Pest Management Science (2018) 74, 1441-1448

Daniela M. Okuma, Daniel Bernardi, Renato J. Horikoshi, Oderlei Bernardi, Aline P. Silva and Celso Omoto (2018)
Inheritance and fitness costs of Spodoptera frugiperda (Lepidoptera: Noctuidae) resistance to spinosad in Brazil
Pest Management Science 74 (6), 1441-1448
Abstract:
Background
Spodoptera frugiperda is a pest of economically important crops in South America. In Brazil, this species is considered the most destructive pest of maize. Use of spinosyn insecticides in insect resistance management (IRM) has been one strategy to control this pest. In this study, we selected a strain of S. frugiperda resistant to spinosad and evaluated the inheritance and fitness costs of the resistance.
Results
Estimated LC₅₀ (concentration required to kill 50% of larvae) values were 0.011 and 9.80 µg cm^-2 for the spinosad-susceptible (Sus) and -resistant (Spin-res) strains, respectively. This represents an 890-fold resistance ratio. LC₅₀ values for reciprocal crosses were 0.18 and 0.14 µg cm^-2, indicating that resistance to spinosad is an autosomal incompletely recessive trait. Backcrosses of the F₁ progeny from reciprocal crosses with the parental Spin-res strain showed a polygenic effect. The estimated minimum number of independent segregations was ~ 2.45, indicating that resistance to spinosad is associated with multiple genes. In greenhouse assays, third-instar larvae from the Spin-res strain showed >92% survival on spinosad-treated maize. By contrast Sus and reciprocal crosses exhibited 0% and <5% survival, respectively, indicating that resistance is recessive. Life history studies to investigate the fitness cost of resistance revealed a 41% reduction in the rate of survival to adulthood and a 49% lower reproductive rate in the Spin-res strain compared with the Sus strain.
Conclusions
The autosomal, incompletely recessive and polygenic resistance to spinosad in S. frugiperda and the fitness costs associated with this resistance can be exploited in IRM strategies to preserve the lifetime of spinosad for control of S. frugiperda in Brazil.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Celso Omoto, Oderlei Bernardi

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Spodoptera frugiperda