Optimized monitoring of host populations of the Bois noir vector, Hyalesthes obsoletus, based on flight phenology observations

The flight activity period of Hyalesthes obsoletus, the vector of Bois noir, depends on temperature and on the plant host species. Vector populations associated with the host-plant field bindweed emerge in any given year about two weeks ahead of populations associated with stinging nettle, but the beginning of the flight varies among years by about one month in both populations. A cumulative degree-day model was developed for nettle populations and compared to a previously published model for bindweed populations. With both models, the emergence of adult vectors can be predicted with a sufficient precision to aid the timing of weed control and vector sampling. Monitoring of three complete flight periods of a nettle population suggest that the peak and the end of flight activity are also related to cumulative degree-days. Sampling of live animals is most effective during three weeks around peak flight, while sticky traps are useful to describe the complete flight period. The degree-day models and the results of the flight phenologies of H. obsoletus are useful for the integrated control of Bois noir as tools for the timing of weed control and the sampling of vectors.