Plant parasitic nematode relative abundance and population suppression under Chromolaena odorata (Asteraceae) fallow

Abstract

An experimental investigation into the suppressive potential of the shrub Chromolaena odorata (L.) (Asteraceae) (also known as “Siam Weed” or “Jack-in-the-Bush”) fallow to the management of plant parasitic nematodes was undertaken between April 2008 and April 2010. The experiment involved comparing nematode population densities in: (i) pure planted fallow of C. odorata, (ii) a mixture of C. odorata with other weeds, and (iii) natural re-growth of weeds from the seed bank in the soil in the field with C. odorata excluded. The population densities of several nematode species were determined at the outset, and then at 6-month intervals for 24 months. The nematode taxa identified as being present prior to fallowing were Meloidogyne spp. (Heteroderidae), Pratylenchus spp. (Pratylenchidae), Helicotylenchus spp., Rotylenchulus spp. (Hoplolaimidae); Rhabditids (Rhabditidae) and Dorylaimus spp. (Dorylaimoidea). Chromolaena odorata fallow significantly reduced the population densities of Meloidogyne spp., Pratylenchus spp., and Helicotylenchus spp. after 2 years of fallow, by 77.2%, 75.3% and 81.3% respectively. Under natural re-growth, reduction in populations of Meloidogyne spp., Pratylenchus spp., and Helicotylenchus spp. ranged between 0.12% and 17%. Densities of non-parasitic species (Rhabditids and Dorylaimus spp.) significantly increased under both C. odorata + natural re-growth fallow. However, a 16% increase in the population density of Rotylenchulus spp. was observed under C. odorata fallow in contrast to a significant (54.1%) reduction observed under the natural re-growth fallow. Bush fallow with C. odorata may become part of an integrated management practice in the management of nematode pests in crop production by indigenous farmers in south-western Nigeria.