In this paper, the toxicity of DDT and BHC dust to the aphids and their natural enemy, the lady beetle (Harmonic axyridis PALLAS) of pear orchards has been compared in the laboratory. The results are summarized as follows: 1. BHC is more toxic than DDT to the aphids, Toxoptera piricola MATSU, and Nippolachnuspiri MATSU. 2. BHC is less toxic than DDT to the various stages of the lady beetle, Harmonia axyridis PALLAS 3. From the above mentioned results it may be said that BHC is recommended for the control of these aphids.
With a view to determining the effectiveness of organic insecticides upon the injurious insects of various fruit trees, a series of experiments has been carried out with results as given in the summary that follows: 1. DDT dust is effective for the persimmon fruit moth (Kakivoria flavofasciata NAGANO) as well as lead arsenate, without causing any trace of damage to the tree. DDT with bentonite or kaolin as the carrier is more effective than with other carriers. 2. DDT wettable spraying is able to control the infestation of growing peach shoots by the oriental peach moth (Grafolitha molesta BUSCK.) and of leavs by the leaf hopper (Erythria zonata MATSU.) while their population densities are small, resulting in increase of red spider mite. 3. The damage to pear by the oriental peach moth and to peach by the fruit moth (Dichocrocispunctiferalis GUEN.) are not well controlled by the sprayings of the various organic insecticides. such as DDT, BHC and Clordane though capable of being controlled by the paper bag painted with DDT emulsion. 4. DDT emulsion spraying indicates no toxicity to the larva of Ceroplastes rubens MASKELL, though capable of better controlling the overwintering adult by spraying with a mixture of machine oil and DDT emulsion than with the former only. 5. The mixture of BHC and pyrethrum emulsion acts as an evasive factor for the attachment of citrus leaf miner (Phyllocnistis citrella STAINTON) and it is used as a substitute for nicotine sulphate.
1. The efficiency of honey-bee in the pollination of Japanese persimmons was studied at Okitsu, Tokai Branch of Agricultural Horticultural Experiment Station in 1949 and 1950. 2. The female flowers situated in the near of male flowers were better pollinated than those situated distant from male flowers. 3. Most of honey-bees visited to the male flowers of Zenjimaru had pollen pellets on their legs. 4. Most of honey-bees visited to the female flowers of Fuyu had not pollen grains. 5. The roles of honey-bees in the pollination of Japanese persimmons were discussed.
1. A study was made on pollen germination and tube growth in relation to low temperature, in broad-bean and garden-peas, flowered in midwinter, and the limit of setting in low natural temperature was studied. 2. The optimum temperature for germination of pollen was about 20°C for broad-bean, and 25°C for garden-peas. But the resistance to low temperature of these pollen was so strong, that they germinated and developed at 0°C for thereabout. 3. After certain period of time the tube growth would go at 0°C or thereabout just as much as at optimum temperature in broad-bean, but it was not true of garden-peas, the growth being very weak. And in the diary variation of room temperature, the tube growth was retarded when the temperature decreased to about 10°C in garden-peas, but it was not effected in broad-bean. 4. There was no injurious effect of low temperature, 0°C or thereabout, on already developing pollen tubes, in both broad-bean and garden-peas. 5. It seemed that the power of tube growth at low temperature was greater in broad-bean than in garden-peas. 6. The flowers opened at low temperature, 0°C or thereabout, were not dropped in out-door condition.
(1) Studies of flower bud differentiation and development of Koshu and Delaware grape varieties had been conducted at Osaka and Gitu 1927 to 1931. (2) The growing points of both varieties were recognized in the shape of crotch or Sympodium in mid-June. The symptom in this stage is like that of egg plants and tomatoes. (3) Time of flower clusters differentiation of these varieties was mid-June in the buds of the young shoots and formation of secondary clusters in the differentiated clusters was late June. (4) Second dusters formation of Delaware in the buds was observed in June 20 to July 10, third clusters July 8 to August 7, the forth August 29 to September 19 and their subdivision of the differentiated clusters, that is development of secondary, tertiary and quaternary clusters, observed from November 16 to December 28. (5) Second flower clusters in the buds of Koshu began to differentiate on July 10, and the differentiation of third flower cluster was rare. Time of the third flower cluster differentiation was from July 30 to October 19. (6) Calyx formation of Delaware was observed at first April 11 in the next year when individual flower bud was to differentiate. Flower buds were observed with the unaided eye on May 9 and pollen grains and ovules appeared on May 16. (7) Flower buds of grape vines are much like to those of persimmons and chestnuts, showing delayed development of flower organs during winter. Calyx or petals are formed from March to April and make rapid development until flowering and fruiting.
1. In the rooting of Vitis Berlandieri of our cuttings experiments green shoot cuttings were prior to those matured ones, and further striking effects were obtained in the Ca(OH)2 0.3% solution and Ca(OH)2 0.3%+C12H22O11 10% solution treated. 2. Those striking effects of liming in the rooting of green shoots, especially in the upper parts, however, might be seemed to the writers not from their physico-chemical natures, but their degree of maturity. 3. The younger shoot with higher C/Nm, Nn roots best.
There are some opinions not coincident in relation to the flower bud initiation of Easter Lilies (Liliumlongiflorum var. insulare Hort.). Hereupon, the experiments were carried out to determine the correct time of flower bud differentiation in the favorite plant. The bulbs used were transported from Tanegashima Island and were selected conveniently as being 36gr. in average weight. Under the normal conditions in Yokohama, the intial primordia were apparently growing out from some of bulbs on March 12. Ten days after, on March 22, two primordia, the one being more or less larger than the other, appeared on the bulbs showing 35%. It is the predifferentiation stage of flower buds, must be. On March 31, the outer tepals of the first flower were observed in differentiating as individual primordium. This should be called as the differentiation stage of flower buds, at least in Easter Lilies. On April 10, about 10 days after the differentiation stage, the intial development of the inner tepals and stamens were individually distinguished. After then, the initial formation of pistils and of initial pollens and ovules were normally progressed, occurring on April 20 and May 20, res pectively. The flowers commenced to bloom on June 18.