IOBC wprs Bulletin Vol 22(9), 1999
Observations on the flight activity of codling moth, Cydia pomonella L.
Erzsébet Voigt
Research Institute for Fruitgrowing and Ornamentals, BudapestAbstract: In the observations made by sex-pheromone traps, it could be conducted that codling moth males were found not only in orchards planted with the hosts of the pest, but also in the ones, which were far from these orchards or well isolated from them (non-bearing apple orchard, walnut, roadside poplar trees). The data of these flights were not always similar to the ones recorded in the bearing apple orchard. A decisive number of codling moth males were caught also by the traps placed in the sour-cherry orchard, 800 m far from the assumed source. These data confirm that Cydia pomonella L. is a well flying microlepidoptera. We suppose that a part of codling moth males does not leave the orchard, remains there, another part of them flies out of the orchard to other eventual host plants or to a tree-silhouettes making quite a long distance.
Key words: codling moth, flight activity, sex-pheromone trap
Introduction
Synthetic sex-pheromone traps have been playing an important part in the observation of the flight of insect pest, especially of lepidopteran species for more than twenty years. They provide us with data especially reflect the reaction given to a certain active substance (composition of the active substance, dosage etc.), the behaviour, time and mode of reflection, by all means is characteristic of the species.
Codling moth (Cydia pomonella L.) is one of pests known for the longest time, at the same time, it is among the mostly studies insect species. Its sex-pheromone is long ago known, as it was one of the first pheromones with identified attracting compound (Roelofs et al., 1971). Data having obtained since then allow us to draw up the flight phenology most characteristic of codling moth in Hungary, but at the same time, it can be stated that this species flies well, within in the orchard but this insect also leaves it frequently.
The codling moth is otherwise known to be a well-flying microlepidoptera. It is an internal migrator according to the researchers dealing with the migration of Lepidoptera species. Bues et al. (1995), who conducted biochemical studies with populations originated from France and Switzerland, observed that there were no significant differences among populations from various areas. They think that it can be mainly attributed to their behaviour of leaving the orchard and flying far away from it.
Peter Schumacher and his Swiss colleagues (Schumacher et al, 1997) conducted laboratory studies for determing flight capacity of codling moth. Both the females and the males were involved in the test, paying attention to the age of the adults and to the fact whether hey were mated or not. The field conditions were concluded from the results of these laboratory studies. They deem that the flight capacity of certain moth is more than 5 km.
Mani et al. (1995, 1997) made field observations, especially using sex-pheromone traps. They suppose that codling moth can fly 11 km. In other experiments those traps had the higher number of catches which were in plantation of trees with larger canopy (conventional training system). Based on this observation, they concluded that codling moth orientates according to the silhouette of the canopy.
In Hungary, also by using sex-pheromone traps, dispersion of codling moth was studied by Vojnits (Vojnits 1973). Experiments could provide answers to the questions when and under what conditions our most important pests fly to the sex-pheromone traps and the behaviour of these insects how is reflected in the results.
Material and methods
In our experiments in every case the sex-pheromone trap "Csalomon" was used, developed by the entomologists of the Research Institute for Plant Protection of the Hungarian Academy of Sciences.
The site of our observations was the experimental farm of the Research Institute for Fruitgrowing and Ornamentals in "Érd-Elvira", where especially according to the investigation field of the Institute plantations of the various fruit species including germ plasm collections and cultivar collections are available. In our monitoring work, the sex-pheromone traps were placed out as follows:
Lures of the "Csalomon" traps were changed every four week. Evaluations were done at 3-day intervals or weekly, figures show the weekly data. Height of the traps in each orchard was 140-180 cm.
Our experiments were induced by our findings that flight phenology observed in the non bearing orchard or in the roadside alley were not always similar to that of the bearing orchard. It was concluded that a part of the moth population leaves the place where the larvae of the previous generation caused the damage. Therefore the traps were placed on plants closer and farther from the orchard, on the host plants of codling moth (apple, walnut), and in an orchard or single tree which do not belong to the primary host plants (sour-cherry, poplar) of the pest.
The main objective of these experiments was to determine the direction and distance of the flight of codling moth, supposing that moths caught by the traps originate from the apple orchard, as damage caused by them was not observed at other places. During the evaluation of the data, however, it should not be ignored that they were obtained from sex-pheromone traps, reflecting behaviour of male moths.
Results and discussion
Monitoring has been done since 1995, accounts were given on the preliminary results (Voigt 1998) Among the obtained flights, data of the last two years (1997 and 1998) were chosen, but they do not considerably differ from the ones recorded in the previous years.
Fig. 1 shows the flight observed in experimental farm "Érd-Elvira" in 1997 at four of the monitoring sites. It is conspicuous in the figure that the traps, placed at the non-bearing apple orchard, e.g. in a hybrid walnut plantation or in poplar trees, caught codling moth adults also at dates other than in the apple orchard where IPM or conventional pest control was applied.
Figure 1
In 1998, number of adults caught by the traps was higher than in 1997, in every variation (Fig. 2), but the same behaviour of the codling moth was observed. The sour-cherry orchard was included in the monitoring in 1998. In spite of the fact that the source suspected by us, the apple orchard is 800 m far, the number of moths caught by the traps cannot be ignored.
In order to get an answer to the question, how the flight phenology of codling moth is changed on non-typical food plants; they were compared with the data recorded in the conventionally treated apple orchard.
The flight to be first shown is the one in the non-bearing orchard; they are only data obtained in 1996, as the plantation was established in spring 1995 the migration of the pest in it was observed the next year (Fig. 3). Unfortunately, traps were placed out only in early June; therefore the data can be compared only from 12 July. In the new plantation, codling moth adults were found in the trap every week, even when there was none in the conventionally treated orchard (late July, early August).
Flight observed in the non-bearing apple orchard
The flight to be first shown is the one in the non-bearing orchard; they are only data obtained in 1996, as the plantation was established in spring 1995 the migration of the pest in it was observed the next year (Fig. 3). Unfortunately, traps were placed out only in early June; therefore the data can be compared only from 12 July. In the new plantation, codling moth adults were found in the trap every week, even when there was none in the conventionally treated orchard (late July, early August).
Flight in the walnut plantations
Walnut is a host-plant of codling moth. Damage caused by the first generation is questionable in Hungary. Turkish investigators published that codling moth is most important pest of walnut, damage by the first generation leads to fruit fall ( Güclü et al. 1995)
Körtvély (1979) observed in Hungary during the feeding of the first generation of codling moth, walnut kernels are still liquid, therefore, larvae cannot chew them. In our monitoring sites no significant damage of either the first or the second generation was observed. Larval damage of the second generation did not exceed 10 % in any of the studied years.
Comparing flight recorded in walnut with that of the conventionally treated apple orchard in 1997, number of moths caught in walnut was less than in the apple orchard (Fig. 4).
In 1998, flight was observed from early May to middle of September, at each evaluation (Fig. 5). Considering that the damaging larvae population was low in every case, it could be concluded that a part of the adults in the traps was continuous immigration. A separate evaluation shall be done in the cases when the traps were placed on non-host plants of codling moth.
Roadside trees (poplar)
Flight curves recorded in 1997 and 1998 are shown in fig. 6 and 7. Place of the traps was, from one side open and from the other side sheltered from the wind by shrubs. From this side cultivar collections of pear and apple are found, thus it can be supposed that the captured moths started from here. It is obviously confirmed by the data that the males of codling moth are an intensively flying microlepidoptera.
Sour-cherry orchard
Fig. 8 shows the flight observed at the edge of the sour-cherry orchard (15 years old trees with conventional training system) in 1998. The number of caught adults cannot be ignored either, there is no such orchard in the surroundings where these moth could have developed. Therefore, it is believed that these individuals could approach the trap from far distances, confirming the good ability of codling moth to fly.
Results concluded from the several years monitoring could be summarised as follows:In the observations made by sex-pheromone traps, it could be conducted that codling moth males were found not only in orchards planted with the hosts of the pest, but also in the ones, which were far from these orchards or well isolated from them. The data of these flights were not always similar to the ones recorded in the bearing apple orchard. A decisive number of codling moth males were caught also by the traps placed in the sour-cherry orchard, 800 m far from the assumed source. These data confirm that Cydia pomonella is a well flying microlepidoptera.
We suppose that a part of codling moth males does not leave the orchard, remains there, another part of them flies out of the orchard to other eventual host plants or to a tree-silhouettes making quite a long distance.
It would be useful to make other types of observation focused on determing the reason and the eventual distance of the flight.
It should be stressed, however the question has still not been answered whether the number of imagoes in the sex-pheromone traps reflects the real flight activity of codling moth or it reflects something else what we need more knowledge about.
References
Bues, R. Toubon, J.F. & Poitout, H.S. 1995: Variabilité écophysiologique et enzymatique de Cydia pomonella L. en fonction de l'origine géographique et de la plante hôte. Agronomie 15: 221-231.
Güclü, S., Hayat, R. & Özbek, H. 1995: An investigation on phytophagous insect species on walnut (Juglans regia L.) in Erzurum and its neighbouring provinces. Türkiye Entomoloji Dergisi 19: 137-145.
Körtvély, A. 1979: Diót károsító almamoly. Kert és Szol., 28: 29:35.
Mani, E., Wildbolz, T. & Riggenbach, W. 1995. Effect of pheromone trap position in large and small trees and in the open field on the catch of codling moth, Cydia pomonella males. Mitt. Schweiz. Entomol. Gesell. 68: 69-78.
Mani, E., Wildbolz, T., Riggenbach, W. & Staub, H. 1997: Popultionsschwankungen des Apfelwicklers Cydia pomonella (L.) in ungestörten Apfel /beständen der Ostschweiz. Mitt. Schweiz. Entomol. Gesell. 70: 117-132.
Schumacher, P., Weber, D.C., Hagger, C. & Dorn, S. 1997: Heritability of flight distance for Cydia pomonella. Entomol. exp. appl. 85: 169-175.
Roelofs, W., Comeau, A., Hill, A. & Millicevic, G. 1971: Sex attractant of the codling moth: characterization with electroantennogram technique. Science, 174: 297-299.
Schumacher, P. Weyeneth, A., Weber, D.C. & Dorn, S. 1997: Long flights in Cydia pomonella L. (Lepidoptera: Tortricidae) measured by a flight mill: influence of sex, mated status and age. Physiol. Entomol. 22: 149-160.
Voigt, E. 1998: Honnan hová repülnek az almamoly imágók ? (Szex-feromoncsapda adatok alapján) 44. Növ. Véd. Tud. Nap. 78.
Vojnits, A. 1973: An investigation of the vagility and dispersal of the codling moth (Laspeyresia pomonella L.). Folia Entomol. Hungarica 26: 193-208.