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

: PART IV. young plantation, it will usually be found that vhe leeward side of the trees is the worse affected, and those trees which have been so grown that the lower primaries are bunched thickly together and touching the ground. There are therefore two means at our disposal of helping the climate to control the Mealy-bug; firstly the avoidance of wind-breaks to ensure a free circulation of air through the plantation, and secondly a system of pruning that will avoid numerous primaries touching the ground, thus maintaining a good circulation of air in the tree itself, especially round its base. The rigorous suppression of weeds will also help to keep the relative humidity at a lower figure. These recommendations are naturally only made from the point of view of controlling the mealy-bug, though they will also assist in the control of several other insect pests of coffee in this country. It is realised that in parts of the country wind-breaks may be essential, although in those districts where mealy-bug attack is most prevalent, they do not appear to be so, at any rate after the coffee has become well established. The suggested elimination of the lowest primaries has however, in the opinion of the Senior Coffee Officer and of the Mycologist, several other advantages, apart from the question of insect pests. As regards the destruction of alternative food supplies, it is possible that not very much can be accomplished in this direction. Theoretically, a belt at least fifty yards wide should be cleared at the edges of a coffee plantation, and if possible not planted with any crops at all, but at any rate not .with a crop that can be a host of mealy-bug or any other coffee pest. This will minimise the risk of infection being carried to the coffee by man or animals; but nothing can eliminate the risk of wind-borne infection; and the principal cause of mealy-bug suddenly appearing in a hitherto uninfected locality is wind—especially ‘“ dust-devils ’ which may pick up leaves and carry them long distances. Thirdly, the utilisation of indigenous parasites. Only one internal parasite of the common coffee mealy-bug has so far been found in this country, and that appears to be exceedingly rare, so that it has not been possible to obtain enough to breed them. Two mealy-bugs, both of them closely related to that on coffee, have been found on two species of wild plants, and both these mealy-bugs are heavily parasitised by two different species of Hymenoptera. Unfortunately, neither of these parasites can be induced to attack the coffee mealy- bug: indeed, were they capable of it, they would probably have done so long ago without any artificial aid. Practically nothing therefore can be expected from parasites, but in the utilisation of the predatory enemies of the mealy-bug lies the chief hope of combating this pest. There are already known to exist in this country nearly forty different species of insects which feed on the coffee mealy-bug. Though some of these are scarce and of little practical importance, it will be of interest to give the full list. ORDER Psocoptera. About nine species of these small insects are known to prey on the coffee mealy-bug; only one of which, the commonest, has so far been named—Ectopsocus briggsi, Mel. This is mainly a dry-weather insect 190)

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