An investigation on the chemotactic responses of different entomopathogenic nematode strains to mechanically damaged maize root volatile compounds.

Entomopathogenic nematodes (EPNs) respond to a variety of stimuli when foraging. In a laboratory investigation, we tested the chemotactic responses of 8 EPN strains (Steinernema and Heterorhabditis) to three mechanically damaged maize root compounds (linalool, α-caryophyllene and ß-caryophyllene). We hypothesized that the EPN directional response to the tested volatile compounds would vary among the species and volatile compound and may be related to foraging strategies. The nematodes with an intermediate foraging strategy (Steinernema feltiae) proved to be less active in their movement toward volatile compounds in a comparison with the ambushers (Steinernema carpocapsae) and cruisers (Steinernema kraussei and Heterorhabditis bacteriophora); ß-caryophyllene was found to be the most attractive substance in our experiment. The results of our investigation showed that the cruisers were more attracted to ß-caryophyllene than the ambushers and intermediates. The foraging strategy did not affect the movement of the IJs toward the other tested volatile compounds or the control. Our results suggest that the response to different volatile cues is more a strain-specific characteristic than a different host-searching strategy. Only S. carpocapsae strain B49 displayed an attraction to linalool, whereas S. kraussei showed a retarded reaction to ß-caryophyllene and α-caryophyllene in our experiment. The EPN strains showed only a weak attraction to α-caryophyllene, suggesting that this volatile compound could not have an important role in the orientation of IJs to the damaged roots of maize plants. These results expand our knowledge of volatile compounds as the cues that may be used by EPNs for finding hosts or other aspects of navigation in the soil.

Assessment of Insecticidal Efficacy of Diatomaceous Earth and Powders of Common Lavender and Field Horsetail against Bean Weevil Adults.

In the search for an effective and sustainable control method against the bean weevil Acanthoscelides obtectus (Say), an important insect pest affecting stored common beans and other legumes, three different powders were tested against adult been weevils under laboratory conditions. The three powders were diatomaceous earth (DE) (commercial product SilicoSec®), common lavender (Lavandula angustifolia) powder and field horsetail (Equisetum arvense) powder. The substances were tested at five temperatures (15, 20, 25, 30, and 35°C), two relative humidity levels (RH) (55 and 75%), and four concentrations (100, 300, 500, and 900 ppm). The mortality of adults was measured after the 1st, 2nd, 4th, and 7th days of exposure. The efficacy of the powders increased with the temperature, whereas in general, RH did not have a significant effect on the adults' survival. According to common practice of storing common beans, we recommend the use of DE against the pest in question, as this inert powder showed the highest efficacy at lower temperatures and concentrations. Concerning the wider use of common lavender and field horsetail powders, we suggest studying their combined use with other environmentally friendly methods with the aim of achieving the highest synergistic effect possible.

Two years research on efficiency of two intercrops, birdsfoot trefoil and summer savory, to reduce damage caused by onion thrips(Thrips tabaci Lindeman, Thysanoptera, Thripidae) on leek.

In 2009 and 2011, a field experiment was carried out at the Laboratory Field at the Biotechnical Faculty in Ljubljana, Slovenia, with the aim to investigate suitability of two intercrops, birdsfoot trefoil (Lotus corniculatus L) and summer savory (Satureja hortensis L.), for reducing damage caused by onion thrips (Thrips tabaci Lindeman) on leek (Allium porrum L.). Four leek cultivars--'Columbus', 'Forrest', 'Lancelot' and 'Lincoln'--were used in the research (Bejo Zaden B.V., Netherlands). In both years, the mean index of damage caused by feeding of the pest on the leek leaves increased from the first evaluation (13 July 2009 and 18 June 2011) in both treatments with intercrops and in control treatment (without intercrop). Leek grown with birdsfoot trefoil as intercrop was in both years statistically the least damaged from thrips. Also summer savory was efficient in the same context in comparison with control treatment. In year 2009 cultivar 'Lancelot' was the least damaged in all treatments, and in year 2011 'Lancelot' and 'Forrest'. In both years intercrop and cultivar also had a significant influence on the yield of leek. The highest yield was obtained on the control plots, meanwhile birdsfoot trefoil and summer savory were pretty competitive and yield of leek grown with them as intercrops was therefore significantly lower.

Population dynamics of banded thrips (Aeolothrips intermedius Bagnall, Thysanoptera, Aeolothripidae) and its potential prey Thysanoptera species on white clover.

In 2002, the occurrence of banded thrips (Aeolothrips intermedius Bagnall) and some other Thysanoptera species on white clover (Trifolium repens L.) was monitored at two locations in the continental part of Slovenia. White clover presents in many countries important intercrop in integrated vegetable production. Light blue sticky boards were placed on grasslands (one parcel on each location) with high percentage of white clover. Sticky boards were changed in about 10-days intervals from the end of April till the beginning of October. Number of caught individuals on the boards was counted. They were classified in three different groups: 1. Aeolothrips intermedius, 2. representatives of Haplothrips, Odontothrips and Frankliniella genera, 3. representatives of Thrips genus. We stated that, compared with the other Thysanoptera species in the open, predatory thrips occurs in lower number. Predatory species Aeolothrips intermedius was the most numerous during the flowering of white clover. It was established that other Thysanoptera species (the most of them are facultative phytophagous species) were more numerous also in the periods of less favourable weather conditions and during the non-flowering growing stages of white clover. Based on the results of present research we concluded that A. intermedius has a potential to control onion thrips (Thrips tabaci Lindeman), especially in July and August, when in the open both species occur in high numbers.

Investigation on the optimal term of one-fold insecticide application for decreasing onion thrips ( Thrips tabaci Lindeman, Thysanoptera, Thripidae) damage on early white cabbage.

An impact of the term of one-fold insecticide application to reduce the damage of the onion thrips in early white cabbage was established. During the growing season plants were treated with insecticide (abamectin) in three different terms (treatment 1: 9 June, treatment 2: 16 June, treatment 3: 23 June, and treatment 4: untreated). On the exterior leaves of cabbage heads, treated with the insecticide, statistically significantly lower mean index of damage was determined as compared to the untreated plants. No significant differences were found between three different terms of application. The majority of the economically important damages in all of the treatments was found between the 3rd and 6th exterior leaf in the head. The highest mean weight of heads (1517.3 g) and mean net weight of heads I = mean weight of heads - weight of damaged and removed leavesl (1166.3 g) were established in plants which were treated the last. These parameters were the lowest in untreated plants (1083.3 g / 805.6 g). The yield loss due to damaged leaves removal amounted from 22.9% (treatment 2) to 25.6% (treatment 4). Based on the results obtained in this research we concluded that yield loss due to onion thrips attack in plants with one-fold insecticide application is not substantially lower as in untreated plants (though statistically significant differences between them were established), because insecticide cannot reach the interior leaves in the head. Substantial differences in the total and net weight of heads between the treatments and especially between the treated and untreated plants are explained by the fact that feeding of numerous thrips populations in the heads and on the exterior cabbage leaves negatively affects plant physiology and yield. The highest average yield in plants which were treated the last indicates a possibility that insecticide also inhibits plant growth and development to a certain extent.

Research on the influence of red deer (Cervus elaphus L.) grazing on grassland production in the south-eastern part of Slovenia.

Almost 60% of Slovenian territory is covered by forests and only Finland and Sweden are known as the more forest abundant countries in Europe. Among game that intensifies difficulties in the field of agricultural production, especially in north-eastern and south-eastern parts of the country, roe deer (Capreolus capreolus L.), wild boar (Sus scrofa L.) and red deer (Cervus elaphus L.) prevail. Negative impact of game on agricultural production in the above mentioned parts of Slovenia has risen significantly in the last decade. The data about the population density of game in Slovenia is often based on the payments of their damage on the cultivated plants that are usually performed by the hunting societies. Grassland represents around 60% of agricultural land in Slovenia, and herbage is a very important component of the red deer diet. At the forest border where ruminant ungulate animals spend most of their life, the grassland production for a farmer is often decreased because of the grazing of this hoofed animal. Hitherto, decrease of grassland productiveness from a farmer's perspective, caused by the red deer grazing, was not yet researched in Slovenia. Similar studies were also very rare in other European countries. With the intention of gathering data and learn more about the potential harmfulness of the red deer on grassland production the experiment was performed in the south-eastern part of Slovenia in the year 2002. The influence of red deer grazing on grassland production for forage conservation at the forest border during the vegetation period was studied on three locations (Mala gora, Cvislerji and Mackovec) in the Kocevje region. The experiment lasted from the third decade of March until the first decade of October. Portable cages of size 1x0.5x0.5 m were used to exclude red deer from grazing the herbage. At four sampling dates in the season herbage air dry matter (DM) yield was measured at three different observations (cage-protected plot, cage-protected plot only two to three weeks before sampling date, otherwise freely grazed--removed and unprotected plot). The results from the experiment showed us that red deer grazed on grassland through all seasons and that the regeneration capability of sward was the highest in summer, middle in spring and smallest in autumn. On unprotected plots an average 50% reduction of herbage DM yield was found with the most distant sites also up to 80% reduction.

The effectiveness of ecologically acceptable ways of protection of field-grown tomato (Lycopersicon lycopersicum (L.) Karsten) from tomato late blight (Phytophthora infestans (Mont.) de Bary) in extreme weather conditions.

During the extremely wet vegetation season in 1999 the efficiency of protection of two cultivars of field grown tomato (Lycopersicon lycopersicum (L.) Karsten), 'Pick Rite' and 'GO 101', against tomato late blight (Phytophthora infestans (Mont.) de Bary) using three ecologically acceptable growing techniques and agrochemical measures (growing on black plastic mulch with no fungicides used, spraying with Dithane M-45 (mancozeb), spraying with Cuprablau-Z (Cu-hydroxide) and control) have been studied. It was found out that under such extreme weather conditions none of these measures can ensure an adequate protection of tomato. The highest yield of healthy fruits (0.30 kg per plant) was obtained after a threefold spraying with Dithane M-45 (mancozeb), the highest percentage of non infected fruits (38.1%) after a twofold spraying with Cuprablau-Z (Cu-hydroxide). The black plastic mulch, used with the intention to reduce the plant contact with the potential inoculum in the soil proved to be ineffective.