Influence of Soil Conditions on White Grub Infestations in Sugarcane in Northern Tanzania

ABSTRACT The white grub Cochliotis melolonthoides (Gerstaecker) (Scarabaeidae: Melolonthinae) is a pest of sugarcane fields in northern Tanzania. Larvae damage root systems and, in severe infestations, reduce sugarcane yields by up to 45%, with long‐lasting effects as the dead stools do not produce new stalks and create gaps in succeeding ratoon crops. Because of their economic importance in sugarcane, white grubs (Dynastidae, Melolonthinae, Rutelinae) have been extensively studied worldwide; however, their management is species‐dependent. This study aims to determine which parameters create C. melolonthoides grub infestation hotspots by focusing on soil health factors and agricultural practices. A spatiotemporal statistical analysis of 928 locations in TPC Limited (Tanzania, Arusha chini) with two white grub counts and soil analysis per location from 2022 to 2024 showed that alkaline and sodic soils had significantly higher grub density than neutral or solely alkaline soils. The presence of trash cover did not influence white grub density, nor did the irrigation method. Sugarcane varieties were a less important variable than pH and sodicity interaction in predicting white grub infestation. Pest management strategies based on changing soil conditions and agricultural practices are discussed.