Phoretic mite infestations associated with Rhynchophorus palmarum (Coleoptera: Curculionidae) in southern California

The South American palm weevil, Rhynchophorus palmarum (Coleoptera: Curculionidae), established in San Diego County, California, USA sometime around 2014. Attached to the motile adults of this destructive palm pest, we identified three species of uropodine mites (Parasitiformes: Uropodina), Centrouropoda n. sp., Dinychus n. sp. and Fuscuropoda marginata. Two of these species, Centrouropoda n. sp. and Dinychus n. sp. are recorded for the first time in the USA and were likely introduced by R. palmarum. Several species of mites, primarily of Uropodina, have previously been recorded as phoretic on Rhynchophorus spp. In this study, we examined 3,035 adult R. palmarum trapped over a 2.5-year period, July 2016 to December 2018, and documented the presence of and species composition of phoretic mites and their relationship with weevil morphometrics (i.e., pronotum length and width). The presence and species composition of mites on weevil body parts changed over the survey period. No mites were found under weevil elytra in 2016 and mite prevalence under elytra increased over 2017–2018 due to an increased abundance of Centrouropoda n. sp per individual beetle. Mite occurrence levels were significantly correlated with reduced pronotum widths of male weevils only. The significance of this finding on male weevil fitness is unknown. Potential implications of phoretic mites on aspects of the invasion biology of R. palmarum are discussed.

Perspectives for Synergic Blends of Attractive Sources in South American Palm Weevil Mass Trapping: Waiting for the Red Palm Weevil Brazil Invasion

Coupling several natural and synthetic lures with aggregation pheromones from the palm weevils Rhynchophorus palmarum and R. ferrugineus reveals a synergy that results in an increase in pest captures. The combined attraction of pure pheromones, ethyl acetate, and decaying sweet and starchy plant tissue increases the net total of mass-trapped weevils. The 2018 entrance of the red palm weevil (RPW) into South America has threatened palm-product income in Brazil and other neighboring countries. The presence of the new A1 quarantine pest necessitates the review of all available options for a sustainable mass-trapping, monitoring, and control strategy to ultimately target both weevils with the same device. The effective lure-blend set for the mass-trapping system will attract weevils in baiting and contaminating stations for entomopathogenic fungi that the same weevils will spread.

The American Palm Cixiid, Haplaxius crudus

The American palm cixiid, Haplaxius crudus, is a common species of insect that belongs to the order Hemiptera, family Cixiidae. It is widespread and abundant in the state of Florida, but also occurs as far north as South Carolina and as far west as Texas. Furthermore, it is common throughout the Caribbean basin. This insect feeds on a wide variety of palm species as adults while the immature stages feed on a wide variety of grass species. This species is of high economic concern due to its ability to transmit the lethal yellowing (LY) phytoplasma (Howard and Thomas 1980) and is also the putative vector of lethal bronzing (LB) in Florida. Major revision of Howard, Forrest. 2007. “American Palm Cixiid, Myndus Crudus Van Duzee (Insecta: Hemiptera: Auchenorrhyncha: Fulgoroidea: Cixiidae)”. EDIS 2007 (10). https://journals.flvc.org/edis/article/view/116586. Revised 2015.

Haplaxius crudus (American palm cixiid).

Haplaxius crudus, commonly known as American palm cixiid, is native to the American tropics and subtropics. The species was first described from Jamaica in 1907 and is currently known from northern South America, Central America, certain islands of the Caribbean, and Florida and southern Texas in the USA. The adults of H. crudus feed mainly on palms, particularly coconut palms, while the nymphs feed mainly on grasses. The main economic impact of H. crudus is as a vector of coconut (or palm) lethal yellowing (LY) caused by Candidatus Phytoplasma palmae, a highly destructive disease that affects at least 37 species of palms, including coconut palm (Cocos nucifera) and date palm (Phoenix dactylifera). Control of LY is best achieved by the planting of resistant cultivars integrated with cultural measures such as ground cover management because chemical control of H. crudus is not practical. International trade in palms from LY-infected areas is prohibited because of the threat of the disease and vector spreading not only to coconuts and date palms, but also to palms that are important as ornamental plants or as local sources of food or fibre.

Paysandisia archon (South American palm borer).

P. archon is a Neotropical castniid species. It is not considered a pest in most of its native range, probably because it lives mainly on wild palm trees and not on crops; however, Houlbert (1918) and Bourquin (1933) reported that it had the potential to become a serious pest of palms. It was accidentally introduced to Europe from Argentina, as larvae hidden in imported palm trees, mostly Butia yatay and Trithrinax campestris. In Europe, where it is spreading rapidly, P. archon was first found in 2001 in Spain (Aguilar et al., 2001), France (Drescher and Dufay, 2001; Sarto i Monteys and Aguilar, 2001) and Italy (Espinosa et al., 2003; Riolo et al., 2004) and is considered an invasive species in these countries. It is already an invasive pest in France, Italy and Spain, where serious damage and plant mortality has been reported (1000 palm trees have been destroyed) and has become a pest in Buenos Aires, where it was introduced from north-east Argentina (Sarto i Monteys and Aguilar, 2005). The moth is currently listed in the EPPO A2 List (n. 338) of 'Pests recommended for regulation as quarantine pests' (OEPP/EPPO, 2008) and in European Phytosanitary Legislation in AnnexII/Part A/Section II (COMMISSION DIRECTIVE 2009/7/EC of 10 February 2009 amending Annexes I, II, IV and V to Council Directive 2000/29/EC on protective measures against the introduction into the Community of organisms harmful to plants or plant products and against their spread within the Community).

Antennal transcriptome sequencing and identification of candidate chemoreceptor proteins from an invasive pest, the American palm weevil, Rhynchophorus palmarum

For decades, the American palm weevil (APW), Rhynchophorus palmarum, has been a threat to coconut and oil palm production in the Americas. It has recently spread towards North America, endangering ornamental palms, and the expanding date palm production. Its behavior presents several parallelisms with a closely related species, R. ferrugineus, the red palm weevil (RPW), which is the biggest threat to palms in Asia and Europe. For both species, semiochemicals have been used for management. However, their control is far from complete. We generated an adult antennal transcriptome from APW and annotated chemosensory related gene families to obtain a better understanding of these species' olfaction mechanism. We identified unigenes encoding 37 odorant-binding proteins (OBPs), ten chemosensory proteins (CSPs), four sensory neuron membrane proteins (SNMPs), seven gustatory receptors (GRs), 63 odorant receptors (ORs), and 28 ionotropic receptors (IRs). Noticeably, we find out the R. ferrugineus pheromone-binding protein and pheromone receptor orthologs from R. palmarum. Candidate genes identified and annotated in this study allow us to compare these palm weevils' chemosensory gene sets. Most importantly, this study provides the foundation for functional studies that could materialize as novel pest management strategies.

Quantification of the Life Time Flight Capabilities of the South American Palm Weevil, Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae)

The life time flight capabilities of an invasive palm pest, Rhynchophorus palmarum, were assessed using flight mill assays under controlled conditions in the laboratory. A total of 101 weevils were used for experiments and subjected to repeat flight assays. A total of 17 flight trials were run, of which the first 14 provided useful data prior to weevil death. Male and female weevils exhibited a strong capacity for repeat long distance flights. Flight metrics of interest were not affected by weevil sex or mating status. Cumulative lifetime flight distances for male and female R. palmarum averaged ~268 km and ~220 km, respectively. A maximum lifetime cumulative flight distance of ~758 km and ~806 km was recorded for one male of unknown mating status and one unmated female weevil, respectively. Dispersal data for individual flights (i.e., trials 1 through 9, 10–14 combined) and all flight trial data (i.e., flights 1–14 combined) exhibited platykurtic distributions. The results presented here may have important implications for modeling the spread of this invasive pest and for the development of monitoring and management plans.

The Complete Mitochondrial Genome of The American Palm Cixiid, Haplaxius Crudus (Hemiptera: Cixiidae)

The authors have withdrawn this preprint due to author disagreement.

The Complete Mitochondrial Genome of The American Palm Cixiid, Haplaxius Crudus (Hemiptera: Cixiidae)

Background Haplaxius crudus (the American palm cixiid) is a major insect pest of various economically important palms. H. crudus persists in tropical and subtropical regions where it is known to transmit the lethal yellowing (LY) phytoplasma. It has been implicated as the putative vector of Lethal bronzing (LB), a destructive phytoplasma-induced palm disease affecting over 16 species of ornamental and agricultural palms. To date, no mitochondrial genomes for species in the family Cixiidae are sequenced. Analysis of mitochondrial DNA sequences of H. crudus has proven useful for proper species diagnosis and population studies which could benefit management programs aimed at moving infective insects. These analyses describe the first mitochondrial genome from the American palm cixiid, Haplaxius crudus and an insect in the family Cixiidae. Results In this study, the complete mitochondrial genome of H. crudus was assembled and characterized from PacBio Sequel II long sequencing reads using the University of Florida’s HiPerGator supercomputer. The circular mitogenome of H. crudus is 15,845 bp long and encodes 37 mitochondrial genes (including 13 protein coding genes (PCGs), 22 tRNAs and 2 rRNAs) in addition to a putative non-coding internal control region. The nucleotide composition of H. crudus is asymmetric with a bias toward A and T (44.8 %A, 13.4 %C, 8.5 %G and 33.3 %T). Protein-coding genes (PCGs) possess the standard invertebrate mitochondrial start codons with few exceptions while the gene content and order of the H. crudus mitogenome is identical to most completely sequenced insect mitochondrial genomes. Phylogenetic analysis indicated that H. crudus is closely related to the planthopper in the family Delphacidae: N. lugens, which is the established sister group to Cixiidae. Conclusions Our studies have elucidated the first reference mitochondrial genome of Haplaxius crudus, providing structural analysis of the circular genome and encoded gene regions. The present results provide future opportunities to assess the diversity and origin of H. crudus. This study demonstrates the significance of understanding the structure and function of the mitochondrial genome to inform effective diagnostic and management strategies for insect pests.