Central Rice Research Institute Annual report...2011-12

Strategic Research on Pathogens/
Pest Population Dynamics, Crop
Losses and Forecasting
Studies on Pest/Natural Enemy Population
Dynamics
Studies on off-season biology and resurgence
of major rice insect pests
White backed planthopper (WBPH) was found to
complete its life cycle successfully on the ratoon plants
of rice variety TN1 and succeeded to next generation in
the harvested field having stagnate water and served
as its off-season habitat. WBPH completed two generations
in 35 days in ratoon rice recording more than 90
% survival. Off-season biology of WBPH studied on
eight weeds, indicated that nymphs could develop only
on Echinocloa colona and become adults.
Three granular insecticides viz., Carbofuran, Cartap,
Phorate and three microbial insecticides involving Verticillium
lecani, Metarhizium anisoplae and Beauveria
bassiana were tested under field condition for their possible
role in inducing leaf folder (LF) resurgence. A
maximum of 34.5% leaf damage was observed under
carbofuran treatment compared to 23.3% in control indicating
resurgence of LF. Application of Cartap significantly
reduced LF incidence to 8.2% leaf damage.
Seasonal prevalence of rice insect pests
recorded through light traps
YSB population reached a small peak of 774 moths
in 14 th standard meteorological week (SMW) of 2011
and remained low throughout the wet season. It
reached a small peak of 384 moths week -1 in the 40 th
SMW and another with 434 moth week -1 in the 44 th
SMW and declined thereafter. This population was too
small as compared to other years (excepting 2011).
Based on the duration of life cycle it may be presumed
that the parent brood emerges about six weeks before
the peak emergence pesticide application during 34 th
and 38 th SMW can protect rice crop from the attack of
the peak brood.
Population of Chilo sp. followed a similar pattern
and reached a peak of 265 moths in the 6 th SMW and
another peak of 42 moths in the 44 th SMW. Population
of YSB was predominant (95.00%) while Chilo species
represented 4.0% and other stem borers only 1.0%. Leaf
folder population increased in January-2011 and
reached a peak in 7 th SMW with 152 moths week -1 and
then declined. During wet season, it reached another
peak of 90 moths week -1 in 40 th SMW in October.
Case worm population during dry season started
increasing from the 1 st week of January and reached
peak of 312 moths week -1 in the 6 th SMW. It appeared in
good numbers in the wet season and reached a peak of
580 moths week -1 in the 39 th SMW. Green leaf hopper
population started increasing from September (32 nd
SMW), remained high throughout September and October.
It reached a peak of 28,449 in the 43 rd SMW.
Light trap catch of Cnaphalocrocis medinalis (Guenee)
at Central Rice Research Institute; Cuttack from 1990 to
2009 was analyzed to study the population trend of the
pest over the years. During 1990 – 1999, a major peak
was observed at 19 th SMW with two small peaks at 10 th
and 16 th SMW. In the wet season, the peak pest population
was observed at 42 nd SMW and two small peaks at
38 t h SMW and 46 th SMW. During 2000-2009, in the dry
season, one major peak was observed at 7 th SMW with
two small peaks at 14 th and 18 th SMW. In the wet season,
the major peak was observed during 45-46 SMW
and another three small peaks were observed corresponding
to 38-39, 42-43, 49-50 SMW. The mean annual
leaffolder population from 1990 to 1999 and 2000
to 2009 indicated that over the past few years, the magnitude
and number of peaks in the season has increased.
Earlier (1990 to 1999), there were two peaks of leaffolder
population in the dry season and grossly two peaks in
the wet season, whereas, in the recent years three small
peaks in the dry season and four peaks in the wet season
were evident. The study indicated that leaffolder
population has increased in recent years.
78 CRRI ANNUAL REPORT 2011-12