699Survival mechanism of leaphoppers Scientia Agricola, v.58, n.4, p.699-702, out./dez. 2001 ALTERNATION OF HOST PLANTS AS A SURVIVAL MECHANISM OF LEAFHOPPERS Dilobopterus costalimai AND Oncometopia facialis (HEMIPTERA: CICADELLIDAE), VECTORS OF THE CITRU

are two of the most important species of citrus leafhoppers, vectors of bacterium Xylella fastidiosa which causes the Citrus Variegated Chlorosis (CVC) disease. To develop a rearing technique for these species under laboratory conditions, the egg laying preference and nymph development were studied in different breeding systems: Rangpur lime (Citrus limonia) and “falso boldo ” (Vernonia condensata) as host plants. Trials were set up in a randomized block design with three treatments (n=8). Females of D. costalimai had particular preference for ovipositing on Rangpur lime leaves while O. facialis females placed a higher number of eggs on “falso boldo”, but it did not differ statistically from the Rangpur lime. The nymphal viability of D. costalimai was null in Rangpur lime and 58 % in “falso boldo”. For O. facialis the nymphal viability was 25 and 78 % in Rangpur lime and “falso boldo”, respectively. “Falso boldo ” is more suitable as a host plant to rear the two species of citrus leafhoppers. The alternation of host plants seems to be an important survival mechanism of the CVC-vector species, as shown in natural conditions. Key words: biology, nutritional ecology, host preferenc