PART IV. J
Mr. RITCHIE said that at Morogoro, on the experimental plot,
there was 100% infection of streak disease on maize. The insects
present were Aphis maidis and Peregrinus maidis. The possibility of
msect vectors other than that found in South Africa must be
considered
~ Mr. KIRKPATRICK had found only one insect on streak that
was likely to be a vector; this was an undetermined Jassid.
Mr. RITCHIE considered that soil and weather conditions were
the chief factors which predispose plants to this disease.
Mr. ANDERSON, in reply to Mr. Ritchie, stated that there was
no record of Peregrinus on maize in Kenya.
Mr. McDONALD said that streak had never been reported on
sugar cane in Kenya, and it had not been possible, in Kenya, to
transmit streak disease experimentally by insects. (Nore: Since this
statement was made streak disease has been found on sugar cane in
Kenya.)
SUGAR MOSAIC DISEASE.
Mr. FULLER read the following note contributed by Mr. Storey,
Myecologist, Union of South Africa:—
(1) The situation in South Africa is unusual, since 99.8% of the
cane area is planted to the variety Uba, believed to be truly immune
to mosaic. Among the balance the spread of mosaic has been rapid,
since the distribution ten years ago of diseased stocks of the tolerant
P.O.J. seedling varieties.
(2) The proposal to eradicate the small quantity of susceptible
cane has not yet been adopted owing to difficulties over compensation.
(3) A local eradication campaign conducted by one concern
controlling 20,000 acres has given very promising results.
(4) This campaign has shown the great difficulty in completely
destroying the roots of cane, even where ploughing out is followed by
fallow and planting with such a rank grower as Uba. We consider
occasional row-by-row inspections to be necessary periodically for two
years after the ploughing out.
(5) We are importing (under strict quarantine) immune varieties
from different countries, and in future years will be in a position to
supply cuttings to other African territories.
ROSETTE DISEASE OF GROUND NUTS.
Mr. FULLER read the following note contributed by Mr. Storey,
Mycologist, Union of South Africa:—
(1) We have fully established the relation of Aphis leguminose
Theo to the transmission of this disease.
(2) We are endeavouring to find the manner of over-wintering
of the virus, as offering the greatest prospect of devising control
measures.
(3) In the normal season effective control of losses is obtained
by planting at as early a date as will allow of good growth of the plant
‘November in N. Transvaal).

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