Effects of root feeding by Diaprepes root weevil, Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) on four woody ornamental plant species

We tested the hypothesis that larval root feeding by Diaprepes root weevil (DRW) reduces biomass and leaf gas exchange of the following landscape plant species: buttonwood (Conocarpus erectus L.), Surinam cherry (Eugenia uniflora L.), mahogany (Swietenia mahogani Jacq.), and pond apple (Annona glabra L). Mean leaf gas exchange values were significantly higher for non-infested than infested treatments of buttonwood and Surinam cherry with few or no significant differences between mahogany and pond apple. Fresh and dry weights were also higher for non-infested than infested plants with the differences for buttonwood the most often significant, followed by Surinam cherry, mahogany, and pond apple. There were no significant effects of larval root feeding on plant height, stem diameter, or the total number of insects recovered per plant for all host species. There was a significant difference among plant species in mean head capsule width (thus larval instars) recovered from the soil. Although plant growth and biomass of pond apple were not affected by larval feeding, it exhibited root-feeding damage as did the other three plant species. All four plant species are thus hosts of DRW. In addition to adding pond apple to the list of DRW host plants, the present study supports previous work showing that buttonwood, Surinam cherry and mahogany are susceptible to damage from DRW larvae. Our findings also suggest that of the plant species tested, buttonwood and Surinam cherry are the most vulnerable to root feeding followed by mahogany and pond apple.