Climate change will cause a surge in the crop-destroying insects threatening California's supply of fruit and nuts, a study has found.
California's specialty crops of almonds, peaches and walnuts are under particular threat as insect populations increase due to warmer temperatures, a team of researchers from UC Merced, the climate hub at the University of California and the U.S. Department of Agriculture California Climate Hub reported in a Science of the Total Environment study.
The researchers estimate that three major species— the codling moth, the peach twig borer and the oriental fruit moth—will increase in numbers and start appearing earlier in the year as temperatures increase.
"These three pests are notorious for infesting most of the walnut, almond and peach orchards of California, causing extensive damages by reducing quality of fruits and nuts," study co-author Jhalendra Rijal, the UC Cooperative Extension integrated pest management adviser and entomologist for Stanislaus, San Joaquin and Merced counties, said in a press release detailing the findings.
Climate change causes unpredictable seasonal changes, including hotter summers and warmer winters, which in turn, disrupt the normal life cycle of pests such as these.
In the study, scientists found that the three species of insects are set to appear 28 days earlier than usual in the spring. The time between each generation was found to shorten by up to 19 days, the study reported.
These changes will not occur all at once, but scientists expect more and more to appear in the next 20 to 30 years.
"Codling moth is the primary pest of California's walnuts, which occupies over 365,000 acres," Rijal said. "Similarly, peach twig borer and oriental fruit moth are two major economic pests of peaches.
"Growers must control almost every generation of these pests to protect the fruit. Additional generations of these pests within the same growing season will likely increase crop damage.
"It certainly increases the number of sprays needed to control these pests, increasing the production cost for growers. Plus, more use of insecticides has consequences for beneficial insects and the environment."
If these findings are correct, it means that current pest management methods will need to be reviewed. As the pest populations increase, Rijal warns it will post a serious threat for the speciality crops.
"In the last seven years, likely due to warmer winter, as suggested in this study, we observed the beginning of the moth's activity in traps (also called biofix) as early as Feb. 14," Rijal said, "meaning that the trap placement date must move earlier to capture the first moth activity. We are revising the guidelines to change the trap placement date to Feb. 7 for the entire Central Valley."
Guidelines set out by the UC Integrated Pest Management currently recommend putting moth traps out by February 15 in the San Joaquin Valley and February 20 in the Sacramento Valley.
"Climate change impacts on pests and resulting impacts on agricultural production are significant but not often researched or quantified," said Tapan Pathak, the UC Cooperative Extension specialist in climate adaptation in agriculture based at UC Merced.
"Information from this research will not only help farmers to understand impacts for strategic planning, but also will inform the agricultural industry to invest in making varieties more resilient to these damaging agricultural pests," Pathak added. "We will use this information to update the CalAgroClimate tool, which informs farmers on the progress of these pests during the season so that they can take steps for effective pest management."
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Robyn White is a Newsweek Nature Reporter based in London, UK. Her focus is reporting on wildlife, science and the ... Read more
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