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SummaryA survey of entomopathogenic nematodes was conducted in Croatia between 2016 and 2017. The steinernematids were recovered in two out of 100 soil samples from agricultural land characterized as loamy soils with acidic reaction. Molecular and morphological identification was used to distinguish the nematodes. The isolates were identified as two different strains conspecific with Steinernema feltiae. The variations in morphometrical characteristics of infective juveniles (IJs) and males were observed among Croatian strains and with the original description. The analysis of ITS region revealed the greatest similarity of Croatian strains with Slovenian B30 and English A2 strains, which together comprised a monophyletic group in evolutionary analysis. This is the first record of steinernematids, namely S. feltiae in Croatia.

Soil samples from 100 cultivated and natural sites were assessed for the presence of entomopathogenic nematodes. Heterorhabditid nematodes were recovered from three soil samples during spring months, with the overall positive sample rate of 3%. The isolates of entomopathogenic nematodes were identified as three different strains conspecific with Heterorhabditis bacteriophora (Heterorhabditidae). They were found from natural sites and vineyard, while no recovery occurred from intensively cultivated agricultural fields. The morphometrical characteristics of infective juveniles and males showed differences between all Croatian strains and from the original description. Heterorhabditis bacteriophora ISO9 was bioassayed on Lasioptera rubi (Cecidomyiidae) (the raspberry gall midge) larvae at different nematode concentrations under laboratory conditions. The significantly highest mortality was observed in treatments with 50 and 200 infective juveniles per insect larvae within 8 days after inoculation. This is the first report of entomopathogenic nematodes of the family Heterorhabditidae from Croatia, and susceptibility of L. rubi larvae to entomopathogenic nematodes. The Croatian strain H. bacteriophora ISO9 was proved to possess strong insecticidal properties against L. rubi larvae.

Adverse storage conditions impair the quality of stored grain, contribute to the growth and propagation of the fungi leading to an even greater deterioration of the grain quality. Antifungal biopreparations can help preserve grain quality. Lactic acid bacteria (LAB) and their metabolites with antifungal properties can potentially be used in storage conditions or for the decontamination of stored products. The aim of this study was to determine the antifungal activity of Lactobacillus casei, Lactobacillus brevis and Leuconostoc mesenteroides on the inhibition of mycelial growth of pathogenic fungi Aspergillus niger, Penicillium chrysogenum and Fusarium graminearum. The biocontrol potential of LAB against fungi was tested under laboratory conditions in culture media as an ideal substrate for fungal growth and wheat grains as a model of natural substrate. A liquid culture media (MRS broth) was inoculated with cells or cell-free supernatants (CFS) of each LAB species and the fungal spores. The fungal growth was evaluated by measuring the increase in mycelial biomass after 7, 14, 21 and 28 days of incubation. The second antifungal assay was performed on the wheat grain treated with LAB CFS and inoculated with fungal spores. Biopreparation containing cells or CFS of all LAB species significantly inhibited the fungal growth of P. chrysogenum (mean inhibition 69-75% LAB cells and 80-81% LAB CFS) and F. graminearum (mean inhibition 60-83% LAB cells and 83-88% LAB CFS) in the culture media. In the treatment with wheat grain, the CFS of all the tested LAB species significantly inhibited only the growth of F. graminearum (83-90% mean inhibition). There is inconsistency in the efficiency of LAB preparations when comparing assays. The results indicate that media used in the experiment affect the activity or tolerance of the tested bacteria and fungi. L. casei, L. brevis and L. mesenteroides proved their antifungal properties in the culture media and natural substrate. F. graminearum was the most susceptible, and A. niger was the most tolerant to treatments with LAB cells and LAB CFS. More research is needed to reveal the mode of action of the LAB against phytopathogenic fungi in different conditions for their application on stored grains.

The current series of experiments was conducted to assess the allelopathic potential of fennel, rue, and sage seed and plant biomass on weed species hoary cress (Lepidium draba). The effect of plants was evaluated through: seed cogermination in Petri dishes, effect of water extracts from fresh and dry plant biomass in two concentrations (50 and 100 g l -) in Petri dishes and pots, and effect of fresh and dry plant residues in rates of 10 and 20 g kg -1of soil. The cogermination of seeds affected germination and seedling length of hoary cress with fennel seeds having the highest inhibitory effect and reducing germination up to 34.9%. The water extracts in Petri dish essay had various effects, however the dry plant biomass in higher concentration reduced germination and seedlings growth for up to 100%. The applications of the extracts from fresh biomass in pots with soil differed from results in Petri dishes. Sage extract in higher concentration inhibited germination for 34.2%, and fennel extract reduced root length for 22.7%. The effect of incorporation of plant residues depended on the plant species and amount of the plant residues and was both stimulatory and inhibitory. The emergence reduction was the highest with incorporation of fresh rue residues.