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An overview of the results of previous research on the effectiveness of entomopathogenic nematodes against harmful Thysanoptera species and so-far recorded entomophilic (parasitic) nematodes of the genus Thripinema is given. Probably in the near future entomopathogenic nematodes will partly substitute for insecticides in controlling thrips and other plant pests. Investigation of the mode of action and the bionomics of entomophilic nematodes will be required to improve their effectiveness in controlling thrips.

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112 species have been listed in the last published check-list of thrips in Serbia. In this paper we introduce three new thrips species for this country. Orothrips priesneri , an aeolothripid species, has a discontinuous Mediterranean distribution. In Serbia it was found at several localities along the course of the Danube, a region with a warm, submediterranean influence. Its general distribution pattern makes its presence in Serbia unexpected. The hygrophilous species Iridothrips iridis was collected on the leaves of Iris pseudacorus in the vicinity of Grocka, near Belgrade. Platythrips tunicatus , which is widespread in Europe, is an oligophagous species related especially to plants from the genus Galium .

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The gladiolus thrips (Thrips simplex) is a common pest of gladioli. The insect causes damage to leaves, flower stalks and buds by sucking. The present study was intended to investigate the susceptibility of four Gladiolus cultivars as well as the colour preference of the thrips tested on different coloured flowers of the cultivars. The experiment was carried out in 2006 at two locations in central Slovenia. After planting the corms on April, 27 and May, 2 on three occasions with successive plant stages the percentage of infested foliage surface and flowers was assessed. Of the cultivars tested, the ‘Nova Lux’ was the only cultivar suited for cultivation without insecticide application. The flowers of gladioli with a light colour (white ‘White Prosperity’, yellow ‘Nova Lux’) were less infested in comparison with cultivars with dark coloured flowers (orange ‘Hunting Song’, red ‘Oscar’).

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In 2001 Echinothrips americanus Morgan was first recorded in Slovenia. The thrips was first recorded in Europe in 1989, but did not begin to spread to a greater extend until 1993. This polyphagous pest is believed to cause direct damage, especially on the leaves of its host plants. The present contribution describes genetic structure of Echinothrips americanus Morgan rooting in polymorphism of the ITS1-5,8S-ITS2 region of the ribosomal DNA. Echinothrips americanus Morgan is less resistant to insecticides and its ability to inhabit new areas is smaller, compared to the Western flower thrips [Frankliniella occidentalis (Pergande)]. It can be concluded that its economic importance in the future will not reach that of the latter. We gave a detailed description of the species, its geographic distribution, and deal with its host plants as well as bionomics and its potential natural enemies.

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The effect of spraying speed (5, 8.5 or 12 km/h) on deposition quality of fungicide on a winter wheat head, yield, grain quality, occurrence of Fusarium head blight (FHB) and deoxynivalenol (DON) content in grains was investigated in 2011 and 2012. Asymmetric double flat fan air-injector nozzles were used in the trial at a spraying pressure of 5.0 bars. A prothiconazole + tebuconazole fungicide mixture was used for spraying. An increase of spraying speed significantly lowered coverage values at the front and rear parts of a wheat head. At all three spraying speeds, the rear part of a wheat head reached a better coverage value. The effect of spraying speed was significant in 2011, when the 5 km/h spraying speed generated a significantly higher grain yield and a significantly higher thousand-grain weight in comparison with the other treatments. In both trial years, the lowest grain yield occurred on the unsprayed control. In 2011 and 2012, the latter also reached the lowest hectolitre weight and thousand-grain weight. In both trial years, the unsprayed control had a significantly higher DONcontent than the other treatments. In 2012, the DONcontent on the unsprayed control exceeded the allowed maximum level. The spraying speed did not affect the DON content in the grains. The effect of spraying speed was also noted in the FHB incidence. A significantly lower FHB incidence occurred at the 5 and 8.5 km/h spraying speeds.

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In 2005 the damage caused by onion thrips (Thrips tabaci) on a susceptible hybrid of early cabbage (cv. ‘Parel’) was studied in a block field experiment. The cabbage was grown in four treatments: 1) on non-mulched surfaces, 2) on surfaces mulched with barley straw, 3) on surfaces mulched with hay and 4) on surfaces mulched with black PE mulch. The trial consisted of two parts: the first part included plots that were mulched as indicated from the very beginning (normal), while in the second part the soil was first covered with black PE mulch for about one month, than this was removed and replaced either by organic mulches or left non-mulched (postponed). In this way, we wanted to diminish the yield loss because of low temperatures and abundant precipitation. Under cold and wet conditions in spring which led to late appearance and low levels of the pest, the growing of cabbage under black PE mulch proved most effective and these plants exhibited the greatest head mass as well as the greatest net mass, although they also suffered most damage from the pest. The cabbage in the second part of the experiment exhibited higher head mass as well as higher net head mass compared to the first part.

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In the period of 2001-2002 the susceptibility of five varieties of early white cabbage to onion thrips (Thrips tabaci) attack has been studied. The variety with the longest growth period (72 days) and the firmest head (19.5-21.5 kg/cm2), i.e. Vestri, had the highest mean weight of the head (1220.0 g/head) and the highest net weight of the head (1050.6 g/head), while the mean index of damage (1.18) and the mean yield loss (13.9%) were the lowest in this variety. At higher plant density (16.6 plants/m2) both parameters of the weight of the head were approximately less than half as compared to lower plant density (8.2 plants/m2). Results of the mean net weight of the heads did not show significant differences between different plant densities if the yield was calculated per area unit (m2). The mean content of epicuticular wax differs among varieties, although all varieties show similar relations in its content; the lowest mean content in the third and the fourth exterior leaves of the head, the highest mean content was within the first and the second, and the ninth and the tenth exterior leaves of the head. In spite of the apparent correlation between the content of epicuticular wax and the mean index of damage (with both plant densities its values were the highest between the third and the sixth exterior leaf of the head) caused by feeding of onion thrips hardly perceived negative correlation (Pearson coefficient of correlation between -0.338 and -0.436) were found between these two parameters using statistical analysis.

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In 2014 and 2015, we studied the effect of fungicide spraying with 11 different nozzles on the quality and quantity of head and leaf fungicide deposit, the percentage of Fusarium head blight (FHB) incidence, FHB index, the DON content, yield and grain quality parameters. The best quality and quantity of fungicide deposit on the front and rear head sides was achieved with the TeeJet Turbo FloodJet TF VP2 nozzle (FLOOD) and the Albuz AVI-TWIN 110-03 nozzle (AVI). In comparison with the majority of treatments, the FHB incidence and the FHB index was the highest on the unsprayed control. The FHB index was higher using the Lechler IDK 120-03 nozzle (IDK) than with the other nozzle types. In all the treatments, the DON content in the grain was less than 50 μg/kg. At this very low level of infection this is not surprising. The grain yield was the smallest on the unsprayed control. Better fungicide coverage of wheat heads with the FLOOD and AVI nozzles did not result in a statistically higher yield or better grain quality parameters. Negative correlations were confirmed between yield and variables as DON content, FHB incidence and FHB index and also between falling number and variables as fungicide coverage, FHB incidence and FHB index. Positive correlations were determined between DON content and FHB incidence, between hectolitre weight and variables as spray deposit and coverage and between protein content and variables as spray deposit and coverage.

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Authors: S. Trdan, N. Valič, L. Andjus, I. Vovk, M. Martelanc, B. Simonovska, J. Jerman, R. Vidrih, M. Vidrih and D. Žnidarčič

In a field experiment on the natural resistance of cabbage ( Brassica oleracea var. capitata ) against onion thrips (Thrips tabaci) , 20 cabbage genotypes were included: 9 early, 5 mid-early, 6 mid-late (regarding the longevity of the growing period), 3 red, 17 white (regarding colour), 14 hybrids and 6 varieties (regarding genetic origin). For comparisons between genotypes, we determined significant differences in the mean index of damage on the exterior leaves of cabbage heads (1.12–2.83), the net weight of heads (281.40,151169.6 g), and yield loss (5.8–47.4%). The concentration of several compounds from cabbage leaves (epicuticular wax, α-amyrin, β-amyrin, lupeol, sucrose, glucose, fructose, vitamin C, palmitic acid, stearic acid, and arachidic acid) are measured. For all groups of cabbage genotypes the only confirmed negative correlation was between the extent of damage caused by the sucking of onion thrips and epicuticular wax content on the cabbage leaves (in groups where we artificially placed genotypes with similar characteristics). After this preliminary experiment, the research must be extended in order to determine the effect of the remaining analysed compounds in cabbage leaves for resistance (sensitivity) of cabbage to onion thrips attack.

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