Disrupting Mating Behavior of Diaphorina citri (Liviidae)

Wing buzzing as a mechanism for generating vibrational signals in psyllids (Hemiptera: Psylloidea)

Psyllids, or jumping plant lice (Hemiptera: Sternorrhyncha: Psylloidea), are a group of small phytophagous insects that include some important pests of crops worldwide. Sexual communication of psyllids occurs via vibrations transmitted through host plants, which play an important role in mate recognition and localization. The signals are species-specific and can be used to aid in psyllid taxonomy and pest control. Several hypotheses have been proposed for the mechanism that generates these vibrations, of which stridulation, that is, friction between parts of the forewing and thorax, has received the most attention. We have investigated vibrational communication in the European pear psyllid species Cacopsylla pyrisuga (Foerster, 1848) using laser vibrometry and high-speed video recording, to directly observe the movements associated with signal production. We describe for the first time the basic characteristics of the signals and signal emission of this species. Based on observations and analysis of the video recordings using a point-tracking algorithm, and their comparison with laser vibrometer recordings, we argue that males of C. pyrisuga produce the vibrations primarily by wing buzzing, that is, tremulation that does not involve friction between the wings and thorax. Comparing observed signal properties with previously published data, we predict that wing buzzing is the main mechanism of signal production in all vibrating psyllids.

Evidence of Receptivity to Vibroacoustic Stimuli in the Spotted Lanternfly Lycorma delicatula (Hemiptera: Fulgoridae)

The spotted lanternfly Lycorma delicatula White (Hemiptera: Fulgoridae) is a polyphagous insect pest that invaded the United States in 2014, in Berks County, Pennsylvania. It has since spread to several northeastern states and poses a significant threat to northeastern grape production. Most studied species of Hemiptera are known to communicate intraspecifically using some form of substrate-borne vibrational signals, although such behavior has not yet been reported in L. delicatula. This report demonstrates that adult and fourth-instar L. delicatula were attracted towards broadcasts of 60-Hz vibroacoustic stimuli directed to a laboratory arena and test substrate, which suggests that both adults and fourth instar nymphs can perceive and respond to vibrational stimuli.

The Development and Evaluation of Insect Traps for the Asian Citrus Psyllid, Diaphorina citri (Hemiptera: Psyllidae), Vector of Citrus Huanglongbing

Simple Summary

Citrus cultivation is affected in many parts of the world because of a devastating disease, huanglongbing (HLB) or citrus greening. In Florida, nearly all commercial citrus is compromised due to HLB, and the disease has spread to other citrus-growing regions of the United States, California and Texas. In California, testing Asian citrus psyllids (ACPs) for the HLB pathogen has been an essential part of integrated pest management. ACP and HLB surveys are essential for disease management in areas where HLB is not widespread. We developed improved ACP traps that can be deployed in the field along with the standard yellow sticky traps. The reusable traps were designed with Rhinoceros computer software and a 3D printer. These traps can be deployed for several months and provide a dynamic sampling mechanism for an improved disease survey strategy. In the present study, ACPs from the 3D-printed traps are collected in a preservative and appear suitable for HLB testing. The evaluation of traps in Florida and California under laboratory, greenhouse, and field conditions indicates that the 3D-printed traps can capture ACPs with about the same efficiency as the sticky traps. They are easy to handle and provide an important field tool for HLB management.

Abstract

Citrus huanglongbing (HLB) is a severe problem for citrus cultivation. The disease management programs benefit from improved field tools suitable for surveying the ACP vector (Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae)) and the associated pathogen. In the present study, we utilize three-dimensional (3D) printers and design tools to develop traps that can capture and preserve ACPs. Three novel, 3D-printed traps were designed and evaluated: stem trap, and cylinder traps 1 and 2. The traps and yellow sticky cards were deployed weekly for 8 months in 2 non-commercial citrus groves in Florida; in California, the traps were evaluated for 12 months in field cages and 4 citrus groves. The stem traps captured lower numbers of ACPs at all experimental sites compared to the cylinder traps. Capture rates in the cylinder traps were comparable to the sticky trap, making the device a viable tool for monitoring field ACPs. The two main advantages of using the reusable 3D traps over standard methods of ACP and HLB surveys include dynamic sampling that can be conducted year-round and the capture of ACPs that can be preserved and tested. Improved trapping may facilitate quick management decisions and mitigate HLB.

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.

Identification of putative abdominal vibration-related genes through transcriptome analyses in the brown planthopper (Nilaparvata lugens)

The sexually mature female brown planthoppers (BPHs) send out abdominal vibration (AV) signals through the rice so that the males can obtain intraspecific, gender, and localization information to prepare for mating. Destroying vibration signals is an alternative biological method for pest control. However, the regulatory mechanism of AV in female BPHs remains elusive, which presents an obstacle to pest control. We observed that before mating female BHPs emitted abdominal vibration signals that disappeared immediately after mating and reappeared after 6 days. Therefore, ovarian and brain samples of female BPHs from Unmated-6h⁺ (with AV), Mated-6h^- (without AV) and Mated-6d⁺ (with AV) individuals were collected for transcript analyses. By transcriptional sequencing analyses, 33 candidate genes that might involve in the regulation of female AV were obtained. After selecting 4 candidate genes of them for verification by RNA interference (RNAi), it was found that interference of juvenile hormone binding protein (JHBP) could greatly reduce the probability and frequency of AV for female BPHs. In general, this study identified AV-related candidate genes in female BPHs through transcriptome analyses and provided an important basis for future research on pest control in BPHs.

Vibrational communication and mating behavior of the greenhouse whitefly Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae)

The greenhouse whitefly (GW), Trialeurodes vaporariorum is considered one of the most harmful insect pests in greenhouses worldwide. The GW mating behavior has been partially investigated and its vibrational communication is only in part known. A deeper knowledge of its intraspecific communication is required to evaluate the applicability of control methods based on techniques of behavioral manipulation. In this study, for the first time, we provided a detailed ethogram of the GW mating behavior and we characterized the vibrational signals emitted during the process of pair formation. We characterized two types of male vibrational emissions ("chirp" and "pulses"), differently arranged according to the behavioral stage to form stage-specific signals, and a previously undescribed Male Rivalry Signal. We recorded and characterized two new female signals: The Female Responding Signal and the Female Rejective Signal. The mating behavior of GW can be divided into six different stages that we named "call", "alternated duet", "courtship", "overlapped duet", "mating", "failed mating attempt". The analysis performed with the Markovian behavioral transition matrix showed that the "courtship" is the key stage in which male exhibits its quality and can lead to the "overlapped duet" stage. The latter is strictly associated to the female acceptance and therefore it plays a crucial role to achieve mating success. Based on our findings, we consider the use of vibrational playbacks interfering with GW mating communication a promising option for pest control in greenhouses. We discuss the possibility to start a research program of behavioral manipulation to control the populations of GW.

Inhibitory Copulation Effect of Vibrational Rival Female Signals of Three Stink Bug Species as a Tool for Mating Disruption

Simple Summary

In this work, we investigated the effects of conspecific female rival signals in vibratory communication and mating behavior of three species of stink bugs. In the presence of rival female signals, as noisy background vibrations, couples (a male and a female) of the three species showed negative effects in their sexual vibratory communication that resulted in reduced mating and copulation in relation to pairs not exposed to rival signals. The results suggest that female rival signals could be used to disrupt mating and may be a tool for stink bug management by reducing their population increase.

Abstract

Stink bugs are major pests in diverse crops around the world. Pest management strategies based on insect behavioral manipulation could help to develop biorational management strategies of stink bugs. Insect mating disruption using vibratory signals is an approach with high potential for pest management. The objective of this work was to investigate the effect of conspecific female rival signals on the mating behavior and copulation of three stink bug species to establish their potential for mating disruption. Previously recorded female rival signals were played back to bean plants where pairs of the Neotropical brown stink bug, Euschistus heros, and two green stink bugs, Chinavia ubica and Chinavia impicticornis were placed. Vibratory communication and mating behavior were recorded for each pair throughout the experimental time (20 min). Female rival signals show a disrupting effect on the reproductive behavior of three conspecific investigated stink bug species. This effect was more clearly expressed in E. heros and C. ubica than in C. impicticornis. The likelihood of copulating in pairs placed on control plants, without rival signals, increased 29.41 times in E. heros, 4.6 times in C. ubica and 1.71 times in C. impicticornis. However, in the last case, the effect of female rivalry signals in copulation was not significant. The effect of mating disruption of female rival signals of the three stink bug species may originate from the observed reduction in specific vibratory communication signals emitted, which influences the duet formation and further development of different phases of mating behavior. Our results suggest that female rival signals have potential for application in manipulation and disruption of mating behavior of stink bugs. Further work needs to focus on the effects of female rival signals used in long duration experiments and also their interactions with chemical communication of stink bugs.

Performance of a Low-Cost Acoustic Insect Detector System with Sitophilus oryzae (Coleoptera: Curculionidae) in Stored Grain and Tribolium castaneum (Coleoptera: Tenebrionidae) in Flour

Reduction of postharvest losses is gaining increased priority in warm regions where insect infestation may cause rapid deterioration of staple commodities. Acoustic detection can be used to assess the likelihood of insect infestations in bags of grain, flour, and other commodities that are stored in small holdings in developing countries, enabling rapid targeting of treatments. A portable postharvest insect detection system was developed with the goal to provide low-cost capability to acoustically assess infestations in small-scale storage facilities. Electret microphones input pest insect sounds to a 32-bit microcontroller platform that digitized and stored the signals on a digital memory card transferable to a portable laptop computer. The insect sounds then were analyzed by custom-written software that matched their spectra to those of known pests. Infestations of Sitophilus oryzae (L) in 2.6-kg bags could be detected down to densities of 1.9 adults/kg in grain and Tribolium castaneum (Herbst) down to 3.8 adults/kg in flour in laboratory settings. Also, differences in the rates of sounds per insect in treatments with different numbers ranging from 5 to 50 insects suggested that the sound rates of adults of different species at different population densities may be noticeably affected by aggregation pheromones or other behaviorally active semiochemicals. Further testing is needed but previous experience with acoustic detection systems suggests that the prototype has potential for use in small storage facilities where early detection of infestations is difficult to provide.

Can Vibrational Playbacks Disrupt Mating or Influence Other Relevant Behaviours in Bactericera cockerelli (Triozidae: Hemiptera)?

Behaviours of insects can be manipulated by transmitting vibrational signals to host plants in order to develop pest management techniques. Bactericera cockerelli is an important pest and uses vibrations for mate-finding. In order to design a future control strategy for B. cockerelli, three different bioassays were performed to assess whether vibrational signals could affect relevant behaviours. Single males or pairs were treated with a female playback in test 1 and 2, respectively. In test 3, mixed sex groups received either different disturbance playbacks. The use of a female playback significantly reduced the mating success of males, since they were attracted towards the source of the stimulus. Moreover, test 2 revealed that B. cockerelli females are competitive, since they used their signals to cover the playback and to duet with males, while in test 3, the disturbance playback, consisting of broadband noises significantly reduced male signalling activity. However, none of the treatments of test 3 negatively affected the mating success of males, which tended to mount the other conspecifics present on the same leaf. The role of vibrations in sexual communication and their potential application as control technique for B. cockerelli are discussed as well.

Effects of Diaphorina citri Population Density on Daily Timing of Vibrational Communication Calls: Potential Benefits in Finding Forage

Adult Diaphorina citri (ACP) use visual and chemical cues to locate young citrus flush shoots on which they forage and oviposit, and they use vibrational communication duetting calls as cues to help locate mates. For individual pairs, calling and mating usually peaks between 10:00 and 15:00. To explore whether call rates (calls/h) are affected by interactions with nearby conspecifics, rates were compared in small citrus trees on which either 5 or 25 ACP female and male pairs had been released at 17:00 for later recording from sunrise (06:00) to 22:00. Final ACP locations were noted 40 h after release. Call rates were similar in both treatments during normal mating hours. However, rates were significantly higher for low- than high-density treatments between 06:00 and 10:00, which suggests calling during this period may be affected by conspecific density. Both sexes aggregated on flush at both densities. We discuss the potential that ACP producing calls near sunrise, outside of normal mating hours, might benefit from gains in reproductive fitness in low-density contexts if they call not only to locate mates but also to locate preferred flush—in which case, co-opting of vibrations to disrupt both mating and foraging may be feasible.

Vibrational mating disruption of Empoasca vitis by natural or artificial disturbance noises

BACKGROUND

The green leafhopper, Empoasca vitis, is a polyphagous pest of grapevine and tea plants. To date population density is controlled primarily by insecticides and there is a demand for more sustainable controls. To develop a vibrational mating disruption method, the natural occurrence of a 'disruptive signal' was investigated. Further, the efficacy of natural and artificial 'disruptive signals' was determined.

RESULTS

With behavioral trials we described male rivalry and recorded a species-specific disruptive signal (DP). The DP, a single pulse overlapping the competitor male call, interfered with the rival's ability to locate the female. Laboratory playback disruption trials revealed that the pair formation process was prevented by artificial disturbance noises that included the following features: E. vitis DP, Scaphoideus titanus disturbance noise, and a pure tone (250 Hz). Among these, the pure tone was most efficient at preventing mating.

CONCLUSION

Results support development of a vibrational mating disruption method as a control strategy for E. vitis. To simultaneously disrupt the mating of E. vitis and S. titanus, the possibility of applying the S. titanus disturbance noise combined with the pure tone is discussed. © 2018 Society of Chemical Industry.

Mating disruption of Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) by playback of vibrational signals in vineyard trellis

BACKGROUND

Glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) is an important vector of the bacterium Xylella fastidiosa, the causal agent of Pierce's disease of grapevine. Area-wide insecticide applications have suppressed GWSS populations for ∼ 25 years, but reduced levels of insecticide susceptibility have been reported. Therefore, alternative methods of control are needed. Objectives of this study were to evaluate the efficacy of playback of vibrational mating communication signals for disrupting mating of GWSS in a natural vineyard setting and to evaluate spectral properties of signal transmission through vineyard trellis.

RESULTS

Playback reduced mating of GWSS on grapevines. A total of 28 (of 134) male-female pairs mated in the control treatment (silence) and only one (of 134) pair mated when treated with the vibrational signal playback. Playback of vibrational signals through vineyard trellis was affected by distance from the signal source, with frequency composition being the highest at the source and lowest on vines positioned away from the source. Frequency composition in canes housing test insects decreased exponentially as distance from the source increased, whereas the relative amplitude of analyzed frequencies decreased linearly.

CONCLUSION

Although further studies are needed prior to method implementation, data from this study continue to support integration of vibrational mating disruption with current methods to suppress GWSS populations. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Putative sex pheromone of the Asian citrus psyllid, Diaphorina citri, breaks down into an attractant

Under laboratory conditions, mating activity in Asian citrus psyllid (ACP) started 4 days after emergence, peaked at day 7, and showed a clear window of activity starting 8 h into the photophase and extending through the first hour of the scotophase. We confirmed that ACP males are attracted to emanations from conspecific females. Traps loaded with a candidate compound enriched with female extract, lignoceryl acetate (24Ac), at various doses were active only after being deployed for several weeks in the field, suggesting that a degradation product, not the test compound, was the active ingredient(s). Lignocerol, a possible product of 24Ac degradation, was not active, whereas acetic acid, another possible degradation product, was found in the airborne volatile collections from lures matured under field conditions and detected in higher amounts in volatiles collected from females at the peak of mating activity than in male samples. Acetic acid elicited dose-dependent electroantennographic responses and attracted ACP males, but not females, in Y-type and 4-way olfactometers. Field tests showed that acetic acid-baited traps captured significantly more males than control traps. Surprisingly, captures of females in acetic acid-baited traps were also higher than in control traps, possibly because of physical stimuli emitted by captured males.

Design of a candidate vibrational signal for mating disruption against the glassy-winged sharpshooter, Homalodisca vitripennis

BACKGROUND

The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, is an important pest of grapevines due to its ability to transmit Xylella fastidiosa, the causal agent of Pierce's disease. GWSS mating communication is based on vibrational signals; therefore, vibrational mating disruption could be an alternative to insecticides for suppression of the GWSS population. Our objectives were to identify spectral features of the female signal that elicit male signaling, design disruptive signals able to alter male perception and acceptance of a female, and determine the signal intensity required for future field applications.

RESULTS

Male responses to playback of modified female signals were significantly reduced by 60-75% when part of the female signal spectral components above or below 400 Hz were deleted. Playback bioassays showed that transmission of an 80 Hz pure frequency tone to plants completely suppressed male signaling to female signal playback, even if the disruptive signal amplitude was 10 dB lower than the female signal playback.

CONCLUSION

Although the mechanism underlying cessation of male signaling activity in the presence of disruption is not yet understood, results suggest that an 80 Hz vibrational signal should be tested in laboratory and field experiments to assess its efficacy in disrupting mating of GWSS. © 2017 Society of Chemical Industry.