Browsing by Subject "biologinen torjunta"

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  • Kangas, Niina (Helsingfors universitet, 2013)
    The aim of this study was to look into the possibility of using predatory mites as a biological control agent in the nursery production. This study focuses on the biological control of two phytophagous mites, Tetranychus urticae and Aculus schlectendali that occur as pests in apple seedling production. The directive 2009/128/EY of the European Union obligates the farmers to follow the principles of the integrated pest management and favour other control methods, such as biological control, rather than chemical pesticides. This study is a part of The Finnish Nursery Producers Association’s project that aims to develop biological control practices for the nursery production in Finland and promote integrated pest management in nursery production. The experiments for this study were carried out outdoors in a field and indoors in a seasonal greenhouse, where the population development of T. urticae and A. schlechtendali on apple seedlings was followed. Population density of mites was counted from leaf samples gathered from the seedlings in two week intervals from May until the end of August. Biological control of T. urticae was tested with Phytoseeid mites, Neoseiulus barkeri and Phytoseiulus persimilis. Chemical control was used as a comparison treatment. The effects of the biological control were followed by comparing the population densities of phytophagous mites in the area of biological control to the mite densities in the area of chemical control. N. barkeri and P. persimilis were not able to prevent nor stop T. urticae population growth in the greenhouse where the densities of T. urticae grew higher in the area of biological control than in the area of chemical control. Outdoors the population densities of T. urticae remained low throughout the experiment in both treatment areas. Population densities of A. schlechtendali grew high indoors and outdoors within both treatments. Even though biological control did not succeed in these experiments, the conditions in the greenhouse were suitable for Phytoseeid mites and in theory it should be possible exploit them as control agents in nursery production. The high densities of A. schlechtendali were surprising. In the future it would be important to consider the importance of this species as a pest and find effective means to control it.
  • Roivainen, Osmo Heikki (University of Helsinki, 1960)
  • Salmi, Andreas (Helsingfors universitet, 2017)
    Biological sprout control with Chondrostereum purpureum (Pers. ex Fr.) Pouzar was integrated to mechanized early cleaning. In this method, liquid with hyphae of C. purpureum was sprayed on the freshly cut stumps. C. Purpureum has been studied for biological sprout controlling since 1980’s. This species is a common basidiomycete saprophytic fungus found in Finland, and thus does not cause a biological risk. Early cleaning and pre-commercial cleaning of young forests have not experienced major innovations since the brush saw. Mechanizing of work has been thought to be a solution for increasing working costs. Chemical sprout control has been restricted to special targets, which addresses more interest on alternative biological methods. In this research, effectivity of biological stump treatment and factors affecting the results were investigated. Early cleaning was done in eight study sites during June–September 2014. Inside the sites, area was partly treated with mechanical cutting and by applying C. purpureum stump on freshly cut stumps, and partly with mechanical cutting only (a control treatment). 15 circular sample plots with a radius of one meter per treatment were founded in studied young forest stands (altogether 480). All stumps and saplings with a diameter over 5 mm were studied in 9-10/2015. The data includes altogether 2030 hardwood stumps. Stump mortality, number of living sprouts and the height of the sprouts were modelled for birch, rowan, aspen and willow. Results revealed that sprout control with C. Purpureum affected mortality, sprout number and height of birch sprouts. Mortality increased with time lag after treatment and with increasing stump diameter. The results showed that mortality level of 50 % was reached after two growing seasons. Sprout number increased with increasing stump basal area and decreased with time lag after treatment. Number of other saplings on the plot and soil moisture effected negatively on sprout number. Sprout height increased with increasing stump basal area and stump height. Number of other saplings and stumps on the plot affected birch sprout height negatively. Results of C. Purpureum stump treatment were weaker for other studied hardwood species (rowan, aspen, willow) and other factors affected more than biological sprout control. Effectiveness of sprout control in this study was weaker than in other studies presented recently. Time span of this study was considerably short and final results are seen some years after stump treatment. Another factor to consider is the spreading method used in this study. Stump treatment integrated to mechanized early cleaning of young conifer plantations need to be developed further so that this method would be profitable in practical silviculture.
  • Poutanen, Jari (Helsingfors universitet, 2014)
    Gray mold (Botrytis cinerea) is an important disease of strawberry. The pathogen is spread by spores to strawberry flowers, from where the disease spreads to the developing berries. It progresses fast especially in high humidity and without any control. It can destroy even half of the crop. In conventional production, the strawberries have been sprayed by fungicides several times in beginning of summer. Only approved biological fungicides in Finland are Prestop- ja Prestop mix (Verdera Oy), and those can be spread to strawberries by honey bees (Apis mellifera), witch visits in the flowers of strawberry. For this task, the special additional equipment must been installed to hives. Inquiry survey have been made for the strawberry growers, witch have used the entomovectoring control method. The survey clarifies the problems of beginning to use the method, laboured and profitability, problems relating to bees and the needs of develop. Result of the survey is, that the growers have quite committed to use entomovectoring control method, even that many growers told that it was laboured and the efficency could not been seen clearly. The main reasons for the use of method were control of gray mold, reduce of chemical control and safety for user and environment. In addition to method gave image benefit to grower and improved pollination of strawberry. Getting started and use of method were more often trouble-free. The main development points were to extent the time between the addition of pesticide to the spreader equipment and to develop the method for commercial bumble-bee (Bombus terrestris) hives.
  • Kallio, Tauno (Suomen metsätieteellinen seura, 1976)
  • Kallio, Tauno (Suomen metsätieteellinen seura, 1973)
  • Andersson, Johanna (Helsingin yliopisto, 2014)
    Bacterial soft rot and blackleg are amongst the major diseases of potato (Solanum tu-berosum L.). In Finland Pectobacterium atrosepticum, Pectobacterium carotovorum subsp. carotovorum, Pectobacterium wasabiae and Dickeya-species cause rotting of the tuber and softening of stems on potato. These diseases cause major postharvest losses and weaken the quality of the crop, which is a problem in seed potato production. The aim of this study was to determine whether the antagonistic bacteria are toxic to in vitro plants, as well as to study the ability of the antagonistic bacteria to spread inside or on the in vitro plants. It was also investigated if the antagonistic bacteria can prevent soft rot of potato in in vitro plants, as well as the ability of the antagonistic bacteria to prevent the spreading of soft rot bacteria from soil to the plants. This study was carried out in laboratory and in greenhouse conditions in the University of Helsinki at the Department of Agricultural Sciences. As potato material cultivar Melody was used and as antagonistic bacteria 10 different bacteria were chosen: Serratia plymuthica A30 (NR), Flavobacterium sp. strain B17 (A3), Agrobacterium sp. (A6), unsequensed bacteria isolated from potato root (A4), Serratia j5h9 (S1), Alcaligenes faecalis (R8), Bacillus M1ju27 (BC1), Bacillus S3H53 (BC2), Burkholderia M1423 (BK3) and Pseudomonas S2h50 (PS3). Dickeya solani and Pectobacterium carotovorum were used as pathogens. Although BC1, BC2, S1 and BK3 antagonists did not influence negatively the potato in vitro seedling growth they did not, however, properly prevent soft rot of in vitro plants. Further studies on preventing soft rot of in vitro plants is needed.
  • Keva, Maaria (Helsingfors universitet, 2017)
    Pollen beetle is one of the most harmful pests of rapeseed and turnip rape in Europe. It can cause considerably high yield losses. In addition, due to routine use of pyrethroids, pyrethroid resistant strains of pollen beetle have developed in several European countries, including Finland. One alternative for pesticides is biological control, which can be enhanced by improving the survival of natural enemies of pests. In Finland two species of natural enemies of pollen beetle occur: Phradis morionellus and Diospilus capito. The aim of this study was to investigate long term changes in percent parasitism and test if certain factors have influence on it. The main data on percent parasitism was collected during 1985-1995 from different locations of the turnip rape cultivation area in Finland. To get some current data, percent parasitism was observed in 2015, though from smaller area than in the main data. In addition to data on total percent parasitism, specific data on both parasitoid species was available for most of the years. Also the density of pollen beetle larvae was observed during 1990-1995. Supplementary data was collected on soil types, growing zones, precipitation and average temperature and annual severity of aphid and pollen beetle attack. To test differences between geographical areas, the observed locations was divided into 18 minor areas, and further into six grand areas. Several statistical analyses were ran on such a diverse data. The results show that percent parasitism differed significantly between years, geographical areas and growing zones. Percent parasitism was significantly relative to temperature in May and rain in July, but no differences were found between related soil types. Percent parasitism was not relative to density of host larvae, but correlated negatively with host density in the following year. Strong negative correlation between both severity of aphid attack and annual sale of dimethoate indicates that the parasitoids are exposed to pesticides in those years with high annual abundance of aphids. From the two parasitoid species, P. morionellus occurred much more abundant than D. capito. As observed, percent parasitism can be very high, but in some years and geographically it can be diminished due to several factors. By decreasing harmful activities, parasitism could be enhanced and biological control of pollen beetle could be improved.
  • Ojanperä, Taru (Helsingfors universitet, 2008)
    The causal agents of Potato scab, S. scapies, S. turbidiscapies and S. aureofaciens spoil the quality of tubers, slow down the formation of potato seedlings, increase the number of small sized tubers and therefore can have a significant impact on the potato harvest. Sometimes the technical methods applied in the potato farming are not effective enough and there are no chemical means available to prevent potato scab. In this work the properties of selected Finnish Actinomyces-isolates were studied from the point of view of biological control. Both potato scab forming and stains that do not cause visible signs of potato scab in tubers were selected for the study. The purpose was to study the ability of the stains to inhibit the growth of potato scab bacteria in different pH-conditions. In addition the ability of Streptomyces-strains to inhibit the growth of silver scurf, stem cancer and black scurf was studied. The competitive balance between different Actinomyces and fungal strains was tested on plates. Greenhouse tests were used to study the root infesting of Actinomyces strains. Streptomyces strains inhibited each others growth. This inhibition was not linked to scab. All strains tested prevented the growth of silver scurf and ps pathogens but strains S.griseoviridis ja 16IV turned out being especially effective in preventing. All strains grew in pH-conditions 5.5-8.0. An unknown Streptomyces strain 16IV did not grow well in pH 5.5 and S. turbidiscapies which is known to persist in acidic conditions grew well also in pH 8.0. All tested strains colonized potato root. The study showed that some of the isolates had potential for future studies in biological control. More research is needed to study the root colonization and the antagonism properties of selected strains in root conditions. The causal agents of Potato scab, S. scapies, S. turbidiscapies and S. aureofaciens spoil the quality of tubers, slow down the formation of potato seedlings, increase the number of small sized tubers and therefore can have a significant impact on the potato harvest. Sometimes the technical methods applied in the potato farming are not effective enough and there are no chemical means available to prevent potato scab. In this work the properties of selected Finnish Actinomyces-isolates were studied from the point of view of biological control. Both potato scab forming and stains that do not cause visible signs of potato scab in tubers were selected for the study. The purpose was to study the ability of the stains to inhibit the growth of potato scab bacteria in different pH-conditions. In addition the ability of Streptomyces-strains to inhibit the growth of silver scurf, stem cancer and black scurf was studied. The competitive balance between different Actinomyces and fungal strains was tested on plates. Greenhouse tests were used to study the root infesting of Actinomyces strains. Streptomyces strains inhibited each others growth. This inhibition was not linked to scab. All strains tested prevented the growth of silver scurf and ps pathogens but strains S.griseoviridis ja 16IV turned out being especially effective in preventing. All strains grew in pH-conditions 5.5-8.0. An unknown Streptomyces strain 16IV did not grow well in pH 5.5 and S. turbidiscapies which is known to persist in acidic conditions grew well also in pH 8.0. All tested strains colonized potato root. The study showed that some of the isolates had potential for future studies in biological control. More research is needed to study the root colonization and the antagonism properties of selected strains in root conditions.
  • Wuorenrinne, Heikki (Suomen metsätieteellinen seura, 1974)