Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
INSECT PEST - NATURAL ENEMY- HOST PLANTINTERACTION STUDIES WITH SPECIAL
REFERENCE TO THE BROWN PLANTHOPPER,
Nilaparvatalugens (Stal).
ByHASEENA BHASKAR
THESIS
Submitted in partial fulfilment of therequirement for the degree of
Joctorof Philosophyin RgritulturtFaculty of Agriculture
Kerala Agricultural UniTersity
1gepadmtnt of J\gritultural lItntl1m111oguCOLLEGE OF HORTICULTUREVELLANIKKARA, THRISSUR. 680656
KERALA, IND IA1999
CERTIFICATE
Certified that this thesis, entitled "Insect pest - natm'al enemy - hostplant interaction studies with special reference to the brown planthopper,
Nilaparvata lugens (Stal)" is a record of research work done independently by
Ms. Haseena Bhaskar, under my guidance and supervision and that it has ,Dot
previously formed the basis for the award of any degree, diploma, fellowship or
associateship to her.
Vellanikkara ~2Professor
Chainnan, Advisory Committee
ABSTRACT
Field surveys were conducted in Kole land and Kuttanad to assess the
population of rice BPH, Nilaparvata lugens (Stal) and its natural enemies. Field
investigations on the population dynamics of BPH and its natural enemies were
carried out on susceptible (laya), moderately resistant (Jyothi) and resistant
(Kanakom) rice varieties at the rice fields of Rice Research Station, Moncompu
during 1997-98. The influence of these varieties on the biology of the pest, the
biocontrol efficiency of the major natural enemies and the biology of the mirid
predator Cyrtorhinus !ividipennis Reuter was studied. in the laboratory.
Histological and chemical investigations were undertaken to evaluate the factors
that contribute to the resistance/susceptibility in them.
Results of field survey in Kole land revealed that the population of BPH
was far below the economic threshold level (ETL). In Kuttanad, in kayal area
during Rabi season and in karappadam tract d~g Kharif season outbreaks of
BPH occurred in some localities due to the indiscriminate use of insecticides
resulting in the mortality of natural enemies.
The results of the study on population dynamics revealed that the BPH
population was significantly high on the susceptible laya and low on the resistant
Kanakom y.'ith the population reaching a peak ttom February to March. The
predatory complex of the BPH comprised of the mirid Cyrtorhinus lividipennis,
Lycosa pseudoannulata, Tetragnatha maxillosa, Atypena formosana, Microvelia
douglasi atrolineata, Pseudogonatopus sp. and Ophionea nigrofasdata. C.
lividipennis was the most predominant predator regulating the hopper population
and there exists a density dependent host-predator relationship.
The population of the mirid predator on laya and Kanakom did not
differ significantly. The prey-predator ratio was lowest on the resistant variety and
highest on the susceptible variety. Of the weather parameters studied, the minimum
temperature showed a highly significant negative correlation with the population of
N. lugens in all the varieties.
BPH reared on the resistant variety recorded longer nymphal duration,
decreased nymphal survival and shorter adult longevity indicating the prevalence
of antibiosis in the variety. Lesser number of eggs laid, longer pre-oviposition
period and shorter oviposition period recorded on Kanakom indicate the
antixenosis factor in it. Macrpterous forms ofBPH did not develop on the variety .
The predator C. lividipennis and Micraspis sp. fed more BPH when
reared on the resistant variety. The veliid bug M d. atrolineata, the spider
L. pseudoannulata and the dryinid Pseudogonatopus sp. predated significantly
more BPH nymphs on resistant variety at a higher prey density only. However, the
dryinid parasitoid consumed significantly fewer number of hoppers on Kanakom at
the higher host density.
C. lividipennis recorded longer nymphal duration, shorter adult
longevity and low fecundity when fed on BPH reared on Kanakom which can be
attributed to the low fecundity of N lugens on Kanakom leading to less availability
of food to the mirid. Nymphal duration and adult longevity of C. lividipennis' did
not vary between the varieties Jaya and Jyothi.
Well developed bundle sheath with more fTequently distributed
schlerenchyma tissue in the culm of the resistant variety seemed to impart
resistance in Kanakom along with thicker cuticle.
Higher amounts of silica, Zn and Mn and lower amounts of N, K, Ca
and Mg were recorded in the cuhn of the resistant variety compared to moderately
resistant and susceptible varieties.
The findings strongly suggest the mechanism of antibiosis and
antixenosis in the resistant variety Kanakom.