Evaluation of fungicides for the control of coffee berry disease in Kenya

Some sixty fungicides were tested in the laboratory for ability to ( a ) depress sporulation of Colletotrichum coffeanum on the maturing bark of coffee shoots and ( b ) inhibit spore germination. On the basis of these tests over twenty products were selected for testing in the field during 1968-70. Nine of these (50 % copper formulations, Ortho-Difolatan, Daconil, Benlate, Topsin, Top-sin M, Tecto 60, Delan and Du-Ter) could be recommended for control of coffee berry disease (CBD) in Kenya.
Field evaluation of fungicides is complicated by multiple flowering which creates a succession of overlapping crops, and by high variability in cropping potential which is often aggravated by normal pruning practices; in some circumstances other diseases and pests may also be a complicating factor. As a result, yield, which should be the most sensitive measure of CBD control, is at times even less satisfactory than disease estimates based on a small sample of the developing crop. Disease incidence in the ripe crop, which is easy to measure, is unfortunately not always well correlated with disease and crop loss earlier in the season. Consequently, critical assessment of fungicide performance requires estimates of both disease progress and crop loss.
Consideration of fungicide performance indicates that physical characteristics, particularly persistence and capacity for redistribution, are especially important for effective control of CBD.     

Germination of Stored Cassava Seed at Constant and Alternating Temperatures

Cassava seed is only capable of germinating over a restrictedrange of constant temperatures. During storage the optimum constanttemperature for germination decreases from about 35 to 30 °Cor possibly less. The rate at which the optimum temperaturechanges during dry storage increases with increase in storagetemperature over the range 0 to 40 °C. Some alternating-temperatureregimes (16 h at the lower temperature; 8 h at the higher temperature)can provide conditions as favourable for germination as theoptimum constant temperatures. Furthermore, it has been shownthat temperature alternation itself is stimulatory because whenthe range of the alternation does not include the optimum constanttemperature value, percentage germination is often higher thancould be obtained at any constant temperature within the range,though this stimulatory response declines during storage. Forthese reasons it is provisionally recommended that cassava seedshould be germinated at 25/35 °C which is as stimulatorya treatment as any which has so far been investigated and hasthe advantage of encompassing the range over which the optimumconstant temperature changes during storage. Manihot esculenta Crantz, cassava, germination, dormancy, seed viability, storage of seeds, after-ripening     

Some problems of evaluating fungicides for use on coffee in Kenya

As part of a programme testing fungicides for control of coffee berry disease (CBD) promising materials were also tested in the field against leaf rust of coffee. In all, fourteen fungicides were tested, five of which have been recommended for control of CBD. Only Perenox (representative of 50% copper fungicides) and Du-Ter (not highly effective against CBD and no longer recommended) gave good control of rust; Difolatan gave some control but Benlate and Daconil were virtually ineffective.
Where only CBD is present there is generally a good relationship between disease control and yield, but in these experiments where leaf rust was also present, this relationship was seriously disturbed. The implications of this for testing fungicides for use on coffee in Kenya are discussed.