Vlatka Rozman

Evaluation of natural diatomaceous earth deposits from south-eastern Europe for stored-grain protection: the effect of particle size.

BACKGROUND The use of diatomaceous earths (DEs) provides a promising alternative to the use of contact insecticides in stored-product IPM. Geographical origin and the physical properties of a given DE may affect its insecticidal activity. In the present study, DE samples were collected from different locations of south-eastern Europe, and their efficacy was evaluated in the laboratory against Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujiidae), Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). In addition, three fractions comprising particles of different size were obtained from each DE sample and assessed with regards to their effectiveness against the above stored-product insect pests. RESULTS DE from the Greek region of Elassona was the most effective against C. ferrugineus and S. oryzae, whereas the DE Kolubara 518, mined in the Serbian region of Kolubara, was the most effective against R. dominica. Smaller particles were more effective than larger particles against the three tested species, although significant differences in the efficacy of fractions containing particles of 0-150 microm and particles with sizes of < 45 microm were not always recorded. CONCLUSIONS Deposits from south-eastern Europe appeared to be very effective against the tested species, and therefore this region should be further evaluated as a source of development of commercial products. Particle size is a physical property that should always be taken into account during the DE manufacturing process, as it can strongly influence the insecticidal action of a given product.

Insecticidal activity of some aromatic plants from Croatia against granary weevil ( Sitophilus granarius L.) on stored wheat

These investigations proved that aromatic plants from Croatia like lavander, laurel, rosemary and thymus, had insecticidal activity against Sitophilus granarius L on stored wheat.

Croatian diatomites and their possible application as a natural insecticide

In recent decades, there has been an increase in the use of diatomaceous earth (DE) as a natural insecticide because of its low mammalian toxicity, worker safety, low risk of food residues and the occurrence of resistant insect populations associated with the use of chemical insecticides.Therefore there is potential for research into known but previously undescribed Croatian mid-Miocene marine diatomites from the perspective of their potential as proper DE that could be mixed with plant extracts as a new formulation for grain storage protection. The marine diatomites belong to the Paratethyan near shore environment, deposited in the upwelling zone during a mid-Miocene temperate climate. Palaeontological, mineral and geochemical analyses were done on ten promising marly sediments from 26 outcrops and one borehole from the North Croatian Basin. The most important ingredient of diatomaceous sediments is silica (biogenic opal-Aand SiO2 bound in other silicate minerals including quartz, clay minerals, micas, etc.). The amorphous silica content of the tested Croatian diatomites is relatively low (<50%) in comparison with the Celatom® MN 51 standard (medium to high efficient DE) (73.6%), nevertheless they show insome part even slightly better efficacy against insects. It seems that the enhanced content of smectite in diatomaceous sediments also influences increased absorption of DE. Based on palaeontological results, the most efficient diatomites from the Podsusedsko Dolje and Markusevec (Medvednica Mt.) consist of the mid-sized planktonic Coscinodiscus group of species whereThalassionema nitzschioides dominate and is positively correlated with their absorption. The usage of Bostroms’ standard formula for getting opal-A from geochemical data was abandoned because of negative results and the modified Murdmaas’ formula for hemipelagic sediments was applied. Preliminary results on the aforementioned diatomite (as inert dusts) show good efficacy against tested insects Sitophilus oryzae (LINNAEUS), Tribolium castaneum (HERBST) and Rhyzopertha dominica (FABRICIUS).

Toxicity of naturally occurring compounds of Dalmatian (Croatia) Lamiaceae and Lauraceae to maize weevil ( Sitophilus zeamais motsch)

Maize weevil (Sitophilus zeamais Motsch.) is the major stored pest of Coleoptera order. It belongs to the group of economically important pests of stored grain. In Croatia, maize weevil can be more frequently found in storages of small-scale farms than in large storage facilities or silos. This is ascribed to its higher resistance to lower temperatures in distinction from the remaining pests of Sitophilus genus. Present measures of stored pest control are mainly based on application of synthetic insecticides and fumigants. However, their non-selective and uncritical application in storage facilities brings up some serious issues, such as toxic effects to the grain that is used in diet for people and livestock (Fishwick, 1988), and contamination of the environment (WMO, 1995). In practice in Croatia, phosphine is presently in use in stored pest control. However, fumigation with phosphine should be also limited for evident increase in the resistance of some pest species to a phosphine compound, which has been observed in more than 45 countries (Bell and Wilson, 1995). This means that phosphine in use can and has to be limited on the global level. Therefore, there is a necessity to find safe alternatives to the conventional insecticides and fumigants that would protect grain and its products (Rozman et al. 2006). This investigation proved that certain compounds (monoterpenes) of Dalmatian essential oil extracts of the families Lamiaceae and Lauraceae, respectively: lavender (Lavandula angustifolia Ch.), laurel (Laurus nobilis L.), rosemary (Rosmarinus officinalis L.) and thyme (Thymus vulgaris L.) exhibited toxic activity against maize weevil S. Zeamais which could be used as a new alternative in protection against the pest species.

Maize inbred lines resistance to fusarium ear rot

Ear rot of maize caused by Fusarium species results in yield decrease as well as in decrease of grain quality. Seven inbreed lines were sowing during three years (2001–2003) at two locations (Kutjevo-pseudogley, Nova Gradiska-amphigley). If comparing average values of examined inbreed lines, planting years and soil types, there were significant differences in occurrence of maize ear rot caused by Fusarium species . The most tolerant lines in all the years examined on both locations were OS 89-9 and OS 86-39. The least infection intensity was observed in OS 138-9 inbreed line.