Synoptic Weather Conditions Associated with Long-Range Movement of the Potato Leafhopper, Empoasca fabae, into Wisconsin1

Abstract

The potato leafhopper, Empoasca jabae (Harris), winters only in the extreme southern portions of the United States. Each year in April and May a northward movement occurs, associated with the warm south winds and air masses moving up the Mississippi Valley. The synoptic weather conditions associated with the initial arrival of the potato leafhopper in Wisconsin were studied for the 10-year period 1951–60. These weather systems were generally made up of a low-pressure area over the Great Plains, a high-pressure area over the Atlantic Coast, a north-south cold front moving east, an east-west front over Wisconsin, and rain in the fall-out area. The counterclockwise movement of air around a low and the clockwise movement of air around a high tended to force a mass of warm, moist air up the Mississippi Valley. Examples are given showing the presence of winds of a speed and temperature sufficient for the transport of leafhoppers at relatively high altitudes over these long distances. If occurring in conjunction with conditions suitable for their pickup, the warm-air movement could continue to carry leafhoppers until forced over a cooler air mass.