Behavior-modifying effects of methanolic seed extract of Garcinia kola (Clusiaceae) against Colorado potato beetle [Leptinotarsa decemlineata (Say)]

Cultivated potato, Solanum tuberosum (Solanaceae), is a key host of the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae). This important defoliating pest is recalcitrantly resistant to multiple classes of synthetic insecticides when overused. Hence, there is a continual search for novel active ingredients, such as biopesticides, which hold promise but are poorly explored. Here, variable doses [stock, high, mild, and low at 0.2, 0.1, 0.05, and 0.01 g/ml respectively] of methanolic seed extract of Garcinia kola ( Clusiaceae) or bitter kola were tested for ovicidal effect, antifeedance, and repellency against the Colorado potato beetle. Behaviors of the first and third instars, and adults were investigated in dual and no-choice Petri dish experiments, alongside olfactory response to treated leaves in a wind tunnel. The extract was not ovicidal. All three tested stages consumed significantly less from stock-, high-, and medium-dose treated leaves compared to the low-dose and control leaves. The results were consistent for dual-choice and no-choice experiments. Garcinia kola deterrence intensity depended on beetle stage, and exposure time; it remained high (>80%) at stock/high doses, declined swiftly at medium, transient at low, and absent in control. These outcomes support observed feeding attenuation and higher antifeedance at increasing dosage that limit leaf damage to < 10%. The beetles differed in wind-tunnel response, taking a longer time to reach the initial 30-cm observation point for untreated leaves, while treatment effects and odds of reaching the final 50-cm observation point were nonsignificant. Thus, G. kola seed extract has promising short-distance behavior-modifying properties against Colorado potato beetle, and may delay resistance associated with synthetics, while minimizing their attendant deleterious effects on non-target species.