Modern corn diets are giving crop pests a dangerous new edge

What looks like a quiet cornfield is actually a busy biological factory. Corn earworm larvae eat through kernels, transform in the soil, and later rise into warm night currents as long-distance fliers.

Scientists now find that these insects evolve faster than expected in modern agriculture. A single generation raised on today’s mixed corn hybrids can emerge with very different wings – and very different abilities to travel and spread resistance.

Corn diet changes earworm wings

Corn earworm development depends on nutrient quality inside corn ears. Nontoxic kernels shape a compact wing outline. Bt kernels supply toxin exposure that introduces stress during growth, which influences several traits linked to flight.

A blend of nontoxic and Bt kernels produces conditions that surprise many researchers. Narrow, long, tapered wings emerge from larvae raised on that blend.

Such wings resemble edges seen on fast-moving aircraft and support greater lift during long seasonal journeys.

Geometric morphometric work reveals clear separation among groups under different corn types. Moderate selection pressure produces the most dramatic forms. Pure nontoxic lines show round shapes.

Pure Bt lines with two or three toxins show short, broad shapes. Mixed refuge kernels create sharp, elongated forewings with a taper near the tip. Size does not drive these outcomes, and sex plays a strong role in variation.

Wind shaping wing behavior

Finite element models help researchers understand how each wing form bends under wind forces. Elastic deformation values reflect stiffness in venation.

Moderate selection creates wings that bend more under high airspeed, indicating lower rigidity.

Nonselected populations show moderate bending. Intense selection creates stronger support frames with reduced bending. Mixed refuge wings bend the least, pointing to enhanced lift support during long glides.

Wind speed increases bending across all groups, yet each form reacts along a unique curve. Females resist bending more than males.

Structure within venation governs these differences and may influence dispersal roles across seasons. Narrower venation angles in mixed refuge wings appear to reduce bending under high wind loads.

Flight is powering earworm migration

Corn earworm influences major crops across the United States. Large areas rely on Bt hybrids for pest control. High exposure over decades has shaped resistance patterns across many regions.

Migratory capacity supports rapid spread. Noctuid species can cross hundreds of kilometers under favorable winds. the forewings support ascent into air layers where convection lifts insects into stronger currents.

Slender wings formed under mixed refuge diets provide ideal support for high-altitude movement. Genetic monitoring detects fast shifts in allele frequency under such exposure.

Cross pollen movement between toxin and nontoxin kernels strengthens selective pressure inside seed-blend fields.

Corn earworms evolved fast

Long-range movement creates ideal routes for resistance expansion. Narrow, elongated wings allow long glides with lower energy costs.

Fliers with larger spans and tapered edges gain more lift from upper air currents. Wing morphology passes across generations, enabling expanding fronts to hold individuals with strong flight potential.

Related species display similar patterns. Larval exposure to Bt toxins alters flight behavior in armyworms and bollworms.

Wing stiffness correlates with resistance history in codling moths and corn rootworms. Wing venation strength influences movement potential and colonization speed.

Hybrid cornfields reshape traits

Researchers link mixed refuge conditions with rapid morphological shifts. Pure Bt hybrids create different stresses than pure nontoxic lines. Mixed diets create inconsistent exposure with pockets of nontoxic pollen and kernels.

Such exposure encourages survival of resistant lineages and shapes wing outlines suitable for long-distance travel.

“Wings from insects eating a blended toxic and non toxic corn diet were stiffer and more able to travel in higher wind speeds,” said co-author Dominic Reisig of the North Carolina State University. “These insects are able to get up into the winds and ride them longer distances.”

Seasonal patterns show high migration rates for corn earworm adults across many southeastern states. A large share of adults entering cotton and soybean regions during peak summer arrives from distant cornfields far to the south.

How earworm wings are built

Wing venation analysis shows strong differences across treatment groups. Narrow, tapered forms from mixed refuge kernels concentrate stiffness near leading edges.

Short, rounded forms from pure nontoxic lines distribute stiffness more evenly. Bt-only lines show intermediate patterns with some broadening that reduces aerodynamic efficiency.

Finite element models based on round-bar skeleton simulations reveal how stress distributes along veins under wind loads.

Mixed refuge forms experience lower deformation at high wind speeds compared with moderate selection under pure Bt conditions. Wing frames from intense selection react with moderate bending.

Resistance on the move

Corn earworm larvae exposed to Bt toxins undergo strong selection during early growth. Genomic analysis reveals rapid accumulation of resistance-related signatures following single-season exposure inside seed-blend fields.

Several regions near Vip3A and Cry families show divergence in allele frequencies.

Long-range fliers can carry resistant genotypes far from origin fields. Slender wing forms allow insects to ascend into high-altitude layers at night.

Upward convection and strong winds carry adults over long distances in a short period. Such movement complicates regional resistance planning.

Controlling corn earworm spread

Ongoing research highlights gaps in current refuge strategies. Seed-blend designs mix toxin and nontoxic kernels within the same field.

Cross-pollen movement reduces toxin concentration in kernels consumed by larvae. Inconsistent exposure creates strong selective pressure and shapes flight-related traits.

Morphometric analysis combined with biomechanical modeling offers more sensitive insight than flight mill tests alone.

Pupal mass, body ratios, and larval environment also influence dispersal potential. Flight behavior arises from multiple interacting factors beyond wing outline alone.

Corn earworm populations continue to evolve under shifting agricultural systems. One generation can produce marked change in wing form that supports longer travel. Continued study will be vital for interpreting resistance trends across landscapes.

The study is published in the journal Environmental Entomology.

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