Control of pearl millet downy mildew by seed treatment with metalaxyl*

Abstract

SUMMARY Three formulations of the systemic fungicide metalaxyl were tested in various seed treatments for the control of pearl millet downy mildew in three field experiments with downy mildew‐susceptible pearl millet hybrid NHB‐3. Uniform, high levels of sporangial inoculum of the causal fungus, Sclerospora graminicola , were provided throughout the growth of the test crops from inoculated infector rows of NHB‐3, planted earlier between the test plots. Significant reductions in downy mildew were obtained with all fungicide treatments. Best control was obtained when seed was soaked in a 0.5% aqueous solution of a liquid formulation (mean infection index of 9.8% compared with 94.8% in the untreated check). The degree of control with the wettable powder formulations was directly related to fungicide dosage, and there were no significant effects of application method. Simple dusting of seed at 2 g a.i./kg, a rapid and simple operation requiring small quantities of fungicide and no special application equipment, gave a high level of control (infection index of 12.6% compared with 78.9% in the untreated check). In two experiments grain yields from all the treated plots were significantly greater than from the untreated plots (means of 1234 and 1534 kg/ha for treated plots compared with 485 and 743 kg/ha, respectively), and in the third, the treatment with the least downy mildew gave significantly more grain than the untreated check (1228 compared with 727 kg/ha).