Sulfonamide derivative as harmful-organism control agent for agricultural/horticultural use

A novel sulfonamide compound represented by this formula (I). This compound exhibits an excellent control activity against harmful organisms, specifically pathogenic bacteria, insects, mites, nematodes and the like which harm agricultural/horticultural plants; hence, the compound is extremely useful as a new agrochemical. R 1 , R 2 , R 3 , R 4 : H, COOR, etc. A: phenylene, etc. B: a) phenyl, etc., b) C 1-6 straight-chain/branching alkyl, etc., c) SiR 5 R 6 R 7 , d) COOR, etc., e) H (R 5 , R 6 , R 7 : C 1-6 straight-chain/branching alkyl, phenyl, R: C 1-8 straight-chain/branching alkyl, benzyl, cyclic ether, etc.) (given a), b), B may be substituted with formyl, halogen, haloalkyl, cyano, nitro, etc.)