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The host-finding ability of 28 Heterorhabditis sonorensis isolates and one H. indica isolate from southern Benin and one H. indica isolate from India was examined in vertical migration sand bioassays against workers of a target citrus termite pest, Macrotermes bellicosus. Thereafter, nine selected isolates were subjected to further investigations on virulence. Our results revealed that both H. sonorensis and H. indica isolates exhibit a cruiser type of search strategy and were capable, to various degrees, of migrating, infecting and killing workers of M. bellicosus in sand columns up to 20 cm long over a period of 3 days. However, only three isolates of H. sonorensis caused 100% mortality to M. bellicosus at the greatest depth tested. The exotic H. indica isolate (LN2) did not show strong finding ability compared to the indigenous one. Concerning virulence, differences were observed among isolates for their ability to invade workers of M. bellicosus. After 12 h post exposure, H. sonorensis from Ze (Ze2) and H. sonorensis from Azohoue (Azohoue2) exhibited the lowest invasion time with IT50 = 3.35 and 3.67 h, respectively, and a higher penetration rate (11.4% and 10%, respectively) compared with the other isolates. In the concentration-mortality test, we found that, based on 95% confidence limits, all H. sonorensis and H. indica isolates appeared to be equal, with LC50 values ranging from nine to 16 infected juveniles (IJ) termite I. Interestingly, 40 II termite(-1) were enough to cause 80% mortality to M. bellicosus. Contrary to the LC50, the results of our studies clearly demonstrate that M. bellicosus exhibits a time-dependent susceptibility to the tested nematode isolates. So, the lowest LT50 was observed for H. sonorensis Ze2 (LT50 = 23.30 h), the highest for H. sonorensis Yokon (34.76 h). The LT50 of the indigenous H. indica isolate was estimated to 24.07 h. In addition, all selected isolates were able to reproduce in M. bellicosus workers. The highest reproduction potential in M. bellicosus was observed with H. sonorensis Yokon with 20 213 IJ/termite followed by H. sonorensis Ze2 with 19 368 IJ/termites. All tested Beninese EPN isolates were pathogenic to the citrus termite pest M. bellicosus, with H. sonorensis Ze2 being the most virulent

Root rot pathogens were found through diagnostic surveys in all departments (regions) of Bénin, West Africa, to affect 86 to 100% and 96 to 100% of cassava fields during the dry and rainy seasons, respectively. Disease incidence in individual fields ranged between 0 and 53%, and averaged 16 to 27% per department. Nattrassia mangiferae was consistently the most frequently isolated root rot pathogen (56% in the dry season and 22 to 52% in the rainy season). Pathogenicity of N. mangiferae was confirmed on four cultivars of cassava using stem cuttings and storage roots. For all four cultivars, N. mangiferae significantly reduced the number of roots. Lesions (3 to 15 cm long) formed on the lower stem portion of all inoculated plants, whereas control plants remained symptom free. On storage roots, the disease profile was similar to that formed on stem cuttings. Other root rot pathogens detected during the dry season were Macrophomina phaseolina (14.2%), Fusarium spp. (11.8%), Botryodiplodia theobromae (7.7%), and Pythium spp. (2.9%). During the rainy season, Fusarium spp. were the second most commonly isolated root rot pathogens in three departments (Atlantique, Borgou, and Mono). In Oueme and Zou, B. theobromae was the second most isolated root rot pathogen (ranging between 24 and 28%) during the rainy season. During the same season, Pythium spp. were pronounced in Borgou (18%), followed by Mono (11%), Atlantique (9%), Atacora (8%), Oueme (5%), and Zou (6%). Results of the study are discussed with a view to creating awareness of the destructive power of N. mangiferae, a hitherto poorly recognized root rot pathogen of cassava in Bénin and West Africa in general.