Introduction. Yam is a tuber affected by a large number of organisms such as viruses, bacteria and fungi, being Colletotrichum, which causes anthracnose, the most important. Objective. The objective of the present research was to determine, through an in vitro test, the inhibition exerted by commercial fungicides on the mycelial growth of seven fungal isolations that had been obtained from foliar lesions in yam. Materials and methods. The study was carried out at the Instituto Tecnológico de Costa Rica, in the period between October 2016 and June 2017. Ten fungicides —azoxystrobin, benomyl, benzotiazol, carbendazine, chlorothalonil, mancozeb, mancozeb + copper oxychloride, methylthiophanate, propiconazole, and propineb— were evaluated at different concentrations, on five isolates of Colletotrichum, one of Bipolaris and one of Mycoleptodiscus. With this purpose, two tests were performed; in the first, the growth of the isolates in PDA was analyzed in five different concentrations of each fungicide. The results obtained were subsequently used in the second test to calculate the percentage of inhibition of mycelial growth (PICM) of each isolation. Results. The results indicate that, in the concentrations used and with the fungal isolates studied, no treatment reached 100 % inhibition. Propineb was the most effective fungicide on the fungus Mycoleptodiscus sp., with a PICM of 64.51, carbendazim had a similar behavior on Colletotrichum truncatum with a PICM of 43.83, and propiconazole had it on Colletotrichum gloeosporioides with a PICM of 49.79. Azoxystrobin was not effective at any concentration on any isolation. Conclusion. The results obtained suggest that the pathogens associated with anthracnose in Costa Rican yam plantations could be developing resistance to fungicides. Introducción. El ñame es afectado por gran cantidad de organismos como virus, bacterias y hongos, el más importante es Colletotrichum, causante de la antracnosis. Objetivo. El objetivo del presente trabajo fue determinar, por medio de un ensayo in vitro, la inhibición que ejercen fungicidas comerciales sobre el crecimiento micelial de siete aislamientos fúngicos que habían sido obtenidos de lesiones foliares en ñame. Materiales y métodos. El estudio se llevó a cabo en el Instituto Tecnológico de Costa Rica, Sede San Carlos, en el período comprendido entre octubre del 2016 y junio del 2017. Se evaluaron diez fungicidas (azoxistrobina, benomil, benzotiazol carbendazim, clorotalonil, mancozeb, mancozeb + oxicloruro de cobre, metil-tiofanato, propiconazol y propineb), con diversas concentraciones, sobre cinco aislamientos de Colletotrichum, uno de Bipolaris y uno de Mycoleptodiscus. Para ello, se realizaron dos ensayos, en el primero se analizó el crecimiento de los aislamientos en PDA con cinco diferentes concentraciones de cada fungicida. Los resultados obtenidos se utilizaron posteriormente en el segundo ensayo para calcular el porcentaje de inhibición del crecimiento micelial (PICM) de cada aislamiento. Resultados. Los resultados indican que, en las concentraciones utilizadas sobre los aislamientos fúngicos estudiados, ningún tratamiento alcanzó el 100 % de inhibición. El propineb fue el fungicida más eficaz sobre el hongo Mycoleptodiscus sp., con un PICM de 64,51, el carbendazim tuvo un comportamiento similar sobre Colletotrichum truncatum con un PICM de 43,83 y el propiconazol lo tuvo sobre Colletotrichum gloeosporioides con un PICM de 49,79. La azoxistrobina no fue eficaz a ninguna concentración sobre ningún aislamiento. Conclusión. Los resultados obtenidos sugieren que los patógenos asociados a antracnosis en las plantaciones de ñame costarricenses podrían estar desarrollando resistencia a los fungicidas.

Background: The accidental invasive insects pose a growing threat to agricultural productivity and food security worldwide. Objective: To report for the first time the pepper thrips Thrips parvispinus in Costa Rica. Methodology: Specimens were collected from May to October 2024 in commercial crops Capsicum annuum, Citrus sinensis, Coriandrum sativum, Cucumis sativus, and ornamental Croton spp. in the western region of the country, encompassing both protected environments and greenhouses. The thrips identification was carried out using external morphological characteristics and partial sequencing of the mitochondrial cytochrome c oxidase subunit I (COI) gene. Results: Morphological and molecular analyses confirmed the species identity of T. parvispinus. Implications: The observed damage included feeding scars on young leaves, margin curling, necrosis of foliar tissue, and floral deformation; with relevant implications for the health of these crops in Costa Rica. Conclusion: The detection of this invasive species represents a phytosanitary concern in Central America and underscores the necessity for continuous monitoring and implementation of effective insect management strategies throughout the region.

The new species Metaxonchium toroense n. sp. from natural habitats of Costa Rica is described, including light microscopy (LM), scanning electron microscopy (SEM) and molecular (D2–D3 28S rDNA) analyses. The new species is characterized by its general size, the dimensions and appearance of its lip region, the length of the odontostyle and its fusiform aspect, the length of the neck and its pharyngeal expansion, the reduction of the anterior genital branch to a very short uterine sac without any rudiment of ovary or oviduct, tripartite and non-echinophor posterior uterus, the somewhat posterior vulva position, the length and shape of the caudal region, and the absence of males. Molecular analyses, the first to be performed on a Metaxonchium species, show a close relationship of the new species with representatives of the genera Axonchoides and Syncheilaxonchium.

A new dagger nematode,Xiphinema poasensen. sp., is described and illustrated from three populations extracted from soil associated with a combined plantation ofEucalyptussp.,Cupressussp. andPennisetumsp. and wild plants from a tropical pre-montane forest in Costa Rica. The new dagger nematode is characterised by a moderate body size 2612 (2416-3042) μm long, a rounded lip region 15.0 (13.5-16.5) μm broad, separated from the body contour by a shallow depression, amphidial fovea large, stirrup-shaped, a very long odontostyle (175 (164-188) μm), stylet guiding ring located 167 (136-181) μm from anterior end, vulva situated anterior to mid-body (36-40%), anterior genital branch complete but strongly reduced, without uterine differentiation, female tail short, hemispherical to convex-conoid with a c′ ratio = 0.7 (0.6-0.8) and bearing two pairs of caudal pores, and male absent. Integrative diagnosis was completed with molecular data using D2-D3 expansion segments of 28S rRNA, ITS1 region, partial 18S-rRNA and the partial mitochondrial gene cytochrome c oxidase subunit 1 (coxI). The phylogenetic relationships based on D2-D3 segments of this species with otherXiphinemaspp. of theX.non-americanumgroup indicated thatX. poasensen. sp. clustered with other species with a reduced anterior genital branch from the morphospecies Group 2,viz.,X. costaricenseandX. krugi. However, the phylogeny ofcoxIand partial 18S rRNA gene revealed that the new species did not cluster withXiphinemaspecies having the anterior genital branch absent or reduced (i.e., morphospecies Groups 1 and 2, respectively).

Introduction. Sweet potato (Ipomoea batatas) is a root crop very susceptible to viral diseases, which have been associated with crop yield reductions of over 50 %. In the Costa Rican sweet potato plantations the presence of feathery mottle virus (SPFMV), chlorotic stunt virus (SPCSV), and leaf curl virus (SPLCV) have been reported, for the development of adequate control programs, early detection and identification is necessary through the use of sensitive and efficient techniques. Objective. The objective of this research was to estimate the incidence of SPFMV, SPCSV, and SPLCV in sweet potato plantations using qPCR. Materials and methods. In 2018 foliar tissue samples were collected from eighty plants showing viral symptoms from twenty-five sweet potato plantations distributed in four provinces in Costa Rica. The detection of the three viruses was performed by qPCR with the use of primers and specific hydrolysis probes. Results. In 92 % of the plantations studied, the presence of virosis was found. The Sweet potato virus disease (SPVD) defined as the combined infection of SPFMV and SPCSV, was the most common viral disease found in all plantations. The plantations located in Sabanilla, El Cacao, and La Guacima were the only ones to present the three viruses studied. The SPLCV virus was only detected in the Limón and Alajuela provinces. Conclusion. It is possible to make an early detection of three of the most frequent sweet potato viruses with the use of qPCR which would contribute to certified seed production programs.