Oviposition and larval survival of Dasineura tetensi on four blackcurrant Ribes cultivars

Monitoring of an unsprayed infested fieldsite using watertraps in S.E. Kent revealed four generations of Dasineura tetensi (Rubs) (Diptera: Cecidomyiidae) occurring between April and September 1996. Ribes nigrum L. cultivars `Baldwin' (susceptible), `Ben Alder' (susceptible) and `Ben Connan' (resistant) were sampled for eggs in the field and assessed for midge damage throughout the season. Oviposition was indiscriminate, but plant damage varied significantly between cultivars. In laboratory choice experiments, mated female midges showed no preference between susceptible shoots of `Ben Alder' and resistant shoots of `Ben Connan' for oviposition. Olfactory responses of D. tetensi to leaf volatiles of `Ben Alder' and `Ben Connan' were also tested in a 4-way olfactometer. Mated females did not discriminate between volatiles of susceptible and resistant host plants. Larvae reared on cv. `Ben Connan' shoots were significantly smaller than those reared on shoots of cv. `Ben Alder'. Larval antibiosis and not female antixenosis appears to be the main mechanism for resistance to D. tetensi in 'Ben Connan'.