This is a significant pest of cereals and grasses in South and Central America, and in the Southern part of the US. It is considered one of the main pests for sugar cane. It has economic significance in rice crops, sugar cane, corn, pasture, sorghum and wheat.
Life cycle and appearance of sugarcane stalk borer
The eggs have a flat, oval shape and measure approximately 1.16 mm in length and 0.75 mm in width. The colour varies from white, at the time of laying, to orange with a black hue at the time of hatching, which occurs four to nine days after laying. Egg-laying begins in the evening and continues during the night. The eggs are placed in clusters and overlap like the scales of fish. An egg cluster may contain 5 to 50 eggs. The caterpillar is white with a brown head and, depending on the season, may also display different colours. In summer it may display brown spots, with a thick hair on each of these spots. In winter, the hairs originate from the places where these spots may appear. Generally, the larvae go through five or six instars, and the first instars tend to congregate at the whorl and feed through the leaf tissue or tunnel in the midrib. The average duration of the larval stage is 44 days. After the first moulting, they penetrate the stalks through the softest part, close to the leaf sheath, making tunnels from the bottom up. The pupae are 16-20 mm long and have prominent pointed tubercles at the distal segments. They are yellowish brown to dark brown and are formed within a tunnel created by the caterpillars. After 9 to 14 days the adult moth – with yellow to yellowish-brown colouring – emerges. The wingspan is 18-28 mm in males, and 27-39 mm in females. The forewing also bears numerous narrow brown lines extending the length of the wing. The moths are nocturnal.
Symptoms and damage
The caterpillars form tunnels inside the stem, causing failure to grow and loss of weight. When these tunnels are big and circular, they can cause the crop to break. Other symptoms are dying back of the inner whorl, also known as dead heart, mainly in younger plants, broken stalks, plants with reduced development and lower number of stalks. The tunnels made by the caterpillars also serve as an entrance for various fungi which can cause rot, reducing the purity and yield of the sugar.