Browsing by Subject "Phyllotreta"

From the beginning of 2013, the European Commission restricted the use of neonicotinoid based insecticides on honeybee attracting plants, such as Brassica oilseeds. This was done because neonicotinoids were believed to cause the death of honeybees. The initiative for this study came from the need to adapt to the change in insecticide use on oilseed crops. Adaptation had to happen at a time when the environmental effects of chemical control agents are evaluated from all sides. The aim of the study was to investigate if there was a correlation between seedling stage trichome abundance, or seed glucosinolate content, and flea beetle damage in Brassica rapa subsp. oleifera. The usability of trichomes and seed glucosinolates in increasing plant resistance against flea beetles was evaluated according to the results. The significance of seedling stage trichome density on the amount of flea beetle damage was investigated in field assays at Jokioinen 2015, and Loimaa 2016. Total glucosinolate content of different lines was determined from crushed seeds. Leaf trichome density, or seed total glucosinolate content, didn´t have a statistically significant effect on the formation of flea beetle damage. However, there is a multitude of scientific literature repeatedly suggesting that leaf trichomes can decrease flea beetle damage. This raises a question about the purposefulness of the methods used in exploring the phenomenon. Despite of this, the study revealed lines which suffered little beetle damage, because of an unknown reason. In the case of future research focus should be aimed at determining the resistance mechanisms in these lines. The role of glucosinolates, and their various hydrolysis products, as flea beetle repelling agents should be examined one compound at a time. This is because of their varied effects on flea beetle behaviour. Repelling substances are needed especially at the early seedling stage, because plants are most vulnerable to flea beetle damage at this growth stage. To maintain good nutritional and feed value, glucosinolates appearing in the seed should be avoided.