The drugs and speciality chemicals company bought a US-based fungicide business from Japan's Ishihara Sangyo Kaisha (ISK), which it said would help lift it to number two position from eighth in the global $5bn fungal control business.
It also acquired international distribution rights to four fungicides, herbicides and pest control products newly introduced by ISK which will provide a further lift to sales from the turn of the century.
The ISK acquisition follows Zeneca's purchase of Dutch biotechnology company Mogen earlier this year, which strengthened its research into genetic modification of plants to overcome fungal resistance.
News of the latest move pushed Zeneca shares up 4p to pounds 20.77.
Zeneca Agrochemicals chief executive Michael Pragnell said that ISK's well-established fungicide Chorothanolil together with Zeneca's newly- launched fungicide Amistar would allow it to offer a disease-beating package to farmers.
"It is part of a whole disease management programme. Disease control is fundamental and this is all about disease control in agriculture," he said.
He said Chorothanolil would be an important complement to Amistar, which has been launched in 19 countries and approved in a further three.
Zeneca Agrochemicals is eighth in the world in the sale of fungal control products, which account for 20 per cent of the agrochemical market. This compares to its number three position in agrochemicals as a whole.