Tito Bacca1, Khalid Haddi2,3, Maria Pineda4, Raul Narciso C Guedes3, Eugênio E Oliveira3. 1. Facultad de Ingeniería Agronómica, Universidad del Tolima, Ibagué, Tolima, Colombia. 2. Programa de Pós-Graduação em Entomologia, Universidade Federal de Viçosa, Viçosa, MG, Brasil. 3. Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG, Brasil. 4. Facultad de Ciencias Agrícolas, Universidad de Nariño, Pasto, Nariño, Colombia.
Abstract
BACKGROUND: The Guatemalan potato tuber moth, Tecia solanivora, has been the most important pest species in Hispanico-American potato fields since its first record on potatoes in 1956 in Guatemala. This insect pest has been spreading to other parts of the world, including the Canary Islands in Europe. Tuber moth control relies heavily on the use of insecticides, including pyrethroids. Here, we assessed the likelihood of control failures and performed concentration-response bioassays in five Colombian strains of T. solanivora to evaluate their susceptibilities to the pyrethroid permethrin. RESULTS: Evidence of control failures was observed in four strains tested, which exhibited moderate resistance levels (i.e. ranging from 5.4- to 24.4-fold). However, no spatial dependence was observed between the permethrin LC50 values and the geographic distances among the tuber moth strains. In order to evaluate whether permethrin resistance was mediated by potential mutations in the para-type sodium channels of T. solanivora, the IIS4-IIS6 region of the para gene was PCR amplified and sequenced from the five strains tested. As demonstrated across a range of different arthropod species that exhibited knockdown resistance (kdr), we observed a single point substitution (L1014F) at high frequencies in the para gene of all four resistant strains. CONCLUSION: This is the first identification of a target-site-alteration-based resistance in the Guatemalan potato tuber moth T. solanivora, which is widespread and exhibits high frequencies among geographically distant strains, indicating that pyrethroids are probably becoming ineffective for the control of this pest species.
BACKGROUND: The Guatemalan potato tuber moth, Tecia solanivora, has been the most important pest species in Hispanico-American potato fields since its first record on potatoes in 1956 in Guatemala. This insect pest has been spreading to other parts of the world, including the Canary Islands in Europe. Tuber moth control relies heavily on the use of insecticides, including pyrethroids. Here, we assessed the likelihood of control failures and performed concentration-response bioassays in five Colombian strains of T. solanivora to evaluate their susceptibilities to the pyrethroidpermethrin. RESULTS: Evidence of control failures was observed in four strains tested, which exhibited moderate resistance levels (i.e. ranging from 5.4- to 24.4-fold). However, no spatial dependence was observed between the permethrin LC50 values and the geographic distances among the tuber moth strains. In order to evaluate whether permethrin resistance was mediated by potential mutations in the para-type sodium channels of T. solanivora, the IIS4-IIS6 region of the para gene was PCR amplified and sequenced from the five strains tested. As demonstrated across a range of different arthropod species that exhibited knockdown resistance (kdr), we observed a single point substitution (L1014F) at high frequencies in the para gene of all four resistant strains. CONCLUSION: This is the first identification of a target-site-alteration-based resistance in the Guatemalan potato tuber mothT. solanivora, which is widespread and exhibits high frequencies among geographically distant strains, indicating that pyrethroids are probably becoming ineffective for the control of this pest species.