Arthropod pests cause significant problems in agricultural crops all around the world. As chemical pesticide use becomes less desired, there is a need for alternative methods of pest control.... Show moreArthropod pests cause significant problems in agricultural crops all around the world. As chemical pesticide use becomes less desired, there is a need for alternative methods of pest control. Inspired by the natural adhesiveness of arthropod trapping plants, we examined the effectiveness of adhesive droplets made from oxidised and cross-linked plant-derived oils for control of western flower thrips. Two filter paper droplet adhesiveness assays and three detached chrysanthemum leaf assays were carried out to test efficacy against thrips. Suspensions containing adhesive droplets and other constituents were applied to filter papers and leaves via spraying or dipping. On filter papers, droplets made from oxidised rice germ oil (RGO) of different sizes caught 40–93% of thrips. Droplets made of a mixture of sunflower, olive, and linseed oil (MIX) caught up to 94% of thrips. Likewise, adhesive droplet-treated filter papers showed higher thrips mortality than untreated or control solution-treated filter papers. On chrysanthemum leaves, thrips were caught by both RGO (up to 40%) and MIX droplets (up to 20%) and thrips damage and reproduction were reduced. On MIX-treated leaves, thrips mortality was also increased. Within treatments, droplets of different size classes occurred and larger droplets were more effective at catching thrips in general. Droplets were also robust to rinsing with water, which is of importance for their application in horticulture. In conclusion, adhesive droplets made from edible plant oils show potential for use in control of western flower thrips. Show less
We showed that constitutive and inducible chemical and morphological defenses against Western flower thrips differ between tomato and chrysanthemum plants. Furthermore, we demonstrated that both... Show moreWe showed that constitutive and inducible chemical and morphological defenses against Western flower thrips differ between tomato and chrysanthemum plants. Furthermore, we demonstrated that both plant species respond differently to bacteria-derived defense elicitors, such as the phytotoxin coronatine. This highlights the plant species-specificity of these interactions and the possible limitation for the use of pathogen-associated molecular patterns to enhance the plant immune system. This study thus provides knowledge and novel strategies for Western flower thrips control. Yet, further comprehensive work is needed to evaluate the influence of these induction strategies on plant fitness. Show less
Plants produce a vast array of secondary metabolites (SMs). Some hypotheses were put forward to explain the diversity of structurally related SMs within the framework of plant defense against... Show morePlants produce a vast array of secondary metabolites (SMs). Some hypotheses were put forward to explain the diversity of structurally related SMs within the framework of plant defense against herbivores:1) SMs could be Selectively Neutral; 2) SM diversity is a result of the __Arms Race__ between plants and the herbivores; 3) Plants benefit from the SM diversity because of the Synergistic Effects among the SMs; 4) The SM diversity may be a response to the Selection from Multiple Herbivores. In this thesis, a hybrid family originated from an artificial cross between Jacobaea aquatica and Jacobaea vulgaris was used as a model system to study the selective forces from insect herbivores on pyrrolizidine alkaloids (PAs) evolution. The Jacobaea hybrid family showed great variation in PA variation and herbivore resistance. By means of three bioassays, one with a specialist (Tyria jacobaea) and two with generalist insect herbivores (Frankliniella occidentalis and Liriomyza trifolii), I could show that Jacobaea hybrid genotypes differed in the resistance to these herbivores and these differences were related to PA variation in the plants. Several PAs were involved in the resistance to insect herbivores. These results support the three hypotheses except Selectively Neutral Theory. Show less
