Changes in Morphological Stage of Development, Canopy Structure, and Root Nonstructural Carbohydrate Reserves of Alfalfa Following Control of Potato Leafhopper (Homoptera: Cicadellidae) and Weed Populations

Abstract

Impacts of weed and insect control measures on populations of the potato leafhopper, Empoasca fabae (Harris), and various alfalfa plant parameters were studied from 1983 through 1985. Application of summer annual herbicides for the control of grass weeds produced a dual effect, increasing alfalfa density by reducing competition from grass weeds, and encouraging the presence of potato leafhopper (PLH) and thus increased crop damage by reducing plant stage of growth and stem length. Use of winter annual herbicides was associated with an increase in root total nonstructural carbohydrates (TNC) and reduced stem density, suggesting possible herbicide damage to the alfalfa crop. Insecticide applications reduced PLH damage (hopperburn) and were associated with a more fully developed and taller alfalfa crop. By separately correlating both PLH population levels and incidence of hopperburn with the plant parameters analyzed, identical trends were noted. Thus, hopperburn may be a possible indicator of insect abundance.