Proceedings of the South & East African combined agricultural, cotton, entomological and mycological conference held at Nairobi, August, 1926

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Monograph

Identifikator:: 1738588467

URN:: urn:nbn:de:zbw-retromon-115043

Document type:: Monograph

Title:: Proceedings of the South & East African combined agricultural, cotton, entomological and mycological conference held at Nairobi, August, 1926

Place of publication:: Nairobi

Publisher:: East African Standard

Year of publication:: 1926

Scope:: VI, 337 Seiten; Ill.

Digitisation:: 2020

Collection:: Economics Books

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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part IV. Etomology & Mycology

Collection:: Economics Books

ENCLOSURE TO PART IV. Dysdercus spp. have been credited with several different forms of injury, one of which, namely direct staining of the lint with their excreta, is not now held to be of serious importance by any investigator: there remain: — 1) Transmission of Internal Boll Diseases; (2, Causing shedding of young bolls without the intervention of disease; 3) Inducing failure of the bolls to open normally; (4) Injury to the young seeds resulting in failure of lint to develop normally. (5) Injury to seeds affecting germination and impairing their commercial value for crushing. Of the above the first would appear to be the most important. Internal boll diseases, including lint staining, are prevalent in this Colony and if Dysdercus spp. is to be regarded, as the main cause these insects must clearly be accorded a very prominent place amongst cotton pests. Other sucking insects large enough to pierce the carpels are more or less negligible in numbers in comparison. In carrying out investigations into the question of the trans- mission of disease by insects, it is obviously helpful if an accurate method of identifying the disease is known. In the present instance, however, there appears to be some degree of uncertainty in this connection. It would appear first of all that one form of boll rot may be separated at once from the others, namely that caused by Bacillus malvacearum which has been shown definitely to be independent of extraneous aid in obtaining entrance to the interior of the bolls. "* Soft Rot * caused by a species of Phytophthora would also appear to be a specific and readily recognised disease (Nowell). In Southern Rhodesia Mr. F. E. Eyles, Botanist and Myecologist, Agricultural Department, records the following of bacteria and fungi, which have been associated with boll rot elsewhere, namely: Pseudomonas malvacearum, Smith; Bacillus gossypii, Stedman; and Colletotrichum gossypii, Sout. (Rhodesia Agricultural Journal, June 1926, p. 637). Of these B. gossypii, Stedman, has been found in association with Bolirot, and Colletotrichum with compaction and discolouration of lint in Southern Rhodesia. The careful experiments carried out by Nowell in the West Indies, Pomeroy and Golding in S. Nigeria, and Ballard and Holdaway in Queensland, although implicating Dysdercus and other sucking insects in the transmission of bollrot, afford comparatively little enlightenment as to the specific organisms causing the disease. Marsh, however, appears to have associated lint staining in Nyasaland tentatively with Nematospora sp. A fungus of this genus was also isolated by Nowell in the West Indies and he mentions that Bartlett apparently isolated a similar fungus. Ballard and Holdaway, however, do not mention this genus amongst the fungi bred from samples of cotton in Queens- land. In point of fact, the only genus of fungi associated with “ Bollrot ’’ in all countries, where these have been really studied, seems to be Alternaria. 92929

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