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. a prepared to recommend this method of control. As a whole, the results obtained have been most discouraging. I might add that our laboratory experiments on the effect of calcium arsenate on the larva of the Sudan bollworm seem to indicate that this poison has no effect, in that the larvee reject the poisoned rind of the cotton boll. TraPPING ADULTS. No experiments have been conducted along this line of insect control. I certainly think that this method of control is worth serious consideration. I have found that one female moth of the Sudan boll- worm lays nearly 500 eggs. HAND-PICKING AND COLLECTING LARVAE IN THE FIELD. An experiment on stripping the cotton plants, at a certain date when the infestation seemed to warrant it, of all squares and bolls (infested and sound), and another similar experiment followed by a dusting with calcium arsenate were conducted last season. The results were negative in each case. An experiment on picking the flared squares was also tried. This also gave negative results. To find out what percentage of the flared squares contained live bollworm larve, counts were made at a certain place last season. It was found that 319 of the bollworm-punctured flares (those fallen and on the plant) had live Sudan bollworm larve in them, that none contained American bollworm larve, and that 1 or 29 contained larvee of spiny bollworm. During cool or wet weather, a higher percentage of live larvee of the Sudan bollworm stayed in the flares. The mortality of larvee in these fallen flares was not worked out but it was found that the larger larve could live for a considerable time in the larger fallen bolls. With us, labour is too high to make this method of control practical; and, in any case, it appears that the results obtained do not warrant its use as a control measure. Trap CroprING. Only observations have been made on the use of maize as a trap-crop for the American bollworm. It has been noticed that, in some Instances, American boll worm attacks on cotton have followed the *“ hardening off * of the maize crop. No direct experiments have yet been conducted. Crose SEeasow. Few, if any, cotton growers in the Union of South Africa have attempted to apply a strict close season to their programme in cotton culture. As a rule, it only occurs when brought on by frosts or when pickings cease early in the winter. If connected with autumn or winter ploughing, I think it would have a very beneficial effect. With us, a close season is so closely linked up with the establishing (planting) of the following season’s crop that it seems inadvisable to enforce it at present. Hardships might be imposed unless the matter was carefully studied. However, in principle, I am in favour of a close season, and I think that the subject should receive careful study. The following conclusion was adopted : — That, although a great deal of experimental and investiga- tional work has been done on Sudan, American, and Spiny Boll Worms, this Section is not in a position to make any general recommendation. No economic means of control have yet been devised, and we are of opinion that further investigations are desirable and necessary. 29"

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