The effect of seed applied pesticides on growth and nitrogen fixation in pea pisum sativum lentil lens culinaris and faba bean vicia faba
Rennie, R.J.; Howard, R.J.; Swanson, T.A.; Flores, G.H.A.
Canadian Journal of Plant Science 65(1): 23-28
Conflicting recommendations exist on the effect of seed-applied pesticides on nodulation and N2 fixation by Rhizobium leguminosarum. This paper reports the effects of captan, thiram, metalaxyl, Evershield, DL-PLUS and B-3 in a 2-yr field experiment on emergence, nodulation, acetylene-reducing activity and shoot yield of pea (P. sativum L.), lentil (L. culinaris L.) and faba bean (V. faba L.) inoculated with seed-applied R. leguminosarum multi-strain inoculum. Seedling emergence was not detrimentally affected by pesticide application. While most of the pesticides had either stimulatory or minimally detrimental effects on nodulation and nitrogenase activity, captan reduced both in all 3 legumes. Captan-containing compounds such as B-3 (33.5% captan) and Evershield (29.5% captan) also reduced nodulation or nitrogenase activity in some of these legumes. DL-PLUS (15% captan) was not harmful, which suggests that compounds containing over 29.5% captan may not be compatible with seed-applied R. leguminosarum. Captan, which was consistently harmful, is considered the best wide-spectrum pesticide for use with these legumes. Thus, it will be necessary to select superior N2-fixing strains of R. leguminosarum that are tolerant of, if not resistant to, recommended rates of captan or to identify alternate pesticides that are more compatible with rhizobia.