En México se siembran más de 100 variedades de chile (Capsicum annuum L.), es un cultivo altamente redituable y representa una actividad económica de importancia nacional. Actualmente, enfrenta graves problemas fitosanitarios por la presencia de enfermedades como la marchitez del chile, causada por un complejo de patógenos de suelo. Para el control de estas enfermedades, se utilizan fungicidas tóxicos y residuales, que contaminan el ambiente e inducen resistencia genética en los fitopatógenos. Por ello, es necesario buscar alternativas de control para solucionar este problema, por tanto, el objetivo de este trabajo fue evaluar el efecto antagónico de Trichoderma spp., contra los agentes causales de marchitez en confrontaciones in vitro mediante cultivos duales. El estudio se llevó acabo en 2016, en la Universidad Intercultural de Estado de Puebla, Huehuetla, Puebla, México. Se evaluaron tres aislamientos de Trichoderma provenientes de la rizósferas de árboles de aguacate, T. viride, T. harzianum y T. asperellum y tres aislamientos de los fitopatógenos P. capsici, F. oxysporum y R. solani obtenidos de las raíces de plantas de chile con síntomas de la marchitez. Los aislamientos se caracterizaron morfológicamente para su identificación. Los tres hongos antagonistas presentaron alto porcentaje de inhibición, T. asperellum mostró el 88.25%, T. viride 87.22% y T. harzianum con 87.8%. En las condiciones del estudio, T. asperellum, T. viride y T. harzianum, resultaron microorganismos antagónicos eficientes contra los fitopatógenos. Se sugiere realizar evaluaciones de biocontrol con estos aislamientos en invernadero y a campo abierto.
Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) is one of the most economically important pests of potato, tomato, and peppers in Central America, Mexico, the United States, and New Zealand. Its control is based on the use of insecticides; however, recently, the potential of the eulophid parasitoid Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) for population regulation has been studied. Because T. triozae is likely to be exposed to insecticides on crops, the objective of this study was to explore the compatibility of eight insecticides with this parasitoid. The toxicity and residual activity (persistence) of spirotetramat, spiromesifen, beta-cyfluthrin, pymetrozine, azadirachtin, imidacloprid, abamectin, and spinosad against T. triozae adults were assessed using a method based on the residual contact activity of each insecticide on tomato leaf discs collected from treated plants growing under greenhouse conditions. All eight insecticides were toxic to T. triozae. Following the classification of the International Organization of Biological Control, the most toxic were abamectin and spinosad, which could be placed in toxicity categories 3 and 4, respectively. The least toxic were azadirachtin, pymetrozine, spirotetramat, spiromesifen, imidacloprid, and beta-cyfluthrin, which could be placed in toxicity category 2. In terms of persistence, by day 5, 6, 9, 11, 13, 24, and 41 after application, spirotetramat, azadirachtin, spiromesifen, pymetrozine, imidacloprid, beta-cyfluthrin, abamectin, and spinosad could be considered harmless, that is, placed in toxicity category 1 (<25% mortality of adults). The toxicity and residual activity of some of these insecticides allow them to be considered within integrated pest management programs that include T. triozae.
Bactericera cockerelli es una de las plagas más importantes en solanáceas en México. Su manejo se basa en el uso de insecticidas y recientemente se ha explorado el uso del parasitoide Tamarixiatriozae dentro de un programa de MIP, por lo que el objetivo del presente trabajo fue explorar la compatibilidad de insecticidas con este parasitoide. En este trabajo se evaluó, en condiciones de laboratorio (25 ± 2 ºC, 60 ± 5% H.R.), la toxicidad de azadiractina, spinosad, imidacloprid y abamectina sobre T. triozae y B. cockerelli. Los cuatro insecticidas resultaron tóxicos tanto para el psílido como para el parasitoide, aunque el grado de toxicidad dependió de la especie, insecticida, estado biológico específico, dosis y forma en que los insectos se expusieron a los productos. De acuerdo a la IOBC, la abamectina y el spinosad fueron los productos más tóxicos (categoría 3), mientras imidacloprid y azadiractina presentaron niveles bajos de toxicidad (categoría 1). Las ninfas del psílido fueron más tolerantes a los insecticidas que los adultos y la toxicidad se incrementó cuando los insectos se sumergieron directamente en los productos. El imidacloprid a dosis de 1.0 L ha-1 aplicado directamente sobre las pupas nulificó la emergencia del parasitoide. Spinosad fue el producto más persistente para el psílido y abamectina para el parasitoide, el efecto de ambos perduró hasta los 29 días. Por tanto, en condiciones de laboratorio ningún insecticida mostró compatibilidad con el uso de T. triozae al ser aplicados de manera simultánea, ya sea porque no fueron efectivos contra B. cockerelli durante el tiempo y forma de exposición (azadiractina e imidacloprid) o porque fueron muy tóxicos al parasitoide (abamectina y spinosad). En este trabajo se discuten algunas de las posibilidades de la combinación de estas estrategias de control, particularmente se indica la importancia de evaluar los productos bajo condiciones de campo.
Charcoal rot is an emerging disease for peanut crops caused by the fungus Macrophomina phaseolina. In Mexico, peanut crop represents an important productive activity for various rural areas; however, charcoal rot affects producers economically. The objectives of this research were: (a) to identify and morphologically characterize the strain “PUE 4.0” associated with charcoal rot of peanut crops from Buenavista de Benito Juárez, belonging to the municipality of Chietla in Puebla, Mexico; (b) determine the in vitro and in vivo antagonist activity of five Trichoderma species on M. phaseolina, and (c) determine the effect of the incidence of the disease on peanut production in the field. Vegetable tissue samples were collected from peanut crops in Puebla, Mexico with the presence of symptoms of charcoal rot at the stem and root level. The “PUE 4.0” strain presented 100% identity with M. phaseolina, the cause of charcoal rot in peanut crops from Buenavista de Benito Juárez. T. koningiopsis (T-K11) showed the highest development rate, the best growth speed, and the highest percentage of radial growth inhibition (PIRG) over M. phaseolina (71.11%) under in vitro conditions, in addition, T. koningiopsis (T-K11) showed higher production (1.60 ± 0.01 t/ha−1) and lower incidence of charcoal rot under field conditions. The lowest production with the highest incidence of the disease occurred in plants inoculated only with M. phaseolina (0.67 ± 0.01 t/ha−1) where elongated reddish-brown lesions were observed that covered 40% of the total surface of the main root.
Microbial volatile organic compounds may act as semiochemicals, inciting different behavioral responses in insects. Beauveria bassiana is an entomopathogenic fungus, and physiological and environmental factors are positively related to fungal virulence. In this study, we examined the volatile profiles produced by eight B. bassiana strains, isolated from soil plots and mycosed insect cadavers, with different speeds of kill and determined if these compounds induce oviposition behavior in Spodoptera frugiperda. Fungal volatilome analysis revealed differences between the isolates. Isolates from mycosed insects showed higher virulence, larger egg mass area and length, and a higher number of eggs by mass, than those obtained from soil. Furthermore, a dilution of the fungal odoriferous compounds increased the insect response, suggesting that S. frugiperda is highly susceptible to the fungal compound´s fingerprint. Otherwise, the insect response to the natural blend of volatiles released by the fungus was different from that obtained with 3-methylbutanol, which was the most abundant compound in all isolates. The ability of an entomopathogen to produce volatiles that can induce olfactory stimulation of egg-laying behavior could represent an ecological adaptive advantage in which the entomopathogen stimulates the insect population growth.
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