Yohan Solano Rojas

Using a recursion model with real parameters of Nabis pseudoferus, we show that its filial cannibalism is an optimal foraging strategy for life reproductive success, but it is not an evolutionarily optimal foraging strategy, since it cannot maximize the descendant’s number at the end of the reproductive season. Cannibalism is evolutionarily rational, when the number of newborn offspring produced from the cannibalized offspring can compensate the following two effects: (a) The cannibalistic lineage wastes time, since the individuals hatched from eggs produced by cannibalism start to reproduce later. (b) Cannibalism eliminates not only one offspring, but also all potential descendants from the cannibalized offspring during the rest of reproductive season. In our laboratory trials, from conspecific prey Nabis pseudoferus did not produce newborn nymphs enough to compensate the above two effects.

Amblyseius swirskii is a predatory mite that is widely used for biological control in greenhouses. One way this predator is released is in a formulation in slow-release sachets. These sachets are prepared with the predatory mite, the factitious prey mite Carpoglyphus lactis, and a food substrate for the latter. The objective of the present study was to study the effects of microclimatic conditions in this type of formulation on the population dynamics of mites inside the sachets and on the release of predatory mites. These experiments were conducted under laboratory conditions in two trials. The ambient relative humidity affected the water content of the food substrate of the prey mite inside the sachets, with an initial value of 21.49 ± 0.42%, which was reduced to values of 4.7 ± 0.25%, 10.87 ± 1.03% and 17.27 ± 0.82% after 21 days of trials when they were exposed to low, medium and high ambient relative humidity levels, respectively. Relative humidity significantly altered the dynamics of the populations of both species inside the sachets and the exits of the predator from the sachets to the external environment.

Predatory mite species (Acari: Phytoseiidae) are essential tools in the biological control of greenhouses pests. The natural enemies can be released directly into a crop. A better, partly preventive system is to place slow-release sachets on the plants. Inside such sachets is a factitious prey’s food substrate—which also acts as refuge—and the predator. The objective of this study was to develop a new methodology to evaluate the population dynamics of this sachet system, based on the factitious prey Carpoglyphus lactis and the predatory mite Amblyseius swirskii. Through two tests carried out under laboratory conditions, the sachets were first compared to the traditional extraction method that uses Berlese-Tullgren funnels and an extraction method using flotation in hexane. The latter method proved more effective at sampling the motile states (larvae, nymphs, and adults), both for the predatory species and for the factitious prey, extracting up to 3.7 × more mites than the Berlese-Tullgren funnel. Second, the population dynamics of both mite species was studied in a laboratory test, both inside and outside the sachets. In this way, a positive correlation was demonstrated between the number of predatory mites and the number of prey mites inside the sachets. Conversely, no correlation was found between the interior population of predatory mites and the number that venture outside. We can conclude that hexane extraction is very useful both in quality control of predatory mites and in studying how the sachets behave when faced with various factors.

The potato tuber moth (PTM), Phthorimaea operculella, is the main potato pest in the world, having managed to adapt to a wide range of climatic conditions, and causing damage to stored tubers. The effectiveness of a biological control using the parasitoid Trichogramma cacaeciae and the predatory mite Blattisocius mali was evaluated in PTM under conditions that simulated those of tubers in storage. The number of adults found at the end of the trial was significantly higher in the control (181.75 ± 11.00 adults/container) than in treatments where B. mali (24.50 ± 7.22) or T. cacaeciae (102.00 ± 14.61) were released. The biological control’s effectiveness using the Abbot formula was 86.52% for the predator and 43.88% for the parasitoid. In addition, the PTM population data was fitted by logistic models, and the best fit was found for the simple logistic function. Using the data generated from these functions, the control efficiencies for the mite and the parasitoid were 94.85% and 73.77%, respectively. B. mali showed greater potential for being incorporated into integrated PTM management programs than T. cacaeciae. Based on logistic functions, a novel way of estimating the effectiveness of predators and parasitoids is also presented and discussed.

Rhynchophorus ferrugineus (Olivier, 1790) is an invasive pest species that constitutes one of the most important problems around the Mediterranean region and has been responsible for the loss of over 100,000 palm trees with an estimated annual cost of EUR several hundred million since its introduction into Europe. Methodological approaches of conservation ecology, such as multidisciplinary modelling, also apply in the management of cultural landscapes concerning ornamental plants, such as palm trees of the area. In this paper, we propose a dynamic model for the control of the red palm weevil, contributing in this way to the sustainability of an existing cultural landscape. The primary data set collected is a sample from the density-time function of a two-cohort pest population. This data set suggests a bimodal analytic description. If, from this data set, we calculate a sample from the accumulated density-time function (the integral of the density-time function), it displays a double sigmoid function (with two inflections). A good candidate for the analytical description of the latter is the sum of two logistic functions. As for the dynamic description of the process, a two-dimensional system of differential equations can be obtained, where the solution’s second component provides the analytical description of the original density-time function for the two-cohort population. Since the two-cohort waves appear in all three cycle stages, this reasoning applies to the subpopulations of larvae, pupae and adults. The model fitting is always performed using the SimFit package. On this basis, a mathematical model is proposed, which is sufficiently versatile to be of help in the control of this pest species in other geographical areas.

El ozono ha sido utilizado como estrategia de control de hongos e insectos que afectan los granos y productos almacenados, debido a su alta capacidad de reacción y a su fuerte actividad oxidante. En esta investigación se evaluó su efectividad como insecticida sobre adultos del gorgojo Sitophilus oryzae (L.), insecto plaga del arroz y maíz almacenado. Para esto, se aplicó ozono a una concentración de 20 ppm, durante 15, 30, 45 y 60 minutos, en prototipos de silos vacíos y silos llenos de maíz. El diseño del experimento fue completamente al azar con arreglo factorial. Se presentaron diferencias significativas (P < 0,001) en el porcentaje de mortalidad del gorgojo en los silos vacíos (53,5%) y en aquellos llenos de maíz (16,88%). El tiempo de exposición al ozono también produjo un efecto significativo sobre la mortalidad (P < 0,001), la cual incrementó con el tiempo y alcanzó su valor más alto a los 60 minutos (58,25%). De igual forma, la interacción condición de silo por tiempo de exposición a ozono también fue significativa (P < 0,001), y permitió observar diferencias relevantes en la mortalidad de S. oryzae, cuyos porcentajes fueron mayores en los silos vacíos que los silos con maíz. Estos resultados muestran que el ozono tuvo un moderado efecto insecticida sobre S. oryzae.

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Parámetros biológicos de Olla timberlakei Vandenberg (Coleoptera: Coccinellidae) alimentada con dietas artificiales

Agroindustry requires rice varieties that allow obtaining whole grains during its processing and also to resist insect attacks. In this study was determined milling quality of varieties SD20A and Payara 1FL, and their resistance to Sitophilus oryzae (L.) and Rhyzopertha dominica (F.). In the first phase, the whiteness ratio (WR) and grain yield in a mill (GY) were calculated for both varieties, while in the second phase, those were through the attack of S. oryzae and R. dominica, in paddy and milled rice condition, during three months. The resistance was interpreted based on the number of adults emerged at the end of the experiment. There were statistical differences (p< 0.01) between WR and GY of rice varieties SD20A (32.40 ± 1.87°Kett and 44.40 ± 2.55%) and Payara 1FL (35.90 ± 0.63°Kett and 48.20 ± 1.69%). Adult emerged numbers of S. oryzae and R. dominica was different between SD20A and Payara 1FL (p< 0.01), being higher in milled rice than those registered on paddy rice. The amount of adult of R. dominica was always higher than S. oryzae, except for Payara 1FL milled rice in where no significative difference (p> 0.01). Results showed that Payara 1FL had a higher yield in the mill than SD20A, and higher resistance to S. oryzae attacks than to R. dominica. La agroindustria requiere de variedades de arroz, que permitan obtener granos enteros durante su procesamiento y que resistan el ataque de insectos. En este estudio, se determinó la calidad molinera de las variedades SD20A y Payara 1FL y su resistencia a Sitophilus oryzae (L.) y Rhyzopertha dominica (F.). En la primera fase, se calculó el índice de blancura (IB) y rendimiento en molino (RM) de ambas variedades, mientras que, en la segunda, fueron sometidas a los ataques de S. oryzae y R. dominica, en su condición de arroz paddy y pulido, durante tres meses. La resistencia a los insectos, se interpretó con base al número de adultos emergidos al finalizar el periodo de evaluación. Hubo diferencias estadísticas (p< 0,01) entre el IB y el RM de las variedades de arroz SD20A (32,40 ± 1,87°Kett y 44,40 ± 2,55%) y Payara 1FL (35,90 ± 0,63°Kett y 48,20 ± 1,69%), respectivamente. El número de adultos de S. oryzae y R. dominica fue diferente entre SD20A y Payara 1FL (p< 0,01), siendo mayores los valores registrados para las variedades en condición de arroz pulido que sobre arroz paddy. La cantidad de adultos de R. dominica fue siempre superior a la de S. oryzae, excepto para el arroz pulido de Payara 1FL, donde no hubo diferencias significativas (p> 0,01). Los resultados muestran que Payara 1FL presentó mayor RM que SD20A y mostró mayor resistencia a los ataques de S. oryzae que a los de R. dominica.

Con la finalidad de conocer las especies de trips y ácaros presentes en cultivos comerciales de fresa, se realizaron estudios en las localidades de Bailadores (estado Mérida), Cabimbú (estado Trujillo), La Colonia Tovar (estado Aragua), Cubiro, Paso Real, Páramo Abajo y Tarabana (estado Lara), en Venezuela. En el campo, se examinaron brotes foliares, hojas, botones florales, flores y frutos, para colectar inmaduros y/o adultos de trips y/o ácaros en diferentes cultivares de fresa. En el laboratorio, los trips y/o ácaros en estado inmaduro, fueron criados hasta la fase adulta. Los especímenes adultos fueron montados en láminas microscópicas, etiquetados y depositados en la colección de insectos del Museo de Entomología José M. Osorio (MJMO) de la Universidad Centroccidental “Lisandro Alvarado” (UCLA). De la revisión taxonómica realizada, fue posible identificar las especies Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) y Tetranychus urticae Koch (Acari: Tetranychidae). El reporte de estas especies en cultivos de fresa, constituye nuevos registros para Venezuela.