Efficacy of Carbofuran in Controlling Root-Knot Nematode (Meloidogyne javanica Whitehead, 1949) on Cultivars of Bambara Groundnut (Vigna subterranea (L.) Verdc.) in Yola, Nigeria

Bambara groundnut (Vigna subterrenea L. Verdc.) is an important crop produced in Adamawa State of Nigeria. However, the production of the crop is seriously threatened by root-knot nematodes (RKNs; Meloidogyne spp.). Since cultural methods have not been very effective in controlling RKN, carbofuran was evaluated to determine its efficacy in controlling M. javanica in Yola during 2002 and 2003. Three bambara groundnut cultivars (Kwachanjiwa, Kwaheuma, and Kwatolotolo) were evaluated using three application timings (at planting, 3 and 6 weeks after planting, and none). Results indicated that applying carbofuran at planting provided the greatest reduction in M. javanica population levels, which lead to increased yields in bambara groundnuts compared to the other two application timings. Furthermore, both Kwachanjiwa and Kwatolotolo provided similar high yields compared to Kwaheuma, which was most likely related to the M. javanica tolerance in these cultivars. 1. Introduction Bambara groundnut (Vigna subterranea L. Verdc.) is a tropical leguminous crop. According to Rowland [1], the crop contains 4.6% oil, 16–21% protein, and 50–61.3% carbohydrate. It is cultivated throughout northern Nigeria and many African and Asian countries [2]. Unlike other legumes particularly cowpea, bambara groundnut is known to have less insect pests, but it is highly susceptible to root-knot nematode [1]. Bambara groundnut yields are generally low in Africa, averaging between 650 and 850？kg/ha [2]. One of the major causes of the low yield of bambara groundnut apart from genetic potential is the effect of diseases and pests like nematodes. Therefore, to increase the yield of the crop, pest and disease management is a critical criterion. Farmers in this locality have used several cultural methods to manage pests but have recorded little or no success. Several of them have thus opted for other crops thus reducing the cultivation of bambara groundnut. This has negative effects on the production of the crop. Carbofuran has been reported to control nematodes [3]. Low galling index in soybean plants treated with carbofuran by both soil drench and soil drench + foliar application has been reported [4]. Furthermore it has been reported that the application of 700？ppm on soyabean plants as soil drench reduced the number of M. incognita eggs that hatched into juveniles [4]. In an experiment where carbofuran 3G was applied at the rates of 0, 100, 200, and 300？kg/ha to three hybrid yam varieties in southwestern Nigeria [5] there was an increase in the yield of the three hybrid yam varieties,