Large crop fields need more insecticide

https://www.eurekalert.org/pub_releases/2017-05/uoc--doi050817.php

Public Release: 8-May-2017
Drivers of insecticide use
The effects of certain landscape characteristics on insecticide use depend on context and crop type, according to UCSB scientists
University of California - Santa Barbara

Over the past half century, food production has intensified to meet the growing demand. And as agricultural fields have become ever larger, more pesticides are required to enhance yield.

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The analysis by Larsen and Noack, a postdoctoral researcher at the Bren School, demonstrated potentially valuable benefits to crop diversity and to smaller fields. However, these benefits were highly dependent on crop type. Their research showed that while crop diversity reduced insecticide use, its impact was small in comparison to the differences in insecticide use between different crops.

"The choice of crops we produce or the type of crops we eat has a much larger impact on overall insecticide use than do landscape characteristics such as crop diversity or cropland extent," Noack said.

Take table grapes as an example. As surrounding crop diversity increased, insecticide use fell by nearly 8 kilograms per hectare. "Grapes use about 49 kilograms of insecticide per hectare, so an 8 kg reduction is a fairly substantial fraction," Larsen explained. "For oranges, the reduction is less than 2 kilograms per hectare, which is not significant, and for carrots there is no effect at all."

In addition, the investigators consistently found that larger fields use more insecticide. A huge swath of single crop may serve to meet growing demand, but it also provides an uninterrupted breeding ground for insects, which in turn may promote increased chemical treatment to control the pests.

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