Premature wilting and death of groundnut plants in Northern Nigeria was caused mainly by termites excavating the xylem tissue of the root. Lepidopterous larvae which damaged the crown of the plant were a less common cause. Occasional wilted plants had discoloured vascular systems from which Pythium myriotylum was consistently isolated. Wilting was also caused by mechanical damage inflicted during weeding operations. Complete severance or blockage of the water-conducting tissue of the primary root did not result in immediate death of plants, because the pods and pegs were able to absorb sufficient moisture to maintain the leaves above permanent wilting point until the onset of the dry season.