Stem girdler: Threat to mesta growers

M ESTA HIBISCUS plays an effective role in supplementing the short supply of jute fibre. In Karnataka it is extensively grown as sprinkle crop with pigeonpea, pearlimillet, groundnut, setaria during kharif season for fibre and seed. The crop is found to be severely affected by the stem girdler Nupserha bicolar postburnnea Dutt. (Cerambicidae: Coleoptera) causing great loss in yield and quality.

Main damage is caused by the adult beetles at night. The female makes two rings by cutting a strip of cambium and then a slit is made which reaches as par as pith, where the beetle deposits one egg, resulting in breakage of fibre length at the ring portion and falling of plant to ground, leading to reduction in quality and yield of fibre.

Since, a female lays on an average 35 eggs in her life time, many mesta plants are damaged within 2-3 weeks. The eggs are yellow and hatch in 3-4 days. Emerging larvae on the pith travelling downwords along the central hollow of the stem. The larvae becomes full grown in 30-50 days and pupates in the chamber made in the hollow portion of the stem.

In winter, the larvae cut out small portion of the stem in which they encase themselves and dipause. The larval stage continues upto the next spring and pupation takes place only after rains have started. The pupation and adult emergence synchronise with the availability of mesta plants or other alternative hosts (Jute). However, not much damage is caused by the feeding activity of larvae or adult like egg laying injury by adult females.

The beetles can be managed by:

- Encouraging the population of most common and important larval parasitoids like Neocatolaccus nupserhae and Norbanus accuminatus.

- Mixing of 25 kg of phorate 10 g/ha in the top soil followed by light irrigation when the stem girth of the plnts reaches 0.8-1.0 cm (around 120-130 days after sowing).

- Spraying of contact insecticides like quinalphos 25 EC at 2 ml. or endosulphan 35 EC at 2 ml. or melathion 35 EC at 2 ml. per litre of water reduces the incidence considerably.

A.P.Biradar, A.K.Guggari

& B.M.Biradar

Regional Research Station

Bijapur-586 101

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