Jesús Ricardo Sánchez-Pale

Spatial distribution of head smut (Sporisorium reilianum) of corn in Mexico

Knowledge about the spatial distribution of agricultural diseases is important for the elaboration of integrated pest management programs. Such knowledge allows the exact and adept development of sampling methods, control methods and risk valuation. Despite its importance, there have been few studies of the spatial distribution of head smut of corn in Mexico. This study aimed to determine the spatial distribution of this disease during the year 2007 in the State of Mexico and to establish its spatial behavior with geostatistical techniques. Five points per plot were chosen for sampling. For each sampling point, 100 plants in a single row were counted, and the plants that presented symptoms of the disease were recorded. The geostatistical analysis used this data to estimate the experimental semivariogram, which was adjusted using theoretical models (spherical, exponential, Gaussian and logarithmic), in the Variowin 2.2 program. The semivariogram was verified by the geostatistical interpolation method or kriging through the cross validation, and cluster maps were subsequently made. The disease was present in 32 locations of 31 counties in Mexico State. All the locations presented a spatial behavior aggregated to the disease. Twenty-four locations were adjusted to the spherical model, seven locations were adjusted to the exponential model, and one location was fit to the Gaussian model. Lastly, it was possible to set aggregation maps in all models

Determinación de Estadios Larvarios de Conotrachelus perseae Barber (Coleoptera: Curculionidae)

Resumen. El objetivo de este estudio fue determinar el número de estadios larvales de Conotrachelus perseae Barber. Se midió el ancho de la cápsula cefálica de trescientas veintitrés larvas extraídas de frutos de aguacate de las variedades Hass, Fuerte y “criollo” (Persea americana var. drymifolia). Los datos fueron analizados con la regla de Dyar y el programa Hcap. El análisis de distribución de frecuencias mostró cuatro picos de distribución distintos del ancho de las cápsulas cefálicas. La constante de Dyar tuvo un promedio de 1.49, donde la relación entre el logaritmo natural del ancho de la cápsula cefálica y el número de estadios larvales resultó en un crecimiento geométrico perfecto para cada estadio larval. El ajuste excelente del modelo lineal, indica que no existe traslapo entre estadios larvales y permite determinar la presencia de cuatro estadios larvales en C. perseae.

An approach to the model for conservation of Central Mexico native grapevines

Several and diverse native populations of wild grapevines have been reported growing in the States of Puebla, Mexico and Morelos, Central Mexico. After collection, successfully rooted vines were planted in Zumpahuacán, State of Mexico, and since 2013, their fruit were analyzed, mainly in relation to berry-weight and sweetness. Recently, the seed oil content was analyzed. Most berries harvested in 2013, 2014 and 2015 weighted less than 1 g and only berries of accession Puebla-41 (P-41) weighted nearly 2.5 g. On the other hand, most berries had lower than 18°B. Four accessions, three native of Puebla and one from Morelos had the higher fruit production (2.5, 1.5 and 1.4; and 0.68 kg per plant) and might be the genetic material proposed to be planted in Zumpahuacán, Mexico. Seed oil analysis confirmed the presence of linoleic acid as the main fatty acid in Central Mexico wild grape seed oil. Nowadays, the extraction of seed oil in Central Mexico native grapes seems to be the better alternative to interest locals and agro-industrial related companies in conserving and cropping this plant genetic resource.

Sympatry of Two Species of Heilipus Germar, 1824 (Coleoptera: Curculionidae) Infesting Avocado (Persea americana Mill.) in Central Mexico

Mexico is cited as the center of origin and diversification of the avocado, Persea americana Mill. (Lauraceae). This assertion is supported by the notable genetic diversity ofP. americana inMexico, which has given rise to three of the main botanical races: Persea americana var. drymifolia (Mexican or “criollo” avocado), P. americana var. guatemalensis (Guatemalan avocado), and P. americana var. americana (West Indian o “pahua” avocado). These are well known among horticulturists and valued by plant breeders (Galindo-Tovar et al. 2008). Avocado trees are attacked by many species of phytophagous insects, including the stalk-, fruit-, and branch-boring curculionid weevils of the genera HeilipusGermar,ConotrachelusDejean, andCopturus Schönherr. These insects have apparently evolved with avocado in the center of diversification of this plant (Equihua-Martı́nez 2001) and have now come to be designated as quarantined pests in the commercial cultivation of avocado, constituting a limiting factor for local and international commercialization (SAGARPA 2002; Peterson and Orden 2008). This situation has required the implementation of diverse pest control strategies in avocado orchards, which have successfully excluded the big avocado seed weevil, Heilipus lauri Boheman, and the small avocado seed weevil,Conotrachelus perseaeBarber, fromMichoacán, Mexico’s main avocado-producing state. However, the species are present in more remote agroecosystems where management programs are virtually nonexistent, converting these areas into natural reservoirs of these weevil pests of avocado. In Mexico, there are reports of the presence of two species ofHeilipus that cause damage to avocado:H. lauri and the avocado stem weevil borer, Heilipus albopictus Champion (Casta~neda-Vildózola et al. 2013b). However, there is no evidence of interaction between these species or other Heilipus species within the same agroecosystem in the Americas. Recently, in Mexico H. lauri has been reported interacting in the same agroecosystem with other avocado fruit-boring insects such as C. perseae (Casta~neda-Vildózola et al. 2013a). In October 2003, we recorded two Heilipus species in a backyard orchard of “criollo” avocado trees with no phytosanitarymanagement in the community of El Salitre (18°49ʹ28.1ʹʹN, 99°39ʹ50.2ʹʹW, 1,685 m elevation), municipality Ixtapan de la Sal, Estado de México. Three specimens of Heilipus sp. 1 were boring into stems, and five specimens ofHeilipus sp. 2 were perforating fruits; both species were attacking the same avocado trees. These beetles were later identified asH. albopictus (Figs. 1 and 2) andH. lauri (Figs. 3 and 4), using characteristics given in Champion (1902), Barber (1919), and Casta~nedaVildózola et al. (2013b).

Distribución Espacial de Candidatus Liberibacter solanacearum y Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) en Papa (Solanum tuberosum L.)

Resumen. La enfermedad de Zebra chip afecta la producción de papa (Solanum tuberosum L.) en México y sur de Estados Unidos. Esta enfermedad se ha asociado con la bacteria Candidatus Liberibacter solanacearum, transmitida por el psílido Bactericera cockerelli (Sulc). Su control se basa en aplicaciones de insecticidas sobre las parcelas, debido a que se desconoce la forma en que se distribuye espacialmente la enfermedad y su vector. En este estudio se determinó la distribución espacial de B. cockerelli y Ca. Liberibacter solanacearum con técnicas geoestadísticas y la detección de la bacteria mediante técnicas moleculares. Al final del ciclo del cultivo los centros de agregación de esta enfermedad no coincidieron con los tres estadios del insecto ya que la agregación del adulto se presentó en plantas asintomáticas. La incidencia de la enfermedad en una parcela fue de 57%, mientras que en la otra 45%. En la parcela con menor incidencia, de 66 plantas asintomáticas en 11 se detectó la presencia de la bacteria. De acuerdo con los resultados obtenidos, la distribución de Ca. Liberibacter solanacearum y B. cockerelli presentaron diferentes tipos de agregación. Los centros de agregación de la bacteria y el insecto no se presentaron en el mismo punto, lo que sugiere que las diferentes alternativas de manejo del insecto, no implican el control de la bacteria. Además indica la presencia de infestaciones previas del vector, o bien la existencia de la bacteria en la semilla utilizada.

Análisis Espacial de Thrips spp. (Thysanoptera) en el Cultivo de Gladiolo en la Región Sureste del Estado de México, México

Resumen. Los Thrips spp., son la principal plaga que afecta al cultivo de gladiolo en las diversas regiones del Estado de México. Su manejo ha sido poco satisfactorio debido al desconocimiento de su distribución espacial. El objetivo del presente trabajo fue determinar la distribución espacial de Thrips spp., con técnicas geoestadísticas que permitan su visualización a través de los mapas generados. Se determinó que las poblaciones de Thrips spp. presentaron una distribución espacial de tipo agregada en todo el ciclo fenológico del cultivo de gladiolo. El modelo gaussiano, indicó agregaciones de forma continua, ésto favorece el avance de las infestaciones de los insectos a plantas aledañas, posiblemente debido a la preferencia por la variedad. Con el modelo esférico, las agregaciones fueron de forma aleatoria dentro de la parcela lo que propició infestaciones en zonas específicas, que permitirá direccionar las diferentes medidas de control sobre los puntos de agregación de los insectos. Los mapas obtenidos reflejaron la estructura agregada de las poblaciones en puntos específicos de las parcelas.