Although regarded as harmful wherever it occurs, the best authorities have raised the question whether real injury results from Crown Gall. Its progress is slow, and cases are on record where trees affected in the nursery, when planted in the orchard, made productive and profitable trees. On the contrary it is held that if a peach is affected at planting, it will never fruit successfully, and will show a marked dwarfing. It would seem, therefore, that the question of the effect of Crown Gall on peaches and other fruit-trees needs further attention. In certain regions as much as 75 per cent of the trees in nurseries are affected. Referring to extreme cases illustrating the possible economic importance of Crown Gall to peaches, it is reported that peach orchards are unprofitable because of the disease. The disease appears to be more easily communicated to the peach under ordinary orchard conditions than to the apple, consequently great precaution should be taken against setting peach - trees in soil where another galled plant has been removed.
For a fuller discussion of the disease, see Apple, page 108.
Fig. 79. - Peach - trunk injured by frost.
In New York, New England and elsewhere peaches suffer from the cold. Trees are even killed, a phenomenon which makes the trouble an important one. Trees which are winter-injured show blackened bark in the spring; this injured bark becomes more or less separated from the trunk and the brown wood is evident (Figs. 79 and 80). Such injuries are commonly found at the crown, in which case the disease is called crown Rot or collar Rot (Fig. 79); on the trunk and larger limbs, where it is called frost canker or sun-scald (Fig. 80); and on the twigs, where it is often referred to as Die Back (see also page 300). Toward midsummer frosted trees exhibit foliage which at first is yellow, then pinkish here and there. If the injured spots are left untreated, bark-beetles and fungi frequently follow the work of the frost. The most common fungus in this connection is Valsa leucostoma var. cincta (see page 301). In the past, orchards, which probably would have recovered if proper treatment had been given, have been cut down. If the bark clings tightly or is only partly loosened, the trees may recover. Moderate pruning back, removing not more than one-third to one-half of the previous year's growth, good cultivation, and moderate fertilization is regarded as a good course to pursue. See more detailed discussion of Frost Injury, its nature and treatment, under Apple, page 35.
Fig. 80. - Frost canker on peach - limb.