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Mediated pathogenicity of the baculovirus AcMNPV by the venom from Euplectrus comstockii Howard (Hymenoptera:
T A Coudron1, M Iqbal, W C Rice
1Biological Control of Insects Research Laboratory, US Department of Agriculture, Agricultural Research Service, Columbia, MO 65203-3535, USA. coudront@missouri.edu
Abstract:
The compatibility of the venom from the parasitic species Euplectrus comstockii Howard (Hymenoptera: Eulophidae) with the pathogenicity of Autographa californica (Speyer) (Lepidoptera: Noctuidae) MNPV baculovirus (AcMNPV) was tested in third and fourth instar larvae of Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae). The presence of AcMNPV did not alter the ability of the venom to arrest ecdysis in T. ni larvae. The presence of the venom delayed the rate of viruses by AcMNPV but increased the total mortality rates from days 9 to 14 in both third and fourth instar T. ni larvae. The delay in viruses was minimized by administering the virus prior to envenomation. In the presence of the venom, the final LD50 values were lower for fourth instar larvae than for third instar larvae. Surface response equations were developed to visualize the effect of the venom on the viruses caused by AcMNPV.
Insights
The venom of Euplectrus comstockii parasitoid did not affect Autographa californica MNPV baculovirus efficacy in Trichoplusia ni larvae. However, venom delayed viral progression but increased overall mortality, especially when the virus was administered before envenomation.
Area of Science:
- Entomology
- Insect Pathology
- Chemical Ecology
Background:
- Parasitoid venoms can influence host physiology and susceptibility to pathogens.
- Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a significant pathogen of Lepidoptera.
- Understanding interactions between venoms and baculoviruses is crucial for integrated pest management.
Purpose of the Study:
- To investigate the compatibility between Euplectrus comstockii venom and AcMNPV.
- To determine the impact of venom on baculovirus pathogenicity and host mortality.
- To analyze the effect of venom and virus administration timing on larval survival.
Main Methods:
- Larval bioassays using third and fourth instar Trichoplusia ni.
- Co-administration and sequential administration of E. comstockii venom and AcMNPV.
- Ecdysis monitoring, viral progression assessment, and mortality rate calculation.
- Determination of lethal dose 50 (LD50) values and development of surface response equations.
Main Results:
- E. comstockii venom did not inhibit the ecdysis-arresting properties of AcMNPV.
- Venom delayed AcMNPV replication but increased overall larval mortality between days 9 and 14.
- Administering AcMNPV before envenomation minimized the delay in viral spread.
- Lower LD50 values were observed in fourth instar larvae compared to third instar larvae when venom was present.
Conclusions:
- E. comstockii venom and AcMNPV can act synergistically to increase host mortality.
- The timing of virus and venom application significantly influences their combined effect.
- These findings provide insights into the complex interactions between parasitoid venom and baculovirus pathogens in Lepidopteran hosts.