Journal of Economic Entomology (2019) 112, 349-354

Dionei S. Muraro, Tiago Giacomelli, Regis F. Stacke, Daniela N. Godoy, Paula Marçon, Holly J.R. Popham and Oderlei Bernardi (2019)
Baseline susceptibility of Brazilian populations of Chrysodeixis includens (Lepidoptera: Noctuidae) to C. includens nucleopolyhedrovirus and diagnostic concentration for resistance monitoring
Journal of Economic Entomology 112 (1), 349-354
Abstract: The Chrysodeixis includens nucleopolyhedrovirus (ChinNPV: Baculoviridae: Alphabaculovirus) is a registered insecticide for the management of soybean looper, Chrysodeixis includens (Walker, [1858]) in Brazil. We conducted studies of baseline susceptibility of Brazilian populations of C. includens to the ChinNPV (Chrysogen, AgBiTech, Fort Worth, TX) as valuable knowledge in support of Integrated Pest Management and Insect Resistance Management programs. In bioassays, neonates were infected with different concentrations of ChinNPV using the droplet feeding bioassay method. Larvae were then transferred to artificial diet and mortality was assessed at 7 d. Results confirm that neonates from Brazilian populations of C. includens are susceptible to ChinNPV. Concentrations from 1.0 × 10³ to 1.0 × 10⁸ occlusion bodies (OBs) per ml caused mortality from 1.5 to 99%, respectively. The LC₅₀ ranged from 1.4 × 10⁵ to 7.7 × 10⁵ OBs per ml for populations of C. includens (5.5-fold variation). Similar variation was detected for the LC₉₀ which ranged from 1.6 × 10⁷ to 7.7 × 10⁷ OBs per ml (4.8-fold variation). Importantly, the field-collected populations showed equivalent susceptibility to the reference susceptible population. This indicates a low interpopulation variation in susceptibility of Brazilian populations of C. includens to ChinNPV, representing natural geographic variation and not variation caused by previous selection pressure. The candidate diagnostic concentration of 2.9 × 10⁸ OBs per ml was estimated based on the pooled data and caused mortality ranging from 98.6 to 100%. This concentration will be used in proactive resistance monitoring programs. The Chrysogen will be a valuable tool as a new mode of action in C. includens resistance management in Brazil.
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Link to article at publishers website
Database assignments for author(s): Holly J.R. Popham, Oderlei Bernardi

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Chrysodeixis includens	Soybean (Glycine max)
Alphabaculovirus chrincludentis (entomopathogen)	Chrysodeixis includens	Soybean (Glycine max)