Technical Abstract: Entomopathogenic (insect-killing) nematodes are candidates for use as biological control agents for important pecan insect pests such as the pecan weevil, Curculio caryae. In deciding which kind of nematode (species or strain) is the best one to use, it is important to consider which one is likely to survive the longest in the orchard. Therefore, we compared the longevity of 29 different strains representing 11 entomopathogenic nematode species. A series of five laboratory experiments were conducted over 42 to 56 day periods. The experiments were conducted in soil from a pecan orchard in Byron, GA. Overall, we estimated S. carpocapsae (Sal) and S. diaprepesi to have the highest survival capability. The lowest level of longevity was observed in H. indica and H. marelatus, and H. mexicana. Although nematode persistence can vary under differing soil biotic and abiotic conditions, baseline data on longevity such as those reported herein may be helpful when choosing the best match for a particular target pest. The superior longevity observed in S. carpocapsae (Sal) is especially intriguing because this species has previously been shown to possess superior virulence to pecan weevil relative to other nematodes.