MATING DISRUPTION OF GRAPHOLITA MOLESTA BUSCK. TO IMPROVE QUALITY AND HEALTHY OF PEACH FRUITS

In Bulgarian fruit growing agriculture mainly chemical plant protection is applied. Applications with organophosphates and pyrethroids are carried out to control the economically most important peach pest - the oriental fruit moth (Grapholita molesta Busck.). Annually during the vegetation season 7-8 insecticide treatments are applied. This leads to contamination of fruit products and the environment, which is a prerequisite for seeking other approaches. Regarding to fruit moth, sex pheromones are one of the most widely used environmental control methods, but they are most commonly used in apples. Their introduction in the monitoring of the main peach pest can lead to a reduction of chemical treatments and production with less pesticide residues. A promising direction is the use of pheromones to control the pests through sexual disorientation of males. The trial of mating disruption in the present study were carried out with ISOMATE® OFM TT dispensers in 0.9 ha peach orchard in 2020 and 2021. Pheromone traps type "Delta" of the Hungarian company CSALOMON® were used. The ISOMATE OFM TT dispensers, installed before the first flight of OFM at the rate of 250 units per ha, efficiently reduced fruit damages - down to 0.1-0.2% at harvest. In the reference orchard with 6 insecticide treatment against OFM, the damages reached 3.0-3.6%. The results indicate that mating disruption for control of Grapholita molesta Busck. can be used in production of quality and healthy peach fruits.

Oviposition Preferences of Oriental Fruit Moth Grapholita Molesta (Lepidoptera: Tortricidae) To Pear HIPVs

Herbivore-induced plant volatiles (HIPVs) are regarded as an indirect plant defense against herbivores, since they attract natural enemies to the infested plant. On the other hand, HIPVs also affect behavioral responses of herbivores. In a previous study, Lytopylus rufipes, a parasitoid of the oriental fruit moth (Grapholita molesta), showed positive responses to pear HIPVs, but the influence of pear HIPVs on G. molesta is still unclear. To better understand these responses, we first tested oviposition preferences of G. molesta to uninfested and infested pear shoots (US and IS, respectively) and uninfested mature leaves (ML) in dual-choice bioassays with a cylindrical tube. Then, preferences to volatile components were also assessed. Results show that G. molesta females preferred US-, IS-, and ML-treated areas compared to the control area (no leaves), respectively. Subsequently, G. molesta females preferred IS over US, and US more than ML when comparing pear tissues. Furthermore, G. molesta females didn’t show any significant preference to individual volatile components, but more eggs were laid in the area treated with a synthetic pear HIPV blend, compared to the hexane-treated area (control). These results indicate that G. molesta females do not avoid infested pear shoots nor HIPVs. Moreover, HIPVs may recruit not only natural enemies, but herbivores to the release point of HIPVs. Thus, it is important to examine the responses of G. molesta females to HIPVs in the field before employing them for pest management.

Associative learning and memory through metamorphosis in Grapholita molesta (Busck) (Lepidoptera: Tortricidae)

Learning of chemical stimuli by insects can occur during the larval or adult life stage, resulting in changes in the imago chemotaxic behaviour. There is little information on learning in Tortricidae, and associative learning through metamorphosis is unknown in this group. Here, we evaluate the influence of olfactory aversive learning in Grapholita molesta (Busck) (Lepidoptera: Tortricidae) during the immature stage and determine if memory persists after metamorphosis. Larvae (10–12 days old) were conditioned to associate the odour of ethyl acetate with pulses of aversive electric shock. Insects were exposed to air, to the ethyl acetate odour, and to shock, in isolation or combination. After conditioning, both larvae and adults were tested in a two-choice olfactometer. Larvae exposed only to air or ethyl acetate increased legibility. Larvae trained with ethyl acetate and shock simultaneously exhibited significant avoidance to ethyl acetate. Avoidance was still present for at least 72 hours after metamorphosis. Thus, G. molesta has the ability to associate an odour to an aversive stimulus precociously, and this association is maintained through metamorphosis and persists into adulthood.

Different Population Phenologies of Grapholita molesta (Busck) in Two Hosts and Two Nearby Regions in the NE of Spain

Grapholita molesta is an important pest of stone and pome fruits. In commercial orchards, integrated pest management programs use pheromone traps to monitor the population dynamics of G. molesta and adjust treatments. Phenology models can be used to forecast the population phenology of pests and to help optimise the time point at which to spray the orchards with insecticides. In the present study, the adult population phenologies of G. molesta in two provinces of north-east Spain were studied, as well as their fit to the phenology model most used in both provinces. Weekly captures of adults in pheromone traps through the season were recorded over 5 y in a large number of commercial orchards, and these data were used to determine the number of generations of G. molesta in each province. The results show significant differences between provinces in the generation time, being 97 degree days (DD) shorter in the Lleida province than in the Girona province. In Girona province, four generations were registered, while five were detected in Lleida. As a result of the differences found, the phenology model was not able to predict precisely the population dynamics in the Girona province.