Yearly nematode population variation in Stargrass, Tannergrass, Smutgrass and Setariagrass in Alajuela, Costa Rica

Nematode populations can affect productivity in cattle grasslands.Every 30 days from January 2004 to January 2005 we measured nematodepopulations in grass rhizospheres in northeastern Costa Rica.The substrate, sampling moment, and their interaction, were significant factors in the populations (p<0,05). We found Pratylenchus sp.,Helicotylenchus sp., Tylenchus sp. and non-parasitic nematodes (1,02;2,36, 1,28 y 3,87 log10 N° nematodes per 100g of roots respectively)in Stargrass throughout the year. Criconemella sp., Hemicycliophorasp., Ditylenchus sp. and Xiphinema sp. were occasionally identified. In Smutgrass, Meloidogyne sp., Pratylenchus sp., Paratylenchus sp and non-parasitic nematodes were identified (2,56; 2,51; 3,47 y 3,53 log10 N° nematodes per 100g of roots respectively).The size of plant-arasitic nematode populations in the roots was surprisingly high. We also found Pratylenchus sp., Helicotylenchus sp. and non-parasitic nematodes in Setariagrass roots, with densities of 2,92, 2,02 and 3,57 log10 N° nematodes per 100g respectively. Finally, in Tannergrass, Pratylenchus sp., Helicotylenchus sp. and non-parasitic nematodes were present (3,99; 1,47 and 3,79 log10 N°. nematodes roots 100g respectively).