- Author: Kathy Keatley Garvey
"As a result, pest outbreaks are less likely in diverse landscapes," said Paredes, who analyzed a 13-year government database of diversified landscapes encompassing more than 1300 olive groves and vineyards in Spain. The database documented pests and pesticide applications.
The paper, “The Causes and Consequences of Pest Population Variability in Agricultural Landscapes,” appears in the Ecological Society of America journal, Ecological Applications. Co-authors are UC Davis distinguished professor Jay Rosenheim of the Department of Entomology and Nematology, and Daniel Karp, associate professor, Department of Wildlife, Fish, and Conservation Biology. The research is online at https://bit.ly/3a64WRN.
Pest variability: an understudied but critical topic
Although population variability is often studied in natural systems, the need for long-term pest population data collected across many farms has largely prevented researchers from studying pest variability in agricultural systems, said Paredes, a postdoctoral fellow in the Karp lab.
What causes a pest population to be variable?
Having shown that more pest-population variability is more likely to cause problems for farmers, the researchers then set out to discover what farmers could do to manage variability.
One key factor that emerged was the type of landscape the crops were grown in, specifically whether the landscape was dominated by vast fields of a single crop variety or more diversified. Pest populations were both more abundant and more variable in crop monocultures.
However, while landscape type influenced both pest population sizes and variability, this was not always the case for other variables. “This research shows that the factors that promote high overall mean pest density are not necessarily the same factors that promote high variability in pest density,” Rosenheim said. “So, mean densities, which is what researchers have been studying for decades and decades, are only part of the story. Variation in density, and in particular unpredictable severe outbreaks, need to be studied separately.”
The take-away message?
“In Spain, planting multiple crops and retaining natural habitats would help stably suppress pests and prevent outbreaks,” said Paredes, a native of Spain who holds a doctorate in environmental sciences (2014) from the University of Granada. “Diversifying agricultural may be a win–win situation for conservation and farmers alike.”
"Therefore, we encourage agricultural stakeholders to increase the complexity of the landscapes surrounding their farms through conserving/restoring natural habitat and/or diversifying crops," the researchers wrote in their abstract.
Tapping into other large datasets such as this one, will be key to understanding whether diversified landscapes also help mitigate pest variability and outbreaks in other areas, they said.
This project was funded by the National Science Foundation with funds from the Belmont Forum via the European Biodiversity Partnership: BiodivERsA. It was also supported by the USDA National Institute of Food and Agriculture.
- Author: Kathy Keatley Garvey
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.
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.