Monitoring of an unsprayed infested fieldsite using watertraps in S.E. Kent, UK revealed four generations of D. tetensi occurring between April and September 1996. R. nigrum 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 'Ben Connan' shoots were significantly smaller than those reared on shoots of 'Ben Alder'. Larval antibiosis and not female antixenosis appears to be the main mechanism for resistance to D. tetensi in 'Ben Connan'.