HOST PLANT DISPERSION, LEAFHOPPER MOVEMENT AND DISEASE TRANSMISSION

1. The plant-to-plant movement of the corn leafhopper, Dalbulus maidis Delong & Wolcott, and the spread of the leafhopper-borne maize rayado fino virus were investigated in four patterns of maize (Zea mays) dis persion. 2. D. maidis was less abundant and the spread of the virus wa s slower in dense stands of maize than in sparse stands. 3. When plant density was held constant, leafhoppers were more abundant in maize st ands with relatively equidistant plant spacing (uniform dispersion) th an in stands with densely-sown rows (linear dispersion) or double-sown hills (clumped dispersion), but there was no difference in virus inci dence among these plant dispersion patterns. 4. Leafhoppers were less likely to move to adjacent plants in uniform plant dispersion patterns than in either linear or clumped dispersion patterns. This result may explain the lack of higher virus incidence in uniform stands, despite higher leafhopper abundance. 5. Leafhopper movement was consistent wi th a simple rule: the shorter the distance to the next adjacent plant, the more likely a leafhopper is to move between plants. 6. These resu lts demonstrate that host plant dispersion can affect the abundance an d behaviour of highly mobile herbivorous insects even when plant densi ty is constant.