Host status of six major weeds to Meloidogyne chitwoodi and Pratylenchus penetrans, including a preliminary field survey concerning other weeds

Abstract

Abstract A glasshouse experiment was carried out to investigate the host status of six important weeds in intensive agricultural cropping systems to Meloidogyne chitwoodi and Pratylenchus penetrans. Senecio vulgaris L., Capsella bursa-pastoris (L.) Medic. and Solanum nigrum L. were hosts of M. chitwoodi with reproduction factors of 2.5, 2.6 and 7.8, respectively. Echinochloa crusgalli (L.) Beauv. and Stellaria media (L.) Vill. were non-hosts for M. chitwoodi as no galls or eggs were observed. Galinsoga parviflora Cav. is considered a poor host with one out of eight plants producing an egg mass, but maintaining significantly higher population densities in the soil than were recorded in the fallow pots. Echinochloa crusgalli, S. nigrum and S. vulgaris were hosts of P. penetrans with multiplication factors of 1.6, 1.82 and 4.29, respectively. The multiplication rate of P. penetrans on S. vulgaris was similar to the one recorded on maize, the susceptible control. Galinsoga parviflora, S. media and C. bursa-pastoris were non-hosts as no specimen of the target nematode was found in the roots. After 16 weeks, only 1.22 and 0.08% of the original population was still alive for P. penetrans and M. chitwoodi, respectively. In conjunction with the pot experiment, a field survey was conducted at two sites, each of which was known to be highly infested with either M. chitwoodi or P. penetrans. Based on the survey results, Cirsium arvense Scop. and C. bursa-pastoris can also be considered to be hosts of M. chitwoodi, whilst Cirsium arvense, Chenopodium album L. and Polygonum convolvulus L. were recorded as hosts of P. penetrans. These results call attention to the possibility of weeds acting as carriers and point sources of possible high population densities of plant-parasitic nematodes. It emphasises the importance of adequate weed control in an integrated programme for management of M. chitwoodi and P. penetrans and the possible failure of the successful use of non-host crops and fallow in crop rotations when weed control is inadequate.