Recent Research on the Boll Weevil in Northern Sonora, Mexico, and the Thurberia Weevil in Arizona1

Abstract

In 1962 research was begun in northern Sonora, Mexico, to determine the amount of damage caused by boll weevils, Anthonomus grandis Boheman, occurring in cotton fields as near as 27 miles to fields in Arizona. This research involved the establishment of ecological relationships among boll weevil populations in Sonora, in the old infested areas of the United States, and in southern Arizona, where a variety of the boll weevil, the thurberia weevil, A. grandis thurberiae Pierce, occurs on a wild cotton, Gossypium thurberi Todaro. Square damage in the Mexican cotton reached an areawide level of 10% in late August and severe yield losses occurred in several fields. In Arizona, incipient infestations of thurberia weevils developed in several cotton fields by September 5. It was determined that boll weevils in Sonora developed diapause and entered surface ground trash to survive the winter, The thurberia weevil is not known to hibernate in ground trash. In addition, evidence of considerable winter survival of the Sonora boll weevils in pupal cells within old bolls was observed in northern Sonora cotton fields, This is the only known manner in which the thurberia weevil survives over Winter. Applications of methyl parathion to cotton fields in Sonora in late October and early November considerably reduced overwintering populations.