Susceptibility of the early growth stages of volunteer oilseed rape to invertebrate predation

Chemical and agronomical control of volunteer plants is difficult, especially in reduced-input cropping systems where feeding by natural herbivores may become an important cause of their mortality. The consumption of the early growth stages of winter oilseed rape (Brassica napus L. ssp. napus) by five species of ground-surface invertebrates abundant in rape fields of Central Europe was studied under laboratory conditions. The species were particular in their preferences for growth stages of oilseed rape. The gastropods Arion lusitanicus and Helix pomatia preferred seedlings rather than seeds, whereas all three species of arthropods rejected seedlings. Pseudoophonus rufipes consumed all seed stages with similar intensity, while Pterostichus melanarius readily accepted fresh, dry and imbibed seeds. The overall consumption by the isopod Armadillidium vulgare was low and concentrated on exhumed seeds. Seeds and the early growth stages of oilseed rape are thus susceptible to invertebrate predation, each stage being killed by a specific group of invertebrate predators.