Japanese Pear Orchards Research Articles

Tree Forms for Labor Saving Farm Work

Annual working hours in Japanese pear orchards were compared between two training systems designed for easier tractor operation and one common training system. They were the Y form training, the hedgerow training and the vase form training.Annual working hours were somewhat less in the Y form training and the hedgerow training than in the vase form training.However, the difference was not as large as expected. The main cause of this small difference owing to 1) scanty tractor operation in all three training systems and 2) limitations in machine operations in the hedgerow due to the situation of the hedgerow, i. e. the northern side of the northernmost row had to be mowed by hand and spraying for pest control had to be done over a fence from a road outside the orchard.In the year 1984, total working hours per 10a were, about 243 hours in the vase form, about 224 hours in the Y form, about 250 hours in the hedgerow, with the Y form being somewhat labour saving. All three training systems experimented in our orchard required less working hours compared to statistical data on Japanese pear growing farmlands.However, total working hours per yield were the same as the statistical data for the vase form, but about 20% higher for the hedgerow and about 110% higher for the Y form.The reason why working hours per yield were higher in the hedgerow were that 1) it required more fertillizer due to dense plantation, 2) more mowing and pest control than the vase form and Y form due to the situation of the orchard. The reason why working hours per yield was higher in the Y form was that the yield was lower due to the aftermath of the typhoons in 1982, as mentioned in a previous report3).In the year 1985, total working hours per 10a were, about 216, 172, and 194 hours for vase form, Y form, and hedgerow respectively. That in the latter two were somewhat shorter than in the vase form.Working hours in all three systems were about 80% of statistical data.However, total workig hours per yield were, about 108 hours per ton for vase form and Y form, about 80% of the statistical data. Total working hours per yield were about 85 hours/t for the hedgerow, less than 80% of vase form and Y form, about 60% of statistical data, showing that Y form and hedgerow would be largely labour saving if yield of 2 tons per 10a is maintained.In Y form and hedgerow, trees of proper vigour could produce higher yield than trees of vase form constantly with less working hours.For the pursuit of higher yield and labour saving training systems, investigation of not only plant physiological and ecological aspects, but detailed research on working hours of work such as soil management, spraying, harvesting, etc. are also required. Detailed investigation on working hours of Japanese pear culture in the three training systems are in progress and will be reported in the near future.

Tolerance of Venturia nashicola to thiophanatemethyl and benomyl in Japan.

In 1975, spray applications of thiophanate-methyl and benomyl failed to control scab in several Japanese pear orchards. Mycelia of Venturia nashicola isolates, obtained from these orchards, developed normally on PDA supplemented with 50-800ppm of thiophanate-methyl or benomyl. Sensitive isolates did not grow even at 1ppm. However, conidia, formed in vitro, germinated in suspensions of these fungicides, irrespective of tolerant or sensitive isolate. Tolerant isolates exhibited vigorous germ tube elongation, but sensitive isolates produced only short germ tubes in these suspensions. In a protection test on Japanese pear treated with 100ppm of each fungicide, tolerant isolates developed sporulating lesions. Tolerance of V. nashicola to thiophanate-methyl and benomyl in the field was therefore demonstrated.

Amino Acid Antagonists in Control of Plant Diseases

Diverse amino acid antagonists (AAA) were investigated for control of black spot of Japanese pear caused by Alternaria kikuchiana.Inhibitory action of the AAA to fungus spore germination was rather weak. However, some of AAA induced abnormality or exhibited inhibitory action to the germ tube elongation.Control effect of known AAA, Eth derivatives, 2-amino-4-(ethylthio) butyronitryl (AETB) and its six kinds of salts on black spot of Japanese pear on the young trees grown in pots was studied under greenhouse conditions. The disease was effectively controlled by DL-ethionine (Eth) and DL-m-fluorophenylalanine (FPA) among known AAA. In a series of Eth alkyl esters of 1 to 5 carbon atoms controlled the disease without phytotoxicity, but any with alkyl group more than 6 carbon atoms, particularly n-nonyl ester, was less effective and phytotoxic. Eth Cu salt (Eth Cu) controlled the disease better than those of Zn and Mn salts. AETB was effective, but its salts less effective.In a Japanese pear orchard, 1000ppm solution of Eth, FPA, methy, ethyl and propyl esters of Eth, and Eth Cu were sprayed nine times at 10 to 14 days intervlas from May to August in 1968. All the compounds were effective for control of the disease development without phytotoxicity on leaves, fruits and whole of the trees. The best results were obtained by the treatment with Eth ethyl ester and Eth Cu.