COMPONENTS OF RESISTANCE IN LEUCAENA-COLLINSII (LEGUMINOSAE) TO HETEROPSYLLA-CUBANA (HOMOPTERA, PSYLLIDAE)

The mechanisms of resistance of Leucaena collinsii Rose & Britton agai nst the psyllid Heteropsylla cubana Crawford were investigated by comp aring the plant's response to the psyllid and the psyllid's behavioral and growth responses to the trees, using Leucaena leucocephala (Lam.) de Wit as the susceptible control. Potted trees in the field were tre ated with fenvalerate to remove all insects. Four days later, the numb ers of adults per shoot and the percentage of trees recolonized were 7 6-84 and 65% lower, respectively, for L. collinsii compared with L. le ucocephala. The numbers of eggs oviposited on L. collinsii were 46 and 63% lower than on L. leucocephala in field and laboratory experiments , respectively. There was also well over 90% reduction in adult eclosi on, a smaller adult size and about 67% reduction in nymphal survival o n L. collinsii than on L. leucocephala. Premature leaflet senescence a nd abscission as well as intraspecific competition for feeding sites o n L. collinsii may have a severe effect on nymphal survival. These res ults disclose several mechanisms of antixenotic and antibiotic resista nce that should be considered in resistance selection and breeding pro grams.