Browsing by Author "Prasad, A.R."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Effect of sub lethal dose of insecticides on electrophysiological and behavioral response of Bracon brevicornis Wesmael (Braconidae : Hymenoptera) a parasitoid of coconut black headed caterpillar, Opisina arenosella Walker (Oecophoridae : Lepidoptera)
    (2012) Kesavan Subaharan; Charles Sahayaraj; Prasad, A.R.; Ravikumar, N.
    Bracon brevicornis Wesmael (Braconidae : Hymenoptera) is an effective parasitoid against coconut black headed caterpillar, Opisina arenosella Walker (Oecophoridae : Lepidoptera) a major pest on coconut. During outbreaks, chemical insecticides and bioagents are used in tandem to manage O. arenosella. Traditionally the impact of pesticides on beneficial arthropods was assessed by determining acute toxicity. In addition to direct mortality caused by insecticides, the sublethal effect on sensory physiology and behavior of parasitoids must be considered for complete analysis of their impact. The present study aims to investigate the impact of sub lethal dose of insecticides on B. brevicornis. In olfactory assay, the starved parasitoids oriented to food source, whilst the fed parasitoids responded more to host volatiles. In electrophysiological assay, the antennal responses of B. brevicomis to host volatiles were higher in female. Among the volatiles tested, the host frass and host haemolymph was most preferred by both sexes. Exposure of B. brevicornis to sublethal dose of imidacloprid, malathion and carbaryl (LD20) altered the orientation of B. brevicornis to host volatiles.
  • Thumbnail Image
    Item
    Electrohysiological and behavioral response of Goniozus nephantidis Muesbeck, to plant and host volatiles
    (2011) Subaharan, K.; Ravikumar, N.; Prasad, A.R.
    Experience of parasitoids with host and host related products have effects on their behavior. Learning can be induced by conditioning parasitoids at various stages i.e. pre imaginal or imaginal (after eclosion). Here we studied the volatiles from damaged, undamaged coconut leaflets and Opisina arenosella larval frass that cause electrphysiological and behavioural response in the bethylid parasitoid Goniozus nephantidis. The possibility of using the host frass for conditioning the parasitoids was explored. The damaged coconut leaflets released cyclopentanone, butanol, and alpha pinene and these compounds were absent in undamaged leaflets. Z-3 hexenol, a green leaf volatile was trapped form both damaged and undamaged plants. Alpha pinene released form undamaged leaflets caused the highest electroantennogram (EAG) peak amplitude (O.330mV) in female antennae. This was followed by cyclopentanone (O.30mV), hexanone (O.29mV) and hexanal (O.29mV) which were all at par. G nephantidis reared on Corcyra cephalonica conditioned with the larval frass of O. arenosellla when provided a choice preferred to parasitize O. arenosella as compared to C. cephalonica. Conditioned parasitoids when released in the field caused 59 per cent reduction in larval population per leaflet as compared to 29 per cent reduction by unconditioned parasitoids two months after release. Conditioning of G nephalliidis with odors of O. arenosella will aid to enhance the host searching ability of the parasitoids that were reared on C. cephalonica.