Research Article

Efficacy of water-based mechanical control against sap-sucking insects in tree nurseries. A case study of Ruhande Nursery, Rwanda

Gaspard R. Ntabakirabose¹, Julienne Uwitonze², Alfred Niyobyose³, Gerard Kayiranga⁴, Gilbert Siborurema⁵, Mbabazi Mbabazize⁶ and Charles Halerimana⁷

^1,3,4,5 Forest Research Department, Rwanda Forestry Authority, Huye, Rwanda

²Environmental economics and natural resources, management; University of Lay Adventist of Kigali, Rwanda

⁴Forest Management Department, Rwanda Forestry Authority, Huye, Rwanda

⁵Faculty of Business and Commerce, ISBAT University, Kampala, Uganda

⁶Department of Crop Science and Horticulture, Makerere University, Uganda

*Corresponding author e-mail: gmutago@gmail.com

(Received: 25/03/2026; Revised: 15/05/2026; Accepted: 16/06/2026; Published: 20/06/2026)

ABSTRACT

Sap-sucking insect pests are a major constraint in tree nurseries, causing direct feeding damage, transmitting pathogens, and reducing seedling vigor. This study assessed water-based mechanical control as a sustainable alternative to chemical pesticides for managing sap-sucking pests in Ruhande Nursery, Rwanda. The objectives were to identify major pest groups, compare infestation levels among tree species, and evaluate the effectiveness of water spraying in pest suppression. Field surveys identified six major hemipteran pests: aphids (Aphis spp.), whiteflies (Bemisia spp.), mealybugs (Planococcus spp.), scale insects (Coccidae), psyllids (Trioza spp.), and leafhoppers (Cicadellidae). Aphids were the most abundant pests (35.4%), followed by whiteflies (25.1%). Pest infestation varied significantly among tree species, with Eucalyptus maidenii, Eucalyptus saligna, and Eucalyptus grandis exhibiting the highest pest densities, whereas Schefflera actinophylla, Maesopsis eminii, and Markhamia lutea were comparatively less susceptible. A water-spraying experiment conducted in a randomized complete block design demonstrated significant reductions in pest populations compared with untreated controls. The highest reductions were observed in aphids (78.2%) and whiteflies (79.2%), while moderate reductions occurred in mealybugs, psyllids, and leafhoppers. Scale insects showed the lowest reduction (48.1%), likely due to their protective waxy coverings. No significant decline in pest populations was recorded in untreated plots. The results indicate that water-based mechanical control is an effective, low-cost, and environmentally friendly approach for managing sap-sucking pests in tree nurseries. The method is particularly effective against soft-bodied insects and can be integrated into sustainable pest management programs to enhance seedling health and nursery productivity in Rwanda.

Keywords: Mechanical control, Sap-sucking insects, Tree nurseries, Hemiptera, Seedling

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