Haplaxius crudus (Hemiptera: Cixiidae) Transmits the Lethal Yellowing Phytoplasmas, 16SrIV, to Pritchardia pacifica Seem. & H.Wendl (Arecaceae) in Yucatan, Mexico

A new species of Oecleus (Hemiptera: Auchenorrhyncha: Fulgoromorpha: Cixiidae) from the Osa Peninsula in Costa Rica

Recent palm survey work in Costa Rica focusing on planthoppers has resulted in the discovery of several new taxa, primarily in Cixiidae and Derbidae. In addition to sampling palms directly, light trapping has been utilized to collect a broader range of planthoppers that may not be found on palms. During a light trapping event at the Cotinga Biological station on the Osa peninsula in Costa Rica, a cixiid was collected and subsequently determined to be an unidentified species in the genus Oecleus Stl. Herein, the novel taxon, Oecleus urru sp. n., is described. Supplemental molecular data for the barcoding region (5 half) of the cytochrome c oxidase subunit I (COI) gene, 18S rRNA gene, and histone 3 (H3) gene is provided to support the placement of the novel taxon in the genus Oecleus.

Acquisition and Transmission of the Lethal Bronzing Phytoplasma by Haplaxius crudus Using Infected Palm Spear Leaves and Artificial Feeding Media

Lethal bronzing (LB) is a fatal palm disease caused by the phytoplasma 'Candidatus Phytoplasma aculeata'. This disease causes significant economic losses in palm industries and landscapes. The American palm cixiid, Haplaxius crudus, recently was identified as the vector of the phytoplasma. However, knowledge about LB phytoplasma transmission is limited due to the lack of a method to generate phytoplasma-infected insects in the laboratory. In this study, the acquisition and transmission of the LB phytoplasma by H. crudus were investigated. Successful acquisitions of the phytoplasma by H. crudus were observed at 2 days acquisition access period on LB-infected palm spear leaves. Analyses revealed increased phytoplasma infection rates of H. crudus with longer acquisition access periods and latent periods. A significantly higher phytoplasma infection rate was shown after various acquisition access periods and latent periods than the infection rate of the field-collected H. crudus population. Transmission of the phytoplasma from LB-infected spear leaves to sucrose media by H. crudus also was observed using digital PCR assays. These results further support the vector status of H. crudus and offer valuable information to understand LB phytoplasma transmission. Additionally, these results generate a critical baseline for future LB phytoplasma-vector research by providing a way to generate vectors with high phytoplasma infection rates in the laboratory setting.

Detection of 16SrIV-A phytoplasma DNA in Colpoptera sp. (Hemiptera: Nogodinidae) insects in Yucatan Peninsula, Mexico

Lethal yellowing (LY) is a disease that affects coconut and other palm species. It is associated to phytoplasmas of the group 16SrIV and the only reported insect vector for this pathogen so far is Haplaxius crudus. H. crudus is present in Mexico and has been associated to 16SrIV phytoplasmas, however, it was not detectable during a LY outbreak in the coast of Yucatan, Mexico, suggesting the existence of other vector species. To test this hypothesis a survey of insects was carried out and a total of 3074 insects were captured during a year of monthly sampling. Ten taxonomic orders were identified in this sample, Hemiptera being the most abundant (N=2094), and these were classified into nine families. The leafhopper Colpoptera sp. from to the Nogodinidae family was de most abundant representing 56% of the total number of insects sampled and 23% of these samples resulted positive for LY phytoplasma by PCR detection. The BLAST comparison, virtual RFLP and phylogenetic analyses of the sequenced amplicons relate the detected phytoplasma to the subgroup 16SrIV-A. The findings presented herein suggest that Colpoptera sp. could be considered as a new putative vector of the LY-causing phytoplasmas in Mexico and a candidate for further research.

In vitro transmission of 16SrIV phytoplasmas to coconut plants by Haplaxius crudus in Yucatan, Mexico

The coconut palm is an important crop worldwide. In America, it is affected by lethal yellowing (LY) disease, associated with the presence of 16SrIV ribosomal group phytoplasmas. Studies in Florida using insect-proof cages indicate Haplaxius crudus as a vector of LY phytoplasmas to palm species, including coconut. Here, an in vitro transmission system was used to verify that H. crudus collected in Yucatan, Mexico, transmit 16SrIV phytoplasmas to coconut. Three transmission trials were carried out using micropropagated coconut plants. In each trial, at least one plant was positive to 16SrIV phytoplasmas. In total, there were 4 positive plants out of 34 exposed to insects, and the phytoplasma presence was detected in root, stem, and leaf tissues. The phytoplasmas identified were 16SrIV-A and 16SrIV-D, both found in both plants and insects. In each assay where a plant was positive for either 16SrIV-A or 16SrIV-D, the same phytoplasma was present in the insect or insects used in this assay. This is the first demonstration of transmission of LY phytoplasmas to coconut plants by H. crudus in Mexico and with an in vitro system.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03069-z.

Effects of Lethal Bronzing Disease, Palm Height, and Temperature on Abundance and Monitoring of Haplaxius crudus

Insect vector feeding preference and behavior play important roles in pathogen transmission, especially for pathogens that solely rely on insect vector transmission. This study aims to examine the effects of the 16SrIV-D phytoplasma, the causal agent of lethal bronzing (LB) disease of palms, on associated auchenorrhynchan insects. The numbers of auchenorrhynchans collected during weekly surveys during a yearlong study using yellow sticky traps were analyzed. The cumulative number of H. crudus was 4.5 times greater on phytoplasma-infected relative to non-infected palms. Other auchenorrhynchans showed no difference between phytoplasma-infected and non-infected palms or were greater on non-infected rather than on infected palms. Furthermore, we examined the effects of LB, palm height, temperature, and the interactive effects of these factors on H. crudus abundance. When the palms were infected with LB, at low temperature, H. crudus was more abundant on shorter than taller palms; however, H. crudus was more abundant on taller than shorter palms at the median and higher temperatures. These results may indicate that H. crudus prefers LB-infected palms over non-infected palms. The interactive effects of LB, palm heights, and temperature further suggest that vector monitoring and disease management should be optimized according to seasonal variation in temperature.