the Symposium on Wheats for More Tropical Environments - cimmyt

4320-year period. Also indicated are <strong>the</strong>high temperatures during Septemberwhich. combined with <strong>the</strong> highprecip_tation of <strong>the</strong> area. providesfavorable conditions for diseasedevelopment. The average temperaturefor <strong>the</strong> season is 22°C. Table 1 presentsmonthly mean data for rainfall, relativehumidity and temperature.WindWheat is cultivated during <strong>the</strong> winter,when winds create ano<strong>the</strong>r problem forwheat cultivation. North winds aremore frequent and are more humid.frequently causing lodging of <strong>the</strong> crop.especially after heavy rain. Also, <strong>the</strong>ycause shattering of heads duringmaturity. South winds are strong. coldand wet. and can cause sterility ofspikes due to frost.DiseaseThe most prevalent diseasesencountered are spot blotch caused byHelmtnthosportum sattvum. leaf rustcaused by Pueetnta reeondtta, stemrust caused by Pueetnta graminls tritietand blotch caused by Septoria trttiel;root rots are also becoming important.?P-_sog70't:l~..c:: 60(l)~~ 60c:: :("L ,......__-~----"'T""---~~---~---May, IiiJune July August SeptemberFigure 2. Relative moisture during <strong>the</strong> wheat-growing season, nor<strong>the</strong>rnSanta Cruz, Bollvla (2o-year average)oMaximum--'~~ ~~....... ,'"",-.,.'... --...........,. Average-- .._--------- Minimum................ .............. .",................. .iMayiJuneiJulyiAugustG oFigure 3. Temperature range during <strong>the</strong> wheat-growing season, nor<strong>the</strong>rniSeptemberSanta Cruz, Bolivia (2o-year average)