The control of dry bean anthracnose through seed treatment and the correct application timing of foliar fungicides

In 2005 and 2006, a study was carried out to control anthracnose of dry bean (Phaseolus vulgaris L.), caused by Colletotrichum lindemuthianum, using DCT (diazinon + captan + thiophanate-methyl) and Apron Maxx (metalaxyl-m + fludioxonil) seed treatments and the foliar application of pyraclostrobin and azoxystrobin fungicides under low and high disease pressure at Exeter, ON and Morden, MB. Four single fungicide application timings at the 5th trifoliolate (A), 1st flower (B), full flower (C) and 10 days after full flower (D) were compared to three sequential application timings (A + C, B + C and B + D). The experimental setup was a randomized complete block design with four replicates. Data on disease ratings for leaf veins and pods, plant maturity, dockage, pick, seed weight, yield and return on investment (ROI) were collected. For seed treatments, DCT provided superior disease control on leaf and pod tissue under low and high disease pressure. The combined effect of seed treatments and foliar spray timings improved plant health, extended crop maturity and increased yield over seed treatments alone. The sequential fungicide treatments were superior to the single fungicide treatments in most environments. Under moderate to severe disease pressure, two fungicide applications and a seed treatment are required to maximize economic returns for the grower.

► Seed treatments and foliar fungicides controlled dry bean anthracnose.
► DCT was superior to Apron Maxx for disease control and economic returns, under low and high disease pressure.
► For foliar fungicides, two applications were often better than one.
► Seed treatment combined with a single foliar spray was effective under very low disease pressure only.
► Growers need to consider other factors including the initial seed infection level and environmental conditions.