Screening for the Efficacy of Botanicals and Soaps in Controlling the Banana Aphid Pentalonia nigronervosa (Hemiptera: Aphididae) Under Laboratory and Screenhouse Conditions

TL;DR

This study tests plant-based and soap treatments for controlling banana aphids, finding some mixtures can significantly reduce aphid populations in lab and greenhouse settings.

Contribution

The study introduces effective biorational mixtures of botanicals and soaps for banana aphid control as safer alternatives to synthetic insecticides.

Findings

Binary mixtures of neem oil and botanicals with insecticidal soap reduced aphid populations to less than 20 per plant.

Single applications of garlic, chili-pepper botanicals, and insecticidal soap caused over 50% aphid mortality in 96 hours.

Biorational mixtures showed potential for integrated management of banana bunchy-top disease.

Abstract

The banana aphid (Pentalonia nigronervosa) spreads banana bunchy-top disease (BBTD), an important viral disease of bananas. Controlling aphids is therefore an important component of the integrated management of BBTD. Plant extracts and oils (botanicals) and soaps offer a safer alternative to synthetic insecticides. We screened fresh and fermented botanicals (chili pepper, garlic, peppermint, and neem oil) and soaps (bathing, laundry bar, and liquid soap) singly or in mixtures against banana aphids. The botanicals and soaps were compared with water and commercial products (nimbecidine (Azadirachtin 0.03%), insecticidal soap and inorganic pesticide, and Acetamectin Force). Though not as effective as commercial products, both the botanicals and soaps greatly reduced aphid populations in the laboratory. Single applications of nimbecidine®, garlic, chili-pepper botanicals, insecticidal, and bathing soap reduced aphids’ population by over 50% mortality at 96 hps, while mixtures of chili, garlic, and neem oil with soap caused over 70% mortality. On potted plants, binary mixtures of neem oil and botanicals (fermented and unfermented) with insecticidal soap, and neem oil with bar soap, reduced aphid populations to less than 20 per plant compared to 200 aphids for plants treated with water after week 8. Thus, these botanicals and soaps have the potential to contribute to integrated BBTD management.

Controlling banana aphid (Pentalonia nigronervosa) vectors of banana bunchy-top disease is crucial for integrated disease management. Synthetic insecticides, though effective in aphid control, pose health and environmental risks. Biorational pesticides (including botanicals and soaps) are safer alternatives. This study screened four fresh and fermented aqueous plant extracts (chili pepper, garlic, neem, and peppermint) and three soaps (bathing, laundry bar, and liquid soap) singly or in mixtures against banana aphids through in vitro and in vivo experiments. Aphid-inoculated banana leaf-blade disks were used for the in vitro studies over 96 h. Potted plantlets were used for the in vivo studies over eight weeks. Applying these preparations resulted in significant (p ≤ 0.05) aphid mortality (28.6 to 100%) compared to the water control (3.3%) at 96 h post-spray (hps). In vitro, a single application of nimbecidine® (Azadirachtin 0.03%), garlic, chili-pepper botanicals, insecticidal, and bathing soap caused >50% mortality at 96 hps. Mixed applications of chili pepper, garlic-based, and neem botanicals with soap caused >70% mortality at 96 hps in vitro. Binary mixtures of neem oil, garlic, fermented garlic, or fermented peppermint with insecticidal soap, and neem oil with bar soap, were promising in vivo, reducing the aphid populations to <20/plant compared to the control, which had >200 aphids after week 8. However, these potential preparations incurred a higher cost (USD 1.30/banana mat) compared to the synthetic pesticide (USD 0.022/mat). Thus, biorational mixtures have a potential to effectively control banana aphids.

Figures