Development of a biofix model for Cryptoblabes gnidiella by defining age cohorts of larval instars at the end of winter

Abstract: Modelling Cryptoblabes gnidiella (CG) life cycle can help manage this pest. We
propose to develop an epidemiological model of the dynamics of CG populations in French
vineyards based on the definition of the temporal occurrence of different larval instars.
Morphological measurements such as the width of the head capsule (HCW) are valuable tools for identifying the larval instars of Lepidoptera. We have adapted a statistical method for defining larval instars that we developed for Lobesia botrana to CG. We measured the HCWs of several hundred overwintering larvae collected from mummified clusters during autumn and winter. The measurements obtained enabled us to define the various larval instar boundaries. The next step will be to define uncertainty limits of boundaries and to test this approach by comparing the theoretical distribution with that of population samples collected in the vineyards.