Boric acid toxic sugar bait suppresses male Aedes aegypti (Diptera: Culicidae): wing beat frequency and amplitude, flight activity, fecundity, insemination, and mate-finding Allee effect.

BACKGROUND: Controlling the spread of arboviral diseases remains a considerable challenge due to the rapid development of insecticide resistance in Aedes mosquitoes. This study evaluated the effects of boric acid-containing toxic sugar bait (TSB) on field populations of resistant Aedes aegypti mosquitoes. In addition, this study examined the flight activity and wing beat frequency and amplitude of males and the flight activity, fecundity, and insemination of females after pairing with males exposed to TSB. The population dynamics of Aedes mosquitoes under imbalanced sex ratios were examined to simulate realistic field conditions for male suppression under the effect of TSB. RESULTS: The mortality of male mosquitoes was consistently high within 24 h after exposure. By contrast, the mortality of female mosquitoes was inconsistent, with over 70% mortality observed at 168 h. The flight activity and wing beat amplitude of treated males were significantly lower than those of controls, but no significant difference in wing beat frequency was detected. The fecundity and insemination of treated female mosquitoes were lower than those of controls. A simulation study indicated that considerably low male population densities led to mating failures, triggering a mate-finding Allee effect and resulting in persistently low population levels. CONCLUSION: Boric acid-containing TSB could effectively complement current chemical intervention approaches to control resistant mosquito populations. TSB is effective in reducing field male populations and impairing male flight activity and female-seeking behavior, resulting in decreased fecundity and insemination. Male suppression due to TSB potentially results in a small mosquito population. © 2024 Society of Chemical Industry.

Infection patterns of 'Candidatus Liberibacter europaeus' in Cacopsylla oluanpiensis, a psyllid pest of Pittosporum pentandrum.

'Candidatus Liberibacter' is a genus of plant-associated bacteria that can be transmitted by insects of the superfamily Psylloidea. Since many members of this genus are putative causal agents of plant diseases, it is crucial in studying their interactions with the psyllid vectors. However, previous studies have mainly focused on few species associated with diseases of economic significance, and this may potentially hinder the development of a more comprehensive understanding of the ecology of 'Ca. Liberibacter'. The present study showed that an endemic psyllid species in Taiwan, Cacopsylla oluanpiensis, is infected with a species of 'Ca. Liberibacter'. The bacterium was present in geographically distant populations of the psyllid and was identified as 'Ca. Liberibacter europaeus' (CLeu), a species which generally does not induce plant symptoms. Analysis of CLeu infection densities in male and female C. oluanpiensis with different abdominal colors using quantitative polymerase chain reaction revealed that CLeu infection was not significantly associated with psyllid gender and body color. Instead, CLeu infection had a negative effect on the body sizes of both male and female psyllids, which is influenced by bacterial titer. Investigation on CLeu's distribution patterns in C. oluanpiensis's host plant Pittosporum pentandrum indicated that CLeu does not behave as a plant pathogen. Also, results showed that nymph-infested twigs had a greater chance of carrying high loads of CLeu, suggesting that ovipositing females and the nymphs are the main source of the bacterium in the plants. This study is not only the first to formally report the presence of CLeu in C. oluanpiensis and plants in the family Pittosporaceae, but also represents the first record of the bacterium in Taiwan. Overall, the findings in this work broaden the understanding of associations between psyllids and 'Ca. Liberibacter' in the field.

Infection Patterns of a Liberibacter Associated with Macrohomotoma gladiata, a Psyllid Feeding on Ficus microcarpa.

Almost all known Liberibacters can be transmitted by psyllids. This suggests that there is a coevolutionary relationship between these two groups of organisms. However, detailed investigation of Liberibacters and psyllids have often focused on only a few species, thus potentially limiting knowledge on Liberibacter-psyllid associations. This study investigated the infection patterns of a Liberibacter inhabiting Macrohomotoma gladiata, a psyllid species feeding on Ficus microcarpa. Comparison of the Liberibacter's near-full-length 16S rDNA sequence with those of other known Liberibacters revealed that it is closely related to Candidatus Liberibacter asiaticus. A survey of different M. gladiata populations in Taiwan using conventional and quantitative PCR (qPCR) indicated that the Liberibacter could be detected with variable frequencies in all the tested populations; the proportions of individuals carrying large Liberibacter populations also differed depending on the population. Additional analysis of a larger set of samples collected from one specific population revealed that the psyllid's gender and abdominal color were associated with Liberibacter infection density. Significantly greater proportions of individuals with a blue/green abdomen carried high Liberibacter titers. Analysis of the psyllids' body lengths revealed that body size was not affected by Liberibacter infection status and that females, particularly those with an orange abdomen, tended to be larger. The infection patterns of Liberibacter in nymph-infested and nymph-free twigs of F. microcarpa were also determined, and Liberibacter distribution was found to be associated with the presence of nymphs. These findings broaden the understanding of Liberibacter ecology in general and have implications for managing Liberibacter-associated diseases. IMPORTANCE Despite the ever-increasing interest in Liberibacter-psyllid interactions, most of the current knowledge on the subject has been established from studies focusing on species associated with crop diseases. To obtain a more holistic understanding of Liberibacter ecology, we investigated the infection patterns of a Liberibacter recently detected in Macrohomotoma gladiata, a psyllid pest of Ficus microcarpa. We showed that a Liberibacter closely related to Candidatus Liberibacter asiaticus is widely distributed across M. gladiata populations in Taiwan. The study also identified factors associated with the Liberibacter infection patterns, both in M. gladiata and in F. microcarpa. The effects of Liberibacter infection status on psyllid body sizes were also examined. Some of the patterns detected in this work were similar those found in well-known Liberibacters, while some were the opposite. The findings in this work broaden our understanding of Liberibacter ecology in general and may facilitate development of strategies for managing plant diseases.

Seasonal Dynamics of Flight Phenology of the Euwallacea fornicatus Species Complex and an Associated Parasitoid Wasp in Avocado Groves in Taiwan.

The Euwallacea fornicatus species complex (Coleoptera: Curculionidae: Scolytinae: Xyleborini) is a group of four cryptic ambrosia beetle species. Native to Asia, several members of the complex have invaded other continents, where they cause significant economic losses to agricultural crops (e.g., avocado) and natural ecosystems. We were primarily interested in developing management strategies by focusing on the flight behavior of the beetles. Thus, seasonal differences in flight activity were assessed using panel traps baited with a commercial quercivorol lure, placed in infested avocado orchards in Danei, Tainan, Taiwan. Same traps were used to investigate the flight activity of a natural enemy, an undescribed species of the Braconid genus Eucosmophorus sp. Shothole borer species were identified using a DNA-based, high resolution melting assay. Trap data were compared to the predictions of a simple degree-day model, incorporating developmental data and several environmental parameters known to influence flight. Such as the time period representing most of flight activity in a day and temperature-dependent flight propensity. In stark contrast to the degree-day model which predicted the highest emergence, and by extension flight, of shothole borers during spring and summer (May to November), flight activity was actually lowest during these months, and instead, peaked during the winter (October to March). Abundance of the parasitoid wasp closely mirrored flight activity of the shothole borers. The mismatch of trapping and modeling data can have many causes, heavy precipitation and possibly cooperative brood care may suppress the dispersal behavior of the shothole borers during the summer.

Biotremology: Vibrational communication of Psylloidea.

Psyllids perform duetting via vibrational signals between genders that are important in pre-copulation species specific recognition. To date, vibrational behavior has been recorded in more than 100 species of psyllid, which is still only a small fraction of the ∼4000 described species. In this overview, we categorize the duet behavior into (1) reciprocal duets, (2) engaged duets, (3) three-way duets and (4) loose duets. In species with notable signal differences between genders, typically the male possesses a longer, more complex signal, which is emitted at a higher frequency compared to those of the females. Vibrational signals exhibit species specific characteristics that are taxonomically informative in some cases. Despite only a limited number of vibrational communication studies incorporating phylogenetic analyses, these reveal that signals can have reliable systematic information, but also that evolutionary and/or environmental factors may influence signal characteristics in ways that confound phylogenetic signal. Other possible strategies employed in mate finding in psyllids are chemical and visual signals. The most likely mechanism of vibrational signal production in psyllids involves stridulation between forewing and thorax. In some applied approaches, methods exploiting vibrational signals to disrupt mating may be effective to control psyllid pests in the field.

The Attractiveness of α-Copaene to Members of the Euwallacea fornicatus (Coleoptera: Curculionidae) Species Complex in California and Taiwan.

Species belonging to the Euwallacea fornicatus Eichhoff (Coleoptera: Scolytinae) species complex have invaded the continental U.S. since at least 2003. Three species of this complex are known to have established, two in California (E. fornicatus; and Euwallacea kuroshio), and a third in Florida (Euwallacea perbrevis). Their native ranges are spread across southern and southeast Asia. In Taiwan, all three species occur in sympatry. They attack healthy trees of widely varied species and cause severe damage and death to the trees. The attractant quercivorol is commonly used to promote their detection by passive trapping. Recent studies in Florida have shown that trapping of E. perbrevis can be further improved by adding a synergist, α-copaene, alongside the quercivorol lure. Thus, we were interested in testing the effectiveness of α-copaene for trapping the other invasive members of the complex in California and in an area of Taiwan where all three species co-occur. We found that α-copaene marginally enhanced the trapping of E. perbrevis in Taiwan, but had no effect on the trapping of E. fornicatus or E. kuroshio in either California or Taiwan. We conclude that any enhancing effect of α-copaene is specific to E. perbrevis. This highlights the economic importance of accurate species identification in developing and implementing an efficient, and yet cost-effective, monitoring program for the management of E. fornicatus and E. kuroshio in California and elsewhere.

Invasive and Quarantine Risks of Cacopsylla chinensis (Hemiptera: Psyllidae) in East Asia: Hybridization or Gene Flow Between Differentiated Lineages.

Pear psyllids are major pests and the causal agents of pear decline disease in orchards. In the past two decades, their outbreaks have raised issues pertaining to invasions and taxonomic identification of the dimorphic Cacopsylla chinensis (Yang and Li) in East Asia. The present study elucidated, as an aid to quarantine management, the invasive origins, differentiation history, and putative gene flow and hybridization between C. chinensis and its sibling species Cacopsylla jukyungi (Kwon). Analyses revealed that the ancestors of C. jukyungi might have diverged from C. chinensis approximately 3.5 million yr ago (Mya) and that differentiation between C. chinensis lineages I and II probably occurred 1.5 Mya. The known overlapping distribution of C. chinensis and C. jukyungi in northeastern China and the two C. chinensis lineages in the Bohai Rim region and Taiwan could be attributed to recent population expansion after the Last Glacial Maximum and/or anthropogenic activities. Analyses of the nuclear gene demonstrated that frequent gene flow between the two C. chinensis lineages and the paraphyletic relationship between C. chinensis and C. jukyungi might be caused by incomplete lineage sorting or hybridization events. On the basis of the current distribution, it is evident that C. jukyungi is not present in middle-southern China, whereas C. chinensis is not distributed in Japan and Korea. Preventing new invasions of Cacopsylla psyllids among geographic regions through the transportation of pear scions is thus pivotal in East Asia, particularly for the possible genetic exchanges among differentiated lineages after secondary invasion events.

Trioza turouguei sp. nov. (Hemiptera, Psylloidea, Triozidae), a new psyllid species from Taiwan inducing pea-shaped stem galls on Cinnamomum osmophloeum (Lauraceae), with notes on its galling biology.

Trioza turouguei sp. nov., a new species of jumping plant lice (Hemiptera, Triozidae) from Taiwan, is described and illustrated based on adults and immatures. The latter induce pea-shaped galls on the stems of Cinnamomum osmophloeum Kaneh. (Lauraceae). The gall phenology of the new species is described. A list of species of Triozidae associated with Cinnamomum in the Old World is provided. The following nomenclatorial acts are proposed: Trioza inflata Li, 1992 = Trioza xiangicamphorae Li, 1992, syn. nov.; Siphonaleyrodes formosanus Takahashi, 1932, stat. rev., is removed from synonymy with Trioza cinnamomi (Boselli, 1931).

Anomoneura taiwanica sp. nov. (Hemiptera, Psylloidea, Psyllidae), a new jumping plant-louse species from Taiwan associated with Morus australis (Moraceae).

Anomoneura taiwanica sp. nov. (Hemiptera, Psylloidea, Psyllidae, Psyllinae) is described based on samples from Taiwan that were previously misidentified as A. mori Schwarz, 1896. Morphological and genetic differences between the two species, as well as their distribution, are detailed and discussed. Comments on the pest status of Anomoneura spp. in East Asia are also provided.

Vibrational communication between a myrmecophilous butterfly Spindasis lohita (Lepidoptera: Lycaenidae) and its host ant Crematogaster rogenhoferi (Hymenoptera: Formicidae).

Ants are a dominant insect group in terrestrial ecosystems and many myrmecophilous species evolve to associate with ants to gain benefits. One iconic example is myrmecophilous butterflies that often produce ant-mimicking vibrational calls to modulate ant behaviors. Despite its popularity, empirical exploration of how butterflies utilize vibrational signals to communicate with ants is scarce. In this study, we reported that the myrmecophilous butterfly Spindasis lohita produce three types of larval calls and one type of pupal call, while its tending ant, Crematogaster rogenhoferi emit a single type of call. The results of discriminant analysis revealed that calls of the two species are quantitatively similar in their signal attributes; the potential role of butterfly calls are further confirmed by the playback experiments in which certain ant behaviors including antennation, aggregation, and guarding were induced when one of the butterfly calls was played to C. rogenhoferi workers. The findings in the current study represent the very first evidence on vibrational communication between Spindasis and Crematogaster and also imply that S. lohita may have been benefited from ant attendance due to the ability to produce similar calls of the ant C. rogenhoferi.

Vibrational behavior of psyllids (Hemiptera: Psylloidea): Functional morphology and mechanisms.

Vibrational behavior of psyllids was first documented more than six decades ago. Over the years, workers have postulated as to what the exact signal producing mechanisms of psyllids might be but the exact mechanism has remained elusive. The aim of this study is to determine the specific signal producing structures and mechanisms of the psyllids. Here we examine six hypotheses of signal producing mechanisms from both previous and current studies that include: wingbeat, wing-wing friction, wing-thorax friction, wing-leg friction, leg-abdomen friction, and axillary sclerite-thorax friction. Through selective removal of possible signal producing structures and measuring wing beat frequency with high speed videos, six hypotheses were tested. Extensive experiments were implemented on the species Macrohomotoma gladiata Kuwayama, while other species belonging to different families, i.e., Trioza sozanica (Boselli), Mesohomotoma camphorae Kuwayama, Cacopsylla oluanpiensis (Yang), and Cacopsylla tobirae (Miyatake) were also examined to determine the potential prevalence of each signal producing mechanism within the Psylloidea. Further, scanning electron microscope (SEM) was used to examine possible rubbing structures. The result of high speed video recordings showed that wingbeat frequency did not match the dominant frequency of vibrational signals, resulting in the rejection of wingbeat hypothesis. As for the selective removal experiments, the axillary sclerite-thorax friction hypothesis is accepted and wing-thorax friction hypothesis is supported partially, while others are rejected. The SEM showed that the secondary axillary sclerite of the forewing bears many protuberances that would be suitable for stridulation. In conclusion, the signal producing mechanism of psyllids may involve two sets of morphological structures. The first is stridulation between the axillary sclerite of the forewing and the mesothorax. The second is stridulation between the axillary cord and anal area of the forewing.