Mateo Vargas-Hernández

Molecular delineation of the Agave Red Worm Comadia redtenbacheri (Lepidoptera: Cossidae)

Comadia redtenbacheri (Hammerschmidt) (Agave Red Worm) is the only member of the family Cossidae that has been described as a phytophagous specialist of the plant genus Agave, which is mainly distributed in México. A new extraction protocol adapted from Stewart Via (1993) has been implemented for sequencing the COI gene from samples collected in five states of the North Central (Querétaro and Zacatecas), South Central (Estado de México) and East Central (Hidalgo and Tlaxcala) regions of México with the purpose of contributing to delineation of the species. A Maximum Likelihood (ML) tree based on these COI sequences as well as COI sequences from other Cossinae species was developed to complement the existing morphological and taxonomic approaches to delineation of this species. As expected, our Comadia samples cluster together within a monophyletic clade that includes four C. redtenbacheri sequences previously reported. This group seems to be consistent with our reconstruction, which is supported by a bootstrap value of over 99%. The closely related branches associated with the latter group include organisms known to be the plant and tree borers of the Cossinae subfamily. The COI sequences from our samples were analyzed to determine the percentage of identity among the C. redtenbacheri in a first attempt to detect differences in the sequence that matches a particular region of México.

Colletotrichum fructicola, a Member of Colletotrichum gloeosporioides sensu lato, is the Causal Agent of Anthracnose and Soft Rot in Avocado Fruits cv. “Hass”

Abstract The filamentous Ascomycota Colletotrichum gloeosporioides sensu lato is a fungus that has been reported worldwide as a causal agent of anthracnose disease in avocado and other crops. In Mexico, this species affects fruits from an early stage of development in the orchard until the post-harvest stage. Although fungicides are continuously applied to control Colletotrichum species, pericarp cankers and soft rot mesocarp in fruits are still frequently observed. Considering the lack of a precise description of the causative agent, the aim of the current study was to determine the pathogens involved in this symptomatology. Twenty-four isolates were consistently obtained from the pericarp of avocado fruits cv. “Hass” collected in the central avocado-producing area of Mexico. Morphological features such as colony growth, conidia size, and mycelial appressorium were assessed. Bayesian multilocus phylogenetic analyses were performed using amplified sequences of the internal transcribed spacer region of the nuclear ribosomal DNA; actin, chitin synthase, glyceraldehyde-3-phosphate dehydrogenase partial genes; and APn2-Mat1-2 intergenic spacer and mating type Mat1-2 partial gene from the nine selected isolates. In addition, fruits were inoculated with a conidial suspension and reproducible symptoms confirmed the presence of Colletotrichum fructicola in this area. This pathogenic species can now be added to those previously reported in the country, such as C. acutatum, C. boninense, C. godetiae, C. gloeosporioides, and C. karstii. Disease management programs to reduce the incidence of anthracnose should include C. fructicola to determine its response to fungicides that are routinely applied, considering that the appearance of new species is affecting the commercial quality of the fruits and shifting the original population structure.

A New Methodology to Evaluate Entomopathogenic Fungi and Formulated Insecticides to Control Adults of Aedes aegypti (Diptera: Culicidae)

Summary The use of non-conventional insecticides and entomopathogenic fungi to control adult mosquitoes is increasing; however, the current methods are designed to evaluate the insecticidal action of the active ingredient. We describe the bioassay method to evaluate the effect of non-conventional insecticides and entomopathogenic fungi to control mosquitoes using the Potter tower. Twenty d after application, entomopathogenic fungi produced a proportion of mortality of 0.49 to 0.82, while non-conventional insecticides produced 100% mortality from 15 min after application. Our results showed that this bioassay could provide basic information on the effect of different non-conventional insecticides and entomopathogenic fungi on adult mosquitoes.

Evaluación en Campo de Insecticidas Sobre Melanaphis sacchari (Zehntner)1 en Sorgo

Resumen. El pulgón amarillo, Melanaphis sacchari (Zehntner), se detectó en México en 2013 y se ha dispersado a diversas regiones productoras de sorgo, Sorghum bicolor (L.) Moench, causando daños del 30 al 100%. Se evaluaron en campo insecticidas de diferente modo de acción en dos experimentos que mantuvieron la densidad por abajo del umbral económico establecido de 50 pulgones por hoja. A los 28 días después de la aplicación, imidacloprid sulfoxaflor, flupyradifurone, pymetrozine, spirotetramat, y afidopyropen presentaron las menores densidades de pulgón amarillo. Esta información es relevante, ya que conocer la efectividad de insecticidas con diferente modo de acción permite utilizar los más efectivos y que puedan integrarse con otras medidas que se implementen en el manejo de M. sacchari.

Susceptibility of Bactericera cockerelli Sulc (Hemiptera: Triozidae) nymphs to Sivanto 200 SL (flupyradifurone)

Abstract Sivanto® 200 SL (flupyradifurone) was recently introduced into the Mexican market for the control of Bactericera cockerelli Sulc (Hemiptera: Triozidae) in different solanaceous crops such as potato, tomato, and pepper, which are important crops in Mexico. The objective of this study was to determine the toxicity of flupyradifurone on 5th instar potato psyllids in 3 field-collected populations and a laboratory susceptible one. There were no differences in susceptibility to flupyradifurone among the evaluated populations. The lethal concentration values (LC) at 50% of mortality ranged from 243.2 to 368.1 mg per L at 24 h, after 48 h of exposure, LC50 values were between 51.0 to 62.5 mg per L. The LC95 values at 24 h ranged from 2403 to 5265 mg per L, and at 48 h of exposure were between 506.5 to 936.9 mg per L. The relative toxicity (RT) at 50% of mortality was 4.07 to 4.97 times higher after 48 h than after 24 h. Moreover, an antifeedant effect associated with flupyradifurone decreased the amount of excreta after 24 h of feeding by 51, 42, and 75% at the flupyradifurone dosages of 30, 50, and 100 mg per L, respectively, relative to the untreated control.

CARACTERIZACIÓN DE ESPECIES DEFusariumCAUSANTES DE PUDRICIÓN DE RAÍZ DEL TRIGO EN EL BAJÍO, MÉXICO

The objectives of this study were to identify Fusarium species causing root rot in wheat produced in the Bajío of Mexico, and to determine the response of 28 wheat varieties to this disease. Fusarium spp. isolates were obtained from samples with root rot symptoms in 2014 and 2015. The fungal isolates were identified by morphological characterization and sequence analysis of ITS and TEF-1α, and also using specific primers for the detection of Fusarium species. Pathogenicity of a representative isolate of each Fusarium species was verified by immersion of seeds of 28 wheat varieties in a conidial suspension. The results of the morphological characterization, sequence analysis, and pathogenicity Recibido: 12 agosto 2016. Aceptado: 28 Febrero 2017. ISSN 0719-3882 print ISSN 0719-3890 online