Abstract. The distribution, species association and number of pest insects on winter oilseed rape of varieties ‘Wotan’ and ‘Express’ were studied in field experiments. Three catching methods were used: black plastic basins on the soil surface between plants, yellow flight traps filled with water at the height of the crop canopy and the shaking of plants above a plastic basin. The most abundant pest species was the pollen beetle, Meligethes aeneus, while the number of individuals from the species M. virescens in traps was much lesser. The other  important group of pest insects were weevils Ceutorrhynchus spp., the most common of which was the cabbage seed weevil, C. assimilis.  Three species of flea beetles Phyllotreta undulata, Ph. vittata and Ph. nemorum were typical contents of traps during May. In the last decade  of May, there was a large number of thrips (Thysanoptera, Tripidae) in traps.

Winter oilseed rape began to flower to some extent later, when pest insects of cruciferous plants had ended their hibernation. Therefore, the pests first inhabited weeds and already flowering plants, from where they later moved onto winter oilseed rape.

    In the field of winter oil seed rape, chemical pest control with a pyrethroid, Fastac, did not significantly influence the abundance of  pest insects. In the last decade of May, the total number of beetles in all test variants was relatively small, but, at the beginning of June, it increased almost to an equal extent. On the basis of flight traps, heavy damage of pods could be assumed, however, only a few larvae fell into traps on the soil surface, and virtually no damaged pods were detected. Thus the spraying with Fastac had no significant effects on the number of insects caught in traps.     

Key words: winter oilseed rape, damage, insect pest distributions, pollen beetle, Meligethes aeneus, seed weevil, Ceuthorrhynus assimilis

Abstract. The yield and fruit quality of 6 sea buckthorn (Hippophae rhamnoides L.) cultivars of a Moscow breeding programme were studied at the Rõhu Experimental Station in South Estonia. The chemical contents of fruits of sea buckthorn were analysed after 3 months of cold-storage at –18°C. ‘Trofimovskaya’ appeared to have more sugars (2.9%) than the other cultivars. ‘Otradnaya’ had the lowest acid content (2.1%). ‘Vorobjevskaya’, ‘Trofimovskaya’ and ‘Otradnaya’ had higher ascorbic acid contents (about 65 mg/100 g) than the other tested cultivars. ‘Vorobjevskaya’ gave the highest yield (9.6 kg/tree) in the 3rd year after cutting down the trees to 2.5 m height. In the following year, the yield of the experiment was significantly higher, whereas cultivars Trofimovskaya and Botanicheskaya had the biggest yields.

Key words: sugars, titratable acids, ascorbic acid, yield

Abstract. For many years, Prunus cerasifera Ehrh. seedlings of high vigour have been the most widespread seedling rootstock in Estonia. Plum growers are interested in less vigorous plum rootstocks which are productive with good fruit quality, easily harvested, early fruiting and less expensive to manage. In a new experiment (a collaborative project together with Latvian, Lithuanian and Byelorussian scientists), two plum cultivars, Queen Victoria and Kubanskaya Kometa, grafted onto 16 different rootstocks: Prunus Ackermann, Prunus Brompton, Prunus Brompton S, Prunus G 5–22, Prunus marianna GF 8–1, Prunus St. Julien A, Prunus St. Julien GF 655/2, Prunus St. Julien INRA 2, Prunus St. Julien Noir, Prunus St. Julien d’Orleans, Prunus St. Julien Wädenswill, Prunus Pixy, Prunus domestica Wangenheims, Prunus cerasifera ‘Hamyra’, P. cerasifera (local) and P. cerasifera myrobalana, were planted in an orchard in spring 2001. The objectives of these trials were to give an assessment of newly introduced plum rootstocks and to find out their compatibility with the studied plum cultivars. According to the results obtained in the first growing season, 45 (11.7%) of the 384 trees planted in 2001 died. The lowest tree dimensions both of ‘Queen Victoria’ and ‘Kubanskaya Kometa’ were noted on Prunus St. Julien Wädenswill. Trees of ‘Kubanskaya Kometa’ on different rootstocks started to bear fruit in the 2nd year after planting (except P. cerasifera Hamyra). ‘Kubanskaya Kometa’ trees grown on Prunus St. Julien INRA 2 and Prunus St. Julien Noir produced significantly better first yield than on control rootstocks. ‘Kubanskaya Kometa’ on Prunus St. Julien A and Prunus Pixy gave the largest fruits (41 g and 40.5 g, respectively).

Key words: plum, dwarfing rootstocks, growth, yield, fruit quality, Estonia

Abstract. The experiment was carried out in the strawberry plantations of the Polli Horticultural Institute during two years, 2000–2001. ‘Bounty’ was the strawberry cultivar studied. The objective of the experiment was to evaluate the effectiveness of herbicide Basta 150 SL for problematic weeds and strawberry daughter plants. The strawberry plants were set in spring 1999, using  black plastic mulch. In the experiment, the plot size was 30 m2 (2 x 15 m) and planting scheme 1.2 x 0.3 m. The following treatment variants were used: 1. Untreated (control); 2. Basta 150 SL 3l/ha; 3. Basta 150 SL 5l/ha. Each variant was represented with 4 replications. The herbicide was applied twice by means of  a backpack sprayer: in May before  blooming and in August when new weeds had grown. The results of the experiment indicated that due to Basta 150 SL weed infestation in strawberry plantation was decreased. It was noted that, in both treatment variants, Basta 150 SL destroyed nearly 90–96% of strawberry daughter plants. The results also showed that Basta 150 SL did not cause damage to strawberry plants and berries. The herbicide applied in two doses (5 l/ha and 3 l/ha) did not affect the strawberry yield negatively. It was established that in both treatment variants yields were  increased by 26.9 and 29.2%, respectively. We noted that it was practical to use Basta 150 SL at the rate of 5 l/ha  only in the case of appearing perennial weeds (Taraxacum officinalis, Cirsium arvense, Viola arvensis) in an orchard. For other weeds, the rate of herbicide 3 l/ha suited well.

Key words: Herbicide Basta 150 SL, weeds, strawberry

Abstract. At present it has been firmly established that climate can be influenced by both natural forces and human activities. It is generally accepted that an increase in greenhouse gas (GHG) concentrations in the atmosphere results in the warming of the Earth’s surface. Recent changes in the European fauna of Lepidoptera have been considered as a northward shift of entire distribution areas, caused by global warming. Northern territories are invaded by temperate species, and  the process seemingly has a cyclic nature. An invasion of a new species is often followed by a rapid growth of its population and followed by its penetration into the neighbouring areas.

Key words: Estonia, Lepidoptera, distribution of moths, climate change

Abstract. The study was based on data gathered in 1995–2002 in areas where plant cultivation was discontinued for various reasons and at various times. The objective of the study was to track changes in plant community, biomass production and soil weed seedbank in the abandoned fields.

The discontinuation of cultivation resulted in the emergence of plant communities, which were characterized for the first 1–2 years by a considerable proportion of annual species. The length of the period with annual species having a large representation in a community depended in many cases on the spread of Elytrigia repens in the abandoned fields. In land left idle for 5–6 years, perennial species supplanted annual species. Apart from E. repens, aggressive species turned out to be Cirsium arvense and Artemisia vulgaris (predominantly scattered all over the field). Weed seed density in the ploughed layer (30 cm) of abandoned fields amounted 157,000 to 666,000 seeds m-2, with the upper 10-cm layer accommodating up to 51% of the total seedbank. The biomass produced by plants depended on the texture of the soil and the age of the plant community, being 32.6 t ha-1 at the maximum. The accumulation of organic matter on and in the soil is a positive development in abandoned fields. Abundant residue contributes to an improvement of the physical and mechanical properties of the topsoil layer, reducing soil bulk density and decelerating soil compaction. The surface residue is a favorable environment for soil fauna.

Key words: abandoned fields, weeds, organic matter, weed seedbank

Abstract. The reproductive growth intensity of micropropagated (MP) strawberry plants of cultivars Bounty, Jonsok and Senga Sengana, their three subsequent generations of runner plants (RP), two-year-old conventionally propagated runner (RP) plants, and micropropagated plants of different in vitro ages and origins were evaluated in  two field experiments conducted in South Estonia in 1997 and 2001.

The following conclusions may be drawn on the basis of these experiments: 1. Of the three cultivars included in the experiment, cv. Jonsok gave the highest number of runner plants. 2. The micropropagated runner plant generations of cv. Senga Sengana and the two- year-old conventionally propagated plants did not show reliable difference in their runner plant production. 3. Reproduction rate was influenced rather by the age of the plantation than by the age of micropropagation material. 4. A three-year-old plantation is not suitable for collecting material for further propagation. 5. Younger mericlones produce plants with higher runner production rates than  older ones.

Key words: Fragaria x ananassa, cultivars, in vitro planting material, runner plants

Abstract. The experiments with strawberries were carried out in 1999–2001. There were two cultivation types in the experiment: plastic mulch and straw mulch with burning after harvesting. The present research investigated the influence of mulches and cultivars on strawberry yield and profit. Straw mulch suits for ‘Jonsok’ and ‘Bounty’ because it increases yields. In places, where late-spring frost damages are usual, the growing of early cultivars with straw mulch would be practical. Plastic mulch suits better for cultivars susceptible to grey mould (‘Senga Sengana’). It is useful to grow different cultivars because their  yields are different according to years. The yield of the plant depends on the cultivar and on the cultivation technology. In year 2000 ‘Jonsok’ grown with straw was more productive and profitable than other cultivars. In 2001 ‘Senga Sengana’ grown with straw was the most productive and more profitable than ‘Jonsok’ and ‘Bounty’. The burning of leaves flights pests and weeds and farmers can save on chemicals. Using straw mulch is more perspective for getting higher yields and profit.

Key words: mulch, burning, defoliation, profit, cultivar

Abstract. The abundance of Large White Butterfly (LWB), Pieris brassicae fluctuates from year to year, and a peak in the population is reached in every five to seven years, after which there occurs an abrupt decrease in the abundance. The natural checks of the population are primarily weather, parasitoids and pathogens, but the quality of food is also an important factor. The criteria for estimating the influence of food were the duration of caterpillar stage, the mortality rate of caterpillars and prepupae, the weight of pupae and the winter mortality of diapausing pupae. Foodplants: Brassica oleracea var. capitata f. alba, B. oleracea var. capitata f. rubra, B. oleracea var. gemmifera, B. oleracea var. botrytis, B. oleracea var. acephala, B. napus var. napobrassica, Tropaeolum majus, Armoracia rusticana.

In our experiments, the most unsuitable foodplants for larvae were Tropaeolum majus and Armoracia rusticana. There appeared a high mortality rate among caterpillars feeding on both of them as well as among their hibernating pupae. It can be concluded that one of the reasons for the remarkable decrease in the pest population following the massive reproduction of LWB is the high mortality rate of caterpillars growing on less valuable foodplants. The pupae are underweight and, in most cases, they perish during winter.

Key words: Large White Butterfly, Pieris brassicae, foodplants, larval mortality, pupal body mass, hibernation

Abstract. Both variety genotype and climatic conditions influence the grain yield of oat. The field experiments were carried out in 1998_2002 at the Jõgeva Plant Breeding Institute (PBI) in Estonia to investigate the genetic and environmental variation of oat grain yield. 101 oat varieties from Germany, Sweden, Russia, Canada, USA, and other countries were included in the trial.

    As a result of the trial, the climatic conditions proved to have considerable influence on the grain yield of oat. Oat grain yield was decreased by drought and high temperatures in 1999 and 2002. Heavy winds and rains caused  lodging of oat crop and lowered the grain yield in 1998 and 2001. The oat grain yield was highest in 2000, in rainy vegetaton period with moderate temperature. The coefficients of variation and differences between minimum and maximum values indicate the wide range of genetic variability of grain yield.

Key words:  oat varieties, grain yield, genetic variation, environmental variation

Abstract. The field experiments were carried out in 1999_2002 at the Jõgeva Plant Breeding Institute (PBI) in Estonia to investigate the genetic and environmental variation of agronomic characteristics of malting barley. 57 malting barley varieties were included in the trials. Grain yield, number of tillers per 1m², plant height, lodging resistance and growing time were measured in the trial with malting barley.

 Despite very different weather conditions, the grain yield stability of malting barley varieties was very high. Tillering  showed somewhat lower genetic variability compared to the variation of grain yield. The plant height indicates moderate genetic variability. Lodging resistance and growing time showed  low genetic variability.

Key words: agronomic charactristics, genetic variability, malting barley, grain yield, tillering, plant height, lodging resistance, growing time

Abstract. Late blight monitoring means continual observations of late blight development during potato vegetation period. The aim of potato late blight monitoring is to establish the first appearance of late blight symptoms and to observe the development of potato late blight in different regions of Lithuania.  The Lithuanian Institute of Agriculture (LIA), the Lithuanian Agricultural Advisory Service (LAAS) and the State Plant Protection Service (SPPS) implement monitoring of late blight in Lithuania and have been taking part in the program of late blight monitoring in the Nordic and Baltic countries since 1999 (http://www.web-blight.net).

In 2001 potato late blight monitoring was carried out in 20 districts of Lithuania. Observations were made in 53 fields and 23 potato varieties of different maturity and susceptibility. First symptoms of late blight in Lithuania in 2001 were established on  15 June in Varėna district. During the season, the development of late blight had an epiphytotic character.

Key words: potato, late blight, monitoring, Internet