Efficacy of herbal extracts in the management of cactus pest, Dactylopius opuntiae (Hemiptera: Dactylopiidae) in Tigray Region, Ethiopia

Abstract

Cactus (Opuntia ficus-indica) is a drought-resistant plant and the source of food and income for many farmers during the rainy season, and the only option to feed livestock during the dry seasons, especially in the southern part of the Tigray region of Ethiopia. The region is currently suffering from a damaging parasitoid of cactus called Dactylopius opuntiae- ficus biotype. An experimental study was conducted from August 2022 to February 2023 to investigate the efficacy of herbal extracts against cochineal insects. The experiment was conducted on the insecticidal property of methanol extracts of Solanum linnaenum, Euphorbia tirucalli, Nerium oleander, Tephrosia vogelii, Calpurnia aurea, Argemone Mexicana, Datura stramonium and Ricinus communis. Herbs were extracted, and their efficacy and LC50 were determined. Phytochemical screening for secondary metabolites was performed. There was a statistically significant difference in the mean mortality of insects across the levels of the herbs (F (8, 71) = 57.812, p = 0.0001, ƞ2 = 0.867) and the experimental extract concentrations (F (1, 71) = 4198.3, p = 0.0001, ƞ2 = 0.983). The individual extracts of S. linnaenum and N. oleander caused average mortality rates of 99.3% and 97.4%, respectively, at 5% extract concentration. Tannins and saponins were the major metabolites found in the extracts. The present study demonstrated the promising insecticidal efficacy of herbal extracts against the damaging cacti pest D. opuntia-ficus biotype, providing insights into sustainable pest control strategies for protecting vital cactus resources in the Tigray region.