Occurrence of two different development patterns in Lobesia botrana (Lepidoptera: Tortricidae) larvae during the second generation

Abstract

1 In north-eastern Italy, the second-generation larvae of Lobesia botrana (Den. & Schiff.) (Lepidoptera: Tortricidae) can develop with two different time patterns. In particular, in 'warmer' areas, the developmental time is shorter than in 'cooler' areas and it is associated with an earlier and more economically important third generation. 2 Because the differences in temperature are not sufficient to explain the two patterns, research was carried out aiming to investigate whether the differences in larval development time are the result of a different number of instars and whether the photoperiod is a factor. 3 In the field, second-generation larvae develop through five instars in a 'warmer' area and through six instars in a 'cooler' area. Laboratory and field data showed that decreasing photoperiod, which induces diapause, is also an important cue for inducing larvae to develop six instars. 4 In the light of climate warming and subsequent changes in L. botrana phenology over the last 30 years, the two different development patterns are interpreted as a means to ensure the best fit of the moth to environmental conditions. In 'cooler' areas, third-generation larvae might not complete development before frost or harvest, and hence second-generation larvae develop through six instars before producing overwintering pupae.

The lost generation hypothesis: could climate change drive ectotherms into a developmental trap?

“…At this stage, it is difficult to make sound predictions on the general significance of developmental traps across species and climate zones. Under variable conditions the co‐occurrence of different developmental patterns within a generation may provide resilience at the population level (Pavan et al ). We argue that the profile of species particularly susceptible to developmental trapping are multivoltine species that show strong thermal plasticity of development and use photoperiod as an important cue for life‐cycle regulation.…”

How climate change affects the occurrence of a second generation in the univoltine Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)

“…Altermatt () reported that climate warming increased voltinism based on observation data of Central European Lepidoptera. Furthermore, studies reporting on the effects of local and annual temperature differences on the number of generations per year support the expected effect of climate warming on insect life cycles, for example, in Coleoptera (Hurpin, ; Pineau et al ., ), Hemiptera (Hulle et al ., ; Musolin et al ., ; Takeda et al ., ), and Lepidoptera (Crozier, ; Pavan et al ., ). Under gradual warming conditions, changes in voltinism are expected (Kiritani, ; Musolin, ) and deserve further research.…”

Effects of grapevine bunch exposure to sunlight on berry surface temperature and Lobesia botrana (Lepidoptera: Tortricidae) egg laying, hatching and larval settlement

“…The European grapevine moth Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae) is considered as a major pest in many European and Mediterranean vineyards and was also found recently in the Americas (Ioriatti et al ., ). It is a polyvoltine species with two to four generations per year, depending on latitude, microclimatic conditions and year (Martín‐Vertedor et al ., ; Caffarra et al ., ; Pavan et al ., ; Gilioli et al ., ). From the second generation, larvae are carpophagous and can cause yield losses and favour the spread of grapevine bunch rots, mostly Botrytis cinerea Pers.…”