Life cycle and description

• Adult stage: Cream-colored moths with straw-colored forewings and white hindwings. They have a wingspan of 20 - 42mm. Females are larger than males.
• Egg stage: Fresh eggs are yellow, but develop a red band just before hatching. Eggs are deposited in a scale-like, overlapping manner (similar to fish scales) on the upper and lower leaf surface.
• Larval stage: White with prominent brown/black spots on each segment. Larvae have a yellow/brown prothoracic shield and are 20 to 25mm long when mature. Larvae in diapause are pale-colored.
• Pupal stage: Pupae are dark brown with two rounded processes on their heads. D. lineolata does not create a cocoon.
• During the egg, pupate and larval stages, this species appears very similar to D. saccharalis (sugarcane borer).
• Diapause may occur during a dry period when food quality declines. In these cases, mature larvae will diapause in the lower part of the plant stem and pupate with the first rain.
• Two to three generations can occur per growing season.

Confirmation

Developmental stages of Diatraea lineolata closely resemble D. grandiosella (southwestern maize borer). Larvae of D. lineolate do not girdle stalks at the base and do not overwinter in the base of the stalk below ground level as do larvae of D. grandiosella. Detailed inspection of adult moths may be required to confirm identity.

Problems with similar symptoms

The sugarcane borers and the southwestern corn borers cause very similar damage in the whorl and stalk. Southwestern corn borers, however, girdle the base of the maize stem, unlike other borers.

Why and where it occurs

Lowland tropical regions favor this pest.

Host range

Maize, sorghum, rice, wheat, sugarcane, and teosinte.

Geographical distribution

This borer occurs in Central America, the Caribbean region and northern parts of South America.

Damage

• Mechanism of damage: Feeding in the whorl can lead to destruction of the growing point. Boring in the stems can interfere with translocation of water and nutrients, leading to stunted growth and reduced yields. Boring in the stems can also cause plant lodging, while boring in the ears can favor development of ear rots, which produce various mycotoxins.
• When damage is important: Damage is most severe when the growing part of the plant is completely destroyed. Excessive stem boring will also lead to crop lodging, while boring in the ears will favor the development of mycotoxin-producing ear rots.
• Economic damage: Causes an average of 25% economic crop loss to borers in susceptible regions.

Management principles

Monitoring

• Moth traps can be used to monitor the incidence of adults, while fields should be regularly inspected for presence of eggs and larvae.
• Chemical or biological control should commence when 25% of plants have eggs.

Cultural control

• Management of crop residue infested with overwintering larvae will reduce larvae numbers in the subsequent season.
• Early planting can help avoid periods of heavy pest infestation later in the season.
• Planting early maturing varieties also reduces the number of pest generations per crop.
• Crop rotation with non-hosts can reduce pest incidence.

Chemical control

• Chemical can be applied either as a spray or in granular form in the whorl. If applied as spray, chemicals should be applied to coincide with egg hatching or when larvae are still exposed in the whorl. Anther option is application of pesticide to the soil at planting, which will protect the plants for one month.

Biological control

• There are several natural parasitoids of Neotropical maize borer including various Trichogramma wasp species that parasitize eggs. The larval parasite Cotesia flavipes has also been used to provide control.

References

CAB International. 2002. Crop Protection Compendium. Wallingford, UK: CAB International.

Granados, G. 2000. Maize Insects. In R.L. Paliwal, G. Granados, R. Lafitte, A.D. Violic and J.P. Marathee (eds.), Tropical Maize Improvement and Production. FAO Plant Production and Protection Series 28. Rome: Food and Agriculture Organization (FAO).

King, A.B. and J.L. Saunders. 1984. The Invertebrate Pests of Annual Food Crops in Central America. London: Overseas Development Admin.

Ortega A. 1987. Insect pests of Maize: A Guide for Field Identification. Mexico, D.F.: CIMMYT.

Rodriguez-del-Bosque, L.A., J.W. Smith and A.J. Martinez. 1995. Winter mortality and spring emergence of corn stalkborers (Lepidoptera, Pyralidae) in subtropical Mexico. Journal of Economic Entomology 88:628-34.

Contributors: Gabrielle Turner, David Bergvinson, and Biswanath Das