UC Davis Study: How Landscape Simplification Affects Pest Outbreaks

Natural landscapes surrounding vineyards can decrease pest outbreaks and depress pesticide use, according to a UC Davis paper published in the current edition of the journal Ecology Letters.

A five-member team led by postdoctoral researcher Daniel “Dani” Paredes of the Daniel Karp lab, UC Davis Department of Wildlife, Fish and Conservation Biology (WFCB), analyzed a 13-year government database to assess how the landscapes surrounding 400 Spanish vineyards influenced European grapevine moth (Lobesia botrana) outbreaks and insecticides application rates.

The article, "Landscape Simplification Increases Vineyard Pest Outbreaks and Insecticide Use," is now online.  

“At harvest, we found pest outbreaks increased four-fold in simplified, vineyard-dominated landscapes compared to complex landscapes in which vineyards are surrounded by semi-natural habitats,” said lead author Paredes, who holds a doctorate in environmental sciences (2014) from the University of Granada, Spain.  “Overall, our results suggest that simplified landscapes increase vineyard pest outbreaks and escalate insecticide spray frequencies. In contrast, vineyards surrounded by more productive habitats and more shrubland area are less likely to apply insecticides.”

Landscapes around farms are rarely managed to suppress damaging crop pests, partially because researchers rarely measure the key variables that drive farming decisions. This paper, however “shows how using really huge datasets—in this case generated by government employees working with farmers in Spain--can reveal how natural habitats surrounding agriculture can shape pest outbreaks and pesticide use in vineyards,” said co-author Jay Rosenheim, distinguished professor in the UC Davis Department of Entomology and Nematology.

Their results suggest that landscape simplification could affect not only farm yields, but also  environmental and human health. They noted that insecticide applications doubled in vineyard-dominated landscapes but declined in vineyards surrounded by shrubland. “Habitat conservation thus represents an economically and environmentally sound approach for achieving sustainable grape production in Spain,” said Karp.

Why might pests be more of a problem on vineyards surrounded by more vineyards? One possibility is that vast stretches of vineyards allow pest populations to build up quickly. Another possibility is that simple vineyard landscapes may not contain enough resources to support predatory insects that natural control vineyard pests. Whatever the reason, it seems clear that “cultivating crops in monoculture creates the perfect conditions for specialist pest outbreaks,” they related, so “farmers have consistently turned to insecticides to maintain high yields under constant pest pressure.” 

A solution? At an individual level, farmers may better control L. botrana populations through planting native vegetation in and around their farm. Ideally, they would coordinate with each other to maintain and/or restore large patches of productive, shrubland habitats in the surrounding landscape. 

Other co-authors are Rebecca Chaplin-Kramer, Natural Capital Project, Stanford University; and Silvia Winter, Institute of Plant Protection, University of Natural Resources and Life Sciences, Vienna, Austria.

Their work was financed by the research project SECBIVIT, or “scenarios for providing multiple ecosystem services and biodiversity in viticultural landscapes,” and a National Science Foundation/USA grant.