RESUMO
An insect resistance monitoring program was developed for Mexico to accommodate the commercial introduction and stewardship of Bt cotton. Between 1998 and 2015, field-collected geographic populations of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) were evaluated against Cry1Ac and Cry2Ab proteins of Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) to establish baseline susceptibility data before the commercial use of Bollgard (Cry1Ac) and Bollgard II (Cry1Ac and Cry2Ab) cotton. An annual monitoring program was subsequently established in which a single diagnostic concentration of each Bt protein was used in a diet overlay bioassay. The diagnostic concentration represented the concentration where larvae, evaluated in baseline studies, were reduced in weight by ≥97% relative to untreated controls or failed to molt to third instar after 5 d. In the monitoring study, populations were tested against Cry1Ac from 1998 through 2015, and against Cry2Ab from 2002 through 2004 and again from 2007 through 2015. None of the Cry1Ac-exposed larvae tested during the 18-yr period reached the third larval instar after an exposure of 5 d, and weight reduction relative to untreated control larvae was uniform at about 98-99%. For the 12 yr of Cry2Ab monitoring, no larvae reached third instar, and weight reduction was uniform at >97% relative to controls. These results indicate that H. zea susceptibility to Cry1Ac and Cry2Ab has not changed during the period Bollgard and Bollgard II have been cultivated in Mexico.
Assuntos
Proteínas de Bactérias , Endotoxinas , Proteínas Hemolisinas , Mariposas , Animais , Toxinas de Bacillus thuringiensis , Resistência a Inseticidas , MéxicoRESUMO
The insecticidal properties of foliage´s powder of Peumus boldus Molina against adults and immature S. zeamais were evaluated. The highest toxicity in contact and fumigant activity was reached by concentrations upper to 1.25 percent showing mortality over to 90 percent. The treatments with high mortality showed a lower adult insect emergence (F1) and grain weight loss too. In immature S. zeamais control lower F1 was observed in highest concentrations of powder. The storage of powder under refrigerated conditions not prevents the insecticidal properties lost. All evaluated concentrations exhibited repellent activity against S. zeamais adults. The powder of P. boldus does not affect the grain germination. We concluded that powder of P. boldus has promissory perspectives to stored products pests control.
Se evaluaron las propiedades insecticidas del polvo de follaje de Peumus boldus Molina para el control de adultos y estados inmaduros de S. zeamais. La mayor toxicidad por contacto y fumigación se obtuvo con las concentraciones iguales o mayores a 1,25 por ciento registrando una mortalidad superior a 90 por ciento. Los tratamientos con mayor mortalidad mostraron también una baja emergencia de insectos adultos (F1) y menor pérdida de peso del grano. En el control de estados inmaduros la menor F1 se observó en las concentraciones más altas de polvo. El almacenamiento del polvo en refrigeración no impidió la pérdida en el tiempo de las propiedades insecticidas. Todas las concentraciones evaluadas mostraron efecto repelente contra adultos de S. zeamais. El polvo de P. boldus no afectó significativamente la germinación de los granos. Se concluye que el polvo de P. boldus tiene perspectivas auspiciosas para el control de plagas de los productos almacenados.
