Marleena Hagner

Acute toxicity of birch tar oil on aquatic organisms

Birch tar oil (BTO) is a by-product of processing birch wood in a pyrolysis system. Accumulating evidence suggests the suitability of BTO as a biocide or repellent in terrestrial environments for the control of weeds, insects, molluscs and rodents. Once applied as biocide, BTO may end up, either through run-off or leaching, in aquatic systems and may have adverse effects on non-target organisms. As very little is known about the toxicity of BTO to aquatic organisms, the present study investigated acute toxicity (LC50/EC50) of BTO for eight aquatic organisms. Bioassays with the Asellus aquaticus (crustacean), Lumbriculus variegatus (oligochaeta worm), Daphnia magna (crustacean), Lymnea sp. (mollusc), Lemna minor (vascular plant), Danio rerio (fish), Scenedesmus gracilis (algae), and Vibrio fischeri (bacterium) were performed according to ISO, OECD or USEPA-guidelines. The results indicated that BTO was practically nontoxic to most aquatic organisms as the median effective BTO concentrations against most organisms were >150 mg L-1. In conclusion, our toxicity tests showed that aquatic organisms are to some extent, invariably sensitive to birch tar oil, but suggest that BTO does not pose a severe hazard to aquatic biota. We deduce that, unless BTOs are not applied in the immediate vicinity of water bodies, no special precaution is required

Birch tar oil is an effective mollusc repellent: field and laboratory experiments using Arianta arbustorum (Gastropoda: Helicidae) and Arion lusitanicus (Gastropoda: Arionidae)

Populations of two molluscs, the land snail Arianta arbustorum and the Iberian slug Arion lusitanicus, have increased substantially in many places in the northern Fennoscandia in recent years. This has resulted in considerable aesthetic and economic damage to plants in home gardens and commercial nurseries. Birch tar oil (BTO), is a new biological plant protection product, and was tested against these molluscs. In this study we examined whether 2 types of BTO, used either alone, mixed together, or mixed with Vaseline®, could be applied as 1) a biological plant protection product for the control of land snails by direct topical spray application, 2) as a repellent against snails when painted on a Perspex® fence, and 3) as a repellent against slugs when smeared on pots containing Brassica pekinensis seedlings. Both the fences and the pots with seedlings were placed in each field with a high population of the target organism. When applied as a spray on snails, BTO did not act as a toxic pesticide but rendered the snails inactive for a period of several months. The BTO barriers were effective in repelling both snails and slugs. However, the repellent effect of BTO alone against the molluscs was short-term. Repeated treatments were required to keep the slugs away from the plants and we found that the interval between treatments should not exceed two weeks. A collar fastened around the rim of the pots, combined with the BTO treatment, did not give any additional benefit in hindering slugs from invading the plants. Most noticeably, the BTO+Vaseline® mixture prevented the land snails from passing over the treated fences for up to several months. The results of these experiments provide evidence that BTO, especially when mixed with Vaseline®, serves as an excellent long-term repellent against molluscs.

Effects of birch tar oils on soil organisms and plants.

Koivupuun pyrolyysissa puuaine hajoaa lammon vaikutuksestaerilaisiksi tuotteiksi. Prosessin yhteydessa syntyy muun muassa koivuoljytisletta (birch tar oil BTO). Koivuoljytisle nayttaa useiden viela tarkemmin tutkimattomien todisteiden mukaan toimivan rikkakasvien, tuhohyonteisten ja jyrsijoiden torjunta-aineena. Sen koostumuksesta, vaikutuksista ymparistoon ja myrkyllisyydesta elioille on kuitenkin saatavilla hyvin vahan tietoa. Taman tutkimuksen tarkoitus oli selvittaa koivuoljytisleen 1) vaikutus maaperan ankyri- ja sukkulamatoihin seka mikro-organismeihin seka maarittaa koivuoljytisleen 2) 14 vrk:n LC50 arvo peltolierolle (Aporrectodea caliginosa) ja 28 vrk EC50 arvo hyppyhantaisen (Folsomia candida) lisaantymiselle. Koivuoljytisleen vaikutukset maaperan ankyrimatojen biomassaan- ja sukkulamatojen lukumaaraan olivat vahaisia. Kasvillisuuteen BTO vaikutti tappaen suurimman osan kasvien maan paallisista osista vuorokauden kuluessa. Kasvillisuuden toipuminen alkoi kuitenkin nopeasti eika kenttakokeessa havaittu 2.5 kk kuluttua kasittelyista kasvibiomassassa ja kasvilajistossa eroa, vuohenputkea (Aporrectodea caliginosa) lukuunottamatta, eri kasittelyjen kesken. Sen sijaan mikrokosmoksissa tehdyissa kokeissa kasvibiomassa oli viela 50 vrk kuluttua kasittelyista 100% koivutisleella kasitellyissa maissa merkitsevasti pienempi kuin kontrollimaissa. Koivutisle ei vaikuttanut mikrobien biomassaan. Sen sijaan se vaikutti positiivisesti mikrobiaktiivisuuteen heti lisayksensa jalkeen toimien ilmeisesti lisaresurssina mikrobeille. Negatiivinen vaikutus mikrobiaktiivisuuteen 28 ja 42 vrk kuluttua koivutisleen lisayksesta saattoi johtua kasvien kuihtumisesta: kasvit kuolivat eivatka siten vapauttaneet juurieritteita maaperaan, mutta kuolleesta kasvillisuudesta ei ollut viela ehtinyt modostua kariketta mikrobien ravinnoksi, jolloin ne vaipuivat lepotilaan. Kaiken kaikkian koivuoljytisleen vaikutus maaperan ravintoverkkoon oli vahainen. 14 vrk:n LC50 arvo peltolierolle (Aporrectodea caliginosa) oli 6560 mg BTO1 kg-1 ja 28 vrk EC50 arvo hyppyhantaisen (Folsomia candida) lisaantymiselle oli 5100 mg BTO1 kg-1. Luvut viittaavat koivutisleen olevan elioille myrkyllista vasta suurina pitoisuuksina verrattuna moniin nykyisin kasvinsuojelussa vastaavissa tarkoituksissa kaytettyihin kemiallisiin yhdisteisiin.

Use of Botanical Pesticides in Modern Plant Protection

The European Union has made very clear political decisions to increase environmental awareness. A Thematic Strategy on the Sustainable Use of Pesticides was launched by the Commission of the European Communities in 2006. It was decided to minimize the hazards and risks to health and the environment caused by the use of plant protection products. In 2009, the European Parliament accepted a new framework directive on the sustainable use of pesticides. Directive 2009/128/EC fosters the development of plant protection and integrated pest management (IPM) in the EU. The directive states that “when pesticides are used, appropriate risk management measures should be established and low-risk pesticides as well as biological control measures should be considered in the first place“. Biological control comprises various technologies of which one option is the use of botanical products. Many kinds of plant species and technologies have been used in the production of botanical pesticides. Some but not many of the plant-based pesticides have already become established plant protection products (Isman 2006). There are many methods to extract essential oils and liquids from plant material, the most popular being steam distillation. Other methods are expression, enfleurage, maceration, solvent extraction and pyrolysis. Pyrolysis has been thoroughly described by Tiilikkala et al. (2010), proving that slow pyrolysis has been known for thousands of years. It has been used in the production of charcoal (biochar), tar, pitch and wood vinegar. The liquids which are most useful as biocides and pesticides are tar and wood vinegar. Tar has mainly been used as a wood preservative. The production and use of wood vinegar has increased rapidly in Asian countries, including Japan, China, India and Thailand. As a result of active development numerous botanical pesticides have been put on the market during the last 10 years (Tiilikkala et al. 2010). Simultaneously, pyrolysis has also become a frequently used technology in waste treatment which may lead to a rapid increase in the production of liquids based on the use of organic matter. The raw materials used for the production of botanicals will differ in different parts of the world because of divergent natural resources. In Finland we have a huge reserve of wood

Assessing toxicity of metal contaminated soil from glassworks sites with a battery of biotests

The present study addresses toxicological properties of metal contaminated soils, using glassworks sites in south-eastern Sweden as study objects. Soil from five selected glassworks sites as well as from nearby reference areas were analysed for total and water-soluble metal concentrations and general geochemical parameters. A battery of biotests was then applied to assess the toxicity of the glassworks soil environments: a test of phytotoxicity with garden cress (Lepidium sativum); the BioTox™ test for toxicity to bacteria using Vibrio fischeri; and analyses of abundancies and biomass of nematodes and enchytraeids. The glassworks- and reference areas were comparable with respect to pH and the content of organic matter and nutrients (C, N, P), but total metal concentrations (Pb, As, Ba, Cd and Zn) were significantly higher at the former sites. Higher metal concentrations in the water-soluble fraction were also observed, even though these concentrations were low compared to the total ones. Nevertheless, toxicity of the glassworks soils was not detected by the two ex situ tests; inhibition of light emission by V. fischeri could not be seen, nor was an effect seen on the growth of L. sativum. A decrease in enchytraeid and nematode abundance and biomass was, however, observed for the landfill soils as compared to reference soils, implying in situ toxicity to soil-inhabiting organisms. The confirmation of in situ bioavailability and negative effects motivates additional studies of the risk posed to humans of the glassworks villages.