Field Guide     Pest Management     Southern Corn Billbug

Southern Corn Billbug

CROPS IMPACTED: corn, sorghum

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Family: Curculionidae

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About the Southern Corn Billbug

Reproduction and Life Cycle

Southern corn billbugs have one generation each year. This pest overwinters as an adult in plant debris or along ditches and emerges early in the spring. The females immediately begin to feed and then mate with the males. They lay their eggs soon after; around 200 within their lifetime. The eggs are laid at night and are often placed within a host plant by way of a hole that the female chewed near the basal area. The larvae will hatch 4 to 15 days later. They travel to the outside of the plant and eat the host plants base stalks and roots. Each cornstalk is likely to have only one larva feeding on it at the same time; however, sometimes this number can increase to 5 during bad infestations. Larvae need between 40 and 70 days to mature, which is when they pupate near or in the host plants taproot. After 7 to 10 days the adult southern corn billbugs emerge and begin feeding. Sometimes; however, they will stay in their puparium and overwinter in this state.

Southern Corn Billbug Identification and Habitat:

Identification

The adult southern corn billbug is a gray to brown colored weevil. From spending much of its time in the ground, this beetle is generally covered in soil, making them hard to see. They can often be found on corn seedlings close to the ground fastened upside down to the plant; they have wings, although they rarely fly. Adults are approximately 12mm in length. The eggs hold a shape similar to that of a kidney; they are off-white and about 3mm long and 1mm wide. The larvae are legless and have a rust brown colored head with an off-white colored body. Depending on the stage of development, larvae can be anywhere between 2 and 12mm long. Pupae start as a cream color, but will transform to a rust brown as they mature. It is similar in size to the adult weevil.

Habitat

This pest is most common in the southern and Midwestern areas of the United States. This billbug favors corn, but will occasionally feed on sorghum and some sedge species. They are known to feed on the inside of corn stalks, especially seedlings. The adults are able to use their beak to slice through the leaf sheaths to reach new tissue. This will result in the injury of terminal blades, affecting the plants yield. This feeding can also cause unwanted suckering. This, with the addition of the larvae feeding on the roots, can cause significant damage in your cornfields. The southern corn billbug’s population tends to be much worse in cornfields that do not practice crop rotation or cornfields in close proximity to last year's corn.

Southern Corn Billbug Management and Control Methods

Cultural Control

Crop rotation will help minimize this pests population. Additionally, make sure to plant new cornfields at least a quarter of a mile away from old cornfields to prevent the adults that survived the winter to crawl and find the new seedlings. Planting early has also been shown to help, along with uniform planting and following the advised rate of seeding. Having vigorous corn plants can help them withstand pest attacks. It is recommended that in fields where early growth will take longer, such as no-tillage fields or areas that are cool and wet, use a starter fertilizer to promote faster growth so that the plant is not in the sensitive seedling stage for too long. However, it is important to note that having satisfactory control is often dependent on using an integrated management system that includes the use of both cultural and chemical methods.

Chemical Control

When the southern corn billbug’s population is high and chemical control is needed, terbufos (Counter) has been found to be effective with sweet corn. When treating cornfields, clothianidin (Poncho), and thiamethoxam (Cruiser) applied 1.25 mg per kernel have been successful. Be sure to carefully read the label for cautions and proper application. It is extremely important to never spray on days that are windy. After applying insecticides, irrigate sprayed area to increase the insect control. That being said, a large rainfall or irrigation soon after the application can reduce the concentration of insecticides.

Latin / Alternative Southern Corn Billbug Names

  • - Sphenophorus callosus

Sources

http://ipm.ncsu.edu/AG271/corn_sorghum/southern_corn_billbug.html

http://www.ces.ncsu.edu/plymouth/pubs/ent/billbug99.html