Effect of sweetpotato latex on sweetpotato weevil (Coleoptera: Curculionidae) feeding and oviposition

Abstract

Latex in some laticiferous plants acts as a natural defense system against certain herbivores. The potential of latex produced by the sweetpotato as a defense mechanism against the sweetpotato weevil, Cylas formicarius (F.) was investigated. Genetic and environmental differences were found in latex production in a broad cross section of sweetpotato germplasm (96 lines). Most lines produced 2.6-10 mg fresh weight x vine-1 of latex when the 2nd internode from the apex was severed. Some lines, however, produced more, the highest being 48-3 mg x vine-1. Young vine material produced more latex and had less weevil feeding damage than older more mature portions of the vine. Application of latex to the surface of root cores reduced feeding and oviposition. Addition of latex to a semi-artificial media also significantly reduced the number of feeding punctures. Leaf feeding location (veins) and direction (basipetal), however, were not indicative of a major deterrent role for latex against the sweetpotato weevil.