Collateral impacts of organic farming

Published in Science – Organic and conventional farms are frequently located close to one another because of suitable climate and soil conditions, proximity to marketing channels, ownership, and other local factors. Yet proximity does not necessarily make for compatibility. Drift from pesticide sprays or pollen from genetically modified crops can threaten organic certification status (1). Conversely, insects, fungal spores, and weed seeds from flower strips maintained for natural pesticide control in organic fields can be sources of pest infestation in conventional fields (2), as can mobile insect pests that are inadequately controlled in organic fields. On page 1308 of this issue, Larsen et al. (3) used field observations from Kern County, California, to show that being surrounded by organic fields can help reduce the use of pesticides by organic crop producers but increases their use on conventional fields. Clustering organic cropland has the potential to mitigate the collateral impact on pesticide use for conventional cropland.