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Common Name: Sugarcane borer                            Scientific name: Diatraea saccharalis (F.)

Biology (life cycle):

Adult sugarcane borers are straw-colored moths with a pattern of black dots arranged in an inverted V-shape on the front wings (3/4 inch long). They lay eggs in clusters of two to 100 on the leaf surface. In less than one week, larvae emerge, crawl down the leaf, feed in the leaf sheath, and bore into the plant stem. Larvae are pale yellow-white in color. In the summertime, they have a series of brown spots visible on the back. Overwintering larvae are a deeper yellow with no brown spots. Overwintering sugarcane borer larvae are usually found close to the plant crown. Larvae feed inside the stem for two to three weeks before chewing an exit hole in the stem and pupating. The pupae are brown, about 1 inch long and roughly cylindrical in shape. Adults emerge in about one week. There can have up to three generations per year in rice.

Damage:

Damage caused by larva: Injury to rice results from stem borer larvae feeding on plant tissue as they tunnel inside the stem. Injury is often first noticed when the youngest partially unfurled leaf of the plant begins to wither and die, resulting in a condition called deadheart. Later in the growing season, these rice stems are weakened and may lodge before harvest. Stem feeding that occurs during panicle development causes partial or complete sterility and results in the whitehead condition. The white, empty panicles are light in weight and stand upright.

Management:

Facts: Sugarcane borers overwinter as larvae in the stem of rice and other weedy plants. These larvae pupate in the spring, and adults attack rice when stem diameter is large enough to support larval feeding. Early infestations are noticed when the youngest partially unfurled leaf of the rice plant withers and dies, resulting in a condition called deadheart. Stem feeding during panicle development causes whiteheads. Severe infestations cause stalk breakage and plant lodging. Once larvae enter the stalk pesticides are not effective.

What should you look for: Begin scouting for sugarcane borers at green ring and intensify at early boot stage. Look for lesions caused by the larva that feeds underneath the leaf sheath before it bores into stems. Peel off the leaf sheath to expose the feeding larva or to detect the presence of frass to ensure it is the stem borer and not sheath blight damage. Unfortunately, by the time signs of field infestations (deadhearts, whiteheads) are noted, it is usually too late to apply foliar insecticides effectively. Scouting can be conducted for sugarcane borer adults or egg masses.

How you can manage sugarcane borer: Destroy crop residues after harvest to reduce the overwintering borer population. Plant early, especially in areas with a history of borer infestations. Early planting allows the crop to mature before the beginning of moth migration from other crops and non-crop hosts. Apply insecticides to coincide with larval emergence so larvae are killed before they enter the rice stems. Once larvae enter the stems, foliar insecticides are not effective.

Insecticide option:

• Please see the Rice section of the Insect Pest Management Guide on the LSU AgCenter's Management Guides webpage.