Fruit and berries

Summary
Black currant plantings subsist for 10-12 years. During the project period the plants where produced, planted and 1999 was the first cropping year.

During establishment all five cultivars and all four cover crops gave a sufficient nitrogen supply. The level of nitrogen in leaves and soil and the growth were smallest in the annual cover crop treatment consisting of vetch and rye. Powdery mildew infected ‘Ben Lomond’ very severe and caused a very little shoot growth. Consequently the yield was very little in 1999. The four other cultivars had a yield ranging from 2 to 4 tons per ha. ‘Titania’ had the largest crop. There were no significant differences between the yield in different cover crops.

Black currant production on legs to lighten the mechanical weed cleaning reduced the annual shoot growth. But this did not effect the yield the first cropping year.

Infestations of aphids were smaller and leaf spot infection larger in the ‘Titania’ plants on legs. A stronger growth in the traditional bushes, but a more dense branch structure in plants on legs probably caused this. Mechanical weed cleaning was easier under plants on legs.

If sulphur is used to control pest in the growing season the leaf scorching and leaf discolouring increases when the concentration of sulphur increases over 0-2-4-6-8 kg per ha. There were no significant differences in yield but a tendency towards a lower yield when the sulphur concentration increased this first cropping year. Sulphur treatments had a significant but not sufficient effect against mildew.

Grey mould in strawberries was tried reduces using cultural methods. Post-harvest defoliation and finger harrowing was investigated in two cultivars. Post-harvest defoliation, though having some positive effect on marketable yield, did not reduce the incidence of Botrytis significantly. This was the case regardless of cut leaf material being removed from the plots or not. Finger harrowing, though in some instances having a negative effect on yield, did not control Botrytis significantly either. However, it was clearly demonstrated that, in organic strawberry growing, the incidence of Botrytis increases with plant age. Therefore, a short-term cropping system may be more important in controlling Botrytis than both post-harvest defoliation and finger harrowing.

In a trial 20 cultivars were evaluated for their suitability in organic production. Among all cultivars, ‘Honeoye’ had the lowest susceptibility to Botrytis and is considered a good early ripening cultivar for organic production. During midseason, ‘Kent’ and ‘Cortina’ yielded well, although they were moderately susceptible to Botrytis. In late season, ‘Symphony’ and ‘Pandora’ gave high yields, although they both appeared to be susceptible to leaf spot diseases.

28 black currant cultivars were evaluated. So far ‘Titania’ and ‘Intercontinental’ (Bri 8315-25) were the cultivars less susceptible to diseases. ‘Farleigh’ is resistant to big bud mite but unfortunately it is susceptible to diseases and is not a high yielding cultivar.

Significant differences in the content of hydroxycinnamic acid derivatives were seen when five black currant cultivars were grown under organic conditions. High levels of caffeoyl-diquinic acid and coumaroyl-quinic acid early in the growing season were correlated with disease resistance in blackcurrant cultivars. Analysis of the content of hydroxycinnamic acids could be an important tool to help choosing the resistant cultivars that are suitable for organic production.