Evaluation of Structural Treatment Efficacy against Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae) Using Meta-Analysis of Multiple Studies Conducted in Food Facilities.

The phase out of methyl bromide for the treatment of structures where grain is milled or processed has triggered a need to evaluate the effectiveness of alternative structural treatments such as sulfuryl fluoride and heat. Tribolium castaneum (Herbst) (red flour beetle) and Tribolium confusum Jacquelin du Val (confused flour beetle) (Coleoptera: Tenebrionidae) are primary targets for structural treatments, and impact of treatments on these species was evaluated in this study. Efficacy was measured by comparing beetle captures in pheromone- and kairomone-baited traps immediately before and immediately after treatments. Studies were conducted primarily in commercial wheat mills and rice mills, with the treatments conducted by commercial applicators. A meta-analysis approach was used to evaluate efficacy data collected from 111 treatments applied in 39 facilities. Findings confirm that structural fumigations and heat treatments greatly reduce pest populations within food facilities, but there was significant variation in the efficacy of individual treatments. Generally, the different treatment types (sulfuryl fluoride, methyl bromide, and heat) provided similar reductions in beetle capture using multiple metrics of beetle activity. The novel application of meta-analysis to structural treatment efficacy assessment generated a robust estimate of overall treatment efficacy, provided insights into factors potentially impacting efficacy, and identified data gaps that need further research.

Tribolium castaneum (Coleoptera: Tenebrionidae) associated with rice mills: fumigation efficacy and population rebound.

The red flourbeetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is the most important stored-product insect pest infesting rice (Oryza sativa L.) mills in the United States. Due to the phasing out of methyl bromide in accordance with the 1987 Montreal Protocol, the efficacy of alternative fumigants in controlling flour beetles in mill structures must be evaluated. Long-term trapping data sets (2-6 yr) of T. castaneum in and around seven rice mills were analyzed to assess the efficacy of sulfuryl fluoride fumigation (n = 25). Fumigation efficacy was evaluated as the percentage reduction in mean trap captures of adults and proportion of traps capturing at least one adult beetle. Beetle trap captures fluctuated seasonally, with increased captures during the warmer months, June-September, that dropped off during the cooler months, October-March. Fumigations resulted in a 66 +/- 6% (mean +/- SE) reduction in mean trap captures within mills and a 52 +/- 6% reduction in the proportion of traps capturing at least one adult beetle. Lengths of time for captures to reach prefumigation levels, or rebound rates, were variable, and adult capture levels inside were most influenced by seasonal temperature changes. Temperatures inside mills followed those outside the mill closely, and a significant positive relationship between outside temperatures and trap captures was observed. Inside and outside trap captures exhibited a significant, positive relationship, but fumigations consistently led to reductions in beetle captures outside of mills, highlighting the interconnectedness of populations located inside and outside mill structures.

The endosymbiont Arsenophonus is widespread in soybean aphid, Aphis glycines, but does not provide protection from parasitoids or a fungal pathogen.

Aphids commonly harbor bacterial facultative symbionts that have a variety of effects upon their aphid hosts, including defense against hymenopteran parasitoids and fungal pathogens. The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is infected with the symbiont Arsenophonus sp., which has an unknown role in its aphid host. Our research goals were to document the infection frequency and diversity of the symbiont in field-collected soybean aphids, and to determine whether Arsenophonus is defending soybean aphid against natural enemies. We performed diagnostic PCR and sequenced four Arsenophonus genes in soybean aphids from their native and introduced range to estimate infection frequency and genetic diversity, and found that Arsenophonus infection is highly prevalent and genetically uniform. To evaluate the defensive role of Arsenophonus, we cured two aphid genotypes of their natural Arsenophonus infection through ampicillin microinjection, resulting in infected and uninfected isolines within the same genetic background. These isolines were subjected to parasitoid assays using a recently introduced biological control agent, Binodoxys communis [Braconidae], a naturally recruited parasitoid, Aphelinus certus [Aphelinidae], and a commercially available biological control agent, Aphidius colemani [Braconidae]. We also assayed the effect of the common aphid fungal pathogen, Pandora neoaphidis (Remaudiere & Hennebert) Humber (Entomophthorales: Entomophthoraceae), on the same aphid isolines. We did not find differences in successful parasitism for any of the parasitoid species, nor did we find differences in P. neoaphidis infection between our treatments. Our conclusion is that Arsenophonus does not defend its soybean aphid host against these major parasitoid and fungal natural enemies.