Search Results (4)

Some Pseudococcidae species interact with Coffea arabica’s roots and are associated with basidiomycete fungi. The fungal mycelium envelops the roots, which hinders their water and nutrient absorption. Combined with the feeding activity of the insects, this results in chlorosis, defoliation, and even plant death. Despite the significance of these interactions, they remain under-studied. To investigate the relationship between sporocarps found at the base of coffee trees, the cysts covering their roots, and the mealybug insects within them, samples of these three organisms—sporocarps, cysts, and mealybugs—were collected from 27 coffee plants across three farms in the departments of Norte de Santander and Quindío, Colombia. Fungi and cysts were identified by sequencing a nuclear gene region of the 28S large ribosomal subunit (28S rDNA) using the primers LSU200-F and LSU481-R. Fungal identification was further confirmed through classical taxonomy. Mealybugs were identified by sequencing a region of the mitochondrial gene Cytochrome C oxidase subunit I (COI) with CIF-CIR primers, corroborated through classical taxonomy. This study identified four fungal species associated with four species of Pseudococcidae. The fungus Phlebopus beniensis was associated with the mealybugs Pseudococcus elisae, Dysmicoccus neobrevipes, D. brevipes, and Pseudococcus nr. sociabilis. Phlebopus portentosus was linked to D. neobrevipes, while Xerophorus olivascens and Boletinellus rompelii were associated with other Pseudococcidae species. Additionally, the fungus Pseudolaccaria pachyphylla was found in coffee plants harboring mealybugs. These findings confirm the existence of specific associations between fungal species and mealybug insects that affect coffee plants. Full article

The mealybug can severely threaten agricultural and horticultural crops and has a widespread distribution in tropical regions, particularly in high-risk invasion areas such as Hainan, which is an important trade port with superior geographical conditions. Traditional morphological methods can no longer meet the requirements for the rapid and precise identification of different insect stages or debris. DNA barcoding has been used to establish efficient molecular identification tools. In this study, a multiplex polymerase chain reaction (mPCR) assay based on the cytochrome c oxidase subunit I (COI) gene was successfully constructed for the rapid identification of mealybugs. The 5′ end COI gene fragments of 12 mealybug species were amplified and sequenced. Furthermore, an mPCR assay was established to identify three common mealybug species in Hainan, namely Dysmicoccus neobrevipes, Maconellicoccus hirsutus, and Paracoccus marginatus. Condition optimization, sensitivity detection, and field sample testing results prove that the assay can identify the three target species through a single PCR amplification. A sample DNA concentration of as low as 0.1–1 ng/μL can be detected. Additionally, the assay in conjunction with barcode sequencing can identify mealybugs collected in the field, clarifying the distribution and host plants of 12 mealybug species commonly found in Hainan. Thus, the rapid identification of important mealybug species is realized. The establishment of this technology provides an economical and efficient molecular tool for the quarantine and monitoring of mealybugs in Hainan and other regions, which are essential for the detection, monitoring, and early warning of invasive organisms. Full article

Sisal purple leafroll disease (SPLD) is currently the most destructive disease affecting sisal in China, yet its aetiology remains unclear. In our previous research, it was verified to be associated with phytoplasmas, and nested PCR based on the 16S rRNA gene using universal primers R16mF2/R16mR1 followed by R16F2n/R16R2 was confirmed as the most effective molecular method for the detection of phytoplasmas associated with SPLD (SPLDaP). However, the method has a shortcoming of inaccuracy, for it could produce false positive results. To further manage the disease, accurate detection is needed. In this study, we developed a specific nested PCR assay using universal primers R16F2n/R16R2, followed by a set of primers designed on 16Sr gene sequences amplified from SPLDaP, nontarget bacteria from sisal plants, and other phytoplasma subgroups or groups. This established method is accurate, specific, and effective for detection of 16SrI group phytoplasma in sisal, and its sensitivity is up to 10 fg/μL of total DNA. It also minimized the false positive problem of nested PCR using universal primers R16mF2/R16mR1 followed by R16F2n/R16R2. This method was further used to verify the presence of phytoplasma in Dysmicoccusneobrevipes, and the results showed that D. neobrevipes could be infected by SPLDaP and thus could be a candidate for vector transmission assays. Full article

Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) is an important predator of the mealybug Dysmicoccus neobrevipes (Hemiptera: Pseudococcidae), a major pest of Agave sisalana in China. Limited reports on the efficacy of C. montrouzieri against D. neobrevipes are available. This study reports the predatory efficacy and functional response of C. montrouzieri against D. neobrevipes under laboratory conditions. The prey consumption rate per day of 4th instar larvae of C. montrouzieri feeding on 1st instar D. neobrevipes nymphs (241.3 mealybugs) was the highest among the different larval life stages of the beetle. For C. montrouzieri, the prey consumption per day of adult females (19.8 mealybugs) was significantly higher compared to males (15.2 mealybugs) when feeding on 3rd instar D. neobrevipes nymphs. The functional responses of C. montrouzieri on 1st and 2nd instar D. neobrevipes nymphs were determined as Holling type II. The search rates of C. montrouzieri 4th instar larvae towards the 1st and 2nd instar nymphs of D. neobrevipes were higher than those of the other beetle life stages. In addition, the handling times of 4th instar larvae were shorter than those of the other beetle life stages. The results from this study indicate that C. montrouzieri can be used as a predator of D. neobrevipes and, therefore, it should be evaluated further for use as a biocontrol agent in D. neobrevipes management programs. Full article