Effect of planting date, cultivar, and seed treatment on leaf rust severity of wheat along the Gulf Coast

The effects of planting date, cultivar, and seed treatments on wheat leaf r ust (Puccinia triticina Ericks) were studied in the 1995 and 1996 at two si tes in Louisiana. Three winter wheat (Triticum aestivum L.) cultivars, diff ering in susceptibility to leaf rust, were planted 21 to 35 days early and at a recommended date. FFR 525 was susceptible, Coker 9835 was moderately s usceptible, and Pioneer brand 2566 was moderately resistant to prevalent ra ces of leaf rust. Seed fungicide treatments were: Vitavax (R) 200 and Bayta n (R) 30 plus Captan (R) 30-DD, plus a non-treated control. Across cultivar s, early planting resulted in higher leaf rust levels in both years compare d to planting wheat at the later date. The rust susceptible FFR 525W, when planted at the recommended date, had lower areas under rust progress curves than when planted early. The moderately resistant Pioneer 2566 may be plan ted early or at the recommended date, while Coker 9835 should be planted at the recommended date. Seed treatment fungicides provided limited control o f leaf rust in only one environment. Planting within the recommended planti ng period with a resistant cultivar provided the most reliable disease cont rol.