Dihydropyridazinones, pyridazinones and related compounds as fungicides

A method for controlling phytopathogenic fungus which comprises applying to the fungus or its habitat a fungicidally-effective amount of the formula ##STR91## wherein when the compound is a five member ring A is --CHR.sup.7 --Z--, or S--Z--;

• D is nitrogen
• Q is an aromatic group selected from ##STR92## X is oxygen (O) or sulfur (S);
• Z is carbonyl (C.dbd.O) or thiocarbonyl (C.dbd.S);
• R.sup.1 is alkyl, hydroxyalkyl, cyanoalkyl, hydrazidal, phenylcarbonyl, alkenyl, haloalkenyl, alkynylalkenyl, alkynyl, haloalkynyl, dialkynyl, cydoalkylalkynyl, alkenylalkynyl, hydroxyalkynyl, alkoxyalkynyl, alkanoyloxyalkynyl, formylalkynyl, trialkyisilylalkynyl, trialkyllinalkynyl, haloalkenylalkynyl, carboxyalkynyl, or alkoxycarbonylalkynyl;
• R.sup.3 and R.sup.6 are each independently hydrogen, alkoxy or halo;
• R.sup.4 is hydrogen, halo, alkoxy or nitro;
• R.sup.5 is hydrogen, halo, nitro, alkyl alkoxy, alkylthio, haloalkyl, haloalkoxy, haloalkylthio, phenyl, phenoxy or cyano;
• R.sup.7 is hydrogen, (C.sub.1 -C.sub.3)alkyl, phenyl, cyano, halo, alkynyl, alkynylalkenyl, dialkynyl, haloalkynyl or alkenylalkynyl;
• R.sup.8 is hydrogen, (C.sub.1 -C.sub.3)alkyl, phenyl, cyano or halo;
• provided when Q is phenyl, D is nitrogen, A is --CHR.sup.7 --Z-- wherein Z is C.dbd.O and R.sup.7 is hydrogen, (C.sub.1 -C.sub.3)alkyl or phenyl and R.sup.1 is phenylalkyl or heterocyclylalkyl, the alkyl portion of the R.sup.1 moiety must be a straight chain;
• when Q is ##STR93## R.sup.1 is alkyl, A is --CHR.sup.7 --Z-- and Z is C.dbd.O, R.sup.3, R.sup.4, R.sup.5, R.sup.6, and R.sup.7 cannot all be hydrogen;
• and when A is S--Z--, R.sup.1 cannot be haloalkynyl;
• and agronomically acceptable salts thereof.