Vertical Distribution of Threecornered Alfalfa Hopper Nymphs (Homoptera: Membracidae) and Girdles on Soybean

The vertical distributions of Spissistilus festinus (Say) instars, petiole girdles, and main stem girdles on soybean, Glycine max (L.) Merrill, were investigated by inspecting randomly selected whole plants. Vertical distribution patterns were characterized by dividing sampled plants into three strata: lower (the lower main stem), middle (the lower half of the canopy), and upper (the upper half of the canopy). Most nymphs were located in lower strata on plants of growth stages V2 through V7 and in middle strata on more developed plants. First and fifth instars tended to be distributed higher than third and fourth instars on plants of growth stage ≥ V10. Most main stem girdles occurred in lower plant strata regardless of plant phenology. Petiole girdles were distributed similarly to nymphs except for a scarcity in lower plant strata. Although plant phenology appeared to affect nymphal vertical distribution few nymphs or girdles were ever located in the upper plant canopy.