Girdling Experiments on the Translocation of Topically Applied radioactive γBHC-I-C¹⁴ in certain Woody Plants with insect Galls

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A girdle was made on the stem of a freshly-cut twig of chestnut tree with galls caused by chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu, and/or that of wild willow with bowl-like leaf galls caused by Pontania viminalis. Radioactive γBHC-1-C¹⁴ was then applied topically to such plant tissues as a leaf, a flush terminal shoot, a stem, and galls located above or below the treated portion, respectively, and its penetration in as well as translocation within the plant tissues was traced by autoradiography. γBHC was found to penetrate and be translocated both upwards and downwards, but when applied to the upper part of the treated portion it was hindered in its entirety from moving downwards past the girdle. The experiments with a girdle made on the stem above the treated portion ended in failure by an accident occurred in course of exposure, but those conducted quite similarly in parallel with this by using radiophosphorus P32 showed that P32 was almost checked from upward translocation past the girdle made on the stem above the treated portion. In view of the other substantially equal results of the two sets of experiments, it was considered that radioactive γBHC might have behaved just like P32 under the same experimental conditions. Autoradiograph of the cross section of galls indicated undoubtedly that γBHC mainly persisted in the external surface layer of the gall without penetrating so deeply as to reach the inner part of it. On the above basis, it was concluded that when applied to the aerial parts of the plants examined the γBHC absorbed in the treated portion is capable of being translocated to several plant tissues acropetally as well as basipetally, especially being accumulated in flush terminal shoots and galls where growth is active, phloem being solely responsible for its translocation, under the present experimental conditions. Founded upon this conclusion, the following discussion was made : First, some available foreign works rather historically. Secondly, on the problems of presowing or pretrans-planting soil application or predrilling seed dressing or dipping of γBHC which now are one of the most prevailing topics of discussion in applied entomology, the mechanism of insecticidal effectiveness of BHC was discussed in detail, a special importance being attached to the fact of its phloem translocation observed. Finally, the role of γBHC in the "integrated control" of chestnut gall wasp was reaffirmed as follows: If γBHC is applied to aerial parts of infested chestnut trees once or at most twice in a week at the time when the greater part (ca. 80 per cent. ) of the composite resident parasitic wasps which emerge about 2 weeks earlier than their host wasp, chestnut gall wasp, does so, finished emerging and a very few (ca. 10 per cent.) chestnut gall wasps completed their emergence, i.e. what I call the "period fittest for possible biological or integrated control", then, the eggs already laid by the composite resident parasitic wasps onto various insect galls, inclusive of chestnut galls, will be protected safely from the γBHC toxicity due to contact with it within the inner part of increasingly lignified galls. On the other hand, the remaining majority of chestnut gall wasps (ca. 90 per cent.) which enter gradually upon the period most active emergence after that time will easily killed in contact with γBHC which persisted in the external surface layer of the gall when they emerge out of it. As a natural result of this process, the existing rate of parasitism for the composite resident parasitic wasps will be increased relatively to a great degree, accordingly a system of integrated biological and insecticidal control adjusted to meet chestnut gall wasp being established.
信州大学農学部の論文
1961-12-30

Girdling Experiments on the Translocation of Topically Applied radioactive γBHC-I-C¹⁴ in certain Woody Plants with insect Galls

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信州大学農学部 | 論文

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