The effect of marigolds (Tagetes spp.) and other cover crops on Pratylenchus penetrans and on following potato crops

Root-lesion nematodes (primarily Pratylenchus penetrans) were monitored in two marigold cultivars (Tagetes tenuifolia cv. Nemakill and cv. Nemanon), a nnual ryegrass (Lolium multiflorum cv. Lemtal), red clover (Trifolium prate nse cv. Florex), and soybean (Glycine max cv. Proteus), and in the followin g potato (Solanum tuberosum cv. Superior) crop during three growth sequence s. Meadow fescue (Festuca elatior cv. Miner) and bee plant (Phacelia tanace tifolia cv. Gipha) were added to the trial in the second year. Black-eyed S usan (Rudbeckia hirta, unidentified cv.) and two additional marigold cultiv ars (T. patula ssp. nana, unidentified cv., and T. erecta cv. Crackerjack) were included in the final sequence. Population levels of root-lesion nemat odes were consistently lower under marigolds compared to the other cover cr ops tested. Correspondingly, average potato tuber yields were significantly higher (8-14%) when potato followed marigolds. The highest levels of root- lesion nematodes occurred under red clover and soybean, and the average pot ato tuber yields were lowest following these crops.