1. 4. Jute Stem-girdler: Nupserha bicolor (Lamiidae: Coleoptera)

Distribution and status: Jute tracts of India and Bangladesh. Has become a major pest in the past two decades.
Host range: Jute, mesta, Sesbania aegyptiaca (dhaincha)

Bionomics

The female beetle makes two rings by cutting a strip, the space in between the rings being   1.0 -1.4 cm. In this area, a slit is made, which reaches as far as the pith, where the beetle deposits one egg. Female lays, on an average, 35 yelowish eggs. They hatch in 3-4 days and the emerging larvae  feed and travel downwards.The larvae become full-grown in 30-50 days and measure about 1.4 cm. During the active season, the larvae pupate in a chamber made in the hollow of the stem. With the advent of winter, the larvae cut out small portions of the stem in which they encase themselves and diapause. The larval stage continues up to the next spring and pupation takes place only after the rains have started. The pupation and the emergence of beetles seem to synchronize with the availability of jute plants. There is only one generation in a year.

Damage symptoms

The main damage occurs because of oviposition, resulting in the breakage of fibre length at several places. Thus, both the quality of fibre and the yield suffer. The damage (6-30%) is more in younger plants than in the older ones. Not much damage is caused by the feeding of larvae or adults.

Management

• Grow resistant species of jute (capsularis)
• Mix 25 kg of phorate lOG per ha in the top soil followed by light irrigation.
• Conserve larval parasitoids Neocatolaccus nupserhae and Norbanus acuminatus (Chalcididae)