Sirvi Autor "Veromann, Eve (advisor)" järgi
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Kirje Effect of host plants and land use on cabbage seed weevil infestation and associated parasitoids(Eesti Maaülikool, 2018) Kovács, Gabriella; Veromann, Eve (advisor); Luik, Anne (advisor); Kiss, József (opponent)The need for more sustainable pest management strategies has been increasing in light of the harmful effects that insecticides have on non-target organisms and recent regulation changes. This study aimed to provide a basis for sustainable plant protection approaches to control an important oilseed rape pest, the cabbage seed weevil (Ceutorhynchus obstrictus). Firstly, to find potential biocontrol plants that could increase the parasitism rates of C. obstrictus, the infestation rate, and parasitoid communities of this pest were assessed on different spring-sown brassicaceous plant species during small plot studies. Out of the studied plant species, Raphanus sativus showed potential to be a biocontrol plant by having the highest proportion of parasitized weevil larvae and eggs, and by providing a habitat for egg parasitoids (Mymaridae) that are less common but effective parasitoids of C. obstrictus. Secondly, to be able to create landscapes that supress C. obstrictus, we studied the effect of land use in the surrounding landscape on the infestation and parasitism rate of C. obstrictus in winter oilseed rape. Herbaceous habitats close to the crop increased both the proportion of C. obstrictus-infested pods and parasitism rates, while infestation rates were also affected by habitats at larger distances. Throughout the study, parasitism rates were remarkably high (up to 87%), and sufficient to control the cabbage seed weevil without insecticide use. These findings offer useful and novel implications to develop habitat management in cropping systems for natural pest suppression.Kirje Examining thiacloprid, essential oils and double-stranded RNA for potential use in biosafe management of pollen beetle(Eesti Maaülikool, 2021) Willow, Jonathan; Veromann, Eve (advisor); Smagghe, Guy (advisor); Cook, Samantha (opponent)Throughout Europe, one of the most severely damaging threats to oilseed rape (Brassica napus) cultivation is the pollen beetle Brassicogethes aeneus; and routine use of pyrethroid insecticides has led to resistance development among B. aeneus populations. Moreover, exposure to pyrethroids can be detrimental to many nontarget insect taxa that inhabit agroecosystems. While studies have demonstrated some potential for relying on biological control (biocontrol) organisms, especially parasitoid wasps, for biosafe management of B. aeneus populations, the most effective B. aeneus management strategy will likely involve insecticide applications that show efficacy against B. aeneus while simultaneously minimising the impact on nontarget organisms. We examine the potential utility of three types of insecticide within a biosafe integrated B. aeneus management strategy. The first is the neonicotinoid thiacloprid, which has previously shown efficacy against B. aeneus, yet must be tested for biosafety in a model parasitoid wasp. Second, we examined potential for using seven different plant-based essential oils (EOs) in B. aeneus management. Last, we investigated the potential for applying B. aeneus-specific double-stranded ribonucleic acid (dsRNA), representing a potentially species-specific biopesticide option, within a B. aeneus management strategy. Exposure to residues of thiacloprid resulted in significant reductions in Aphelinus abdominalis (model biocontrol organism) survival and mobility. Moreover, simultaneous exposure to residues of thiacloprid and tebuconazole (a fungicide commonly tank-mixed with thiacloprid) resulted in synergistic reductions in A. abdominalis survival and mobility. Cinnamon (Cinnamomum verum) bark EO was the most effective EO tested against B. aeneus via topical application. However, subsequent assays using C. verum EO-sprayed leaf- and bud surfaces showed significant control efficacy only at concentrations too high for practical field application of an EO. Field relevant dietary routes of exposure to dsRNA targeting B. aeneus coatomer subunit alpha (αCOP) resulted in significant gene silencing and gene silencing-induced mortality. However, refinements to B. aeneus larval bioassay setups, as well as developing dsRNA formulations that enhance transport past the oilseed rape bud epithelium, and/or enhance dsRNA uptake in B. aeneus, represent critical steps to understanding the potential for RNAi-based management of B. aeneus. Most notably, we observed that RNAi efficacy is enhanced by chronic dsRNA feeding in B. aeneus. This result has implications for the economics and development of a potential dsRNA spray approach for managing B. aeneus; and it highlights the need for research into the development and potential future use of RNAi oilseed rape cultivars, given the enhanced RNAi efficacy resulting from chronic dsRNA feeding in B. aeneus.Kirje Sustainable approaches to oilseed rape pest control : steps towards to integrated pest management(Estonian University of Life Sciences, 2024) Vilumets, Silva; Veromann, Eve (advisor); Institute of Agricultural and Environmental Sciences; Beckmann, Michael (opponent)ABSTRACT. Intensive agricultural has diminished the natural and semi-natural habitats in the agricultural landscapes, negatively impacting biodiversity. To maintain a biologically diverse agricultural landscape supporting various species, diversity and heterogenity are crucial. Oilseed rape, one of the most important crops in agriculture, is an attractive food source for many arthropods. However, it faces challenges from several insect pests such as the pollen beetle and cabbage seedpod weevil. Synthetic insecticides are mainly used to control the pests but both pests have developed resistance. Therefore, finding effective environmentally friendly pest control methods is crucial. The study revealed that winter oilseed rape fields located over 500m from the previous year's field had significantly fewer pollen beetles and cabbage seedpod weevils compared to fields closer than 500m. Field-adjacent habitats had minimal impact on pest abundance, highlighting the significance of temporal and spatial separation of crop fields in mitigating pest populations. The study also explored parasitoid presence, revealing high parasitism rates in all years, even up to 90%, consistently exceeding the 32% threshold for effective natural pest control. Parasitism rates were not significantly affected by the distance from the previous year's oilseed rape fields but thrived in landscapes with diverse natural and semi-natural areas. Essential oils like Cinnamomum verum and Cuminum cyminum proved to be effective against the cabbage seedpod weevil. However, the results also showed their lethal effect on parasitoids, both adults and larvae. Moreover, monitoring for species that may benefit from the changing climate conditions, build up their populations and reach to pest status, is crucial. The study identified C. sulcicollis, previously uncommon in Estonia damaging oilseed rape plants. While not presently considered an important pest, climate-induced distribution changes may alter its status. This highlights the urgency of studying various species affecting oilseed rape, especially given the changing climate. The thesis provides an important information about the biology of both pests and their natural enemies, along with practical guidance for producers on crop rotation. It emphasizes the importance of a diverse landscape and finding alternative means of control to reduce the use of synthetic insecticides, aligning with the goals of the European Union agricultural strategy "Farm to Fork".Kirje Utilizing tritrophic interactions to develop sustainable plant protection strategies for oilseed rape(Eesti Maaülikool, 2014) Kaasik, Riina; Veromann, Eve (advisor)Oilseed rape is one of the most important cruciferous crops grown in Europe and other parts with a temperate climate. Today, conventional agricultural practices rely heavily on chemical inputs, which have negative side effects on the environment and pesticides also lose their efficiency. This study investigated 1) the attractiveness and impact plant species and nitrogen fertilisation have on M. aeneus and its parasitoids and 2) the impact of nitrogen fertilisation on volatile organic compounds’ emission. The aim was to gain knowledge on how to manipulate M. aeneus’ abundance through their preferences. The feeding and oviposition preferences of M. aeneus and its parasitoids were studied on plants from the genus Brassica, Sinapis, Eruca, and Raphanus (Capparales: Brassicaceae). The results showed that although M. aeneus oviposit and/or feed on all studied plant species, their attractiveness differed. During the green-yellow bud stage S. alba and B. nigra were the most attractive. For oviposition, species of the genus Brassica were preferred over S. alba and E. sativa but not over R. sativus. The larval abundance was generally higher on B. napus although, depending on year the attractiveness of B. nigra was almost the same or even higher. The plant species also influenced the number of buds used for oviposition by M. aeneus. The clutch size was smaller on R. sativus compared to Brassica species. Larval survival rate was studied on all plant species but dead larvae were found only on R. sativus and E. sativa. The attractiveness of R. sativus was comparable to B. napus and one third of larvae failed to survive. The influence of plant species was also confirmed for third trophic level, parasitoids, and their species composition. The percentage of parasitized larvae was equal or higher than on B. napus on all plant species but E. sativa and R. sativus. Four species of parasitoid were found: Tersilochus heterocerus, Phradis morionellus, Diospilus capito and one unidentified species with low occurrence (<1%). Fertilisation also had impact on both pest and parasitoids, probably via VOC emission, which also differed with N fertilisation levels. Larval abundance was the highest on moderate and high nitrogen levels and the lowest at on zero fertilisation level which was attractive to parasitoids. The highest emission rates were for acetic acid, 3-carene, α-pineen and bensoealdehüüdi and emission rates of several VOCs increased with nitrogen fertilisation. The abundance of M. aeneus larvae was positively correlated with emission rates of 3-carene, limonene and indole while β-pinene, (E,E)-α-farnesene, benzaldehyde, methylbenzoate linalool were inhibitory for M. aeneus oviposition. These results show probabilities to use environmental friendly pest management systems for M. aeneus, to collect larvae to certain areas on the field where the trap crop can be destroyed in case of high pest abundance. By using mechanical destruction, it can also be used in organic farming. Brassica nigra and S. alba have potential for conventional trap cropping to prevent damage caused by overwintered M. aeneus adults. The lethal effect of R. sativus on M. aeneus was shown for the first time. Brassica nigra was attractive for oviposition which can be used to influence the next generation. The biological control-assisted trap cropping on B. napus can be promoted by using B. nigra and B. juncea, but also B. rapa and S. alba. By increasing the abundance and species diversity of parasitoids the damage caused by M. aeneus could be kept below economic threshold levels therefore decrease environment pollution. Such precautionary methods can be used in integrated and organic farming. Pest and parasitoid abundance could also be manipulated by optimising nitrogen fertilisation. By using moderate nitrogen input the pressure on the environment could be reduced and the crop might become less attractive to the pest.