| dc.description.abstract | This study was conducted to determine the abundance and diversity of natural enemy of
insect pests in boro and aman rice fields at the farm of Agricultural Training Institute
(ATI), Shahparan, Sylhet during November 2013 to April 2014 for the boro rice season
and May to November 2014 for the aman rice season. The results revealed that 11 and 9
different natural enemies were found in boro and aman rice fields, respectively. The
abundance of natural enemies was higher in boro rice than in aman rice. The incidence of
natural enemies was highest at tillering stage (50 days after transplanting, DAT) and
lowest at seedling stage (30 DAT) in both the rice growing seasons. Among the natural
enemies, ladybird beetle, wolf spider, damsel fly and ant were the most prevalent in the
boro rice field and carabid beetle, mired bug and wasp were the least prevalent. Ladybird
beetle, long-jawed spider, dipteran fly, damsel fly were the most prevalent in the aman
rice field and carabid beetle, lynx spider and wasp were the least prevalent. The diversity
indices of natural enemies varied between habitats and order groups in both rice growing
seasons. The boro rice supported the highest diversity of natural enemies as per
Shannon’ index (H) and Pielou's Evenness (J) whereas, the aman rice supported the
highest richness of natural enemies as per Margalef's Index of richness. The order
Araneae exhibited highest diversity and the order Coleoptera exhibited lowest diversity
as per Shannon’s Index (H), Evenness (J) and Richness (M.I.) in both boro and aman
seasons. The abundance of natural enemies between two seasons ranked as Boro >
Aman. Among the insect orders, the abundance of natural enemies in boro season ranked
as Coleoptera > Araneae > Odonata > Isoptera > Hymenoptera > Diptera > Hemiptera
and the abundance in aman season ranked as Coleoptera > Araneae > Odonata > Diptera
> Isoptera > Hymenoptera. | en_US |
