Impact of combining fungicide use with calcium fertiliser for managing maize downy mildew

Downy mildew is one of the most destructive diseases of maize worldwide. Disease prevention needs to be done at an early stage of plant growth. Maize is most susceptible to downy mildew between 10 and 45 days after sowing (DAS). This study aims to determine the effectiveness of applying fungicides in the early stages of plant growth combined with the addition of calcium nutrients. The research was conducted in Maros Regency, South Sulawesi, Indonesia, using a randomized block design two factor design. The first factor was five levels of fungicide application frequency, while the second included four fertiliser elements. The downy mildew inoculum source plants were planted and inoculated with Peronosclerospora spp. one month before planting the test genotypes. The results showed that repeated fungicide sprays in the early stages of plant growth effectively suppressed the downy mildew infection by 19.30%. Meanwhile, the first fertilisation at 10 DAS with nitrogen, phosphorus, and calcium (NPCa) was the most effective in suppressing downy mildew compared to other fertilisation packages. The treatment combination of three repeated fungicide applications (10, 15, and 20 DAS) with NPCa fertilisation can reduce the incidence of downy mildew by up to 33.23%. However, this combination resulted in lower yields compared to NPK fertilisation. Consequently, further research is required to explore the most effective method for applying potassium and calcium fertilisers.