Frequency Distribution of Larval Codling Moth,Cydia pomonellaL., Aggregations on Trees in Unmanaged Apple Orchards of the Pacific Northwest

Abstract

The codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae), is a key pest of pome fruits in North America. After locating a pupation site, larvae spin a cocoon from which aggregation pheromone disseminates that attracts conspecific larvae. In two unmanaged apple orchards in Wenatchee and Yakima, Washington State, we systematically surveyed cracks and crevices of tree trunks for cocooning C. pomonella larvae. Aggregates of larvae were found significantly more often than solitary larvae. The number of cocooning larvae in aggregates (=group size) was inversely correlated with the frequency occurrence of that group size. Group size ranged between 2 and 20 cocoons. Height above ground had no effect on location of aggregates. In orchard 1, the cardinal direction of the tree trunk had no effect on location of aggregations, but in orchard 2, aggregations were located significantly most often on the south side of trunks. The mean ratio of males and females in aggregations was 1.08:1 and 1.04:1 in orchards 1 and 2, respectively. Moreover, the number of males in aggregates did not significantly differ from that of females. Our data support the conclusion that larvae seek pupation sites not by chance but in large part in response to pheromone signal and microhabitat cues. The probability of aggregates forming is likely proportional to the population density of C. pomonella.

Spatial distribution of Cydia fagiglandana (Zeller) in an exploited holm oak (Quercus ilex L.) forest

“…As it is shown in the maps, decline of larval density coincided with a reduction of the centers of aggregation, and this is due to the fact that both variables are directly related (Jumean et al, 2009). As a matter of fact, a comparison of the distribution maps for C. fagiglandana with the those for the curculionid in the same area and period (Jiménez et al, 2008;Fig.…”

Twenty-five Years of Research Experience with the Sterile Insect Technique and Area-Wide Management of Codling Moth, Cydia pomonella (L.), in Canada

“…Wild moth counts were highest: (1) In traditional orchards with large trees; (2) in low elevation sites; (3) in orchards facing north; and (4) were consistently higher in different regions of the study than in others [124]. Some findings are explained by the greatly reduced numbers of codling moth larvae overwintering in modern high-density plantings in comparison with large, old trees [71,125,126], and by the critical importance of such habitat to the persistence of moth populations [127,128]. The OK SIR program has long recognised that large, older, trees, particularly with highly fissured bark such as pear, are associated with high-risk sites, having very persistent wild moth populations [2].…”

“…The behaviour and ecology of overwintered diapausing larvae and of young adults on trees was also long known to be critical at low population densities [127,128]. Their occurrence and characteristics were studied in nearby Washington State [126], and in France [131,137]. The aggregation pheromone produced by cocoon-spinning larvae was found to attract or arrest other codling moth larvae, and was identified [142,143].…”

Seasonal dynamics and spatial distribution pattern of Parapoynx crisonalis (Lepidoptera: Crambidae) on water chestnuts

“…The aggregation degree of a population spatial pattern can describe some characteristics of population ecology and regulation mechanisms involving density, such as foraging and reproduction under certain circumstances, territorial behavior, diffusion behavior, communication behavior, etc. Codling moth ( Cydia pomonella L.) larvae, after locating a pupation site, attract conspecific larvae staying together by an aggregation pheromone produced by the cocooning larvae [ 13 ]. Aggregation behavior was found to contribute to foraging among an insect population by Sánchez et al ., 2009 [ 14 ].…”