The invention describes gametocidal and microbicidal compositions which contain, as active ingredient, a nitroarylalkylsulfone derivative of the formula I ##STR1## wherein R.sub.1 is alkyl, R.sub.2 and R.sub.3 are each hydrogen, alkyl, alkoxy, haloalkyl, halogen, cyano, nitro or amino or together they complete a naphthalene ring; R.sub.4 is hydrogen or --COR.sub.5, wherein R.sub.5 is alkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkynyl, cycloalkyl, phenyl, benzyl, furyl or tetrahydrofuryl. The invention relates also to the use of these compositions and compounds for stimulating generative plant growth and for obtaining hybrid seeds, as well as to a method of preparing the hydrazinium and ammonium salts within the scope of the formula I, and to a process for preparing agrochemical compositions which contain compounds of the formula I as active ingredient.