[Development and survival of free-living stages of Trichostrongylidae of sheep on irrigated pastures in Zaragoza (Spain)].

Twelve small plots (2 x 2 m) progressively received parasitised faeces on two occasions between July 1980 and February 1983. They were sprinkled from March to October. Egg and larval populations dynamics in faeces and herbage were followed. Teladorsagia and Trichostrongylus could develop all through the year, at lower speed and rate during cold months. Haemonchus larvae were observed only from May to October. With irrigation, eggs developed into infective larvae in 2-4 weeks, peaks of larvae on grass occurred in weeks 4 to 5. The maximum number of L3/100 eggs was 11.3 for Teladorsagia, 6.99 for Trichostrongylus and 10.65 for Haemonchus, after July faeces deposit.