The impact of~owers on the population growth of Frankliniella occidentalis was characterized on wax~ower plants\ Impatiens walleriana[ In the presence of~owers\ the populations grew exponentially while in their absence\ the thrips populations only maintained themselves and showed no growth The di}erence in number and in size of thrips reared in both conditions suggested that the~owers were essential for the success of thrips development[ In the presence of~owers\ the distribution of females between the leaves and the~owers varied strongly according to the availability of owers[ By contrast\ the proportion of _rst larvae in the~owers increased up to the last day of the experiment[
In less than 3 years (1986–1988) Frankliniella occidentalis, imported from USA, had spread throughout Europe. It is a polyphagous Thysanoptera which causes important yield loss in greenhouses, in both vegetable and ornamental crops. However, insufficient data are available on its basic biology. The purpose of this work was thus to establish its life table. A cohort of 95 individuals were observed daily during their whole lifetime. The development time is short, 14.2 days, and no significant difference has been observed between males and females. The mean fecundity is high, as 43.17 larvae were produced by a single female. The intrinsic rate of natural increase is 0.140, meaning that the theoretical population may double in 4.94 days.
Physiological aspects of damage caused by spider mites on tomatoes leaflets The two‐spotted spider mite Tetranychus urticae Koch is one of the most common plant pests, feeding on leaves. The damage caused by this mite on tomato Lycopersicon esculentum Mill was classified in five visual degrees of a damage on leaflets index, each related to a mean spider mites density. According to these visual damages, the injury to leaflets was further investigated by analysing two important physiological processes: photosynthesis through assimilation of CO2, and transpiration through stomatal resistance to water diffusion. As results, the assimilation of CO2 decreased exponentially with the increasing damage, whereas the density of the total spider mites was related to the latest by a positive exponential relation. On the other hand, the resistance to water diffusion was not well related to spider mite damage; it only appeared that the stomatal resistance increase was very limited until damage degree three, corresponding to a mean of 23 spider mites by dm2, was reached. Résumé L'acarien tisserand commun Tetranychus urticae Koch est l'un des ravageurs phytophages les plus courants, rélisant sa nutrition au niveau foliaire. Les dégǎts provoqués par cet acarien sur tomate Lycopersicon esculentum Mill ont été classés en cinq niveaux visuels d'une échelle de dégǎts sur folioles. A chaque niveau correspond une densité moyenne d'acariens. Sur base de cette échelle de dégǎts, les dommages sur folioles ont été précisés en étudiant deux processus physiologiques importants que sont la photosynthèse, à travers l'assimilation de CO2, et la transpiration par la résistance stomatique à la diffusion de la vapeur d'eau. Une décroissance exponentielle de l'assimilation du CO2 en fonction de l'augmentation des dégǎts est observée, alors que la densité totale d'acariens augmente de manière exponentielle. D'autre part, la résistance à la difusion de la vapeur d'eau ne présente pas de relation nette avec les dommages causés par les acariens. Il apparaǐt seulement que l'accroissement de la résistance stomatique est peu marquée en‐deçà d'un niveau modéré de dégǎts (degré «3»), ce qui correspond à une densité moyenne de 23 acariens par dm2. Zusammenfassung Physiologische Aspekte von Spinnmilben‐Schäden an Tomatenblättern Tetranychus urticae Koch ist einer der häufigsten Schädlinge an Pflanzenblättern. Schäden, die durch diese Spinnmilbe an Tomatenpflanzen Lycopersicon esculentum Mill hervorgerufen wurden, wurden in fünf Schadklassen eingestuft, wobei jede zu einer mittleren Spinnmilbendichte in Bezug gesetzt wurde. Nach diesen visuell eingestuften Schadklassen wurden die Blattverletzungen durch Analyse zweier wichtiger physiologischer Prozesse weiter untersucht. Die Photosynthese wurde mittels der CO2‐Assimilation bestimmt und die Transpiration durch die stomatäre Resistenz gegenüber Verdunstung. Die CO2‐Assimilation nahm mit zunehmendem Schaden exponentiell ab, wohingegen die Spinnmilbendichte z...
The warehouse pirate bug Xylocoris flavipes is an opportunist predator of many stored product insect pests. Its functional response in relationship with variable densities of prey appears as the Holling's type II model. The predator X. flavipes, collected within small holder granaries in Mayo Danay division in the far North province of Cameroon, feeds on Tribolium castaneum (Herbst) and could perform a good biological control of this pest.
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