Record Details

SPATIAL DISTRIBUTION OF PEST - PREDATOR COMPLEX AND PREDATOR DIVERSITY IN RICE ECOSYSTEM

KrishiKosh

View Archive Info
 
 
Field Value
 
Title SPATIAL DISTRIBUTION OF PEST - PREDATOR COMPLEX AND PREDATOR DIVERSITY IN RICE ECOSYSTEM
 
Creator RAJNA S.
 
Contributor Subhash Chander
 
Subject marketing, sampling, predators, rice, crops, land resources, biological interaction, economics, bugs, planting
 
Description T-8475
The present investigation entitled “Spatial distribution of pest predator complex and predator diversity in rice ecosystem” was undertaken during kharif, 2010 at the experimental farm of Division of Entomology, Indian Agricultural Research Institute, New Delhi. Spatial distribution patterns of two major rice pests viz., planthoppers, Nilaparvata lugens (Stal) and Sogatella furcifera (Hovarth), and rice leaf folder, Cnaphalocrosis medinalis (Guenee) and their predators were analyzed through statistical tests involving variance-mean ratio, discrete frequency distributions such as Poisson, Binomial and Negative binomial, and regression models viz., Taylor‟s power law and Iwao‟s mean crowding regression model. Variance-mean ratio of planthopper to be > 1.0 during most of the crop stages indicated aggregated distribution. The planthopper counts fitted to Poisson model at 30, 79 and 86 days after transplanting (DAT) and to negative binomial model at 37, 44, 51, 58 and 65 DAT. Taylor‟s power law aggregation parameter (b=1.614) and density contagiousness co-efficient (β=1.693) of Iwao‟s mean crowding regression revealed aggregation as dominant type of distribution of the pest on the crop. For leaf folder incidence, the variance-mean ratio and discrete frequency models revealed random distribution at most of the crop stages except at 51 DAT, when the distribution was observed to be aggregated. Taylor‟s power law (b= 0.914) and Iwao‟s mean crowding regression (β= 0.935) confirmed random distribution. With regard to predator diversity in rice ecosystem 15 species were observed in the field that included nine species of spiders, Lycosa pseudoannulata, Oxyopes javanus, O. lineatipes, Tetragnatha sp. Phidippus spp., Araneus inustus, Neoscona theisi, Thomisus spp. and Leucauge sp.; one mirid bug species, Cyrtorhinus lividipennis; two carabid species Ophionea sp. and Anoplogenius sp.; one rove beetle species, Paederus fuscipes and two coccinellid species. Variance-mean ratio and regression models revealed aggregated distribution of spiders, mirid bugs, rove beetles and coccinellids while carabids were found to be distributed randomly. Simpson diversity index revealed higher predator diversity at 37 DAT and lesser at 79 DAT with index values being 8.074 and 1.153, respectively. Likewise, The Shannon-Wiener index evinced higher predator diversity at 51 DAT with its value being 2.615 and diversity lesser at 79 DAT with value of 0.394. Berger-Parker index used for determining dominance of species at different stages of the crop showed the spider species, O. lineatipes to
be dominant at 30 and 37 DAT, L. pseudoannulata at 51 DAT, Paederus sp. at 58 DAT and C. lividipennis dominant during 58 to 86 DAT. Sequential sampling plans were developed for planthopper management without and with inclusion of predator effect. Plans were devised with predator effect at two crop growth stages viz., pre-flowering and post-flowering crop stages. The lower and upper decision line values without predator effect after first sample unit were 5 and 15 planthoppers/hill, respectively. In case of indecisiveness, the maximum number of sample units was determined to be about 3. On the other hand with predator effect, the lower and upper decision line values during pre-flowering were 7 and 20 and that during post-flowering were 10 and 28 planthoppers/hill, respectively, which suggested need for management measures at higher population level of the pest. Predator-conditioned sequential plan would thus be useful in avoiding unwarranted pesticide application thereby helping in predator conservation, reduction in environmental contamination and ensuring better benefit cost to growers.
 
Date 2016-11-23T11:31:13Z
2016-11-23T11:31:13Z
2011
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/87193
 
Format application/pdf
 
Publisher IARI, DIVISION OF ENTOMOLOGY