Chemical control of downy mildew of maize caused by Peronosclerospora sorghi (Weston and Uppal) Shaw and its impact on growth parameters and yield of maize (Zea mays L.)

摘要

Downy mildews in general and maize downy mildew caused by Peronosclerosporasorghi (Weston and Uppal) Shaw in particular has attained destructive status in parts of Karnataka and could cause severe yield losses if left unattended to. Infection at theseedling stage normally leads to death of seedlings within 3-4 weeks. Hence, a field experiment on the effect of downy mildew on yield and yield components and growth parameters of maize was conducted during kharif and rabi seasons of 1998 at the Regional Research Station, UAS, V. C. Farm, Mandya, Karnataka. Results revealed that, the seed treatment with Ridomil MZ (72 WP) at 3 g / kg of seed alone suppressed the disease to a very great extent where the incidence was only 1.6 per cent. Seed treatment followed by a spray at 10 days after sowing resulted in 100 per cent disease control. There was a substantial increase in yield due to seed treatment with one spray at ten days after sowing which resulted in 2707.66 kg / ha as against 1260.50 kg/ha in untreated check. Similarly, more fodder was recorded in this treatment (3670.23 kg / ha) than in untreated check (1300.68 kg / ha). There was a great adverse effect on growth and growth parameters of maize plots which received either no or partial seed treatment. The plant height was maximum where seed treatment was followed by one spray at 10 days interval after sowing. A mere seed treatment resulted in a plant height of 142.00 cm as against 115.73 cm in check. The intemodal length varied from 10.16 to 12.76 cm in various treatments compared to 9.58 cm in check plots.