Natural mortality of immature stages of Bactrocera oleae (Diptera: Tephritidae) in traditional olive groves from north-eastern Portugal

Citation

Gonçalves, F.M., Rodrigues, M.C., Pereira, J.A., Thistlewood, H., Torres, L.M. (2012). Natural mortality of immature stages of Bactrocera oleae (Diptera: Tephritidae) in traditional olive groves from north-eastern Portugal. Biocontrol Science and Technology, [online] 22(7), 837-854. http://dx.doi.org/10.1080/09583157.2012.691959

Abstract

From 2006 to 2008, we studied the natural mortality of olive fly, Bactrocera oleae (Rossi), eggs and larvae as collected in fruit on the tree, in two to five 'traditional' olive groves of Trás-os-Montes (north-eastern Portugal), per year. We also studied the fate of 2044 puparia that were buried in the soil from November to May for two seasons, by using exclusion cages to estimate predation. Mortality of eggs inside the fruit was estimated as between 5.4±2.4 and 16.6±6.1%, and as 10.7±2.1 and 100.0% for young larvae. Similarly, the estimated mortality of mature larvae was between 0 and 66.7±33.3%. The highest mortality levels for young larvae could reach 100% during August, and 47.4% during the first fortnight of December, coincident with high temperatures in summer or low temperatures at the end of autumn and early winter. Mortality (winter disappearance) of puparia was estimated at up to 98.5% of the population. Predation of eggs was low, at 0.6±0.3 to 6.3±4.0% in 2006, 0 to 4.1±1.1% in 2007, and 0 to 3.6±3.6% in 2008. Parasitism was insignificant during the study, and only one parasitoid was identified, the eulophid Pnigalio agraules (Walker). We also surveyed entomopathogenic fungi associated with the insect in 12 olive groves, and evaluated three of the latter against larvae, puparia, and adult B. oleae in the laboratory. Of the 15 fungal species identified from immature stages, three were considered to be entomopathogenic (i.e. Cordyceps bassiana, Penicillium corylophilum and Mucor hiemalis). We observed up to 20.0±3.2% and 94.0±2.5% mortality of larvae and puparia, respectively when treated with P. corylophilum and up to 32.5±11.1% of adults when treated with M. hiemalis. © 2012 Copyright Her Majesty the Queen in Right of Canada.

Publication date

2012-07-01