The invention relates to a liquid aqueous composition, which has a pH value of at least 7.0, comprising a pesticide and a base selected from an alkali salt of hydrogencarbonate； a method for preparing said composition comprising a step of contacting a pesticide and a base selected from an alkali salt of hydrogencarbonate； and a method of combating harmful insects and/or phytopathogenic fungi, which comprises contacting plants, seed, soil or habitat of plants in or on which the harmful insects and/or phytopathogenic fungi are growing or may grow, plants, seed or soil to be protected from attack or infestation by said harmful insects and/or phytopathogenic fungi with an effective amount of the composition.
