approach in pesticides science and technology.