Q Macé1,2, S Mkwachu3, B Heuclin1,2 and F-R Goebel1,2
1AIDA, CIRAD, Montpellier, France; quentin.mace@cirad.fr
2AIDA, Université Montpellier, CIRAD, Montpellier, France
3TPC Limited, Moshi, Tanzania
In northern Tanzania, sugarcane produced by TPC Limited has faced severe loss from several species of white grubs. Cochliotis melolonthoides Gerst. (Coleoptera: Scarabaeidae) has been reported as the most damaging white grub both for its large size and high numbers. At TPC, the infestations have been localized in the southern area of the operation for over 80 years. This study aims to understand the factors influencing the location of white grub infestations. The study relies on three years of data collection through a systematic survey after sugarcane harvest in the southern area investigating white grub infestations, soil conditions, and cultural practices. Soils affected by both alkalinity and sodicity had significantly more severe white grub infestations than solely alkaline soils, and alkaline soils are significantly more infested than neutral soils. No relationship with cultural practices is apparent, and Mean Decrease Accuracy (MDA) of the RandomForest Model indicates that the three most influential variables are soil related (pH, CROSS, ECE), though model robustness has to be increased by additional measures before drawing final conclusions. The results suggest that soil reclamation could be of great importance in reducing white grub infestations and complement the evaluation new varieties in the Integrated Pest Management strategy of C. melolonthoides.