Effect of canopy manipulation on cane and fruit Botrytis in protected raspberry.

Botrytis cinerea causes disease on both the fruit and cane of raspberry. The incidence of latent and post-harvest fruit botrytis was examined in 19 commercial open-field and protected crops. Many samples showed a high incidence of infected fruit (>50%), even on protected crops sprayed with fungicides. Differences between open-field and protected crops, between sprayed and unsprayed crops and between two varieties (GLen Ample and Tulameen) were not statistically significant. The incidence of latent infection by B. cinerea in unripe fruit did not correlate with the incidence of botrytis fruit rot developing on ripe fruit. Experiments were conducted in two commercial crops to investigate whether the removal of Lateral Leaves and thinning of primocanes during the flowering and fruiting period could reduce the incidence of fruit and cane infection by B. cinereo. Canopy manipulation resulted in considerable decreases in humidity inside the canopy at one site, where the original cane density was very high, (20 canes/m) and not at the second site where cane density was lower (10 canes/m). Canopy thinning did not significantly reduce the incidence of fruit botrytis at either site but reduced the incidence of leaf and cane infection in the dense crop. Results suggest that a significant reduction of cane infection by canopy manipulation can be realised for situations where cane density and disease pressure are high. The present studies suggest that in dense canopies in a protected crop, cane Lesions are more likely to result from direct infection of canes by the pathogen, although the pathogen can readily invade wounds on canes, including de-leafing wounds.