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Abstract
Mn in apple leaves rose to a late summer maximum prior to or at abscission. The average levels, or the maxima, were not related to the severity of IBN symptoms. There are indications, but no conclusive evidence, that some withdrawal into the bark of shoots may occur. If such movement does occur, the resulting increase in bark Mn concentration is not great and cannot account for levels of bark Mn associated with IBN by Berg, et al. (1). No redistribution of Mn between bark and wood appears to occur during the winter.
Abstract
‘Red Prince Delicious’ apples/‘M7’ rootstocks, growing in sand culture and receiving ½, 5 or 50 ppm Mn, developed internal bark necrosis (IBN), and an Fe-deficiency chlorosis in its severest expression, at the highest level of Mn supply. Fe was as high in leaves of chlorotic as in those of non-chlorotic plants, but the chlorosis was cleared up by increasing the Fe supply.
Ground twigs showed a brownish coloration which had a max reflectance at 700 mμ. Differences in coloration were correlated with the Mn supply, the severity of IBN symptoms and the Mn/Fe ratio in the leaves and bark, but not with the Mn/Fe ratio in the ground twigs.
Abstract
In studies of seasonal trends in apple leaf nutrients, 5 different seasonal leaf sampling methods using the same shoots of young and old apple trees have been compared with a sampling of mid-shoot leaves on different shoots each sampling date to determine whether there would be any differences in leaf P, K, Ca and Mg trends. Sampling methods resulted in significant interaction with the check only in data for leaf concentration of Ca. The methods which were compared with the check had average seasonal leaf concentrations of P, K, Ca and Mg which differed significantly from the check in a few instances. They also produced slightly to considerably lower coefficients of variation than the check in 78 of 100 possible comparisons. This makes such methods very desirable as alternative sampling procedures where they do not otherwise vary from the standard.
Abstract
‘Red Prince Delicious’/East Mailing (EM) VII trees were grown in sand culture and fertilized with a complete nutrient solution containing 0.5, 5.0 or 50.0 ppm Mn. 54Mn was supplied to provide the same specific activity in all treatments. Autoradiographs showed “islands” of radioactivity in bark patches from all treatments 2½ months after initiation of the experiment. These “islands” disappeared after 8 months in the 0.5 ppm treatment, and after 10 months in the 5.0 ppm treatment, but continued to exist in bark patches from the 50.0 ppm treatment through the last sampling at 15½ months. Typical, and some aberrant, symptoms of IBN first appeared after 5½ months in the 50.0 ppm treatment. Pimples occurred at sites where autoradiographs indicated Mn concentrations. As the pimple stage of IBN progressed to necrotic lesions, radioactivity was concentrated around the periphery of the lesions. Data is presented which suggests that, as Mn supply is increased, alteration of mechanisms for regulating uptake and distribution of Mn occurs.
Abstract
Seventeen Malus cultivars and 6 lines of open-pollinated seedlings were screened for susceptibility to attack by the woolly apple aphid (Erisoma lanigerum Hausmann) (WAA) indigenous to western North Carolina. Most cultivars with ‘Northern Spy’-derived resistance were susceptible to infestation by this WAA biotype, distinguishing it from WAA reported in other parts of the United States. Some cultivar resistance followed the pattern reported in New York, including high resistnce in Mailing Merton (MM) 106, MM 107, and MM 112. Robusta 5 [M. X robusta (Carr.) Rehd.] was not infested by either the North Carolina or the New York WAA biotypes.