ITHACA, N.Y. — Landscapes surrounding farm lands strongly influence the dynamics of beneficial insects and insect pests on farms, which in turn affect crop yields, according to a Cornell University study of New York farmlands published in the journal Ecological Applications.
Many previous studies about the impact of landscapes surrounding farms on insect pests and crops have only considered one pest at a time. The Cornell study examined the effects of aphids, flea beetles and leaf-feeding caterpillars; wasps that feed on caterpillars; and crop yields. It also looked at three different types of landscapes that surround farms: agricultural lands, meadows and semi-natural areas (including shrublands, types of forests and woody wetlands).
“Considering multiple insect pests represented a more realistic situation for what farmers experience,” said Ricardo Perez-Alvarez, the paper’s first author and a graduate student in the lab of Katja Poveda, professor of entomology and the paper’s senior author.
In the study, the researchers set up 22 experimental cabbage plots on farms across the Finger Lakes region of New York from June to September in 2014 and 2015. The details and management of each plot were the same, with no pesticides or insecticides used. Throughout the growing season, the researchers measured plant damage by each pest, density and abundance of parasitoid wasps, and they recorded crop yields at the end of each season.
The researchers found that yields and the number of pests were best explained by the presence of non-crop habitats, such as meadows, in the landscape.
When the proportion of meadows surrounding farms was high, the amount of infestation from cabbage leaf-eating caterpillars was lower, likely because of increased parasitism from wasps. On the other hand, these same plots experienced more infestation from flea beetles and aphids. The findings suggest that while some beneficial insects increased as a result of the non-crop habitats, so did the number of certain pests.
By considering the collective effect of multiple pest species on crop yields, management schemes need to consider joint effects of these species to be effective.
The study was supported by U.S. Department of Agriculture’s National Institute of Food and Agriculture via the Cornell University Agricultural Experiment Station.
Cornell University has television, ISDN and dedicated Skype/Google+ Hangout studios available for media interviews. For additional information, see this Cornell Chronicle story.
–Cornell University
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