DIVERSITY OF SPIDERS (ARANEAE) IN TEA
Loading...
Date
2018-01
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
AAU, Jorhat
Abstract
A survey was conducted to study the diversity of spiders in different tea gardens viz., conventional, organic and small grower tea gardens of Jorhat district from May, 2016 to April, 2017. The results revealed a total number of 2954 specimens of spiders collected under 16 genera, 8 families and 20 species viz., Cyrtophoracicatrosa, Nephila kuhlii, Argiope pulchella, Cyclosa mulmeinensis, Neoscona sp, Cyclosa spirifera, Cyclosa bifida, Araneus mitifica, Oxyopes sitae, Oxyopes shweta, Oxyopes sp, Rhene danieli, Phintella vittata, Telamonia dimidiata, Tetragnatha sp, Leucauge decorata, Heteropoda ventoria, Xysticus sp and Perdosa peaudoannulata. Among all the species, Castianeira furva has been recorded for the first time from this region. Species richness (R = 3.07) and evenness (E = 0.96) was recorded the highest in Deha T.E. (organic garden) and was found lowest for Saikia T.E (small grower garden) i.e., 2.51 and0.89 respectively. However, species diversity was recorded highest in conventional garden, Dhloi T.E. (H’ = 2.88). The correlation studies revealed that the spider population exhibited significant positive correlation with total rainfall (r = 0.776) and non-significant for maximum temperature, minimum temperature and evening relative humidity while, a significant negative correlation was observed with morning relative humidity (r = -0.797) and bright sunshine hour (r = -0.676).
Some morphological and biochemical characters of seven selected tea clones (TV 1, TV 2, TV 7, TV 9, TV 12, TV 18, TV 23) in the Experimental Garden of Plantation crops, Assam Agricultural University, Jorhat were examined to determine their effects on common insect pests and spider population. The results showed that all the clones were susceptible to the pests, TV 23 being more susceptible compared to others (H. theivora 6.22 no/bush, O. coffeae 18.35 no/leaf, Hyposidra sp 3.43 no/bush). However, no significant difference for spider populations was found to exist amongst the clones. With respect to morphological characters, the examined clones showed significant difference for total number of branches, leaf area and trichome densities. The differences in leaf moisture contentwere also significant. Moreover, it was found that the phenol content of examined clones gradually decreased due to pest infestation and the reduction was highest in TV 23 (22.43%). The linear correlation among morphological and biochemical attributes of selected tea clones with pests showed that total no of branches and leaf area had a non significant negative correlation with H. theivora (r = - 0.664, - 0.333), O. coffeae (r = -0.277, -0.175) and Hyposidra sp (r = -0.156, -0.179) while trichome density had significant negative correlation with H. theivora (r = -0.643) O. coffeae (r = -0.475) and Hyposidra sp (r = - 0.493). However, the moisture content showed a non-significant positive correlation for H. theivora (r=0.064) but established a negative association with O. coffeae (r = -0.446) and Hyposidra sp (r = -0.370). Regarding insect pests, both the reduction in phenol content and spider population exhibited a significant positive association.
A field experiment was conducted in the Experimental Garden of Plantation crops, Assam Agricultural University, Jorhat, during 2016 and 2017 to investigate the effect of pesticides on common insect pests and spider population in tea plantation. On the basis of the pooled data of two year observations recorded at 1st, 5th and 10th days after application and revealed that all the treatments showed significant differences over control. Among the treatments thiomethoxam 25% WG @ 0.01% was found to be most effective against H. theivora followed by deltamethrin 2.8 EC @ 0.02% and azadirachtin @ 0.003%, whereas spiromesifen 240 SC @ 0.2% was found to be least effective against H. theivora population. The pooled data on the efficacy of different pesticides on O. coffeae revealed that spiromesifen 240 SC @ 0.2% was most effective followed by ethion 50EC @ 0.25%, deltamethrin 2.8 EC @ 0.02% and azadirachtin @ 0.003% whereas thiomethoxam 25% WG@ 0.01% @ was found to be least effective against O. coffeae population. Among all the treatments ethion 50EC @ 0.25% was found to be most toxic on spider population followed by deltamethrin 2.8 EC @ 0.02% and B. bassiana @ 2% was found safer to spider population which was followed by azadirachtin 5 EC 0.003%.
Description
Keywords
null