Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2004
Publication Date: 4/1/2005
Citation: Yee, W.L. 2005. Seasonal distributions of eggs and larvae of Rhagoletis indifferens (Diptera:Tephritidae)in cherries. Journal of Entomological Science. 40(2):158-166
Interpretive Summary: A study was conducted in Washington by personnel at the Yakima Agricultural Research Laboratory in Wapato, WA, to determine the seasonal distributions of eggs and larvae of the western cherry fruit fly, Rhagoletis indifferens, in sweet cherries. The objectives were to determine the seasonal and spatial distributions of egg and larval flies in cherries and the frequencies of fruit with multiple eggs and larvae over the season. The egg was the major stage found during early, mid, and late season. The distributions of eggs were similar during the season, but those of first, second, and third instars were present in greatest numbers in late season. First, second, and third instars occurred in similar numbers in late season, but third instars were sometimes most abundant. Tree quadrant had no effect on egg densities or distributions. The majority of infested fruit had only one egg or larva, but there were increases in percentages of fruit with two or > three eggs or larvae as the season progressed. The results of this study are important for the cherry industry in Washington in that they show how fly stage distributions change in fruit, which can be utilized in sampling protocols and in management and detection of infestations in fruit.
Technical Abstract: ABSTRACT The seasonal distributions of eggs and first, second, and third instar larvae of the western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), in sweet cherries were determined at three sites in central Washington in 2002 and 2003. The egg was the major stage during early, mid, and late season. The distributions of eggs (i.e., the percentages of total immature stages that were eggs) were similar all season, but those of first, second, and third instars were greatest in late season. First, second, and third instars occurred in similar numbers in 2002, but third instars were the most abundant in 2003. Tree quadrant had no effect on egg and larval densities and distributions. The majority of infested fruit had only one egg or larva, but there were significant increases in percentages of fruit with two or > three eggs or larvae as percentages of fruit that were infested increased during the season. When there were two larvae in a fruit, one was larger than the other in 90.8% of cases. Results indicate time of season but not location within trees (1.5-2 m above ground) has differential effects on egg and larval distributions in fruit and on female oviposition behaviors that may result in multiple infestations and larval interactions. Seasonal effects on immature stages are probably related to developmental times and stage-specific mortality, whereas effects on adults may be related to reduced availability of unoccupied fruit for oviposition. Implications for management and detection of larval infestations in fruit are also discussed. Key Words Rhagoletis indifferens, egg distributions, larval distributions, cherries