Introduction. The mealybug (Hemiptera: Pseudococcidae) is known for its importance at commercial level, since it can affect all stages of development on agricultural crops and cause harvest losses. The name is derived from the secretion of white wax that females present around of the body. Objective. The aim of this bibliographical review was to synthesize the main aspects related to taxonomy, biology, damage to host plants, geographic distribution and the impact of the mealybug on Musaceae. Development. Can be transported during the shipment of the crop to be exported, slipping away from the phytosanitary regulations, with a high risk of introduction as a pest of economically important crops to other countries. To identify the individual at species level, adult females are used, males and nymphs lack of the necessary characteristics for their classification. Within the Pseudococcidae family, Pseudococcus elisae (Borchsenius) stands out as one of the first species identified in the Musaceae crop. The State Phytosanitary Service of the Ministry of Agriculture and Livestock, declared by the end of 2013 and the beginning of 2014, a phytosanitary emergency due to the increase of P. elisae, however there are records of up to twenty-four species as vectors of banana streak virus, belonging to fourteen genera with different origins. The feeding period where the transmission, occurs, is associated with the mealybug species and the environmental conditions. They inject toxins, the sugary liquids are secreted from the phloem of the plant, which serves as a means for the establishment of fungi on the surface of the attacked organsthat cause several physiological damages to the crop. Conclusion. It is of great importance to consider related aspects to taxonomy, biology, host plants and the geographical distribution of the different species of the mealybug to develop appropriate strategies that control the pest propagation.

El objetivo de este trabajo fue evaluar a nivel de invernadero el efecto de vermicompost sobre la incidencia y severidad de Phytophthora capcisi en plantas de chile (Capsicum annuum). Esta investigación se realizó entre febrero y marzo del 2012 en el Centro de Investigaciones Agronómicas, Sabanilla, San José, Costa Rica. Se utilizó un diseño completamente al azar con cuatro repeticiones y ocho plantas por unidad experimental en un arreglo factorial con los factores de dosis (0, 25% y 50% v/v vermicompost:suelo) e inoculación (0 y 500 zoosporas por gramo de suelo). Se trasplantaron plántulas de 35 días, que fueron inoculadas dos semanas después del trasplante. La aplicación de vermicompost provocó un aumento significativo del peso fresco foliar y del peso seco foliar y radical; a mayor dosis, mayor fue el incremento. Las plantas de todos los tratamientos que incluyeron inoculación con P. capsici presentaron síntomas de la enfermedad en la raíz. Los valores de incidencia y severidad fueron mayores para el tratamiento con 50% de abono. En este tratamiento se presentaron síntomas de marchitez. La ausencia de diferencias en las variables de peso fresco y seco entre los tratamientos inoculados y sin inocular, a los que se adicionó abono al 25%, sugiere que esta dosis podría compensar el daño causado por el patógeno. Se observó una menor concentración de nutrimentos en los tejidos de las plantas inoculadas lo que indica que el daño causado a la raíz pudo haber afectado la adquisición de nutrimentos.

Celery (Apium graveolens var. dulce) is affected by several plant diseases, such as Fusarium oxysporum f. sp. apii (Foa). Four Foa races have been found in the US. The goals of this study were to determine which races are present in Costa Rica and to quantify the tolerance of the imported commercial cultivars of celery produced in the country. Isolates from 125 symptomatic celery plants from three different geographical locations were analyzed, 65 of which were selected for phylogenetic analysis. All isolates presented a short sequence of five nucleotides that differentiates Foa race 3 in the IGS rDNA region. Three different haplotypes closely related to race 3 were found, which were highly virulent, produced great losses, and affected all cultivars (resistant to races 2 and 4) of imported commercial celery. Additionally, five different cultivars of celery were evaluated against seven pathogen isolates identified as race 3 in greenhouse conditions. Two of the cultivars showed significantly less chlorosis, wilting, mortality, and higher fresh weight. Most of the Foa isolates significantly increased chlorosis, wilting, and mortality compared to non-inoculated control. Celery producers in Costa Rica lack access to seeds resistant to the Foa race 3 present in the country.

Introduction. Common beans (Phaseolus vulgaris L.) and peanuts (Arachis hypogaea L.) are legumes, widely consumed in developing countries. However, those grains could be contaminated with Aspergillus, a genus of fungus that includes mycotoxin-producing species. Objective. To identify the Aspergillus species that colonize the grains of common beans and peanuts in Costa Rica and to identify atoxigenic strains of A. flavus. Materials and methods. Eighty-three samples of common bean grains and nineteen samples of peanuts were collected during the years 2019 and 2020 in regions where those grains are produced in Costa Rica. All samples were used to isolate and identify Aspergillus species by partial sequences of ITS (internal transcribed spacer) and cmd (calmodulin) genes. Atoxigenic strains of A. flavus were also identified by chemical and molecular methods. Results. 46 % and 32 % of the collected common beans and peanuts samples, respectively, were contaminated with Aspergillus spp. In common beans, 85 isolates of Aspergillus were obtained, most of them belonging to A. flavus and A. niger species. Most of the A. flavus isolates were obtained from the Cabécar (fifteen isolates) and Nambí (seven isolates) common bean varieties, while A. niger was mostly isolated from the Cabécar variety (eleven isolates). In the case of peanuts, thirteen isolates were obtained, most of them identified as A. niger. No atoxigenic strains were found in peanuts, however, in common beans, five strains of A. flavus with this characteristic were found. Conclusions. The present study demonstrated the diversity of Aspergillus species that colonize the grains of common beans and peanuts in Costa Rica. Most of the species isolated are producers of mycotoxins that cause adverse effects on human health.

Introduction. The Laboratory of Molecular Techniques applied to Phytoprotection (LTM), Crop Protection Research Center, Universidad de Costa Rica; receives agricultural, ornamental, and forest crops for the identification of microorganisms using molecular techniques. Objective. To identify pathogenic and non-pathogenic fungi, oomycetes, and protozoa in agricultural, ornamental, and forest crops in Costa Rica by molecular methods. Materials and methods. Between 2009 and 2018, plant parts (root, stem, leaves, fruits) and other materials such as water, substrate, and soil were received. A total of 805 isolates were obtained for identification of microorganisms by DNA extraction techniques, end-time and real-time PCR and sequencing using molecular markers. Results. The sequencing allowed the identification of a total of 154 species of fungi, 6 oomycetes, and 1 protozoa. Among the fungi identified, genera such as Fusarium predominated with fourteen different species, followed by Colletotrichum and Aspergillus with eleven species identified for each one. In the oomycetes, species of the genus Phytophthora prevailed, and within the protozoa the genus Plasmodiophora. In addition, the scientific references supporting the presence of the microorganisms identified in each particular crop have been included in the information. Conclusion. It was possible to identify by molecular techniques pathogenic and non-pathogenic fungi, oomycetes and protozoa species isolated from different agricultural, ornamental and forest crops in Costa Rica.

Tomato is one of the most important vegetable crops in Costa Rica, where favorable environmental conditions enabled year-round production but also promote bacterial diseases. In recent years, pith necrosis has been frequently observed; nevertheless, the causal agents remain unidentified in the country. This study evaluated bacteria associated with symptomatic plants collected in the Central Valley of Costa Rica. From 32 plants, 61 bacterial isolates were obtained, described morphologically, and characterized through basic biochemical tests. Partial sequencing of the 16S rRNA gene revealed diverse bacterial taxa, predominantly belonging to the genus Pseudomonas. Thirteen isolates were selected for pathogenicity assays, which confirmed variable virulence levels. Multilocus sequence analysis based on concatenated sequences of the 16S rRNA, gyrB, rpoD, and rpoB genes identified Pseudomonas alliivorans LTM 13.1.2, P. flavescens LTM 14.2.2, and P. capsici LTM 78.3.2 as causal agents of pith necrosis. Additionally, P. straminea LTM 78.2.1 and Cedecea sp. LTM 72.2.1 caused tissue discoloration. Whole-genome sequencing of the two most virulent isolates (LTM 13.1.2 and LTM 78.3.2) supported their taxonomic classification and revealed virulence-associated genes and biosynthetic clusters. This study represents the first report of these Pseudomonas species as tomato pathogens in Costa Rica and expands their known distribution and host ranges.