| dc.description.abstract | The investigations done in this project on
the pathogen Elsinoe phaseo Jenkins vulgare
included etiology epidemiology and control. The
pathogen attacks all parts of foliage. Symptoms on
the stems are elongated raised lesions measuring up
to on~ cm long.They coalesce to cover big portions
of the stem. The lesions on the leaves are ashy
grey, roundish to irregular measuring up to 4 mm.
When the veins are attacked, the saves curve
upwards. Roundish to irregular ashy grey lesions
with brown to brick red margins are found on the
pods. They coalesce to cover large portions of the
pods .
The pathogen is sub epidermal where a sci are
borne in single locale. They contain eight
ascospores which are 1-3 separate and measure up to
13.5 u X 7.5 u. The imperfect state (Sph2celoma
sp.)occurs on the surface of the lesion. Conidia
are borne in acervuli which cO~3ist of indistinct
compact conidiophores. Conidia measure 2.6 u x
590 u. in diameter.
Infection in beans was successful only in
young leaves less than one week old. Older leaves
became resistant. Out of thirty four legumes tested,
Phaseolus vulg3ris. Pha3801us lunatus and Dolichos
1ab1ab were infected. 'Mexican 142' and 'Ree haricot'
bean varieties were found resistant •.
Epidemio1r-gy and control experiments on bean
scab carried out at the University Field Station,
Kabete which is cool and wet, and at Katumani
research station which is warm and dry, showed that
contact was an effective means of disseminating the
pathogen. Dissemination by wind was less efficient
and was greatest in the down wind direction.
Disease intensity was compared in the two
stations and was found to be more severe a4 Katumani
than Kabete. The meteorological factors indicated
that temperature, windrun, relative humidity and
precipitation at the time of inoculation highly
influenced the progress of disease in the two
stations. Shorter incubation and latent periods
raised the level of inoculate more quickly at
Katumani than at Kabete and this also contributed
to a higher disease level. In the later stages of
the epidemic, the rate of disease progress in both
areas depended more on the amount of healthy leaf
tissue remaining. Diseased plants incurred yield
losses up to 70% at Katumani and up to 40% at
Kabete.
In the chemical control experiment, it was
further demonstrated that sprays of three Fungicides,
namely, benlcte (methyl-l-(but,yl-carbamoyl)
benzimidazol-2-yl carbami~e) a systemic fungicide,
and manganese ethylene bisdithiocarbamate) and
copper oxychloride, gave higher yields than the
control. Benlate was the best and gave ap~roximately
13% higher yields than the control. Benlate and
copper oxychloride could be economically used
because they gave Ksh. 635/ha and Ksh. 392/ha
respectively above the control. Dithane M-45 gave
a negligible arno un +t- or~ Ksh. 8. | en |
