Diatraea grandiosella

Dyar, 1911

Southwestern Corn Borer Moth, Southwestern Corn Borer

Diatraea grandiosella is a stalk-boring native to Mexico that has expanded its range into the southern United States since 1913. The is or trivoltine over most of its range and survives winter through facultative larval . Mature pre-diapausing larvae prepare in the stalk crown of plants, frequently girdling the plant near soil level beforehand—a that causes significant economic losses by preventing mechanical harvest of ears. The species is a major pest of corn and sorghum, with diapause induction regulated by and temperature.

SWCB life stages by Steven J. Baskauf. Used under a CC BY-SA 3.0 license.

Pronunciation

How to pronounce Diatraea grandiosella: //ˌdaɪəˈtriːə ˌɡrændiˈoʊsɛlə//

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Identification

Larvae are creamy white and approximately 1 inch long when fully grown, with most body segments bearing conspicuous round brown or black spots. Spots on mature larvae are lighter or absent. Diapausing larvae lack pigmented cuticular pinacula and appear (spot-free), distinguishing them from active summer- larvae which have segmentally-arranged sclerotized pinacula. are white to buff colored. are deposited in clusters of 10–20 that overlap like fish in a shingle-like arrangement on plant leaves.

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Habitat

Agricultural areas; specifically corn and sorghum fields. larvae occupy prepared in the root crown or stalk crown of plants. are more severe in late-planted sorghum.

Distribution

Native to Mexico; expanded into the United States from Mexico around 1913. Currently established in 13 U.S. states from Arizona to Alabama, ranging from approximately 18°N to 38°N latitude. Northern distribution limits appear stable around 38°N latitude in south-central Kansas and southern Missouri due to winter mortality of diapausing larvae.

Seasonality

or trivoltine over most of range. from emerge in mid-May. occurs in late summer; occurs the following spring.

Diet

Larvae feed on corn (Zea mays) and sorghum. Young larvae feed on leaves or leaf axils for several days before tunneling into stalks. Older larvae bore up and down the pith of stalks. Requires sterols for growth and development; cholesterol and phytosterols (β-sitosterol, stigmasterol, campesterol) support larval growth, with cholesterol specifically required for .

Life Cycle

Females deposit clusters on plant leaves; eggs hatch in 3–7 days. Larval stage lasts approximately 25 days; pupal stage approximately 10 days. Two to three per year. Most borers overwinter as fully grown larvae in inside stalks remaining after harvest. Pre-diapausing larvae prepare cells in stalk crown and frequently girdle stalk near ground level. induction controlled by and temperature; chilling not required for diapause termination.

Behavior

Pre-diapausing larvae exhibit stalk-girdling , cutting through stalk tissue a few inches above soil level before entering . This causes lodging and prevents mechanical harvest. Larvae feed in silken tunnels when young. Diapausing larvae show reduced locomotory activity, absence of feeding, and lower metabolic rate compared to active larvae.

Ecological Role

Agricultural pest of corn and sorghum. Tunneling activity increases susceptibility to stalk rot and lodging. Serves as host for including Iphiaulax kimballi (braconid ectoparasitoid) and Chelonus annulipes.

Human Relevance

Major economic pest of corn and sorghum in the southern United States. Yield losses result from dead , stalk tunneling, ear damage, and lodging due to girdling. Management includes early planting, destruction of larvae through stalk shredding or plowing, and application before larvae bore into stalks. using Cotesia flavipes has been implemented in related ' management programs.

Similar Taxa

  • Diatraea saccharalis (Sugarcane Borer)Closely related with similar —both tunnel in stalks of grasses and have white to buff colored . D. grandiosella distinguished by geographical distribution (more western and northern in U.S.) and girdling of pre-diapausing larvae.
  • Diatraea lineolata (Neotropical Borer)Related stalk-boring Diatraea with similar larval appearance and range. D. grandiosella distinguished by distribution and specific characteristics.
  • Eoreuma loftini (Mexican Rice Borer)Related crambid stalk borer with similar damage . Distinguished by more recent U.S. invasion history (1980), faster spread rate, and lack of girdling .
  • Ostrinia nubilalis (European Corn Borer)Stalk-boring pest with similar tunneling damage. Distinguished by different geographical origin, coloration, and larval spotting pattern.

Sources and further reading