Effects of damage to individual leaves on shoot growth and berry production of black currant

The importance of individual leaves on shoot growth and flower and berry production of black currant (cv. Öjebyn) was studied in northern Sweden. One or three leaves were artificially removed from the shoot tips of dominant terminal shoots, simulating attack by larvae of the black currant leaf midge Dasineura tetensi (Diptera: Cecidomyiidae). Removal of one or three leaves significantly reduced the shoot length at the end of the season by about 1.5 and 3.5 cm, respectively, while the production of new leaves was not affected. At the shoot-level, leaf removal had no effect on the number of floral buds, flowers or berries produced by shoots the year after treatment. At the bud-level, buds produced in the axils of removed leaves produced about one flower less than buds from axils of remaining leaves, irrespective of whether a single or three adjacent leaves were removed. The pattern at bud-level was about the same when the shoots were naturally infested by D. tetensi.