Field Guide     Pest Management     Maize Billbug

Maize Billbug

CROPS IMPACTED: Corn

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Family: Curculionidae

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About the Maize Billbug

Reproduction and Life Cycle

The maize billbug will spend the winter as a beetle, either in soil, on plant debris or in grass. They surface when corn starts to emerge from the soil. These beetles have wings but rarely fly; they mainly crawl along the soil to search for plant hosts. While their main source of food is corn, they will also go after other grass types and sedges. Once adults begin feeding, they will lay their eggs approximately 10 days later. The female will gouge a hole into a host plant stem and place her eggs. One female can lay as many as 200 eggs within 2 months. Dependent on climate conditions, the eggs can take between 4 and 15 days to hatch. The new larvae will often feed from within the stem they were born in. They eventually move to the roots and will take about 3 weeks to mature. They then become pupae either in the roots, stem, or soil. The new adults will often remain in the puparium to overwinter in, or will sometimes instead leave the shell. They have one generation annually.

Maize Billbug Identification and Habitat

Identification

As an adult this pest is a snout beetle. These beetles are red-brown coloured, and about 9 to 13mm long with a well-defined beak. They are challenging to catch sight of, and when you disturb the area they are in they tend to ‘play dead’. During the day they will hide beneath the soil’s surface. From spending a good portion of their time in the ground, they are usually coated in soil bits, which is what gives them that rusty coloured appearance. When there is no soil covering them they are more of a blue-gray colour. The eggs are very small, white in colour, and are in the shape of a kidney. When the larvae hatch, they are white, stout, and are without legs. They have a slight humpback and their heads are yellow-brown. They will reach to be about 6mm when they fully mature. As pupae, they are generally white.

Habitat

Maize billbugs are common throughout North America in grassy and cultivated regions. The greatest amount of damage they cause often occurs during the month of May. They mainly target corn, with the adults chewing cavities into the stems for their eggs. These punctures can stunt the growth of the plant and sometimes leads to death. If the plant does not die, as it grows and unfolds its leaves, infested plants will reveal 3 to 4 circular holes on the leaf in rows. The adults will mainly feed at the base of stalks right above the soils surface, or just below. When they eat at the growing point, plant death is likely to occur, especially if the plant is young. As this pest is nocturnal, they will migrate from plant to plant during the evening. The larvae feed below the surface on the corn roots. If larvae numbers are high, plants may lodge. This pest is also very attracted to yellow nutsedge. Therefore, having this weed near or in your corn fields can result in higher maize billbug populations.

Maize Billbug Management and Control Methods

Cultural Control

Control methods for billbugs should only be used if this pest is killing a significant number of corn plants. Unfortunately when the larvae feed from within the stalk, there is no effective treatment. To help prevent the infestation from reaching critical levels, make sure to remove all yellow nutsedge from in, and around your corn fields, especially before planting. Crop rotation can help, and also keeping new corn fields at a safe distance from last year’s corn fields. Keep in mind that corn planted in the middle of April is also at high risk. Having satisfactory control is often dependent on using an integrated management system that includes the use of both cultural and chemical methods.

Chemical Control

Insecticides that have been found to be effective with billbugs in corn fields are clothianidin (Poncho), and thiamethoxam (Cruiser). These insecticides should be applied during planting at 1.25mg per kernel. If treating this pest on commercial turf, use bifenthrin, chlorantraniliprole, chlorpyrifos, deltamerthrin, or imidacloprid. 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 it is important to irrigate sprayed area to increase the insect control. That being said, a large rainfall or irrigation soon after the application can reduce the concentration insecticides.

Latin / Alternative Maize Billbug Names

  • - Sphenophorus maidis

Sources

http://extension.entm.purdue.edu/fieldcropsipm/insects/maize-billbug.php

http://ento.psu.edu/extension/factsheets/billbugs

http://content.ces.ncsu.edu/insect-control.pdf