Rice Insect Management
Rice Stalk Borer
Chilo plejadellus Zincken
Adult moths have about a 2 to 4 cm (1 to 1 1/2 inch) wingspan. The forewings
are white or pale brown with randomly placed black scales. Forewing edges have a
row of metallic gold scales and black dots. Hindwings are white or pale brown.
Larvae are light brown with one dark brown and one light brown stripes along
each side of the body. Mature larvae have a length of about 2.5 to 4 cm.
Commonly found in LA and TX and has been reported from GA on rice and in MN
on wild rice (Zizania spp.). The first confirmed infestation in AR was found in
Chicot Co. in 1981. Since then the rice stalk borer has been found in all
counties with rice in eastern and southwestern AR and including counties in
central AR along the Arkansas river to Pope Co. (near Atkins).
Larvae overwinter in rice stubble. Pupation occurs in the spring and adults
emerge in May. Eggs are deposited in masses (1 0 to 30 eggs) with the individual
eggs overlapping so as to form a pattern similar to fish scales. Egg masses are
placed on the leaf blade (top or bottom) and sometimes behind the leaf sheath.
Eggs hatch in about 5 days. The small larvae enter the rice plant stem by
chewing a hole either behind the leaf sheath or near the base of the panicle.
More than one larvae enter the stem from a single hole. The larvae eat the inner
stem tissues, grow, and eat into the lower larger part of the stem. Mature
larvae chew through tissues until only a single thin layer of tissue covers a
circular hole in the stem above the water line. The adult escapes through the
hole. Very seldom does more than one larvae mature in a single stem.
Damage and Symptoms
Larvae eat inner tissues of the stem and effectively stop any-translocation
of nutrients. If infestation is just after permanent flood, the whole plant may
die or the central culm may die but not the tillers (deadheart). If the stage
infested is just prior to emergence of the panicle (boot stage), the green
panicle emerges but soon all the florets turn white (Whitehead). Whiteheads are
more numerous on edges of fields, edges adjacent to levees, and in barrow
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