Effect of benomyl on the potato cyst nematode, Heterodera rostochiensis

Benomyl is a strong fungistat against certain groups of fungi and it does not have much effect on most plant-parasitic nematodes. Heterodera spp., however, are affected, and the literature indicated a strong effect on Heterodera rostochiensis in the field. Laboratory tests demonstrated that hatching of larvae from H. rostochiensis cysts is strongly inhibited by benomyl in vitro. In a pot trial, benomyl effectively suppressed formation of new cysts on the roots of potatoes grown in sand, clay soil or lightsandy loam. There was no such effect in soil rich in organic matter probably because of strong adsorption of benomyl. Control of H. rostochiensis by benomyl in soil could be due to suppressed hatch or to other mechanisms, such as inhibition of larval penetration of roots. In view of its long persistence in the soil and of its various side-effects, benomyl does not seem very promising for practical control of Heterodera rostochiensis.