Abstract One of the problems with the storage of seeds in corn is the presence of pests that reduce quality. To deal with this problem, materials with little or no susceptibility are used. The native varieties of maize in Yucatan are reservoirs of genes for resistance to storage pests. The objective of this study was to evaluate the attack of weevils (Sitophilus zeamais Motschulsky) in eight populations of corn and two control varieties. To determine the susceptibility, 100 seeds of each population were exposed to the presence of 100 weevils for 15 days, with 10 repetitions, the variables were number of live weevils, weight loss and percentage of damaged grain. Preference was determined by placing 100 seeds from each population and 1 000 weevils in the same container, they were stored for 30 days and repeated five times. The percentage of grain damaged by color was recorded. The highest susceptibility was presented in the populations Chichen Itza, Sac beh and Nal t’eel white, the first two registered the highest percentage of damaged grain, with 15% higher than the other populations evaluated, while the Nal t’eel White population registered 6.1% above the lower loss. The insect’s preference was for white grains. The pericarp (0.495) and scutellum (0.418) showed a relationship with the presence of damaged grains. There are differences in the susceptibility and preference of the evaluated populations, which indicates variability that can be used in genetic improvement programs.

Resumen Uno de los problemas con el almacenamiento de semillas en maíz es la presencia de plagas que merman la calidad. Para hacer frente a este problema, se emplean materiales con poca o nula susceptibilidad. Las variedades nativas de maíz en Yucatán son reservorios de genes para resistencia a plagas de almacén. El objetivo del presente estudio fue evaluar el ataque de gorgojo (Sitophilus zeamais Motschulsky) en ocho poblaciones de maíz y dos variedades testigo. Para determinar la susceptibilidad, 100 semillas de cada población se expusieron a la presencia de 100 gorgojos por 15 días, con 10 repeticiones, las variables fueron número de gorgojos vivos, pérdida de peso y porcentaje de grano dañado. La preferencia se determinó colocando en un mismo recipiente 100 semillas de cada población y 1 000 gorgojos, fueron almacenados por 30 días y repetido cinco veces. Se registró el porcentaje de grano dañado por color. La mayor susceptibilidad se presentó en las poblaciones Chichen Itza, Sac beh y Nal t’eel blanco, las dos primeras registraron el mayor porcentaje de grano dañado, con 15% por encima de las demás poblaciones evaluadas, mientras que la población Nal t’eel blanco registró 6.1% por encima de la menor pérdida. La preferencia del insecto fue hacia los granos de color blanco. El pericarpio (0.495) y escutelo (0.418) mostraron relación con la presencia de granos dañados. Existen diferencias en la susceptibilidad y preferencia de las poblaciones evaluadas, lo que indica variabilidad que puede aprovecharse en programas de mejoramiento genético.

Resumen La diversidad de macro-invertebrados está relacionada con el estado de conservación del suelo, no obstante, la remoción de la cubierta vegetal natural para el establecimiento de sistemas ganaderos extensivos afecta su integridad. Una estrategia para la conservación de estos organismos es la implementación de sistemas silvopastoriles; no obstante, en el sureste de México la información aún es limitada. El propósito del presente estudio fue evaluar y comparar la riqueza y la abundancia de macro-invertebrados en cuatro agro-ecosistemas contrastantes: dos sistemas silvopastoriles conformados por Leucaena leucocephala y pastos asociados (i.e. Panicum máximum cv mombaza y Cynodon plectostachyus), un pastizal convencional de Brachiaria brizantha con árboles dispersos en baja densidad y una selva mediana subperennifolia. En cada sistema se delimitó una superficie de una hectárea y se estableció un transecto de 50 m de longitud en los que se colocaron cinco trampas de caída tipo pit-fall cada 10 m. El muestreo se realizó en febrero y mayo 2018 y en cada mes se realizaron cinco recolectas con intervalos de cinco días. Se recolectaron un total de 1 737 organismos pertenecientes a 10 órdenes de la clase Insecta y uno a la clase Gastropoda. Los sistemas con mayor abundancia de macro-invertebrados fueron el sistema de selva media subperennifolia (923 individuos) y el sistema silvopastoril de L. leucocephala con C. plectostachyus (354 individuos). Los órdenes más abundantes fueron: Hymenoptera, Coleoptera, Araneae y Orthoptera. La mayor diversidad de macro-invertebrados se presentó en los sistemas silvopastoriles de L. leucocephala con P. maximum (H’=1.58) y L. leucocephala con C. plectostachyus (H´=1.44). Los resultados encontrados muestran que los sistemas pecuarios manejados con componentes leñosos (árboles/arbustos) albergan una riqueza y abundancia importante de órdenes de macro-invertebrados en comparación con sistemas como selva mediana subperennifolia. Esta diversidad de macro-invertebrates podría contribuir a la integridad y funcionalidad de los agro-ecosistemas.

Abstract The diversity of macro-invertebrates is related to the state of disturbance of the soil, caused mainly by the land-use change for agricultural activities. A strategy for the conservation of these organisms is the implementation of diversified production systems such as silvopastoral systems. However, in the Southeast of Mexico, information is still limited. The aim of the present study was to evaluate and compare the richness, abundance and composition of macro-invertebrates in four contrasting agro-ecosystems: two silvopastoral systems made of Leucaena leucocephala and associated pastures (i.e. Panicum maximum cv mombaza and Cynodon plectostachyus), a pasture of Brachiaria brizantha with scattered trees in low density and, a medium-statured tropical dry forest. In each system, an area of one hectare was delimited and a transect of 50 m in length was established in which five pit-fall traps were placed every 10 m. The sampling was carried out in February and May of 2018 and in each month five collections were made with five-day intervals. A total of 1 737 organisms belonging to 10 orders of the class Insecta and one of the class Gastropoda were collected. The medium-statured tropical dry forest (923 individuals) and the silvopastoral systems of L. leucocephala with C. Plectostachyus (354 individuals) show the highest abundance of macro-invertebrates. The most abundant genera were: Hymenoptera, Coleoptera, Aracninae and Orthoptera. The higher macro-invertebrate diversity was found in the silvopastoral systems of L. leucocephala with P. maximum (H '= 1.58) and L. leucocephala with C. plectostachyus (H' = 1.44). The results show that livestock systems managed with woody components (trees or shrubs) are home of an important abundance and richness of macro-invertebrates, compared to tropical forests. This diversity of macro-invertebrates may contribute to the integrity and functionality of the agro-ecosystems.

The insect Trioza rusellae Tuthill (Hemiptera-Triozidae) produces galls on the leaves of the Ramon (Brosimum alicastrum Swartz) tree, species with high nutritional value of the Peninsula of Yucatan. The insect was isolated and identified from collections in the municipalities of Muna and Sacalum, Yucatán. Five to 10 years old trees were sampled selecting branches with leaves showing galls. The samples were placed in plastic bags and taken to the laboratory, and placed in entomological cages. Adult insects were collected using a manual vacuum, while galls were dissected to collect the nymphs directly with a brush (0001). The samples were preserved in alcohol (70 %) and in fixative formalin-alcohol-water (FAW). Nymphs and adult insects from the alcohol samples were mounted and observed on a stereoscopic microscope. The samples in FAW were processed and observed under a scanning electron microscope (SEM). As a result, photographs were obtained and development phases of T. rusellae were identified by entomological keys.

El insecto Trioza rusellae Tuthill (Hemiptera-Triozidae) produce agallas en las hojas del árbol de ramón (Brosimum alicastrum Swartz), especie con alto valor nutricional de la península de Yucatán. El insecto fue aislado e identificado a partir de colectas en los municipios de Muna y Sacalum, Yucatán. Los árboles de cinco a 10 años de edad se muestrearon seleccionando ramas con hojas que presentaban agallas. Las muestras se colocaron en bolsas de plástico y se trasladaron al laboratorio confinándolas en jaulas entomológicas. Los adultos se recolectaron con un aspirador manual, mientras que las agallas se disectaron para colectar las ninfas directamente con un pincel (0001). Las muestras se conservaron en alcohol (70 %) y en fijador formol-alcohol-agua (FAA). Las ninfas y adultos de las muestras en alcohol se montaron y observaron en el microscopio estereoscópico. Las muestras en FAA se procesaron y observaron en el microscopio electrónico de barrido (MEB). Como resultado, se obtuvieron fotografías y se identificaron las fases de desarrollo de T. rusellae mediante claves entomológicas.

Spiromesifen is an insecticide that inhibits the synthesis of lipids and, in Mexico, its use against the Tomato-Potato Psyllid, Bactericera cockerelli (Sulc), on chili pepper (Capsicum annum), tomato (Lycopersicon sculentum) and potato (Solanum tuberosum) began in 2005; however more information is needed to understand its toxicity on this insect pest. The aim of this research was to determine the toxicity of spiromesifen against each of the biological stages of tomato-potato psyllid, its effect on fertility and viability of eggs deposited by treated females, as well as the female preference to lay eggs on treated and non treated plants. The relative toxicity at 95% mortality (highest LC95 value /LC95 value of the respective biological stage) of spiromesifen in egg, nymph 1, nymph 2, nymph 3, nymph 4, and nymph 5 were 517.5; 31316.2; 2950.1; 315.6; 18.2 and 1-fold, respectively. There were no differences in the toxicity of spiromesifen between adult males and females. The number of laid eggs was reduced as the spiromesifen concentration used to treat female increased and egg hatch was reduced in all tested doses. In the "no choice" test, females deposited 38.6 ± 2.01 eggs by leaf of non treated chili pepper type jalapeño, while in the treated with 360 mg L-1 we observed 0.3 ± 0.08 eggs by leaf. In the "choice" test, the oviposition decreased as the dose increased. There were no eggs on plants treated with 2400 mg L-1 of spiromesifen.