Sesamia inferens, The Pink Stemborer

Host: This is a polyphagous pest that attacks wheat, rice, sorghum, finger millet, barley, sugarcane, bajra, maize and several wild grasses.

Damage: Larva bores into the stem and hollows it out which results in dead heart.

Life cycle: Adult moths are stout, fast flying insects having a wingspan of about 3.5 cm. They are straw coloured with hairy body with forewing having a dark brown streak in the middle of fore wing. Hind wing is dull whitish in colour, without any markings.

Eggs are yellowish and laid in 1-3 rows like beads on the inner surface of the leaf sheath. Incubation period is about a week. The hatched larvae are pink to purplish pink in colour, lighter on the ventral side, smooth and cylindrical with a reddish-brown head and 25 mm long. They bore into the stem and make it hollow and attack several tillers before becoming full grown in 25-35 days. Pupation normally takes place inside the stem and sometimes outside in hidden places such as between leaf sheath and stem. There is no cocoon formation. Pupa is 18 mm long, dark brown with purple tinge on the head region.

Distribution: The pest is found all over Asia, from western Iran to China, Japan, Burma, Taiwan, Malaysia, Solomon Is. and New Guinea.

Control: Collection and burning of the plants containing dead hearts helps to reduce the population of the pest. Burning of the stubbles or ploughing the field after harvesting crop kills dormant stages.

Spray of insecticides, such as carbaryl 0.02%, diazinon 0.02% at fortnightly intervals helps to contain the pest. Application of 4% granules of diazinon, sevidol or endosulfan in root zone is more effective and does not kill the natural enemies.