Effect of a short-cycle apple tree cultivar on oriental fruit moth (Lepidoptera: Tortricidae) development and larval behavior.

The oriental fruit moth, Grapholita molesta (Busch, 1916) has historically been a major problem in traditional apple-growing regions in Rio Grande do Sul and Santa Catarina; however, a lower occurrence of G. molesta has been observed in early variety ('Eva') than long cycles cultivar 'Gala' in Paraná State. The objective of this study was to evaluate the performance of immature and adult G. molesta in apple cultivars with short and long cycles, in addition to elucidating whether there is adaptive potential for development and fertility from the first generation to the fourth. The experimental treatments consisted of larvae fed 'Eva' and 'Gala' fruit and a commercial diet. Immature development time, head capsule width, longevity and reproductive parameters were compared across the treatments. The larvae of the fourth generation exhibited better performance than those of the first on 'Eva' and 'Gala'. Immature oriental fruit moth development occurred via four or five instars. A greater number of larvae with four instars occurred on 'Eva' than on 'Gala'. The head capsule width was narrower on 'Gala' than on 'Eva' for larvae with four instars. Females reared on 'Eva' also laid more eggs than those reared on 'Gala'. The larvae that were more adapted to the feeding conditions showed reduced cycles/instars, and the females exhibited better performance when new generations originated from the same substrate. The high fluctuation of G. molesta in 'Gala' orchards is not due to the nutritional condition of the fruits.