Influence of chemical profiles of host plants on the infestation diversity of Retithrips syriacus

The onset of biotic stress in the host plants as a result of increased insect population size leads to enhanced levels of secondary metabolites and associated phenolic enzyme activity. Of the three host plants examined, viz.Ricinus communis (castor),Eucalyptus globulus (eucalyptus) andManihot utilissima (tapioca), castor was the host most preferred byRetithrips syriacus. Despite the fact that tapioca had the highest levels of secondary compounds, thrips infestation persisted. However, fecundity and growth were reduced because of the relatively high levels of primary metabolites. Gallic acid was found to be the most toxic of the phenolic acids, followed by pyrogallol, resorcinol, phloroglucinol and vanillic acid. The less toxic phenolic acids and flavanoids were detected in leaves that harboured thrips, while the preponderance of gallic acid was found in uninfested hosts. Thus the interaction ofRetithrips syriacus with the hosts is governed essentially by the biochemical profiles of its hosts, which tend to be altered subsequent to infestation, thus manifesting induced resistance through enhanced production of phenolics

© 2009 Academic Journals

Variation of resistance to endosulfan in tea mosquito bug, Helopeltis theivora waterhouse (heteroptera: miridae) in the tea plantation of the Sub-Himalaya

Effect of aqueous plant extracts on tea red spider mite, Oligonychus coffeae, Nietner (Tetranychidae: Acarina) and Stethorus gilvifrons Mulsant

Four aqueous plant extracts (APEs) of Acorus calamus (L), Xanthium strumarium (L), Polygonum hydropiper (L) and Clerodendron infortunatum (Gaertn) were evaluated under both laboratory and fieldconditions at 2.5, 5.0 and 10.0% (w/v) concentrations against tea red spider mite, Oligonychus coffeae (Nietner). Also, the impact of APEs on survival and feeding of Stethorus gilvifrons, a potent coccinellidpredator of red spider mite was studied. Parameters assessed were ovicidal activity and acaricidal activity in case of red spider mite, and feeding activity and adult mortality for the coccinellid. Strongovicidal action was observed with X. strumarium (87.09%) and A. calamus (70.62%) whereas least action in P. hydropiper (30.86%) and C. infortunatum (20.58%). All the APEs showed > 50% mortality of redspider mite at higher concentrations (5 and 10%) under laboratory conditions. Field evaluation of APEs recorded 46.9 – 81.8% mite reduction at 5.0% and 64.7 – 100.0% at 10.0% concentration. More acaricidal activity was noticed in C. infortunatum and X. strumarium under field condition. The APEs, even at higher concentration (10%), caused no mortality to the adults of S. gilvifrons for 14 days, and nosignificant change in feeding after 24 h in comparison with untreated control. Crude plant extracts of A. calamus, X. strumarium, P. hydropiper and C. infortunatum can effectively be utilized as saferphytopesticidal products in both organic and inorganic tea estates as one of the potent tools in integrated mite management