EFFECT OF SEED DEPTH ON SLUG DAMAGE TO WINTER-WHEAT

In a field experiment drilled at two depths on three dates in autumn 1988, with or without methiocarb pellets broadcast on the soil surface immediately after drilling, 26% of seeds of winter wheat sown at c. 20 mm depth were killed by slugs compared with only 9% of seeds sown at c. 40 mm. The protection from slug damage provided by this additional 20 mm of depth was comparable with that provided by methiocarb pellets. The effects of seed depth and pellet application did not interact and were consistent on all drilling dates. Thus, fewest seeds and seedlings were killed where methiocarb pellets were broadcast on a seed-bed with seeds sown at 40 mm depth. Intermediate damage was recorded where seeds were sown at 40 mm depth without pellets, or where pellets were broadcast on seeds sown at 20 mm depth. Most seeds and seedlings were killed where seeds were sown at 20 mm depth without pellets. Sublethal damage to seedlings was not affected by sowing depth but was reduced where pellets were broadcast immediately after sowing.