Symptom of chrysanthemum disease caused by kumamoto root-lesion nematode, Pratylenchus kumamotoensis Mizukubo et al., 2007 and suppressive effects on nematode population by antagonistic plant cultivation

When rooted chrysanthemum cuttings were transplanted to pots filled with field soil infested with Pratylenchus kumamotoensis, or autoclaved soil with P. kumamotoensis introduced to the rhizosphere of chrysanthemum, the roots showed dark spots or necrotic lesions that often covered almost the entire circumference of the root, causing constrictions at the lesions. Colonies of the nematodes were observed inside roots near the necrotic lesions. Suppression of nematode populations using several antagonistic plants proven to be effective against northern root-lesion nematode, P. penetrans, were tested in greenhouse experiments using 1/5,000 a Wagner pots. Nematode populations in pots planted with peanut, sweet potato, African marigold, French marigold, Senna occidentalis cv. Habusou, or wild oats Avena strigosa were significantly lower (P = 0.05; Tukey-Kramer test) than populations in pots planted with asparagus, chrysanthemum, and even the unplanted fallow pots. The soil in each pot was then re-transplanted with rooted cuttings of chrysanthemum and the nematode populations 118 days after transplantation were examined to elucidate the sustainability of any nematode suppression observed in the preceding crop. In the peanut and sweet potato cultivation treatments both soil and root populations of P. kumamotoensis were significantly suppressed (P = 0.05; Tukey-Kramer test) to a greater extent than the other treatments tested.