PSYLLID POPULATION-DYNAMICS AND PLANT-RESISTANCE OF LEUCAENA SELECTIONS IN FLORIDA

To identify possible sources of psyllid resistance and determine the e ffect of psyllid damage on biomass yield of various Leucaena spp. and hybrids in subtropical Florida, a 3-year trial was conducted at Brooks ville, Florida. Leucaena spp. tested were L. leucocephala K8, K584, an d K636, L. pallida K376 and L. esculenta K948. Three F-2 hybrids in th e trial were L. pallida x L. diversifolia KX1, L. pallida x L. leucoce phala KX2 and L. diversifolia x L. leucocephala KX3. Leucaena esculent a and L. pallida consistently displayed the lowest psyllid damage (P<0 .01), with L. esculenta being essentially free from psyllids and damag e. Leucaena leucocephala selections had the highest damage ratings (P< 0.001) in 19 of 20 high psyllid-infestation events over the 3 years, w hile the F-2 hybrids had intermediate levels of damage. Adult psyllid populations were positively correlated with plant damage (P<0.05) in 1 8 of 20 high psyllid-infestation periods, while nymph populations were positively correlated with damage (P<0,001) at all 20 observations. P syllid damage was positively correlated with edible dry matter (DM) an d total DM for only 2 of 11 harvests. The lack of correlation between psyllid damage and biomass yield suggests that psyllid-susceptible L. leucocephala selections can be grown in subtropical Florida.