Shifting the paradigm: highlights from 2022 demonstrate broad public health impacts of applied urban entomology

In 2022, the dramatic reduction of applied and extension urban entomology positions was highlighted and widely discussed by seasoned and nascent urban entomologists alike. In fact, many urban entomologists are calling for a "paradigm shift" within the discipline given the reduction in niche urban entomology-specific positions. Specifically, many individuals are insisting that movement toward a framework where urban entomologists address complex, cross-disciplinary issues and advocate for research funding through science policy is critical for the endurance of the discipline. In this new model, the purpose of urban entomology does not necessarily change, but rather expands to attack questions that may be of interest to the broader scientific community. In addition, this paradigm shift would necessitate increased engagement of urban entomologists with bureaucratic and administrative agencies to communicate the importance of urban pest management, especially in a landscape where funding opportunities and endowments have been reduced, reallocated, or eliminated. To reflect the ongoing transformation within the field of urban entomology, the objectives of this review were to highlight papers published in 2022 that exemplify the broader impacts of urban entomological studies and urban pest management. Studies with ties to global public health and Entomological Society of America science policy initiatives are highlighted to encourage urban entomologists to consider the far-reaching influence of their research.

Differential Selection on Caste-Associated Genes in a Subterranean Termite

Analyzing the information-rich content of RNA can help uncover genetic events associated with social insect castes or other social polymorphisms. Here, we exploit a series of cDNA libraries previously derived from whole-body tissue of different castes as well as from three behaviourally distinct populations of the Eastern subterranean termite Reticulitermes flavipes. We found that the number (~0.5 M) of single nucleotide variants (SNVs) was roughly equal between nymph, worker and soldier caste libraries, but dN/dS (ratio of nonsynonymous to synonymous substitutions) analysis suggested that some of these variants confer a caste-specific advantage. Specifically, the dN/dS ratio was high (~4.3) for genes expressed in the defensively specialized soldier caste, relative to genes expressed by other castes (~1.7−1.8) and regardless of the North American population (Toronto, Raleigh, Boston) from which the castes were sampled. The populations, meanwhile, did show a large difference in SNV count but not in the manner expected from known demographic and behavioural differences; the highly invasive unicolonial population from Toronto was not the least diverse and did not show any other unique substitution patterns, suggesting any past bottleneck associated with invasion or with current unicoloniality has become obscured at the RNA level. Our study raises two important hypotheses relevant to termite sociobiology. First, the positive selection (dN/dS > 1) inferred for soldier-biased genes is presumably indirect and of the type mediated through kin selection, and second, the behavioural changes that accompany some social insect urban invasions (i.e., ‘unicoloniality’) may be detached from the loss-of-diversity expected from invasion bottlenecks.

Urban Entomology Highlights From 2020-Monitoring and Control of Urban Pests

Pest management professionals aim to answer two primary questions for their customers: 1) 'Where/What is the pest?' and 2) 'How do I kill it?'. These two questions drive at the core of any pest management program. 2020 was an exciting year for entomology research, with much work being done on novel technologies and methods for detecting and controlling pests. The objectives of the current publication were to discuss papers published in 2020 that addressed the key pest management objectives of 1) monitoring and 2) controlling pest populations.

Invasion of Tropical Montane Cities by Aedes aegypti and Aedes albopictus (Diptera: Culicidae) Depends on Continuous Warm Winters and Suitable Urban Biotopes

We provide the first evidence of a recent invasion of Aedes aegypti (Linnaeus in Hasselquist, 1762) and Aedes albopictus (Skuse 1894), followed by dengue virus, in tropical montane cities in south-eastern Brazil, Mariana, and Ouro Preto, at mid and high altitudes, respectively. Long-term temperature variation, dengue public data, and sampling of immature and adult mosquitoes (ovitraps and mosquitraps) in contrasting habitats were used to explain the distribution of Aedes in what in these two cities. From 1961 to 2014, the annual temperature increased significantly due to increases in winter temperatures. In the 1990s/2000s, the winter temperature was 1.3°C warmer than in the 1960s, when it varied from 21.2 to 18.9°C. After 2007, the winter temperatures increased and ranged from 21.6 to 21.3°C. The first autochthonous dengue cases in Mariana and Ouro Preto were in 2007, followed by few occurrences until in 2012, when the mean numbers increased three-fold, and peak at 2013. The continuous 'warmer winter' may have trigged the Aedes invasion. Aedes species benefited from higher winter temperatures, which was an important driver of their invasion of the state of Minas Gerais in the 1980s and, more recently, in the remaining montane urban habitats in this region. In both 2009 and 2011, we found more Aedes in Mariana than Ouro Preto, and more Ae. albopictus in green areas and Ae. aegypti in houses, the expected pattern for well-established populations.

Urban Entomology Highlights From 2019 Help Create Integrated Pest Management Plans

Urban insect pests such as ants, termites, cockroaches, and bed bugs are more than just nuisances; they often negatively impact structures, landscapes, animal health, commercial food production, food safety, and public health (mental, physical, and financial). Due to the tremendous burden these insects can inflict, researchers, manufacturers, and pest management professionals work to create solutions that effectively manage urban and structural pests. One solution that has proven useful in agriculture is the development of an integrated pest management (IPM) plan; i.e., a science-based approach to pest control that utilizes multiple tactics such as preventative tools, chemical control (sprays, fumigation, and baits), biological control, and exclusion. There are many permutations of urban IPM plans, but in general they consist of five components: 1) identifying the pest, 2) monitoring the pest, 3) developing an intervention plan (including prevention and control techniques), 4) implementing the program, and 5) recording and evaluating the results. The objectives of the current publication were to 1) highlight urban entomology research published in 2019 and 2) show how the results from these publications help pest management professionals create and implement IPM plans.

Turning Ultraviolet Light Traps On and Off Increases Their Attraction to House Flies (Diptera: Muscidae)

Pairs of electrocutor-grid ultraviolet light traps were assigned to three treatments to evaluate the effects of illumination events, e.g., light traps turned on, on house fly, Musca domestica L., attraction as indicated by numbers of flies captured by the traps. Both traps in treatment 1 were illuminated constantly (no illumination event). Both traps in treatment 2 were turned on, illuminated for 1 h, then turned off for 1 h, then repeated (1 illumination event every 2 h). Traps in treatment 3 were operated singularly. One trap was turned on for 1 h, then turned off. As it turned off, the other trap turned on for 1 h, then turned off, then repeated (1 illumination event every hour). The mean number of flies attracted per trap pair was significantly greater in treatment 1 than in treatments 2 or 3. However, in treatment 3, with one trap illuminated at a time and hourly illumination events, the mean fly catch was just 27% less, numerically, than the mean number of flies attracted to treatment 1 with both traps illuminated constantly. The effects of intermittent lighting and its potential use are discussed.

Microgeographic Population Structuring of Culex quinquefasciatus (Diptera: Culicidae) From São Paulo, Brazil

The continuing worldwide increase in urbanization can potentially have a major impact on the epidemiology of vector-borne diseases, as anthropogenic changes to the environment are known to favor a few species of mosquitoes that can thrive in urban environments. Culex quinquefasciatus Say (Diptera: Culicidae) is found extensively in urban habitats, where it lives in degraded, polluted areas and is often the only species of mosquito capable to surviving under such conditions. Traditional mosquito control strategies no longer have the desired effect due to the several factors such as insecticide resistance, abundance of breeding sites, lack of proper sewage and sanitation, and absence of natural predator, leading Cx. quinquefasciatus populations to increase its numbers in cities. In this study, five Cx. quinquefasciatus populations were analyzed using 12 microsatellite markers to investigate whether the dynamics of these populations are being modulated by urbanization and how they are structured in the city of São Paulo, Brazil. Our results indicate that only one of the study populations (the population from Anhanguera Park) exhibited evidence of expansion. The populations from Ibirapuera Park and Piqueri Park, the most urbanized regions of the areas studied, did not show signs of expansion. A better understanding of the mechanisms involved in the dispersal of Cx. quinquefasciatus and its colonization of new areas, as well as the species' demographic patterns and how these are associated with urbanization, particularly in areas undergoing a rural-to-urban transformation, such as Anhanguera Park, is of great importance for mosquito control.

Phenology of Asian Citrus Psyllid (Hemiptera: Liviidae), With Special Reference to Biological Control by Tamarixia radiata , in the Residential Landscape of Southern California

Since its discovery in 2008, the pestiferous Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), has become widely established in residential citrus trees throughout southern California. In 2011, Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae), a host-specific parasitoid of D. citri , sourced from Punjab Pakistan, was introduced into California as part of a classical biological program aimed at suppressing D. citri populations in urban areas. Despite these release efforts, little is known about the population dynamics of D. citri in urban citrus or the efficacy of T. radiata in controlling psyllid populations in urban-grown citrus. To address this shortcoming, the population phenology of D. citri was monitored biweekly for 2-3 yr on five different host plants (Rutaceae) at 11 residential sites across Riverside and Los Angeles Counties in southern California. Citrus flush growth patterns and parasitoid activity levels were also assessed. Urban D. citri populations were present year round at each site, with highest densities occurring over July through November. Temperature was an important indicator of overall D. citri densities with positive correlations across all life stages. Regularly flushing lime trees consistently supported the highest densities of psyllid eggs and nymphs, while equally vigorous flushing curry leaf plants supported the highest adult densities. While T. radiata activity was detected at all sites, average year-round percent parasitism was low throughout the study, averaging <5% in 2012, 2013, and 2014.

Establishment of the Brown Widow Spider (Araneae: Theridiidae) and Infestation of its Egg Sacs by a Parasitoid, Philolema latrodecti (Hymenoptera: Eurytomidae), in French Polynesia and the Cook Islands

This paper presents two newly established species for French Polynesia: the invasive brown widow spider, Latrodectus geometricus C. L. Koch, and its potential biocontrol agent, the parasitoid wasp, Philolema latrodecti (Fullaway). The brown widow spider was recorded from the island of Moorea in 2006 and, since that discovery, the occurrence of this species has expanded to two of the five archipelagos of French Polynesia including the main island of Tahiti and four of the Cook Islands. Although the tropical climate contributes to the establishment of L. geometricus, a biotic factor, P. latrodecti, may restrain population from demographic explosion. This eurytomid wasp is present in French Polynesia and is a parasitoid that has been used in biological control of the southern black widow Latrodectus mactans (F.) in Hawaii. This wasp could become a significant limiting factor for L. geometricus distribution on these islands, as it was found in 31% of the Tahitian brown widow spider egg sacs that were dissected. However, thus far, the wasp was only found on Tahiti in association with the brown widow spider. Although the brown widow is generally considered to be less toxic than its black widow relatives, it remains of medical concern in French Polynesia because reactions to its bites can, at times, be severe. The spider remains of public concern because it is a novel species; it has the word widow in its name and dark morphs are mistaken as black widows.

Exposure of Brown Recluse and Brown Widow Spiders (Araneae: Sicariidae, Theridiidae) to a Commercial Sulfuryl Fluoride Fumigation

The body of pesticide research on spiders is sparse with most studies using topical or residual applications to assess efficacy. Data on the effects of fumigation on spider survivorship are scarce in the scientific literature. In this study, we exposed adult male and female brown recluse spiders, Loxosceles reclusa Gertsch & Mulaik, and female brown widow spiders, Latrodectus geometricus C. L. Koch, to a commercial fumigation event using sulfuryl fluoride directed at termite control. General consensus from the pest control industry is that fumigation is not always effective for control of spiders for a variety of reasons, including insufficient fumigant dosage, particularly, for contents of egg sacs that require a higher fumigant dosage for control. We demonstrated that a sulfuryl fluoride fumigation with an accumulated dosage of 162 oz-h per 1,000 ft(3) at 21°C over 25 h (≈1.7 × the drywood termite dosage) directed at termites was sufficient to kill adult brown recluse and brown widow spiders. The effectiveness of commercial fumigation practices to control spiders, and particularly their egg sacs, warrants further study.