Crop genotype and stem cutting portion affect infestation pressure of the cassava root scale Stictococcus vayssierei Richard (Hemiptera: Stictococcidea) in a rainforest in Cameroon

African root and tuber scale (ARTS) Stictococcus vayssierei Richard is a serious constraint to the production of cassava ( Manihot esculenta Crantz) in Central Africa, and the food and income security for smallholder farmers. Therefore, to improve the production of cassava it is urgent to determine the appropriate cultural practices that lower ARTS infestation pressure. This study tests the single and combined effects of stem cutting portion and crop variety on ARTS infestation levels’. A split-plot design with four cassava varieties (TMS 96/0023, Excel, Miboutou and Douma) as the main plots and three stem cuttings portions of these varieties (lower, middle and upper portions of the mother plant) as sub-plots was used. The results showed that at 12 months after planting (MAP), lower portions of the local variety Douma showed the highest fresh shoots (2.95 ± 0.13 kg) than the upper portions (2.08 ± 0.09 kg) of the Excel variety. The portions at lower of the Excel variety were the most infested (118-158.38 and 126.75 ARTS) at 3, 6 and 9 MAP respectively. The yield of local variety Douma was higher (20.00-20.11 t ha − 1 ) in plots planted with portions at middle and lower, followed by yields of TMS 96/0023 variety (19.00 t ha − 1 ) in plots planted with the lower portions. Overall, irrespective of the cassava variety, the lower portion 16.49 t ha − 1 resulted in higher yield than those the upper portion 10.81 t ha − 1 .