[Evolution of the damage caused by Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) on the host plant. Influence of the predation by Amblyseius cucumeris (Oudemans) (Acari: Phitoseidae)]
1993
Gerin, C. | Hance, T. (Universite Catholique de Louvain, Louvain-la-Neuve (Belgium). Unite d'Ecologie et de Biogeographie)
The Western Flower Thrips Frankliniella occidentalis is a well known pest in glasshouses. Little information is available on its biology and biological control. That is why the three trophic plant-phytophagous-predators relationship was analysed. Three kinds of experiments were done: 1) bean plants used as control, were allowed to develop without pest, 2) bean plants were infested with Frankliniella occidentalis at a known density, 3) bean plants infested with the thrips and the predator Amblyseius cucumeris at defined starting densities. The authors measured: 1) the development of the weight/area ratio of 'control' leaves, 2) the leaf damage development, 3) the growth of the prey population, 4) the growth of the predator population. It appears that without the pest, the weight/area ratio remained constant throughout the experiment. In the presence of Frankliniella occidentalis, this ratio and the leaf damage area increased linearly until the death of the plant, on day 36. The predators introduced were unable to change this development. Prey population growth in presence of Amblyseius cucumeris is rather different than without predators, but the reduction in number was not sufficient to protect the plants. This is probably the consequence of the polyphagous diet of the predator or the plant pubescence. In the future, plant thrips relationships will be studied in more details.
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