In order to reduce the cost of fumigation and weed control in seedling nurseries of peach (Prunus persica (L.) Batsch.), a number of herbicides, used with and without Nemagon as a nematicide, were evaluated. While necessary for soil fumigation, the presence or absence of Nemagon did not effect weed control or seedling performance. The best and most economical herbicides were the spring application of simazine at 4.5 kg ai/ha or the fall application of diuron at 3.4 kg ai/ha.
The effects of freeze injury occurring at anthesis upon young developing fruit were studied anatomically. Slight injury was characterized by separation of the hypodermis from the outer cortex during the initial stages of fruit growth. Necrotic tissues were adjacent to the main part of the injury. The internal cortical tissues and vascular bundles in the core line were uninjured. The basin or fruit apex was sensitive to freeze injury resulting in stylar abscission, abortive ovules, and large breaks in the cortical tissue. Growth distortions in the outer cortex were evident 21 days after injury, indicating sensitivity to frost and to the initiation of corking.
Wound healing occurred 1 week after full bloom with the development of callus or proliferated tissues which united the wound areas.
Boron, calcium, and naphthalene acetamide (NAAm) foliar sprays were applied alone or in combination to ‘York Imperial’ apple trees under Eastern Pennsylvania orchard conditions. Mineral content of the leaves and fruit and number of cork spots in the fruits were determined.
B applications alone or in combination with Ca and/or NAAm increased leaf and fruit B content. All Ca applications increased the leaf Ca content, the fruit P content, and the leaf and fruit K and Fe content, but had no effect on fruit Ca content. NAAm sprays increased the leaf Mg and Al content. NAAm applied in combination with Ca increased the leaf Ca content. The NAAm effects appear to be associated with the valence of the element, having no effect on monovalent elements, some effect on divalent elements, and the strongest effect on the trivalent element, Al.
Th B-Ca and B-Ca-NAAm spray treatments reduced the number of cork spots per fruit. Regression analysis indicated that as the B and Ca content increased in the leaves, and fruit peel and flesh the cork spots decreased. Cork spots increased as the P and K content of the leaves increased. Core data showed that cork spots decreased as the B and Mg content increased and the B × Mg interaction decreased. There was no relation between number of cork spots and the leaf and fruit content of Mn, Fe, Cu, Zn, or Al, despite significant effects of the treatments on these elements.
Anatomical changes in ‘York Imperial’ apples were studied sequentially throughout the growing season to discover tissue variances occurring within the fruit at different stages of development. Several abnormalities have occurred during fruit enlargement, some of which may develop into corking disorders, including bitter pit and cork spot. Cellular abnormalities appeared contiguous to large lacunae, senescing vascular bundles or in tissues where cell proliferation was apparent.
Abnormalities adjacent to necrotic vascular bundles in the outer cortical region were apparent early in. the life of the fruit, by 14 days after full bloom. Changes in cellular structure continued 65 days after full bloom from the outer cortex to the epidermis, and extended to the bundles underlying this area. Cell division had ceased, and the cell walls were thick with a distinct demarkation line between the affected and unaffected tissues. Tissues of the basin region were susceptible to the development of corking disorders, while senescent vascular bundles and meristematic tissues were evident within the core line.
Necrosis of vascular bundles extended along the core line in the fruit apex 95 days after full bloom, and tissue proliferation occurred by 115 days. Fruit development 126 days after full bloom revealed large lacunae in the outer cortex and extreme cell proliferation resembling callus tissue in the cavity at the point of fruit-pedicel attachment.
Origin of corking disorders, visible on fruit nearing maturation (112 days after full bloom), could be traced from tissue anomalies in the outer cortex. The spots appeared irregular in outline, yellowish-green in color; while a glossy, scalded appearance surrounded this area. Meristematic activity of the parenchyma cells along the core line was apparent 126 days after full bloom.