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Before its establishment in Estonia at the beginning of the twenty-first century, the Colorado potato beetle Leptinotarsa decemlineata Say was a notifiable quarantine pest for many years. In high-latitude environments it encounters strong evolutionary pressure to adapt to low temperatures due to high overwintering mortality and periodic influx of new individuals from more southern populations. Our study focused on gathering evidence for such a range shift leading to the formation of a permanent local population. The phenology and overwintering success of beetles was investigated from 2008 to 2015. Depending on weather conditions in the different years, the overwintered beetles emerged from the soil from the beginning of May to mid-June. Over 700 degree days accumulated in 2010, 2011, 2013 and 2014 exceeding the limit needed for development of two generations. However, food supply and temperature distribution in the growing period enabled development of the second complete generation only in 2010 a...

The effects of different winter cover crops and their combination with composted cattle manure on weeds and crop yields were investigated within a five-field crop rotation (barley undersown with red clover, red clover, winter wheat, pea, potato) in three organic cropping systems. The control system (Org 0) followed the rotation. In organic systems Org I and Org II the winter cover crops were used as follows: ryegrass (Lolium perenne L. in 2011/2012) and a mixture of winter oilseed-rape (Brassica napus ssp. oleifera var. biennis) and winter rye (Secale cereale L.) in 2012/2013 before pea; winter oilseed rape before potato and winter rye before barley. In Org II system composted cattle manure was also applied. In comparison with the control system, the winter cover crops, depending on plant species used, reduced the biomass and density of the weeds. In both years winter rye was a better suppressor of weeds than the other winter cover crops. Cover crops increased the yield of potato in rotation crops...

In a field experiment based on a five-year crop rotation (pea, potato, barley undersown with red clover, red clover and winter wheat), several soil parameters, porosity, number and biomass of earthworms, total nitrogen, organic carbon, percentage of water stable aggregates and enzymatic activity, were studied during 2013 and 2014, the first and second year, respectively, since the first rotation concluded. This rotation was managed under three organic farming systems: Organic 0 (control), Organic I (with winter cover crops lately incorporated into the soil as green manure) and Organic II (with the same cover crops plus a yearly amendment of 40 t ha−1 of cattle manure). Crop rotation had a yearly positive effect on the soil bulk density, and enhanced the percentage of air filled pores; nonetheless, despite the leguminous crops in the rotation, all the systems presented a yearly decrease in total nitrogen in 2014. Cover crops along with manure only had a significant effect on enzymatic activity; how...

Since 2008, a 5-year crop rotation experiment (winter wheat, pea, potato, barley undersown with red clover, and red clover) has been run in Tartu, Estonia, to evaluate the changes in soil chemical parameters under four fertilizer managements: (1) unfertilized conventional plots (conventional I), (2) conventional plots with addition of mineral fertilizers (conventional II), (3) organic plots with cover crops during the winter period (organic I), and (4) organic plots with the same cover crops plus a yearly amendment of 40 t ha–1 of cattle manure (organic II). After the first rotation, results showed significant differences (P

The effect of thinning on fruit weight, color, biochemical composition, and on leaf insect occurrence was studied in an over 80-year-old orchard on two apple tree (Malus domestica Borkh.) old cultivars: Liivi Sibuloun and Paide Talioun. The study was conducted to restore an old orchard for quality apple juice production. Pruning led to a significant increase in pests, but the number of natural enemies of pests and of neutral insects did not increase. The total number of arthropods was significantly higher on ‘Paide Talioun’ in the second year after pruning. Consequently, more pests were found in both experimental years on this cultivar. Pruning significantly increased leaf SPAD value leading to a decrease in the total phenolics content of the fruit. The effect of thinning on ascorbic acid content was cultivar dependent. Fruit skin was greener, apple flesh color was yellower, and fruit weight increased by up to 60% after pruning. Among apple taste parameters, the sugar acidity ratio was not influenced by p...

We have established for the first time that Colorado potato beetle (CPB) (Leptinotarsa decemlineata Say) (Coleoptera: Chrysomelidae) produced a distinct second generation in 2010 in Estonia. This species has a history, in Estonia, of less than 50 years. Due to their great ability to adapt to variable environmental conditions, the beetles spread very quickly throughout the country and established a permanent population in the 1980s. Before 2010, CPB has been predominantly univoltine. The occurrence of the second generation was the result of rare coincidence of extremely favourable weather as the cumulative degree days (DD) of 927 exceeded the sum needed for two full generations. Constantly high temperatures from the beginning of May caused the formation of summer generation adults already by the end of July and the long day photoperiod, as well the availability of fresh food, kept the beetles in reproductive mode preventing the onset of diapause. Summer beetles continued to oviposit up to the second half o...

The use of synthetic pesticides is very common in conventional agriculture as plant protection measures and for improving storage of food. For increasing food safety, monitoring programmes are taki...

Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae) is a major pest of oilseed rape in Europe and North America. The last decade has seen growing interest in the occurrence, importance and efficiacy of its parasitoids as biocontrol agents. The infestation of pods by C. obstrictus larvae and their parasitism rates were assessed in a total of nine commercially-grown crops and fifteen experimental plots of winter oilseed rape in 2004–2007. Pod samples were collected at the pod maturation stage and incubated in emergence traps. Emerged larvae, their exit holes and parasitoids were counted and identified; the percentage of infested pods and parasitism rates were calculated. Pod infestation by larvae increased continuously over the study period. The parasitism level was lowest in 2005 and increased thereafter up to 96%. The most abundant parasitoid was Trichomalus perfectus (Walker), but Mesopolobus morys (Walker) and Stenomalina gracilis (Walker) (Hymenoptera: Pteromalidae) were also reared from hos...

Blackcurrants are an important berry crop in many European countries. There is increasing demand for new and economically valuable blackcurrant cultivars suitable for organic production. To meet this demand, potential candidates of blackcurrant cultivars have been studied under Estonian field conditions. Our aim was to evaluate blackcurrant cultivars with regard to their productivity, berry quality, and resistance to the blackcurrant gall mite (Cecidophyopsis ribis Westw.). Our results showed that the drop of berries was the highest in the control treatment (no fertilizers used), and the lowest in conventional treatment. Higher yields were obtained from the conventional and organic treatments. The most productive cultivar, with the biggest berries and highest ascorbic acid content irrespective of cultivation system, was the cultivar ‘Pamyati Vavilova’. Organically cultivated berries had a higher content of ascorbic acid than did conventionally cultivated berries. Minor damage by mites was observe...

The impact of minimised (MIN – no plough, direct drilling, no pesticides) and standard (STN – plough, standard application of pesticides) cropping systems on the abundance of old (previously overwintered) and new generations of Meligethes aeneus (Fabricius) (Nitidulidae, Coleoptera) was assessed in spring oilseed rape in 2003 – 2005 in Estonia. Old generation M. aeneus were more abundant in STN than in MIN crops, despite the application of insecticide, probably because the latter reduced M. aeneus damage to the buds, making STN crops more attractive to M. aeneus seeking feeding and oviposition resources. The abundance of new generation M. aeneus showed a strong linear increase over the 3 years, on both MIN and STN systems. In 2005, the abundance of new generation M. aeneus was significantly greater in the STN than in the MIN field. The study showed that the application of insecticides promotes population increase in new generation M. aeneus.

Im Internationalen Organischen Stickstoffdauerdungungsversuch (IOSDV) in Tartu (Estland) wurde in der Kartoffel‐Sommerweizen‐Sommergerste‐Fruchtfolge die Abundanz der dominierenden Schadlinge—Blattlause, Zikaden, Wiesenwanzen, Blasenfuse, Blattwespen —in zwei Pflanzenentwicklungsstadien wahrend der Sommer 1992–1996 bestimmt. Die Ergebnisse der funfjahrigen Untersuchungen wurden mit der Regressionsanalyse ausgewertet, um die Bedingtheit der Abundanz verschiedener Insektengruppen von der Stickstoffdungung unter verschiedenen Temperaturbedingungen zu erklaren. Die einzelnen Insektengruppen haben auf die Dungung in den verschiedenen Entwicklungsstadien der Wirtspflanze sehr unterschiedlich reagiert. Die N‐Mengensteigerung (von 40 bis 160 kg/ha) hat die Blattlause auf der Kartoffel in beiden Phanophasen gefordert. Beim Getreide hat die Dungung mit der N‐Menge 160 kg/ha die Blattlause gehemmt. Die N‐Dungung hat ganz gering die Zikadenabundanz auf dem Getreide beeinflust. Die Wiesenwanzen haben im allgemeinen im...