Effect of Selected Plant Extracts
on Controlling of Brown Plant Hopper (Nilaparvata lugens), Paddy Bug (Leptocorisa
oratorius) & Rice Leaf Folder (Cnaphalocrocis medinalis)

 

Rice
is the staple food in Sri Lanka which accounts an annual per capita consumption
of 100 kg. Cnaphalocrocis medinalis, Nilaparvata lugens and Leptocorisa oratorius are major pests in
rice which cause a considerable loss of annual rice yield. Synthetic pesticides
are widely used to manage pest attacks in rice cultivations in Sri Lanka.
Compared to the synthetic pesticides, plant based extracts are usually safer to
the environment and humans. This study was conducted to test the bio-efficacy
of four selected plant extracts viz Azadirachta
indica (Neem), Annona muricata (Anona), Calotropis gigantean (Wara) and Lantana camara(Gadapana) against Cnaphalocrocis medinalis, Nilaparvata lugens
and Leptocorisa oratorius and to
compare the insecticidal activity of the commonly used synthetic pesticide with
plant extracts against the above-mentioned pests. Extractions of these plant
species were made in three concentrations. i.e. were 10g/100ml, 50g/100ml and
100g/100ml. Tested synthetic pesticides against Cnaphalocrocis medinalis, Nilaparvata lugens and Leptocorisa oratorius were Tebufenozide
(20ml/10l), Thiamethoxam (5g/16l) and Carbosulfan(560ml/ac) respectively. The
experiment was laid out in Complete Randomized Design with fourteen treatments including
a control with three replicates for each pest. Ten second instar larvae of Cnaphalocrocis medinalis, fifteen adult
of Nilaparvata lugens and thirty adult
of Leptocorisa oratorius were taken
as experimental units. Bioassay methodology was used. It was concluded, for
controlling Cnaphalocrocis medinalis, Nilaparvata
lugens and Leptocorisa oratorius, the
most efficient plant extracts and their respective concentrations were Annona muricata 50g/100ml, Azadirachta indica 50g/100ml and Calotropis gigantean 10g/100ml
respectively.

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