Hydramethylnon potentiation in Solenopsis invicta by infection with the microsporidium Thelohania solenopsae

Abstract

Laboratory and field evaluations were conducted in which hydramethylnon treatments were made against Solenopsis invicta individuals and colonies that were either infected or uninfected with Thelohania solenopsae. In laboratory experiments, polygynous T. solenopsae-infected colonies of S. invicta exhibited significantly greater cumulative mortality than uninfected colonies when exposed to hydramethylnon, a respiratory-inhibiting insecticide. By day 21, nearly 100% of the individuals in the T. solenopsaeinfected colonies were dead whereas only about 50% of the individuals in the uninfected colonies were dead. In addition to a higher cumulative mortality among T. solenopsae-infected workers, queens from infected colonies exhibited higher mortality than those from uninfected colonies. Similar results were observed in field studies in which fire ant-infested pasture was treated with hydramethylnon. The number of T. solenopsae-infected colonies decreased much faster relative to uninfected colonies in the same area. The initial rate of decline was 1.3 mounds/plot/day among T. solenopsae-infected colonies compared with a decrease of 0.4 mounds/ plot/day among uninfected colonies. Insecticide toxicity bioassay data supported our hypothesis that T. solenopsae infection can potentiate the toxicity of hydramethylnon. T. solenopsae-infected workers were 2.4-fold more susceptible to hydramethylnon than uninfected workers in toxicity bioassays.

Occurrence of Myrmicinosporidium durum in red imported fire ant, Solenopsis invicta, and other new host ants in eastern United States

“…Whether this hypothesis is correct, and whether a newly acquired, or increasing disease susceptibility can slow the fire ant expansion, or decrease its dominance in the infested areas, needs further investigation. Also, stress factors, such as parasitoid biocontrol agents (Graham et al, 2003;Porter et al, 2004), new chemical pesticides, weather conditions, or the interactions of some of these factors (Valles and Pereira, 2003b), may be important in determining increased susceptibility to diseases. Because parasite populations increase with an increase in the host range area (Strong et al, 1977), the large infestation area may explain an increase in disease incidence on S. invicta populations.…”

Effect of mono- and polygyne social forms on transmission and spread of a microsporidium in fire ant populations

“…Cook (2002) reported colonies with T. solenopsae to have nest sizes, or mound volumes, that were 2.5 times smaller than uninfected colonies in Texas. In addition, colonies with T. solenopsae were more susceptible to Wre ant bait containing hydramethylnon (Valles and Pereira, 2003) and infection by the entomopathogenic fungus Beauveria bassiana (Brinkman and Gardner, 2000). The detrimental impact of T. solenopsae on Wre ants in both laboratory and Weld studies indicate that it may be useful as a biological control for Wre ants.…”

Kneallhazia carolinensae sp. nov., a microsporidian pathogen of the thief ant, Solenopsis carolinensis

“…It has since been spread intentionally throughout the southeastern United States in an attempt to provide widespread control of this invasive ant species . Studies have been conducted to examine the life cycle (Sokolova and Fuxa, 2008), the nature of the host-pathogen interaction (Cook et al, 2003;Shapiro et al, 2003;Valles et al, 2009), spore morphologies (Chen et al, 2004;Sokolova and Fuxa, 2001;Sokolova et al, 2005), effects against field populations of S. invicta Oi et al, 2004), and interactions with traditional insecticides Valles and Pereira, 2003).…”