Thèse (M.Sc.)--Université Laval, 2006. / Titre de l'écran-titre (visionné le 14 mai 2007). Bibliogr.

Cranberry tipworm, Dasineura oxycoccana Johnson (a gall‐making fly), disrupts normal growth of cranberry (Vaccinium macrocarpon Aiton) by injuring the apical meristem of shoots or uprights. The impact of larval feeding injury on reproductive parameters of cranberry was determined, from one growing season to next, at upright (Maine and Massachusetts, 2008 ‐ 2009) and plot levels (Massachusetts, 2009 – 2010 and 2010 ‐ 2011). I also estimated the proportions of uprights injured because of tipworm feeding at several cranberry production sites (Massachusetts and Maine) and the proportions of uprights that produced flowers and fruits in the next growing season. Tipworm‐injured uprights tagged at the end of the growing season did not produce floral‐units (following year) across sites in both Massachusetts and Maine. There was significant variation among the sampled sites in the proportions of tipworm‐injured uprights and also in the proportions of uprights with flowers in the next growing season (Massachusetts and Maine). A trend was apparent wherein sites with higher tipworm injury levels had relatively lower flowering proportions in the next growing season. However, sites in Massachusetts did not differ in the proportions of uprights that set fruit and in a replicated study, significant reduction in tipworm injury at plot level (using insecticide) did not impact flower and fruit production in the next growing season. A two‐year field study was carried out at three different locations to determine the impact of tipworm feeding injury on the reproductive and vegetative growth of two cranberry cultivars (‘Howes’ and ‘Stevens’) in Massachusetts. Individual uprights of cranberry exhibited tolerance to natural (tipworm) and simulated apical meristem injury in the current growing season (fruit production) and results were corroborated by a greenhouse study. In the field study, weight of fruit was higher intipworm‐injured uprights as compared with intact control uprights at the sites with Howes. However, majority of injured uprights (tipworm and simulated) did not produce new growth from lateral buds (side‐shoots) before the onset of dormancy. In the next growing season, fewer injured uprights resumed growth and produced flowers as compared with intact uprights at two of the three sites.

Lic.-avh. Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 2 uppsatser. Felaktigt institutionsnamn i publikationen. Rätt namn: Department of Entomology.

This thesis deals with rape and the possibilities of its protection against pests. The most important pests of this crop include rape stem weevil (Ceutorhynchus napi, Gyllenhal 1837), rape beetle (Brassicogethes aeneus Fabricius, 1775 Meligethes aeneus) and brassica pod midge (Dasineura napi, Loew 1850). In the practical part of the dissertation, 26 variants of application sequences of insecticides were evaluated. The first and last variant was taken as a control and therefore not treated with any insecticide. Insecticides were applied on the basis of pest control. In each variant, an insecticide was first applied, which was primarily intended for rape stem weevil (Ceutonhynchus napi, Gyllenhal 1837). The second insecticide was focused on rape beetles (Brassicogethes aeneus Fabricius, 1775, Meligethes aeneus). The third application of the insecticide was determined for the brassica pod midge (Dasineura napi Loew, 1850). The results were evaluated and entered into tables and subsequently statistically processed using Statistica 12. The aim of this work was to evaluate the most effective sequence of three insecticides against the main rapeseed pests. The view was also taken on an anti-resilient strategy in which insecticides having the same active substance should not be applied.

Les infestations de la cécidomyie du sapin (Paradiplosis tumifex), un ravageur important du sapin baumier (Abies balsamea), surviennent périodiquement et ont été observées dans les plantations du sud du Québec de 2000 à 2002. Divers ennemis naturels causent probablement les fluctuations cycliques d'abondance, tels que la cécidomyie inquiline des galles (Dasineura balsamicola) et diverses espèces de parasitoïdes. Cette étude réalisée en Estrie, visait à documenter leurs interactions, afin d'évaluer leur rôle dans l'effondrement des populations de P. tumifex survenu en 2003. Cinq espèces de parasitoïdes associés à P. tumifex ont été identifiées. Des données relatives à la présence de plusieurs parasitoïdes dans une même galle (multiparasitisme) suggèrent des interactions négatives (interférence) fréquentes entre les ennemis naturels de P. tumifex. De plus, les forts taux d'inquilinisme et de parasitisme indiquent que ces ennemis naturels sont probablement responsables de l'effondrement des populations de ce ravageur, en 2003 dans les plantations du sud-ouest du Québec.