Monoculture of modern cereal crops are popular due to the technical and organizationa lreasons. They are easier in crop husbandry, qua lity and product use. However, in monoculture chemical protection of crops is a norm, due to the fact that they are more susceptible to diseases, pests and sometimes weed infestation. In order to keep high and stable grain yields and quality in monoculture one has to use high inputs. Experimentally and practically it has been proved that cultivar and species mixtures can constitute an alternative to cultivar growing in pure stands. It has been found that in mixtures opperate different epidemiological and ecological factors, which lead to considerable disease reduction, pest and weed control, which finally result in higher and more stable grain yields than in barley varietes grown in pure stands. The results of two years field experiment designed to evaluate epidemiological and economical effects of winter barley cultivar mixtures are presented. The studies were carried out in two sites – experimental lStation for Variety Testing Słupia Wielka (in Wielkopolska region) and Plant Breeding Station Bąków (Opole District). This two sites were 300 km away from each other, and had different soi land meteorological conditions. In the experiment impact of different barley cultivars and their different two- and three-component mixtures were tested with reduced dosages of fungicidies on grain yield in the mixtures compared with pure stands were evaluated.

The results of experiments showed an effect of magnetized water on the effectiveness of some selected zoocides. The control of red spider mite (Tetranychus urticae Koch) by Ortus 05 SC showed the highest effectiveness with strongly magnetized water, with use of one magnetizer and two semi-rings. On the other hand, the application of Magus 200 SC in combination with magnetized water showed a decreased effectiveness of insecticide. In the control of grain weevil (Sitophilus granarius L.), an increase in the effectiveness was found for the zoocides Talstar 100 EC, Karate 025 EC and Winylofos 550 EC in combinations with strongly magnetized water (three magnetizers or one magnetizer with two rings). In case of Sumi-Alpha 050 EC, high effectiveness of the treatment was obtained in combinations where water was magnetized in lesser degree, with use of one or two magnetizers. No significant differences were found in the effect of magnetized water on germination of bean (Phaseolus vulgaris L.) and cuckoo flower (Cardamine amara L.) plants.

The investigations conducted in 1994 and 1996 concerned aphids infesting fields and neighbouring semi-natural habitats – midfield thickets with trees and the vegetation growing on the ditch margins. Aphids were caught into Moericke traps placed at the plant level. The material collected was studied to determine aphid number, dominance of individual species, similarity of dominance structure of aphid communities (Renkonen Index) and diversity of aphid communities (Shannon-Weaver Index). Aphids were collected in the field and in the natural habitats neighbouring the field. In both years black bean aphid (Aphis fabae Scop.) was either the dominant or sub-dominant species in every habitat studied. A relative species diversity of aphids occurring in semi-natural habitats was significantly highe rthan that in the adjacent field. The results of these investigations indicate that the crop affects aphid fauna flying onto neighbouring midfield thickets.

Saprol 190 EC (triforine) and Rubigan 12 EC (fenarimol) diluted in 6 types of water were applied against rose rust Phragmidium mucronatum Cooke. No adjuvants were added to the emulsion except when the spray mix was made using water from Poznań prepared in 2 variants: with an addition of Citowett AL and without it. Independently on the plant protection product type, efficacy of fungicides diluted in well water from Szczepankowo, Kościan or Śmigiel was better than when they were diluted in water after reversed osmosis. However, no type of water exerted any significant effect on efficacy of the investigated fungicides independently on the year of studies, although, in 1999, a better biological activity was shown by Rubigan 12 EC diluted in water from Kościan and Poznań than when they were diluted in water after reversed osmosis. The fungicides were most effective after addition of Citowett AL, however, a visible effect of this adjuvant showing increased rose protection against rose rust was found only in 1998.

Biological activity of 6 fungicides in the inhibition of Phytophthora ramorum sporulation and development of blight on rhododendron leaves and stems were evaluated. All tested compounds at dose 8 μg o fa.i./cm³ already inhibited zoosporangia formation at least in 73%. On leaf petioles and leaf disks, taken from rhododendron one week after treatment with fungicides, formation of chlamydospores was especially suppressed by fenamidone + phosetyl Al and oxadixyl + mancozeb whereas development o fspores was not inhibited by cymoxanil + famoxate. All tested compounds significantly inhibited the development and spread of twig blight on rhododendron. However, furalaxyl, applied as spraying of plants 48 hrs before or after inoculation of leaves and stems by P. ramorum was the most effective.

Investigation of leaf rust disease on spring crops of triticale (× Triticosecale Wittm.), it sdi stribution dynamics, as well as the efficacy of two fungicides, different application doses and timing was carried out at the Lithuanian Institute of Agriculture during 2000–2002. Differences in the disease development were determined by the meteorological conditions, especially the amount of rainfall, and growth stage of plants. Precipitation during 2000 was close to the mean, and the development of leaf rust was moderate. In June of 2001 the rainfall was twice as high as the norm, which created favourable conditions for pathogen development. In 2002 a long droughty period till flowering inhibited the development of leaf rust. The triazole fungicides Juventus (metkonazole 60 g l^–1) and triazole and strobilurine mixture. Allegro (kresoxim-methyl 125 g l^–1 + epoxikonazole 125 g l^–1) were used at full, two-third and half doses once and twice. Both of the fungicides were very effective against leaf rust. Biological efficacy of Juventus applied at any dose or time against leaf rust was 88.3%–99.7%. Allegro efficacy against this disease was slightly higher 94.7%–100%. Application of 1.0; 0.75 and 0.5 l ha^–1 doses twice showed a better efficacy than a single application. The higher doses of fungicides were not markedly superior to the lower ones.

Phytophthora citricola was isolated from diseased seedlings of European beech and Silver fir taken from the most of surveyed nurseries. Fusarium species, Pythium ultimum and Rhizoctonia solani were also found in diseased plant tissues.Isoates of P. citricola fro mboth plants and additionally from heather and rhododendron colonised leaf blades, needles and stem parts of beech and fir. In greenhouse trials on inoculated 1-year-old seedlings necrosis spread about 2 mm/24 hr on beech stems whereas on fir about 1.5 mm/24 hr.

On the basis of the presented studies, it was established that seed dressing by coating protects effectively onion crops against onion fly (Hylemyia antiqua Meig.). In all seed dressing treatments, a significant decrease of number of dam- aged plants was found in comparison to the control. The highest efficacy in protection of onion against onion fly was shown in the case of insecticide Super Homai 70 DS. The effectiveness of this seed dressing reached 80.40% in the year 2001 and 85.44% in the year 2002.

Number of hairs on abaxial leaf surface of 13 apple cultivars differed significantly. The most hairs per 1 cm² on abaxial surface were on cvs. Lodel (2,578.3) and Jonafree (2,462.2). Leaves of cultivars Antonówka and Novamac had the least number of hairs (1,054.4; 1,285.7; respectively). Correlation between number of hairs on abaxial leaf surface of investigated apple cultivars and Tetranychus urticae (Koch) female fecundity decreased during 10 first days of their lives. Along with increased number of hairs, the fecundity of this species declined.

Apple cultivars investigated as new hosts for two-spotted spider mite, Tetranychus urticae Koch appeared to provide good environment for its development and reproduction. The best conditions for two-spotted spider mite development were on leaves of cultivars Novamac and Freedom with a net reproduction (R_o) 22.6 and 20.3 respectively, while the worst on cultivars Pioner and Primula with R_o 8.9 and 10.2 ,respectively.