Mating disruption of the small fruit tortrix (Grapholita lobarzewskii) in organic apple orchards of northeastern Italy

The small fruit tortrix, Grapholita lobarzewskii (Nowicki) (Lepidoptera Tortricidae), is a serious problem in the organic apple orchards of the Friuli Venezia Giulia region (northeastern Italy), particularly in hilly areas. Three trials on mating disruption of G. lobarzewskii were carried out in two organic apple orchards characterized respectively by very high and low population pressure of this carpophagous pest. Red Isomate-OFM (C-plus)® dispensers, used for the control of the Oriental fruit moth, Grapholita molesta (Busck), were applied once a year at a rate of 600 dispensers/ha. The pheromone blend released from the dispensers has remarkable analogies with that of G. lobarzewskii. In plots where the dispensers were applied, the male catches in the pheromone traps were very low or null, indirectly confirming the mating reduction. A reduction of eggs laid on apple fruit was also observed. Mating disruption reduced significantly the percentage of apple fruit attacked by the small fruit tortrix both in the apple orchard with very high population pressure and in the orchard with low population pressure. A not negligible proportion of infested fruit rotted and fell much earlier with respect to harvest time and it suggests partial weight compensation by undamaged apple fruit. In the orchard with a high population pressure, mating disruption was not able to reduce the percentage of attacked apple fruit to acceptable levels. However, since alternative control methods against the small fruit tortrix are not currently available to organic agriculture, the mating disruption approach must be advised in all the apple-growing areas where this pest causes severe damage.