The aim of this study was to test the influence of indol butiric acid (IBA) at four levels (0, 500, 1000, and 2000 ppm) to obtain healthy air layering of Caryocar brasiliense Camb (Caryocaraceae). In addition, we also observed the direct effect of this hormone on the success of leaf gall induction by Eurytoma sp. (Hymenoptera: Eurytomidae), and its indirect effect on galling insect parasitoids. A complete randomized design was used, with three replicates of each plot containing two air layering, and five treatments: 1) no girdling, 2) girdled + 0ppm IBA; 3) girdled + 500ppm IBA; 4) girdled + 1000ppm IBA, 5) girdled + 2000ppm IBA. The rates of air layering rooting, root/air layering, largest root length/air layering, callus formation and girdled shoots survival were not influenced by the different concentrations of IBA (p> 0.05). Furthermore, the number of the parasitoid Quadrastichus sp. (Hymenoptera: Eulophidae) and external morphological traits of the gall induced by Eurytoma sp. were not influenced by the different treatments. However, a positive relationship was found between IBA concentration and galls successfully induced, and between the number of adults of the galling Eurytoma sp. and its major parasitoid, Sycophila sp. (Hymenoptera: Eurytomidae) with 2.000ppm of IBA. These data indicate that the galling insect may select plant modules or plants with higher hormone concentration and that IBA may play a role in gall induction. Due to the low success of this hormone in the asexual propagation of C. brasiliense more studies are needed as this plant is one of the most important species in the Brazilian woodland savanna biome. Further studies are also needed to address hormone role in gall formation and its indirect effect on the community of associated parasitoids.
Pequi; vegetative propagation; galls; Eurytomidae; Eulophidae; growth regulators; indol butiric acid
