ISHS Acta Horticulturae 585: VIII International Rubus and Ribes Symposium
DETERMINATION OF LEAF DAMAGE LEVELS TOLERATED IN A LOW PESTICIDE PRODUCTION SYSTEM OF BLACKCURRANTS (RIBES NIGRUM) |
| Authors: | H.L. Pedersen, T.B. Toldam-Andersen, K. Funke, A. Hann, J.-N. Wünsche |
| Keywords: | Leaf area, shoot growth, yield, photosynthesis, American gooseberry mildew, Sphaerotheca mors-uvae, blackcurrant leaf midge, Dasineura tetensi. |
| Abstract:
With the objective to investigate the effect of leaf removing on annual shoots, simulating foliar feeders, a field trial was established in summer 2000 in 3-year-old blackcurrants ’Ben Rua’, New Zealand. The total number of leaves per bush was reduced during the season from 1932 at flowering to 1440 just before harvest. The data indicates that blackcurrant bushes are very dense and that the older leaves in the centre of the bush are less exposed. The yield ranged from 1.0 to 1.6 kg per bush with a tendency towards lower yields on bushes where leaves were removed on 100 % of the new growth at the beginning of November and December. Removing the leaves on 50 percent of new growth did not reduce the yield. There was a carry-over effect on yield and berry size to the following year. Removing all the leaves on annual growth in the early part of the previous season reduced the yield by more than 75 %. Removing all leaves on every second annual shoot just after flowering reduced the yield by 50 % in the following season. Reducing leaf area by either 50 or 100 % of new shoots per bush significantly increased net photosynthesis of the remaining leaves when compared to the control treatment. If leaves on annual shoots are damaged, older leaves in the lower part of the canopy get more exposed to incident light levels which increases the photosynthesis rates. Further investigation is carried out in Denmark. | |
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