Seasonal changes in english walnut (Juglans regia L.) (Juglandaceae), fruit properties and host use patterns by Rhagoletis zoqui (Diptera: Tephritidae)

Authors: GUILLEN, L - Institute De Ecologia - Mexico; Sivinski, John; RULL, J - Institute De Ecologia - Mexico; ALUJA, M - Institute De Ecologia - Mexico

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2013
Publication Date: N/A
Citation: N/A

Interpretive Summary: Walnut fruit flies can be important pests in the USA and with increased travel and commerce foreign species are potential invaders. Scientists at the USDA-Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, with colleagues at the Instituto de Ecologia, Xalapa, Veracruz, Mexico, investigated host use and development of a species that lives in the temperate mountains of Mexico and may be able to survive as well in the walnut growing regions of the USA and Europe. Some walnut fly populations had changed their seasonal pattern of activity to exploit the relatively early fruiting English walnut although this plant has only been in Mexico for 500 years. This rapid change in development schedule suggests that it could quickly adapt to new environments in the USA as well.

Technical Abstract: Rhagoletis zoqui Bush is a Neosubtropical, univoltine, frugivorous tephritid fly that exploits both native Juglans spp. and the introduced, Palearctic English walnut, Juglans regia. The seasonal development of commercial J. regia fruit and the pattern of host exploitation by R. zoqui were tracked over two growing seasons in Cuapiaxtla, Tlaxcala, Mexico. First adult sightings and recovery of infested fruit occurred when walnuts reached their highest sugar content, and coincided with an initial decline in fruit firmness. The prevalence of adults on trees was significantly related to fruit firmness whereas fruit infestation levels were significantly related to fruit size (weight). Adult fly activity appears to be synchronized with English walnut fruiting, despite the fact that this plant was introduced into Mexico only 500 years ago. Since the fruit of native Juglans species ripen approximately two months later than J. regia, this suggests that certain R. zoqui populations may have become specialized to exploit English walnut