About Stalk Borer
Reproduction and Life Cycle
The stalk borer has one generation each year. The adults emerge late in August and are present until the middle of October. The eggs will be laid from September to October, which can be deposited either in groups or individually among dead grass, leaves or in corn fields. The stalk borer will then overwinter as eggs, later hatching in the spring, typically from the middle of May to the middle of June. They will remain as larvae for anywhere between 9 to 12 weeks, going through 7 to 16 instars. Larvae will then form their pupa in the ground and remain there for approximately 20 days when they will emerge as a moth.
Stalk Borer Identification and Habitat
The adults are dark reddish-brown moths that have a wingspan of about 25 to 40mm. They have white antennae and 5 or 6 spots that are white in colour. The eggs are approximately 0.5mm long and are a pink-brown colour in a sculpted, globular shape. Stalk borer larvae can be as long as 32mm and are slender and cylindrical. Their body is brown and has a thin stripe that runs all the way down its back that is white in colour. They have 2 other white stripes, one on each side of their body. The top third of their body has purple-brown bands that cross through the stripes. Larvae move in a looping movement when disturbed. The pupa is about 16 to 22mm and starts off as a light brown colour but will darken as it ages.
The stalk borer is common in North America east of the Rocky Mountains and tends to eat its way into plant stems and feed from inside the plant. It has been a known problem for over 150 years, often damaging wheat or corn crops and is listed by the United States to be within the top 10 most damaging insect pests. While corn is the most common plant the stalk borer eats, they have been recorded attacking over 200 other stemmed plant species; some cultivated types and others being wild varieties. They tend to be most damaging in no-till plantings or areas with a minimal amount of tilling. Their population is highest in fields that are surrounded by weeds with large stems. The larvae will tunnel into the stem near its base and eat its way up, which will cause the leaves on the plant to wilt and die. Sometimes the larvae will instead enter the stem from the top and eat the rolled up leaves and buds. When the leaves unfold, they will have holes that continue to grow as the leaf expands in size. Soon after, the stem tends to break. If the infestation occurs after the plants whorl stage, it is more resistant and is often able to recover.
Stalk Borer Management and Control Methods
Since the larvae feed from within the plant, it is often hard to control this pest. Therefore, the control methods used should focus on preventing this pest from ever entering your crops. Destroying weeds that grow in your field and any that line the fences around your field can often help eliminate the chance of the stalk borer infesting your crops as this will remove numerous host plants. Also, in choosing to till your fields instead of having a no-till planting can greatly reduce this pest’s population, or in turn, burning the ground cover in order to kill stalk borer eggs can also be effective.
So far there have not been effective insecticides discovered to control the stalk borer.
Latin / Alternative Stalk Borer Names