POTATO LEAFHOPPER (HOMOPTERA, CICADELLIDAE) UTILIZATION OF ALFALFA AS A HOST - THE ROLE OF NONHOST STIMULI

The effect of non-host crabgrass, Digitaria sanguinalis (L.) Scop., on potato leafhopper, Empoasca fabae (Harris) (Homoptera: Cicadellidae), utilization of alfalfa, Medicago sativa L., as host was investigated in binary choice experiments that measured oviposition and residency preference of adults. Leafhoppers preferred to oviposit and reside on pure alfalfa over alfalfa mixed with crabgrass. Successive experiments in which crabgrass was presented to leafhoppers with fewer sensory cures (i.e. tactile, gustatory, visual, olfactory) demonstrated that olfactory cues alone from crabgrass may explain the lower preference equally as well as any combination of other cues. Thus, volatile chemicals from crabgrass reduced acceptability of alfalfa for the potato leafhopper, although visual stimuli are not completely excluded. Additional experiments showed that leafhopper density, lighting, and alfalfa density all may influence leafhopper host utilization in laboratory experiments.