Impact of tillage and crop rotation on ascochyta blight (Ascochyta lentis) of lentil

Abstract

Two trials were conducted from 1996 to 1999; one at Indian Head, SK, to examine the impact of tillage management on the severity of ascochyta blight of lentil, caused by Ascochyta lentis (teleomorph Didymella lentis), and a second at Saskatoon, SK, to assess the impact of crop rotation. In 1995, the blight-susceptible lentil cv. Eston was seeded across both sites and later inoculated with blight-infested lentil residue to provide a uniform level of infection. Treatments were initiated in the spring of 1996. Ascochyta blight severity was assessed on each lentil plot during the growing season. Seed quality and yield were assessed each year. A split-block design was used to minimize movement of inoculum among plots over years. In the tillage management trial at Indian Head, the main plot treatments were 0, 1, or 2 yr between lentil crops, with spring wheat as the alternate crop; the subplot treatments were zero-till vs. conventional tillage. Ascochyta blight severity was substantially higher under zero-till than under conventional tillage in the continuous lentil treatment when conditions were conducive to blight development. However, tillage management had little effect on severity when there were 2 yr between successive lentil crops. We conclude that tillage management is unlikely to have an important impact on blight severity, except in rotations with short re-cropping intervals. In the crop rotation study at Saskatoon, the main plot treatments were two rotation sequences and the subplot treatments were three crop species (canola, barley, pea) planted in 1996. Rotation 1 was seeded to cv. Eston in 1997 and barley in 1998; Rotation 2 was seeded to barley in 1997 and cv. Eston in 1998. Both rotations were seeded to cv. Eston in 1999. Also, a plot seeded continuously to cv. Eston was included at one end of each replicate block as a control. Blight was more severe in continuous lentil than in the other crop rotations, and ascochyta blight levels in 1999 were lowest where barley followed the 1996 lentil crop for both Rotation 1 and 2. However, the intervening nonhost crop had little impact on seed infection or seed yield. We conclude that at least two nonhost crops between successive lentil crops are required to substantially reduce inoculum of A. lentis following a disease outbreak. Key words: Didymella lentis, zero-till management, fusarium root rot, Lens culinaris, barley, canola, field pea