The present paper deals with the results on suitable conditions such as kinds, culture periods and amounts of inoculum for the pot-indicator plant method for screening soil fungicides.
An inoculum could be obtained by pre-culture of wheatbran and soil for 2-5 days. An apparent control effect could be expected when five to ten grams of inoculum per pot were applied.

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Protective effects of EBP (o, o-diethyl-s-benzylthiophosphate), KSM (kasugamycin) and PCBA (pentachloro-benzylalchol) and IBP (o, o-diisopropyl-s-benzylthiophosphate) against rice blast were compared with each other in different ways of application.
Submerged application of these fungicides in irrigation water, 20 and 100g per are, showed that EBP was most effective, giving one-thirds the number of lesions of the control, followed by KSM giving two-thirds the spots of the control.
In dipping or coating treatment of seeds, KSM gave a certain degree of protective effect in the early stage of infection but the effect seemed to be temporay. So far as tested, dipping roots of seedlings in the solution of these fungicides for 3-6 hr before the transplanting had no protective effect for rice blast while EBP applied in the same procedure was not effective.
Submerged application of IBP, 3 and 5 kg per are, gave a better protective effect than KSM- or IBP- dust and the effect was durable. The protective effect of IBP seemed to be more prominent in application to irrigated field than to drained field.
Protective effects of these fungicides were also compared with those of other organophosphorous compounds applying to the irrigation water. IBP showed a prominent effect followed by DF-1991.
When IBP was submerged, 50-100g per are, twice in the irrigation water, neck rot, node blast as well as clum rot disease (H. sigmoidium var. irregulare) were effectively controlled, leading to an increased yield.

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It has been known that ants (Lasius niger LINNAEUS) protect Aphis fabae SCOPOLI, infesting bean plants, from many of its insect predators, and allow it to produce large, dense colonies on rapidly growing apical leaves and stems (BANKS, 1962). Similar results to those of BANKS were confirmed in our own expeiment with the apple aphid (Aphis pomi DEGEER) and the apple leaf-curling aphid (Myzusmalisucuts MATSUMURA), both can severely damage apple trees.
Prior to the assessment of the effects of ants and predators on aphid numbers, the potted apple seedlings in cage experiment and 8-year-old apple trees of Ralls Janet in orchards were infested with Aphis aphids and Myzus aphids. The reproduction of aphids with the attendance of Lasius niger LINNAEUS and that without ants were thus read for comparison. Of course, the ants, attending aphids, and predators (mainly coccinellid adults and larvae, chrysopid adults and larvae and syrphid larvae) were also recorded at the same time.
During these courses, as has already been seen in Tables 1-4, the ant-attended Aphis aphids were always numerous than the ant-free aphids on apple leaves, regardless of the seedling or 8-year-old tree, in the absence or scarcity of predators. This may be depend on the important aspect that the present aphids were partially protected by the ants which drove most of natural enemies of the Homoptera away from their colonies. But when the ants were excluded from the plants by a thick smear of tree-banding grease at the base of each branch or twig, predators were much more common and increased steadily in numbers. Therefore it would be considered that the rapid multiplication of ant-attended aphids was, in part, atributed to the repelling of the predators by the ants. In contrast, sucha a situation did not keenly appear in the relation between Myzus aphids and ants, because of the feeding site different from that of Aphis aphids or other factors which does not clearly shown.
Aside from the above argument, one interesting point is the amount of honeydew excreted by aphids. As will be seen in Table 5, the area of a droplet produced by Aphis aphids, which was spreaded on pH testing paper, was greater than that of Myzus aphids. Moreover, as shown in Fig. 1, many sorts of sugar were determined in the honeydew droplet of the Aphis aphids than in Myzus aphids. This would prove that the honeydew of Aphis aphids is more attractive for the assiduity in repelling activities of ants against predators, attending aphids, on plants.

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The virus of mild symptom developed by graft on indicator plants (Alpine) to the leaf-petioles of commercial strawberry is transmitted to indicator (East Malling) by Aphis gossypii but not by Macrosiphum rosa. Aquisition feeding period of this virus by the vector is 2hr., test feeding period is 0.5 hr., and the virus persists for about 5hr. in the vector. An aphid, after feeding for 24 hr. on infected indicator plant, was retransferred to fresh indicator plant for 2 hr. and subsequently again retransferred from 2 to 24 hr.. When such transfer was repeated with a series of fresh eight plants successively, the virus was transmitted by a aphid to only the first feeding plant. From these results this virus is found nopersistent and identified as strawberry mild mottle virus.

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In the previous paper¹⁾, the authors mentioned that the auxin activity in diseased roots of Brassica rapa var. neosuguki KITAM. infected with Plasmodiophora brassicae WORONIN was higher than that in healthy roots, and gibberellin or gibberellin-like activity was not observed both in diseased and healthy roots.
In the present paper, experiments were undertaken to know further informations on the active principle (s) responsible for the abnormal growth of the infected roots.
Two kinds of auxins, a basic compound and a neutral compound, were recognized on paperchromatogram. The basic compound was found to be in the same degree both in diseased and healthy roots. While, the activity of a neutral compound in diseased roots was higher than that in healthy roots.
After extracting the samples successively with benzene, ethylether and ethanol, an assay was done in order to detect the kinetin-like substance(s) by the following three methods : a) comparison of the fresh weight of young radish leaves by KURAISHI'S procedure²⁾, b) degree of senescence retardation of radish leaves, and c) rate of growth of tabacco callus on MURASHIGE and SKOOG'S medium ⁵⁾ with or without adding the extracts. All the results showed that the activity of the ethylether fraction from diseased roots was higher than that from healthy roots.

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The stimulative effect of phenobarbital (PB) on tobacco mosaic virus (TMV) synthesis in tobacco leaves was studied. PB of 50 ppm stimulated TMV synthesis by 40%, whereas the number of local lesions produced on Nicotiana glutinosa, Nicotiana tabacum cv. Xanthi, nc., and bean (Phaseolus vulgaris cv. Otenashi) was not altered by PB treatment. PB did not significantly affect the RNA content of tobacco leaves ; however, ribonuclease (RNase) activity in tobacco leaves infected with TMV or uninfected was increased by PB treatment. NADPH oxidase activity in tobacco leaves was increased and peroxidase activity in tobacco and bean leaves was inhibited, both by PB treatment. Mixed treatment of tobacco leaves with PB and plant hormones, such as indole acetic acid (IAA) or Kinetin, caused a reduction in TMV titer and NADPH oxidase activity as compared with the treatment of PB alone. The mechanism of the stimulation by PB of TMV synthesis in tobacco leaves is discussed.

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For analysing the damage on citrus root caused by the citrus ground mealy bug, Rhizoecus kondonis, using the apparatus which was deviced by the senior author, the weight of citrus seedling above ground and that of new and old roots were measured when cutting new fine root growing in the upper part of the root (A-cutting) and cutting the lower part of root (B-cutting).
(1) Fall of old leaves was observed by A and B cutting about 5.7 and 3.0 times comparing to the non-treatment, respectively.
(2) In the case of A cutting, the fall of leaves was observed during 60 days in summer and from the lower part of tree to the higher part just after the treatment. In B cutting the fall was found in autumn and at random regardless the part of tree.
(3) In the upper apparatus the new growth of root reached to a peak in summer being almost in parallel with the growth of the over ground part. In the lower part of the apparatus the peak of root growth was in autumn.
(4) The weight of citrus seedling was different in A and B cutting. Percentage of each to the weight of non-treatment was 68.6% and 82.9%, respectively. The same tendency was also observed in the weight of over ground part.
(5) In the case of A cutting, not only the weight of old root of the upper part decreased, but that of new root of the lower part also decreased. In B cutting, the weight of old root of the lower part decreased, while that of new root of the upper part increased in compensating the former case.

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[in Japanese]

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