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Stem weevil menace in Lab lab
INDIAN BEAN( Pandal avarai) Lab lab purpureus is a perennial twining or creeping herb generally cultivated as an annual crop. It is either grown as a bush or made to climb in pandals.
Among the various pests affecting this crop the stem weevil colobodes dolichotis is a serious pest. In South India the pest is noticed attacking plants in Sulur and Pallapalayam districts in Coimbatore.
Nature of damage
Adult female makes small excavations on main stems near the base of the plant to lay the eggs.
On hatching, the grub bores into the tissues of the main stem at the basal region and makes irregular galleries inside, resulting in gall like swellings. Affected stems snap at the swellings and die. The pest appears during October-November.
Life cycle
Eggs are inserted in tissues just below the epidermal layer at the base of the young plant and at the nodal regions in the old plants.
Egg period lasts for 6-7 days. Larval period takes 59-64 days. The grub feeds on the internal stem tissues and pupates within the larval gallery for 10-12 days.
Total life cycle is completed in 75-81 days. The female has a pre-mating period of 3-6 days, pre-oviposition period of 6-10 days and an oviposition period of 43-120 days.
— Dispose the previous crop residues properly to destroy the different life stages of the pest present inside the stem.
— Dust the field/pit with lindane or methyl parathion to protect the seedlings from weevil attack.
— In young plants, spraying of the main stem with malathion (0.1 per cent) or endosulfan (0.07 per cent) or methyl parathion (0.1 per cent) protects the plant from egg laying and entry of grubs into the stem.
— In older plants, swabbing the main stem and thick branches with lindane 20 EC (0.1 per cent) or methyl parathion 50 WP (0.25 per cent) checks the pest damage.
S. Sridharan & M. Manoharan
Krishi Vigyan Kendra,
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Eggs are inserted in tissues just below the epidermal layer and at the nodal regions in the old plants.
Adult female makes small excavations on the main stems to lay its eggs
Tamil Nadu Agricultural University, Coimbatore