Why are leafhoppers spreading further south than usual?

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Leafhopper Spread Linked to Rising Temperatures and Reduced Frosts

Leafhopper populations are expanding southward beyond their typical ranges due to a combination of escalating global and local temperatures, which have led to a significant decrease in frost occurrences. This warming trend, particularly evident with 2023 being the warmest year on record, allows these insects, which are sensitive to cold, to survive and proliferate in areas previously too frigid for them. The diminished frequency of sub-4-degree Celsius nights is a primary driver behind the unusual surge in leafhopper numbers observed across Argentina.
Warmer Temperatures Fuel Insect Proliferation

The increased prevalence of warmer temperatures is directly correlated with the enhanced survival and spread of leafhoppers. These small, four-millimeter-long insects thrive in hotter conditions, and the steady rise in minimum temperatures across Argentina has created a more hospitable environment for their reproduction and migration. This phenomenon is exacerbated by global warming trends, which have contributed to record-breaking warm periods, such as those experienced in early 2024.
Reduced Frost Frequency Aids Southern Expansion

A critical factor enabling the leafhoppers' unusual southward movement is the decline in frosty nights. Leafhoppers are unable to tolerate temperatures below 4 degrees Celsius. Consequently, a reduction in the number of freezing nights, a trend observed over recent decades with cold nights decreasing from an average of 15 days per year to around eight in some regions between 1963 and 2013, allows the insects to survive and establish themselves in areas previously protected by colder climates. The previous winter's decreased frost count is identified as a significant cause for the substantial increase in leafhopper populations.
Unprecedented Infestation Levels and Range

The impact of these climatic shifts is evident in the sheer scale of the leafhopper infestation. In northern Argentina, leafhopper numbers are reportedly ten times above normal levels. Furthermore, the insect has been detected approximately 1,500 kilometers south of its traditional habitats, indicating a dramatic expansion of its geographical range. This unprecedented spread has led to significant crop losses, with projections suggesting millions of tonnes of corn production may be affected, and some farmers are considering reducing corn cultivation in favour of less susceptible crops like soy.

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Why are leafhoppers spreading further south than usual?

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