Abstract: Thienopyrimidines of the formula: ##STR1## wherein R.sup.1 is straight or branched chain alkyl containing from 3 to 11 carbon atoms and optionally substituted with cyano or methoxy, cycloalkyl, benzyl optionally substituted on the .alpha. carbon atom with a lower alkyl group or in the ring with one or more alkoxy groups or halogen atoms, dimethylamino, phenylethyl optionally substituted at the .alpha.- or .beta.-carbon atoms with a lower alkyl group, tetrahydrofurfuryl; R.sup.3 is hydrogen or NH.sub.2 ; or R.sup.1 and R.sup.3 together form a carbon chain bridging group optionally saturated and containing one or more nitrogen atoms; R.sup.2 is hydrogen, methyl, ethyl, or chlorine; R.sup.5 is hydrogen or methyl; and R.sup.6 is hydrogen, methyl or acetylamino; or an optical isomer thereof; or a tautomer thereof; or a salt thereof. These and other thienopyrimidines are disclosed as useful for plant growth regulation and for combating fungal, viral and bacterial diseases of plants and insect pests.