On the value of various chemical substances as a means of destroying infective larvae of horse Sclerostomes in the field

Extract

From time to time attempts have been made to control the spread of sclerostome larvae by treating the manure before use on the pastures or by mechanical means such as ploughing the land to bury the larvae. Various chemicals have been used, including artificial manures and animal waste products. Lucker (1936) buried larvae at varying depths in soils of different quality and measured the percentage that appeared on the surface during periods up to six weeks. Clay soils were almost a complete barrier to vertical migration whereas sandy soils and coarse sand permitted migration, during a period of 3–8 weeks, of appreciable numbers when buried 1–6 inches. He suggests from this evidence that ploughing the land would bury the larvae and therefore reduce the number of infective larvae available to the stock. It would seem to the writer, however, that there is a fallacy in this argument. Ploughing the land would turn the soil over but, even if a plough press were used, many fissures would be left which might form an easier channel for migration to the surface. Infective larvae readily accomplish horizontal migration and the possibility of lateral migration along the overturned turf and up the fissures must not be overlooked. The action of frost and the presence of roots in the overturned sod would possibly be other factors in encouraging vertical migration, not to mention the subsequent preparation of the land required before seeding down again for permanent pasture.