Release and Monitoring of Larinus minutus (Coleoptera: Curculionidae), a Biological Control Agent of Spotted Knapweed in Arkansas
Keywords:
Centaurea stoebe ssp. micranthos, weed biological control, non-native weed, invasive weedAbstract
Spotted knapweed (Centaurea stoebe ssp. micranthos (Gugler) Hayek) is an invasive plant from Eurasia that degrades pastures and rangelands in the western United States and Canada. A biological control program for spotted and diffuse (C. diffusa Lamarck) knapweeds was initiated in the 1960s, with 13 species of insects introduced and established in the United States and Canada. The program has largely been considered a success and Larinus minutus Gyllenhal (Coleoptera: Curculionidae) is considered to be one of the key agents responsible for the reduction of knapweeds. Spotted knapweed expanded its range into the southeastern United States, but biological control was not used against the weed in this region until recently. Larinus minutus were released in 6 counties in Arkansas from 2008 through 2012. Weekly sweep-net sampling to monitor weevil activity showed establishment of the weevils in 5 counties. The numbers of L. minutus captured at each site increased from 2010 to 2012. Larinus minutus in Arkansas was univoltine and sex ratios were 1:1, except during flowering, when the proportion of females captured increased. Eggs were not present in females until 1 week after flowering of spotted knapweed.
‘Spotted knapweed’ (Centaurea stoebe ssp. micranthos (Gugler) Hayek) es una maleza invasiva originaria de Eurasia que degrada los pastizales y praderas del oeste de los Estados Unidos y Canadá. Un programa de control biológico para ‘spotted’ and ‘diffuse’ (C. diffusa Lamarck) ‘Knapweeds’ fue iniciado durante la década de los sesenta, en donde trece especies de insectos fueron introducidos y establecidos en los Estados Unidos y Canadá. En su mayoría el programa ha sido considerado un éxito del cual Larinus minutus Gyllenhal (Coleoptera: Curculionidae) ha sido considerado el agente principal responsable de la reducción de ambas especies de ‘knapweeds’. Larinus minutus fue liberado en seis condados en Arkansas desde el año 2008 hasta el año 2012. Muestreos semanales con redes entomológicas fueron usados para el monitoreo de la actividad del picudo revelando su establecimiento en cinco condados. El número de L. minutus capturados en cada sitio incrementó entre los años 2010 y 2012. Larinus minutus en Arkansas fue univoltino y la proporción entre sexos fue de 1:1, excepto durante la época de floración, donde la proporción de hembras capturadas incrementó. Huevos adentro de las hembras comenzaron a ser hallados una semana después de la floración de la maleza.
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