Hannover, University, Diss., 2002.

No description available.

Nutrition of host plants has been shown to have a direct effect on the productivity of numerous insect pests, including western flower thrips [(WFT) Frankliniella occidentalis (Pergande)] – a major pest on both horticulture and agronomic crops. Plants use constitutive and induced chemical defenses to aid in protection against phytophagous insects. Reductions in WFT abundance in response to decreased nutrient availability has been attributed to the reduced availability of nutrients required for WFT productivity. The goals of this research were to determine the effects of fertilization on chemical defenses, and subsequent effects on WFT feeding and abundance. More importantly, the effects of fertilization and WFT feeding on plant growth, development, physiology, and quality were determined to assess the viability of optimizing fertilization in order to increase host plant resistance in gerbera. Constitutive (i.e. phenolics) and induced (i.e. jasmonic acid) chemical defenses were enhanced when fertilization was reduced. Reducing fertilization increased the total phenolics and wound- and WFT-induced jasmonic acid (JA) accumulation in gerbera. The enhanced chemical defenses in lower fertility plants resulted in reduced WFT abundance and feeding damage. These results indicate that the strategy for some plant species under nutrient stress is to increase constitutive defenses, while maintaining, or possibly increasing inducible defenses instead of growth. Similar to 0X fertility plants (only supplied with initial fertilizer charge in commercial media), 0.3X (received 30% of recommended rate) gerberas had reduced biomass and greater chemical defenses compared to 1X plants, but these plants did not appear to be nutritionally stressed—and 0.3X plants without WFT were rated as marketable. Reducing fertilization by 70% (0.3X) did not affect flower dry mass (DM) or the rate of flowering, but the flower stalks (peduncles) were taller in response to the fertilizer reduction. Hence, reducing fertilization to a moderate level in gerbera production may reduce susceptibility to WFT, while producing marketable crops.

Zugl.: Berlin, Humboldt-Univ., Diss., 2007

Herbivory by Western Flower Thrips (Frankliniella occidentalis Pergande) (WFT) and drought-stress due to limited water availability are currently two major factors that can severely impact cotton (Gossypium hirsutum L.) production. This dissertation examines the effects of drought-stress on cotton and host-plant resistance (HPR) to WFT in laboratory conditions, and seeks to identify the physiological and morphological mechanisms that underlie drought-tolerance and HPR. A life-history systems-approach was developed that provides a new level of detail for understanding how environmental variation impacts adult female WFT. The approach was illustrated by investigating the combined effects of cotton genotype, periodic drought-stress, and prey availability on the adult female omnivorous thrips using a factorial design. Three treatment conditions were significantly different, none of which were predicted based on prevailing ecological-hypotheses. At the same time, the approach produced three novel insights about WFT life-history and reproductive strategy. The roles of negative photo-taxis and leaf biomechanical properties were investigated as potential mechanisms that influence WFT foraging-decisions on individual cotyledons. Results showed that WFT foraging-decisions could be considered adaptive, but there was limited support for either of the mechanisms investigated. The physiological responses to drought stress and drought recovery were investigated for three transgenic cotton cultivars and an untransformed wild-type (WT). At peak drought, ABA levels, stomatal area, and stomatal apertures in the transgenic isolone, AtRAV1-1 were 48% lower, 27.7%, and 16.3% smaller than WT. These results suggest that AtRAV1-1 was the most drought-tolerant and support the hypothesis that changes in stomatal morphology may have functionally contributed to drought-tolerance. Lastly, I investigated whether changes in phytohormone concentrations associated with periodic-drought stress in four cotton cultivars (three transgenic and WT) were correlated with WFT feeding, fitness and state-dependent reproductive responses (i.e., the relationship between initial weight and reproduction). Results showed that JA-Ile and JA were positively correlated with state-dependent egg viability and fecundity, respectively, and negatively correlated with total egg viability and fecundity, respectively, supporting the hypothesis that JA and JA-Ile underlie the negative effects on WFT reproduction and the associated shift to state-dependent reproduction.

Memoria para optar al Título Profesional de Ingeniero Agrónomo Mención: Sanidad Vegetal / Durante la temporada 2011, se estudió el efecto de la concentración del aceite mineral (Elf Purespray 15E) sobre la incidencia del daño producido por el trips occidental de las flores, Frankliniella occidentalis Pergande, sobre cerezas (Prunus avium L.) variedad Sweetheart en etapa de precosecha. El ensayo se realizó en el huerto de cerezos “Agrícola Río Cipreses” en la Comuna de Requínoa, VI Región del Libertador Bernardo O´Higgins. El aceite se aplicó en tratamientos a concentraciones del 0,5; 0,7 y 1% Para el ensayo se seleccionaron grupos de cerezas contiguas a mediados de la etapa de coloración clasificada por la Fundación para el Desarrollo Frutícola (FDF) como “rojo claro”, y se sumergieron en una solución de cada tratamiento durante 5 seg. Posteriormente, fueron infestados con 30 individuos adultos de trips occidental y encerrados en bolsas de tela. La evaluación se realizó a la cosecha, considerando la superficie dañada de cada fruto. Los resultados promedio de las repeticiones por cada tratamiento se clasificaron en una escala que consideró 5 categorías de daño: nulo, bajo, leve, moderado y alto. Se empleó un diseño de bloques completos aleatorizados con 4 tratamientos, 4 repeticiones y 15 cerezas por unidad experimental. Los resultados se normalizaron mediante la transformación angular de Bliss y posteriormente se sometieron a un análisis de varianza y a una prueba de rango múltiple de Tukey. Se concluyó que las aplicaciones de aceite mineral a concentraciones iguales o superiores al 0,7% en precosecha reducen la incidencia de daño de trips en cerezas. / The effect of mineral oil (Elf Purespray 15E) applied at concentrations of 0.5, 0.7 and 1% on the incidence of western flower thrips in Sweetheart cherries was studied during the 2011 season. The trial was done in the Agrícola Rio Cipreses cherry orchard at the Requínoa locality, in the Libertador Bernardo O’Higgins VI Region of Chile. For the trial, groups of adjacent cherries at the middle of the light red coloration stage (as classified by de Chilean Fruit Growing Foundation) were chosen and each group was dipped in its respective treatment for 5 sec. Later they were infested with 30 western flower adult individuals and enclosed in cloth bags. The assessment was conducted at harvest, considering the damaged surface of each fruit. Average replication results per each treatment were classified on a scale considering five damage categories: nule, low, mild, moderate, and high. A randomized complete block design with four treatments was used, with four replications and 15 cherries as the experimental unit. Results were normalized by angular transformation of Bliss before subjecting them to ANOVA test and Tukey’s multiple range test for mean separation. It was concluded that mineral oil applications at concentrations equal to or greater than 0.7% before harvest reduce thrips damage incidence in cherries.

Memoria para optar al Título Profesional de Ingeniero Agrónomo / Durante la temporada 2013-2014 se estudió el efecto de la aplicación de aceite mineral (Purespray 15E) y aceite vegetal (Protek) sobre la incidencia de la mancha anular marrón producida por el Trips de California, Frankliniella occidentalis Pergande, en uva de mesa variedad Thompson seedless durante el periodo de cierre de racimo. Se realizó un ensayo en un huerto comercial ubicado en la comuna de Buin, Región Metropolitana, en el que se evaluó tratamientos de aceites mineral y vegetal con diferentes concentraciones y número de inmersiones. Para el ensayo se seleccionaron racimos sanos y homogéneos de 150 bayas aproximadamente, los que se sumergieron en cada tratamiento durante 5 segundos. Posteriormente se infestaron con 50 adultos de Trips de California y fueron encerrados en bolsas de tul; transcurrida una semana se realizó una segunda inmersión en los tratamientos que correspondía y se repitió la infestación en las unidades experimentales. Los racimos se encerraron nuevamente en bolsas de tul hasta la evaluación. La evaluación se realizó en periodo de cosecha, considerando el porcentaje de bayas que presentaban daño por Trips de California, caracterizado como mancha anular marrón. Se empleó un diseño de bloques completamente aleatorizados con 10 tratamientos y 8 repeticiones, siendo la unidad experimental un racimo. Se consideró cada planta como un bloque independiente. Los resultados se normalizaron mediante la transformación angular de Bliss. Posteriormente se sometieron a un análisis de varianza y prueba de comparaciones múltiples DGC. Los tratamientos de Aceite Mineral (Purespray 15E) al 0.5% y al 0.75% reducen efectivamente el daño causado por F. occidentalis durante el periodo de cierre de racimo. Los tratamientos con Aceite Vegetal (Protek) al 0.5% y al 0,75% reducen parcialmente el daño causado por F. occidentalis durante el periodo de cierre de racimo. / During the 2013-2014 season, the effect of the application of mineral oil (Purespray 15E) and vegetable oil (Protek) on the incidence of brown ringspot caused by the Western Flower Thrips (Frankliniella occidentalis Pergande) on table grape was studied, focusing on the Thompson seedless variety during cluster closing time. Trials were conducted in a commercial orchard located in the commune of Buin, Metropolitan Region, treatments mineral and vegetable oils with different concentrations and number of dives were evaluated. For the test, healthy and homogeneous clusters of approximately 150 berries were selected, and immersed in each treatment for 5 seconds. Then, they were infested with 50 adults of Western Flower Thrips and locked in tulle bags; after a week, a second application was performed of the corresponding treatments and the infestation was repeated in all experimental units. The clusters were again locked in tulle bags until evaluation. The evaluation was conducted in harvest period, considering the percentage of berries that showed damage from Western Flower Thrips, characterized as brown ringspot. Design of completely randomized blocks of 10 treatments and 8 repetitions were used. The experimental unit being a cluster. Each plant is considered as a separate block. The results were normalized by Bliss' angular transformation. Subsequently, they were subjected to a variance analysis and DGC multiple comparisons tests. Treatments with Mineral Oil (Pure Spray 15E) at 0.5% and 0.75% effectively reduce the damage caused by F. occidentalis during cluster closing time. Vegetable oil treatments (Protek) at 0.5% and 0.75% only partially reduced the damage caused by F. occidentalis during the cluster closing.

Thrips are pests in a variety of crops and are responsible for millions of dollars in damage worldwide. In Virginia there are a few key thrips species that cause a large portion of damage to both vegetable and floricultural crops. Three prominent pests include Frankliniella tritici (Fitch), Frankliniella fusca (Hinds), and Frankliniella occidentalis (Pergande). Significant yield losses in row crops such as cotton, peanuts and vegetables have been attributed to feeding and oviposition of these insects in high densities. In addition, both F. fusca and F. occidentalis can transmit plant pathogenic tospoviruses, such as tomato spotted wilt virus (TSWV), in certain susceptible crops. While all of these thrips species are difficult to detect due to their cryptic lifestyles, F. occidentalis is a particularly challenging pest to manage due to its resistance to many insecticides commonly used for thrips treatment. Early spring weeds were sampled for the presence of F. occidentalis in 2008 and 2009 in eastern Virginia. Weed samples consisted of mustard, henbit and wild radish and were collected from several different sites on the Eastern Shore of Virginia. During the summer of 2008, 2009 and 2010 various agroecosystems were sampled for the relative incidence of F. occidentalis. Overall, thrips numbers were very low in weed samples. F. occidentalis was detected in early spring weed samples in 2009 at a few of the sites sampled. In nearly every habitat, the species composition was dominated by F. fusca and F. tritici, with F. occidentalis occurring in very low numbers. Two different lures were evaluated in their ability to attract Frankliniella spp. thrips. The lures included Chemtica P-178 floral kairomone (AgBio Inc., Westminster, CO), a floral iii kairomone lure composed of a proprietary floral compound mixture, and ThriplineAMS (Syngenta Bioline Ltd., Oxnard, CA) pheromone lure, containing the aggregation pheromone of F. occidentalis. In spring 2009 and 2010 lure experiments were conducted in several different agroecosystems including: a tomato and potato field in Painter, VA, a cotton and peanut field in Suffolk, VA, and grass fields near a greenhouse in Virginia Beach, VA, and a high tunnel in Chesapeake, VA, as well as within these structures. Baited and non-baited sticky cards were arranged in a completely randomized design, with a pan trap located in the center of each plot. Traps were collected approximately twice weekly. F. fusca numbers were low and catches on sticky cards were not significantly affected by either lure. Sticky cards baited with the kairomone caught more flower thrips than traps baited with the pheromone, or the non-baited traps, especially when thrips numbers were high. Several biologically derived insecticides including: essential oils, spinetoram, spinosad, pyrethrins, and azadirachtin, were evaluated in their efficacy against thrips in several different crops. Randomized complete block design experiments were carried out in: tomatoes, snap beans, collards, soybeans, cotton and peanuts grown in several locations in southeastern Virginia in 2009 and 2010. Both spinetoram and spinosad reduced thrips numbers the most effectively compared with the untreated control. Peanut and cotton treated with spinosad, and treatments containing spinetoram suffered less thrips injury compared with the control, and yield was higher in cotton plots treated with spinetoram. / Master of Science in Life Sciences

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv., 2006. / Härtill 5 uppsatser.

vegetable crops. Micro-Tom is a model tomato cultivar used for research due to its small size and short time to fruiting. This project evaluated I. walleriana and Micro-Tom transformed with Agrobacterium. The construct contained GFP (green fluorescent protein) and hygromycin antibiotic-resistant selectable markers, and the antisense sequence of open reading frame of INSV nucleocapsid protein (N). The N gene is expected to confer INSV resistance by RNA interference or gene silencing. The presence of transgenes was confirmed by PCR. Transgenic Impatiens was selfed for two generations. Transgenic Micro-Tom was selfed for 4 generations. Spinach was used as an INSV reservoir. Impatiens, spinach and Micro-Tom were mechanically inoculated with INSV and evaluated visually, with assay tests, ELISA testing, and PCR. Spinach was successfully infected with INSV six times of seven attempts. Impatiens and Micro-Tom had no successful inoculations of three and five attempts, respectively. / Master of Science