Invasive slugs: Global status and options for biological control

Although terrestrial slugs have been regarded as pests throughout recorded history, it is only since the 20th century that they have emerged as a major threat to sustainable agriculture, horticulture and floriculture throughout temperate and tropical areas of the world. This increase in pest status is directly linked to intensification of agriculture, and is compounded by both globalization and climate change. Climate change alone will play a major role in defining slug communities over the coming decades, and studies which have investigated the potential impacts of climate change on these mollusks will be discussed. Recently slugs have also been implicated in vectoring bacteria which cause human food poisoning and may have been partially responsible for the recent and highly publicized recalls of contaminated spinach and other salad crops grown in California. Some of the most damaging species belong to the Families Agriolimacidae, Arionidae, Milacidae and Veronicellidae, and many of these pest species have increased their ranges as humans have continued their colonization of the planet. A crucial aspect of modern invasion biology is to determine the origin of exotic populations and here we examine the source locations of selected invasive species which have invaded different parts of the world. With the current global drive towards reduced or zero-tillage, slugs are likely to remain a serious pest of our production systems long into the future. Consequently, alternative sustainable options for slug control will be examined, with a particular emphasis on biological control.