Spread of the Boll Weevil by Drainage Water and Air Currents12

When conditions are ideal, the thurberia weevil, Anthonomus grandis thurberiae Pierce, may be moved in thurberia bolls in flood drainage water from the mountainous areas where thurberia grows into the valleys where cotton is cultivated. However, the necessary conditions seldom occur. Tests in the laboratory indicated that vertical air velocities of 2.5–5.5 meters per second are necessary to suspend passive boll weevils, A. grandis Boheman, and that velocites in excess of 31.3 meters per second may be needed to free a weevil from its foothold on cotton leaves. In the late summer in Arizona and northern Sonora, Mexico, the necessary air turbulences (thermal convection and dust devils) are present to elevate boll weevils into the upper wind currents. Then these upper wind currents and their associated turbulences could move the weevils in the direction of the airflow.