Control of nut weevil menace in mango
bapuj...@gmail.com
The nut weevil or “stone weevil” of mango is a peculiar pest. The
grubs of mango nut weevil burrow through the rind and pulp of tender
immature fruits and finally reach the seed coat.
Exit holes
No external injury is seen on the fruit as grubs feed inside the
endocarp. Adults make exit holes in the seed while coming out through
the pulp rendering the fruits unfit for consumption.
It attacks soft pulped varieties such as Neelum, Bangalora, Alphonsa,
Mulgoa, Himayuddin, Kalepad , Beneshan, etc. It feeds only on mango
seeds and is considered to be the most serious pest of mango.
The adult is a stout greyish brown snout beetle measuring 6-8 mm,
camouflaged by the bark of mango trees. They become active during
mango season, are nocturnal in habit and feign death when disturbed.
Adult females lay eggs on the skin of the fruits. Within a week the
eggs hatch into cylindrical white legless grubs and start tunnelling
into the tender fruits. The larva feeds from inside, grows and moults
five times measuring 6-9 mm long.
The larval period is about 5 weeks. Then it turns into pupa within the
mango nut itself. The pupal period is 7 days.
The adults emerging out of the pupae remain inside the nut till they
are thrown away after the consumption of the pulp. The entire life
cycle is completed in 40-50 days and there is only one generation in a
year.
Management
Avoid close planting of mango trees. Plough the soil under the trees.
Maintain field sanitation. Collect and destroy the affected fruits at
weekly intervals.
Dip the fruits in hot water at 50 degree celsius for two hours to kill
the grubs. This treatment will not harm the fruit pulp.
Treat the bark with kerosene suspension or diazinon 0.05 per cent to
kill the hiding adults before the start of fruiting season.
Apply carbaryl at 4g /lit alternated with monocrotophos at 1.5ml ml/
lit at 22 days interval from the beginning of March to the end of
May .
Dr. J. Jayaraj
& Dr. D.S. Rajavel
Agricultural College and Research Institute
Madurai