| The biologies of the potato stalk weevil (PSW), Trichobaris trinotata (Say), Trichobaris texana LeConte, and Trichobaris bridwelli Barber were investigated in Houston, Brazos, and Robertson counties, respectively, Texas. The temporal distribution of all life stages of each species showed the PSW and T. texana are univoltine whereas T. bridwelli is bivoltine. The PSW oviposits in stem terminals of carolina horsenettle, Solanum carolinense L., and cultivated potato, Solanum tuberosum L.; T. texana, in leaf midribs and petioles of silverleaf nightshade, Solanum elaeagnifolium Cav. Trichobaris bridwelli oviposits in leaves, flowers, and fruits of jimson-weed, Datura stramonium L. The incubation period for eggs of the PSW, T. texana, and T. bridwelli averaged 7.37, 6.20, and 5.89 days, respectively, in the laboratory. The larvae of T. bridwelli develop in fruits and stems. The durations of the larval stages averaged 58.40, 56.01, and 31.11 days, respectively, for the PSW, T. texana, and T. bridwelli. Pupation in all 3 species occurred within the host plant. The pupal stages of the PSW, T. texana, and T. bridwelli averaged 12.07, 11.10, and 8.74 days, respectively. The 3 species overwintered as adults inside the host plants and emerged in April. Eight natural enemies of Trichobaris spp. were identified, including 2 mymarid egg parasites, 2 eurytomid larval parasites, 1 braconid larval parasite, 1 eupelmid larval parasite, 1 pteromalid larval and pupal parasite, and 1 braconid adult parasite. Life and fertility tables were constructed for laboratory cohorts of each species to facilitate calculation of basic population statistics. The capacity for increase was 0.0246 for the PSW, 0.0037 for T. texana, and 0.0355 for T. bridwelli. Two of the species were evaluated as potential biological weed control agents. Trichobaris texana stunted the vegetative growth of silverleaf nightshade whereas T. bridwelli inhibited reproductive growth of jimson-weed. The mature larva and pupa of the PSW were described, illustrated, and compared with those of T. texana and T. bridwelli. The PSW is apparently closely related morphologically to T. bridwelli but is biologically more similar to T. texana. |
