PART TV.
application is to protect the young flush of leaf. In spraying against
leaf disease it is essential to wet thoroughly the undersides of the
leaves, as it is on that surface that infection takes place. The finest
spray nozzle obtainable should be used.
It is not known whether the spraying measures advocated above
would be successful in Portuguese East Africa. In Kenya, coffee is
grown at altitudes of 4,500 and above
Mr. RITCHIE from experience with the disease in Tanyanyika,
recommended as follows: —
1. The industry should only be attempted in areas where
conditions have been observed to be generally suitable for coffee.
2. A robust growing type or types of coffee should be selected
suitable to the particular area, a type with strong primary growth and
ample leafage. Kent's coffee, so far as Tanganyika trials have gone,
is a coffee of this type but other local types (copper tip) appear also
to be equally suitable.
3. So far as trials have gone, there is no decided evidence in
Tanganyika that spraying with Bordeaux or Carbide mixture exerts
any control on Hemileia, indeed many planters have given it up.
They recognise that the great thing is natural plant vigour and general
plantation management to maintain a reserve (i.e., recuperative
power) in the plant.
4. There is evidence that coffee left more or less to a free form
of growth and not made to conform to a humanly devised pruning
system (he referred to vigorous pruning of single stem or low-top
coffee), maintains of itself a satisfactorily balanced growth (crop, cropbearing
 area, leafage) and is less affected by leaf disease.
Causgs oF DIEBACK IN COFFEE.
Mr. McDONALD read the following statement on the causes of
dieback in coffee : —
This short statement deals with coffee dieback as met with in this
part of East Africa and is submitted in response to the request of the
Government of Nyasaland for information on the subject. Much of
what is known of the malady in these parts is due to the work of Dr.
Small, lately Mycologist in Uganda, who began investigations on
dieback at least as long ago as 1915. Experience has shown, however,
that there are few, if any, differences between the problem presented
in Uganda and that in Kenya.
The common form of dieback of coffee is characterised by the
blackening and drying up of the primary branches from their tips
downwards. In bad cases the trouble may even extend to the main
stem. As the dessication of the branches proceeds, their leaves and
berries are naturally involved and also become brown and dried-up.
Eventually such affected branches become reduced, by the shedding
of the leaves and berries, to bare brittle sticks. In severe cases, the
whole bush may be affected, but the commonest condition is that in
which the apical branches and those in the lower half of the bush
remain healthy while there is an intermediate zone affected with
dieback.
Dieback represents a state of exhaustion and indicates that the
affected bush has undergone an excessive strain of some sort. It is
never directly due to attack by parasitic agencies, although it may

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