Dibenzofuran derivatives and their use for controlling fungi

A dibenzofuran derivative of the formula ##STR9## where R.sup.1, R.sup.2 and R.sup.3 are identical or different and each is halogen, unsubstituted or halogen-substituted alkyl or alkoxy of 1 to 4 carbon atoms, cyano or nitro, n, p and q are 0, 1, 2 or 3, X is oxygen or sulfur, m is 2, 3 or 4, A.sup..sym. is quinuclidinium or pyrrolizidinium, or -N.sup..sym. R.sup.4 R.sup.5 R.sup.6, where R.sup.4, R.sup.5 and R.sup.6 are identical or different and each independently of one another is alkyl, alkenyl or alkynyl of not more than 6 carbon atoms, cycloalkyl of not more than 12 carbon atoms or cycloalkenyl of not more than 7 carbon atoms, which acyclic and cyclic radicals may be substituted by halogen, cyano, alkoxy of 1 to 4 carbon atoms or dialkylamino, where alkyl is of 1 to 4 carbon atoms, or is aralkyl which is unsubstituted or substituted by fluorine, chlorine, bromine, alkyl, alkenyl or alkoxy of not more than 4 carbon atoms, trifluoromethyl, nitro, cyano or alkoxycarbonyl of not more than 5 carbon atoms, or R.sup.5 together with R.sup.6 is part of a 5-, 6- or 7-membered saturated heterocyclic ring which contains from 1 to 3 hetero-atoms selected from the group consisting of nitrogen, oxygen and sulfur and may be substituted by methyl or ethyl, and Y.sup..crclbar. is the anion of any desired non-phytotoxic acid HY.