Maximum realised lifetime parasitism and occurrence of time limitation in Gonatocerus ashmeadi (Hymenoptera: Mymaridae) foraging in citrus orchards

Abstract

The relationship between body size (hind tibia length), <12 h egg load, wing wear and parasitoid age was used to estimate realised lifetime parasitism of recently dead Gonatocerus ashmeadi collected in a citrus orchard. Under prevailing field conditions and methodology assumptions, it was estimated that female G. ashmeadi lived on average for 183 ± 17 degree-days, parasitised a total of 87 ± 9 Homalodisca vitripennis eggs, and died with 34 ± 5 eggs remaining in the ovaries. Only 17% of dead G. ashmeadi died with no mature eggs suggesting that 83% of G. ashmeadi were not egg limited at time of death. Estimates of realised lifetime parasitism for female G. ashmeadi under prevailing field conditions in July and August in a southern California citrus orchard indicated that time of year had a significant effect on reproductive output. Additionally, live G. ashmeadi captured daily during June through August 2006 had body size, egg load and wing wear recorded to detect possible monthly changes in parasitoid age and egg load. Foraging G. ashmeadi captured alive in June were older and oviposited more eggs in the field compared with August. Only 0.5% of live G. ashmeadi were captured with no mature eggs in their ovaries indicating that the vast majority of live G. ashmeadi were not egg limited.

Keywords:

• egg load
• realised lifetime parasitism
• time limitation
• wing wear

Acknowledgements

We thank David Morgan, CDFA, Mt Rubidoux Field Station, Riverside, California, for kindly providing parasitoids to initiate our colonies. We would also like to thank Yingzhuo Fu for assistance with statistical analysis, and Mitzie Millard, Lisa Gonzales, Jocelyn Holt, Mike Lewis and Ruth Vega for their assistance with field and laboratory work. George Heimpel provided many helpful comments on an earlier draft of this work.

Funding

This work was supported in part by the California Department of Food and Agriculture (CDFA) Pierce's Disease-Glassy-Winged Sharpshooter Management Research Program.

Additional information

Funding

Funding: This work was supported in part by the California Department of Food and Agriculture (CDFA) Pierce's Disease-Glassy-Winged Sharpshooter Management Research Program.