2005 Pest Management Guide:

Rice Stinkbug
Adult rice stink bugs (Oebalus pugnax) overwinter near the ground in heavy grasses. In the spring, the straw-colored, 3/8- to 1/2-inch long adults become active. A sharp spine on the shoulder helps distinguish this pest from other stink bugs. Females lay two rows containing 10 to 50 cylindrical light green eggs on foliage of heading grasses.

The nymphs—which at first have a bright red abdomen with black head, thorax and legs— lack wings. Rice stink bug feeding reduces both the quantity and quality of grain. Adults and nymphs have piercing-sucking mouth parts, which they use to feed on the kernel. Rice stink bug feeding causes kernel discoloration, called pecky rice. But not all pecky rice is caused by stink bugs. Pecky rice is more apt to break during milling than undamaged rice.

Fall Armyworm
Rice is attacked during the seedling and tillering stages before flooding. Caterpillars hatch from egg masses deposited by female moths (Spodoptera frugiperda) in the field or move into rice from adjoining areas. Larvae are light tan to greenish to brownish and about 1 1/2 inches long when fully grown. They have three yellowish-white, hair-like stripes on the back, a conspicuous inverted “Y” on the head and prominent black tubercles from which hairs arise.

Small larvae are hard to detect. Older larvae feed on leaf blades and can severely reduce plant stands. The action threshold is about 25 percent defoliation or when stands are threatened.

Stalk Borer
Rice stalk borer moths (Chilo plejedellus) are about 1 inch long with pale white fore and hind wings tinged on the edges with metallic gold scales. The larvae hatch from eggs laid on leaves and crawl down the leaf toward the stem, where they may feed for a short time before boring into the stem.

Larvae are pale yellow-white with two pairs of stripes.

Sugarcane Borer
Sugar cane borer moths are straw-colored with a series of black dots, arranged in a V-shaped pattern, on the front of the wings. The adults are about 1 inch long.

After hatching, the larvae crawl down the leaf and bore into the plant stem, where they move up and down and feed for 15 to 20 days. Larvae are pale yellow-white in the summer with a series of brown spots on the back. Overwintering larvae are a deeper yellow and lack the brown spots. Most infestations don’t occur until late summer.

Mexican Rice Borers
Buff-colored Mexican rice borer adult moths (Eoreuma loftini) lay eggs on leaves and stalks of host plants. Borer larvae bear broken dashed lines (left) instead or spots as with the sugarcane borer (right). Larvae typically feed in leaf sheaths before boring into plant stalks several weeks after hatching.

Stalks become smaller and often lodge once borers have inflicted damage. Borer damage also can cause “dead heart” (dead plant whorl), increasing susceptibility to stalk-rotting diseases. The first symptom of dead heart is a dark purple coloring on plant sheaths because larval feeding disrupts normal leaf function.

Rice water weevil
Adult water weevils (Lissorhoptrus oryzophilus) are grayish-brown snout beetles about 1/8 inch long with a dark brown V-shaped area on their backs. In the spring, adults leave overwintering sites in ground litter and bunch grasses and migrate to rice fields during early evenings. Females lay eggs in the stems of submerged rice.

The larvae, sometimes called maggots, are white, legless and C-shaped. They range from 1/32 to 3/16 inch long. After feeding on the leaf sheath for a short time, they drop through the water to the soil and begin feeding on the roots. One larva per plant can reduce yields by 80 pounds an acre, according to data collected in Texas.