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.