Feeding insects with a phytopathogenic fungus influences their diapause and population dynamics

1. A facultative mutualistic relationship between a herbivorous moth, Lobesia botrana, and a phytopathogenic fungus, Botrytis cinerea, both damaging the same plant, the vine, has been demonstrated recently. Laboratory and field studies were carried out to determine the influence of the presence of the fungus in food on larvae during the pre- and post-diapause periods and on the global fitness of the insect. 2. During the pre-diapause period, larvae fed on fungus exhibited a higher survival rate and a faster larval development than insects reared without fungus. 3. After the wintering diapause, insects reared with fungus displayed a better synchronisation of adult emergence and an increased fecundity compared with control insects. 4. These results indicate that food containing fungus provides an improved diet, permitting the herbivorous insect to obtain nutrients required to optimise their life-history traits. 5. In addition, the results emphasise the importance of the nutritional quality of larval diet, improved by addition of the fungus, on diapause termination and on the demography of the insect before and after the wintering diapause.