No-till Establishment of Alfalfa and Canola and Slug Herbivory.

No-till establishment of small seeded crops in fall can be a challenge due to planting issues and pest species. In 2010 and 2011, we observed significant stand reductions of alfalfa (Medicago sativa L.) and canola (Brassica napus) when they were no-till planted in late summer/early fall at the Pennsylvania State University Agronomy Research Farm at Rock Springs. The crops were part of the NESARE Sustainable Dairy Cropping Systems project in two diverse crop rotations comparing two management strategies in a split-plot design with four replications. Alfalfa was planted with a no-till drill in late August; canola was planted with or without tillage in mid-September. Throughout the growing season, we monitored slug populations (Deroceras reticulatum, D. laeve, and Arion fasciatus) weekly in 10 x 30-m plots of alfalfa and canola using two shelter traps (white roofing shingles, 0.093 m²). In each plot, we assessed damage to alfalfa and canola seedlings 40 days post-planting by counting the number of plants present and the number damaged by slugs in five 0.4 m row-sections (alfalfa) or eight 1m row sections (canola). Slug activity-density increased in mid-May, declined in mid-summer, and increased again in mid-September when slugs approached full size. In fall, alfalfa establishment following canola was very poor; half of the stands in 2010 and all stands in 2011 had to be reseeded the following spring. Establishment of fall planted canola varied between years, but no-till canola had more slug damage, higher slug activity-density, and more failed stands than canola planted with tillage. Our results suggest that high slug activity in fall contributed to poor establishment of alfalfa and canola and that planting after tillage or in early spring prior to the increase in slug activity may improve canola and alfalfa establishment.