An experiment to assess the effectiveness of some chemicals to reduce downy mildew caused by Peronoslerospora maydis on maize was conducted at Binhthuy district, Cantho city. The chemicals were salicylic acid (SA), CaCl2 , K2HPO4 and Mataxyl 10WP. The variety of corn was MX10 (sensitive). Leaves were sprayed with chemicals once at 6 days or twice at 6 and 16 days after sowing. Data collected included symptom of disease and yield. Results showed that chemicals were highly effective in inhibitting the symptom of downny mildew. Among them, CaCl2 was the most effective chemical. | JOURNAL OF SCIENCE, Hue University, Vol. 67, No. 4A, 2011 THE EFFECT OF SYSTEMIC ACQUIRED RESISTANCE IN REDUCING MAIZE DOWNY MILDEW CAUSED BY Peronoslerospora maydis UNDER FIELD CONDITION Le Thanh Toan1, Tran Thi Thu Thuy1 and Lam Phuoc Thanh2 1 Plant Protection Department, College of Agriculture and Applied Biology, Cantho University 2 Binhminh sub-Department of Plant Protection, Vinhlong province Abstract. An experiment to assess the effectiveness of some chemicals to reduce downy mildew caused by Peronoslerospora maydis on maize was conducted at Binhthuy district, Cantho city. The chemicals were salicylic acid (SA), CaCl2 , K2HPO4 and Mataxyl 10WP. The variety of corn was MX10 (sensitive). Leaves were sprayed with chemicals once at 6 days or twice at 6 and 16 days after sowing. Data collected included symptom of disease and yield. Results showed that chemicals were highly effective in inhibitting the symptom of downny mildew. Among them, CaCl2 was the most effective chemical. Keywords: downy mildew, maize, SAR. 1 Introduction Maize (Zea mays L.) is one of the major cereal crops and is widely cultivated in the world. Total annual yield of maize occupied the second position after wheat and accounted for ¼ of total crop production all over the world [1]. In Vietnam, maize can grow on many kinds of soil and in many areas; so, it is cultivated widely. Maize is a source of nutrition for humans and a food source in husbandry; it brings about high economic benefit for farmers. However, maize cultivation is always difficult because of pests. One of the most serious diseases is downy mildew. This disease can cause severe damage up to 100% in many provinces such as Nghean, Kontum, Dongnai, Tiengiang, Dongthap, Vinhlong, Cantho [3]. To control downy mildew, metalaxyl was used [5]. The fungus Peronoslerospora maydis causing downy mildew has many races that can resist metalaxyl and other fungicides [10]. A friendly and ecological solution replacing pesticides is using
