On the susceptibility of the different varieties of big-leafed turnip to damage caused by cabbage maggots (Hylemyia spp.)

Abstract

Of all the varieties most generally cultivated in Finland (the »Native» bigleafed turnip, the White Dutch, and the Green Globe) the »Native» big-leafed turnip proved to be the most susceptible to damage caused by cabbage maggots. The damage suffered by the Sirius tetrapl. Svalöv variety included in the tests only for two years, was considerably slighter than in other varieties. In the second test in which the varieties listed on page 272 were included for four successive years, the Zwaans Brabo was damaged least of all, the damage being below the average in every year investigated. As to the Purple Top Mammoth the damage was continually above the average. In this group, too, the number of the damaged specimens of the »Native» big-leafed turnip was above the average. The shape of the turnips (the material was grouped as follows: 1. the flat and flat-round, 2. the round, and 3. the long-round and fairly long turnips) did not seem to affect the extent of the damage caused by the cabbage maggots, not at any rate when the level of damage was slight or moderate as in the cases investigated. It is, however, obvious, that in cases of severe damage the round and long-round varieties which generally have strong roots, endure damage better and recover from it more quickly than the flat and flat-round varieties with their thin roots.