Yield reduction and root damage to cotton induced by Belonolaimus longicaudatus

Sting nematode (Belonolaimus longicaudatus) is recognized as a pathogen of cotton (Gossypium hirsutum), but the expected damage from a given populatio n density of this nematode has not been determined. The objective of this s tudy was to quantify the effects of increasing initial population densities (Pi) of B. longicaudatus on cotton yield and root mass. In a field plot st udy, nematicide application and cropping history were used to obtain a wide range of Pi values. Cotton yields were regressed on Pi density of B. longi caudatus to quantify yield losses in the field. In controlled environmental chambers, cotton was grown in soil infested with increasing Pi's of B. lon gicaudatus. After 40 days, root systems were collected, scanned on a deskto p scanner, and root lengths were measured. Root lengths were regressed on i noculation density of B. longicaudatus to quantify reductions in the root s ystems. In the field, high Pi's (>100 nematodes/130 cm(5) of soil) reduced yields to near zero. In controlled environmental chamber studies, as few as 10 B. longicaudatus/130 cm(3) of soil caused a 39% reduction in fine cotto n roots, and 60 B. longicaudatus/130 cm(3) of soil caused a 70% reduction. These results suggest that B. longicaudatus can cause significant damage to cotton at low population densities, whereas at higher densities crop failu re can result.