RESUMO
Two of the main causes of losses in tomato production are the greenhouse whitefly, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae), and drought, which is becoming a central problem in agriculture due to global climate change. The separate effects of whitefly infestation and drought have been amply studied in many crop systems. However, less is known about their combined effects. To evaluate whether drought stress (DS) affects plant defense against whiteflies, we assessed the joint effects of whitefly infestation and DS on plant vegetative and reproductive performance in four tomato cultivars, and assessed the effects of DS on plant resistance and tolerance (compensatory ability) to whiteflies in a greenhouse experiment. Generally, we found negative effects of DS and whiteflies on plant performance, but the combined effects of DS and herbivory were not worse than those of either stress alone. In fact, plant performance under the combined effect of both stresses was usually similar to that in the presence of whiteflies without DS. Plants growing under DS had greater trichome density. However, plant resistance-as measured by whitefly population growth-decreased under DS in two cultivars and was unaffected in the other two. Compensatory ability decreased under DS in all but one cultivar. These cultivar-specific responses suggest genetic variation in resistance and tolerance to whiteflies and could be associated with differences in drought tolerance among cultivars. Our findings underscore the difficulty in predicting the combined effects of DS and herbivory and point to the need for a better understanding of the mechanisms underlying plant responses to both stresses at the molecular, cellular, and organismal levels.
RESUMO
The tomato, Solanum lycopersicum L. is one of the most consumed vegetables in the world; nevertheless, it is affected by biotic and abiotic factors that reduce its productivity. The whitefly is globally considered as the main pest under protected crop conditions, where biologic control using endophytic fungi emerges as a sustainable alternative. We evaluated the indirect effects of five native endophytic strains of Beauveria bassiana on the reproduction of greenhouse whiteflies and the growth of tomatoes. The plant growth substrate was inoculated with five strains of this endophyte and the resulting plants were then exposed to whiteflies afterwards. The effect that endophytic strains had on phosphate solubilization, iron siderophore production, plant height, and plant biomass were evaluated. The evaluated endophytes reduced the number of eggs per cm2 on leaflets compared to the control and behaved similarly to the commercial synthetic insecticide. Leaflets inoculated with strains RGM-557, RGM-644 and RGM-731 showed fewer nymphs than the control and those treated with insecticide. RGM-557 and RGM-731 produced the greatest plant heights; RGM-731 obtained the greatest plant biomass. Our study provides evidence that native endophytic strains of B. bassiana have a biocontrol effect on whiteflies and could be used to promote tomato growth.
RESUMO
The potato yellow vein disease, caused by the potato yellow vein virus (PYVV), is a limiting potato disease in northern South America. The virus can be transmitted either by the greenhouse whitefly (GWF), Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae), or through vegetative propagules, such as infected tubers. Recently, GWF populations have been spotlighted as one of the main drivers of PYVV re-emergence, and consequently, PYVV management has been predominantly directed toward vector control, which is heavily based on insecticide use. However, the drivers of the PYVV outbreaks as well as the contribution of GWF populations on the spread of PYVV among potato crops are still not completely understood. This study aims to assess the role of the GWF as a driver of the PYVV epidemic in the potato-producing areas in Colombia, one of the countries more severely affected by the PYVV epidemic, and whose geography allows the study of the spatial association between the vector and the disease epidemic across a wide altitude range. The geographical clusters where the PYVV epidemic is concentrated, as well as those of farms affected by the GWF were identified using a novel spatial epidemiology approach. The influence of altitude range on the association between PYVV and T. vaporarioum was also assessed. We found a relatively poor spatial association between PYVV epidemic and the presence of the GWF, especially at altitudes above 3,000 m above mean sea level. Furthermore, GWF populations could only explain a small fraction of the extent of the PYVV epidemic in Colombia. Movement of infected seed tubers might be the main mechanism of dispersion, and could be a key driver for the PYVV infection among potato crops. Agricultural policies focused on improving quality of seed tubers and their appropriate distribution could be the most efficient control intervention against PYVV dispersion.
RESUMO
La biología y ecología de la mosca blanca de los invernaderos, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyroridae), se encuentra ampliamente documentada. Sin embargo, hasta el momento no hay reportes acerca de la tasa de consumo de alimento por este fitófago, un parámetro necesario para modelos de simulación. Por tal motivo, el objetivo de esta investigación fue la medición indirecta del consumo de alimento por el adulto e instares inmaduros de T. vaporariorum basado en metodologías encontradas en la literatura científica. La estimación de la tasa de consumo de alimento por adultos se realizó bajo condiciones de laboratorio, utilizando como unidad experimental una planta de fríjol de dos semanas de edad. El experimento consistió de dos tratamientos: (T1) plantas libres de cualquier fitófago y (T2) plantas sometidas a infestaciones con T. vaporariorum, cada tratamiento con 20 repeticiones y una réplica en el tiempo de todo el experimento. Se registró el peso fresco diariamente en ambos tratamientos. Para el caso de los inmaduros, la unidad experimental consistió en una hoja cotiledónea de fríjol, infestada con una población determinada de inmaduros de cada instar de mosca blanca teniendo así cinco tratamientos (Instar I, II, III, IV y Control) cada uno con 17 repeticiones. Se registró diariamente el peso fresco de las hojas. Se obtuvo un consumo promedio de alimento por el adulto de 0,277 ± 0,0042 mg.dia-1. Para los dos primeros instares ninfales se estimó una tasa de consumo de 0,052 mg.dia-1, en el tercer instar de 0,14 mg.dia-1, y para el cuarto instar de 0,19 mg.dia-1. Un adulto de mosca blanca puede consumir en un día seis veces su peso y un inmaduro ocho veces, gracias a su rápido metabolismo y la constante excreción de mielecilla.
The biology and ecology of the greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyroridae), is widely documented. However, so far there are not reports about the rate of consumption of this phytophagous. Therefore, the objective of this research was to measure the food consumption by the adult and immature instars of T. vaporariorum based on indirect methodologies found in the literature. The estimate of the food consumption rate by adults was conducted under laboratory conditions, using as experimental units plant beans two weeks old. The experiment consisted of two treatments: (T1) plants free from any phytophagous and (T2) plants subjected to infestation with T. vaporariorum, with 20 repetitions each treatment and replicated over time. In the case of the immature individuals, the experimental unit consisted of a bean cotyledon leaf infested with a population of immature individuals of each instar of whitefly, having five treatments (Instar I, II, III, IV and Control) each with 17 repetitions. Fresh weight of leaves was recorded daily. An average food consumption of 0.277 ± 0.0042 mg.day-1 was obtained for the adult. For the first two nymphal instars food consumption rate of 0.052 mg.day-1 was estimated, for the third instar 0.14 mg.day-1, and for the fourth instar 0.19 mg.day-1. An whitefly adult can consume in a day six times its weight and an immature eight times, this thanks to the rapid metabolism and a constant excretion of honeydew of the species.
RESUMO
Life-history parameters of the greenhouse whitefly Trialeurodes vaporariorum (Westwood), an important pest of bean crops in Colombia, were determined in environmental control chambers on two dry bean (Phaseolus vulgaris) cultivars (cv.). Trialeurodes vaporariorum longevity on cv. Chocho decreased as temperature increased from 22.6 d at 19ºC to 5.9 d at 26ºC. Fecundity was significantly lower at 19ºC (8.6 eggs/female), as compared to 22ºC (32.6 eggs/female) and 26ºC (33.3 eggs/female) on cv. Chocho. Fecundity on cv. ICA-Pijao was much higher (127.2 eggs/female) than on cv. Chocho (32.6 eggs/female) at 19ºC. The intrinsic rate of population increase (r m) was highest at 22ºC (0.061), intermediate at 19ºC (0.044) and lowest at 26ºC (0.035) on cv. Chocho, and was 0.072 on cv. ICA-Pijao at 19ºC. Life history parameters of T. vaporariorum are compared to those of one of its natural enemies, the parasitoid Amitus fuscipennis MacGown & Nebeker. Finally, data are presented on the distribution of the parasitoid related to the altitude for the Valle del Cauca, Colombia.
Se determinaron los estadísticos vitales de la mosca blanca Trialeurodes vaporariorum (Westwood), una plaga importante del cultivo del fríjol en Colombia, en cámara ambiental en dos cultivares (cv.) de fríjol. La longevidad media de T. vaporariorum en el cv. Chocho fue mayor a 19ºC (22.6 d), intermedia a 22ºC (17.5 d) y menor a 26ºC (5.9 d). En el cv. ICA-Pijao la longevidad media fue de 35.5 d a 19ºC. La fecundidad media total fue 8.6, 32.6 y 33.3 huevos por hembra a 19, 22 y 26ºC, respectivamente en el cv. Chocho. La fecundidad en el cv ICA-Pijao fue mucho más alta, 127. 2 huevos por hembra, a 19ºC, que la del cv. Chocho. La tasa intrínseca de crecimiento poblacional (r m) fue más alta a 22ºC (0.061), intermedia a 19ºC (0.044) y más baja a 26ºC (0.035) en el cv. Chocho. Ella fue de 0.072 a 19ºC en el cv. ICA-Pijao. Se comparan los estadísticos vitales de T. vaporariorum con los de su enemigo natural, el parasitoide Amitus fuscipennis MacGown & Nebeker y se zonifica la distribución del parasitoide en el Valle del Cauca, Colombia.
Assuntos
Animais , Feminino , Sistemas Ecológicos Fechados , Fabaceae/parasitologia , Hemípteros/fisiologia , FertilidadeRESUMO
Trialeurodes vaporariorum (West.) is a pest of greenhouse vegetables and ornamentals and infests crops in Europe and in the American continent. In Brazil, just a few cases are known on economic crops, being all restricted to greenhouse crops. In 2003, in Itatiba and neighboring localities of State of São Paulo, Brazil, field infestations of T. vaporariorum were observed, mainly on tomato and green bean. So far, whitefly infestation in this area expanded to squash and kale also. Field studies are needed for determining interactions of T. vaporariorum with plants and natural enemies, injury levels, and methods of control.
Trialeurodes vaporariorum (West.) é praga de hortaliças e ornamentais em cultivo protegido e infesta diversas culturas na Europa e nas Américas. No Brasil, as informações sobre sua ocorrência restringem-se a estudos em casa de vegetação. Em 2003, em Itatiba e cidades adjacentes (SP), observaram-se infestações de T. vaporariorum em hortaliças e ornamentais em campo, com maiores níveis populacionais em tomateiro e feijão-vagem. Nos anos seguintes, as infestações se mantiveram, atingindo cultivos de couve e de aboboreiras. São necessários estudos em campo para conhecer as interações dessa mosca-branca com plantas e inimigos naturais, níveis de dano e avaliação de métodos de controle.