Late leaf spot (LLS) (causal agent Phaeoisariopsis personata) and rust (causal agent Puccinia arachidis) are economically important foliar diseases of groundnut (Arachis hypogaea) and have global significance. Aqueous leaf extracts of Datura metel and Lawsonia inermis, known for their high antifungal activity against P. personata, completely inhibited the germination of urediniospores of P. arachidis in vitro. In the greenhouse, extracts of D. metel (25 g/L) and L. inermis (50 g/L) applied as a prophylactic spray reduced the frequency of LLS lesions and rust pustules by 65–74% compared with controls. In field studies, a programme of four sprays of D. metel leaf extract at 45, 60, 75 and 90 days after sowing (DAS) was partially effective against the foliar diseases (LLS and rust) up to 95 DAS. A single spray of chlorothalonil at 45 DAS combined with three sprays of D. metel at 60, 75 and 90 DAS effectively reduced the combined severity of LLS and rust. The increase in pod yield by this treatment (91% over control) was comparable with the sustained application of chlorothalonil. Further validation of integrated applications of D. metel extract and chlorothalonil may reduce the dependency on fungicides in groundnut cultivation.