“ABUNDANCE AND DIVERSITY OF SPIDER AND COCCINELLID PREDATORS AND THEIR IMPACT ANALYSIS ON MAJOR PESTS IN VARIED RICE SYSTEMS
Loading...
Date
2016
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Professor Jayashankar Telanagana State Agricultural University
Abstract
Field studies were carried out in kharif 2014 and 2015 in rice fields of College Farm, Rajendranagar to understand the “Abundance and diversity of spider and coccinellid predators and their impact analysis on major pests in varied rice systems”. Design of the experiment was split plot with three main modules, each with different establishment technique viz., Transplanted rice, broadcasted rice and drumsown rice. Size of each module was 36 X 12 sq.m. with three replications under each treatment. A nursery bed of 100 sq.m was sown in the first week of July and main treatments viz., transplanting, broadcasting and drumsowing were carried out in the last week of July. Recommended packages of practices were administered according to the requirement of various treatment modules. Sub treatments under each main treatment included different types of plant protection measures adopted viz., organic protection, farmers’ practices and ‘no protection’ practices. Weekly counts on pests and predators (spiders and coccinellids) were taken from thirty fourth Standard week to forty seventh standard week and data were subjected to ANOVA.
Studies on pest abundance in various treatments revealed that broadcasted farmers’ practices recorded the least occurrence of dead hearts (2.05%) and white ears (0.46%). Organically protected and farmers’ practices plots of transplanted rice and all drumsown plots registered significantly lesser white ears (0.46% to 0.59%) compared to transplanted farmers’ practices(1.18%). Drumsown farmers’ practices registered lesser incidence of leaf folder and hispa beetle. Predator numbers in ‘no protection’ and organic protection plots of all main
treatments were higher than in farmers’ practices indicating the toxicity of the chemical insecticides and neem sprays.
Twenty two genera of spiders belonging to twelve families were recorded in rice ecosystem in the present study which comprised of seven guilds based on their hunting strategies and microhabitats. Shannon–Wiener diversity index ranged between 1.83 and 2.26 and Pielou’s evenness index of 0.59-0.72 in two years of study indicating a stable ecosystem and even species distribution in rice crop at Rajendranagar. However, coccinellid diversity and species evenness were lesser compared to that of spiders and they ranged between 1.071.15 and 0.37-0.58 respectively in 2014 and 2015, indicative of an uneven coccinellid community system at Rajendranagar. There was an increase in spider density in the second year of study over the first year, but the same was not true for coccinellids.
Pearson correlation studies between pest and predator population indicated that all the spider genera except Atypena and Pholcus were significantly and positively correlated with yellow stem borer. Atypena was found to be negatively correlated with leaf folder and hispa population also. Pholcus,Telamonia, and Tetragnatha sp. were positively and significantly correlated with leaf folder and hispa population. While Heteropoda had a negative relation with the Hispa beetle, Neoscona had positive relation. Pearson correlation studies between coccinellids and pests revealed that Coccinella, Propylea, Cheilomenes and Scymnus had significant positive relation with the stem borer, while Coccinella, Propylea, Cheilomenes and Illeis had significant positive relation with the leaf folder and Coccinella, Cheilomenes and Illeis had significant positive relation with the hispa beetle. Studies on impact of weather factors on pests revealed that population of stem borer in organic and farmers’ practices plots were positively and significantly influenced by minimum temperature. However, all other weather parameters had meagre impact on the borer. Population of leaf folder and hispa beetle were higher in warmer night temperatures 16240C). Genera Araneus, Arctosa, Cheiracanthium, Hamataliwa, Heteropoda, Neoscona, Oxyopes were totally unaffected by weather parameters. Microhabitat of spiders on the crop, their hunting strategies, vegetation structure complexity influenced the complex of spiders in that vegetation. Weather parameters had varying effects on most of spider genera in the second year of study, while in the first year and in pooled values, the impact was meagre. Weather had no impact on Micraspis, Coccinella, Propylea and Scymnus. Harmonia was negatively correlated with minimum temperature; Cheilomenes was positively correlated with minimum temperature, while evening relative humidity and minimum temperature had positive influenceon Illeis sp.
Description
Keywords
null
Citation
D10,174