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The subject of this study was the lesser grain borer Rhizopertha dominica F. The aim of the experiments was to verify the hypothesis suggesting that the course of simultaneous vertical migration and horizontal spread of the R. dominica population is determined by nutritional and habitat selectivity. The following products were used as nutrients in the experiments: wheat, oat flakes, pearl barley and semolina. It was found that the course of a migration process is connected with nutritional preferences determined mainly by a nutrient type and its granulation. At the initial stage of the study the highest emigration was noted in the oat flakes. After a time the highest migration was directed to as follows: wheat, oat flakes, pearl barley and semolina. Females showed a higher migratory activity.
The subject of this study was Rhizopertha dominica F. population. The primary question referred to was the process of the lesser grain borer population spread depending on nutritional preferences of this species. The aim of performed laboratory experiments was to examine the adults’ ability to choose preferred kinds of food i conditions of free migration among them and to analyze the dynamics of population size. Sex ratio and the migration rate were also analyzed. Four types of food were used during the experiments: wheat, oat flakes, pearl barley and semolina. The experiments were conducted at 28°C and 60 ± 5% of relative humidity. Results of the study revealed that oat flakes were the most favourable nutriment for adult R. dominica whereas wheat grain was the most favourable for the population size since larvae were protected by grains and thus their increased number could survive. No population development in semolina was observed. It was the result of too small granulation of this food.
The aim of the study was to evaluate a possibility of propolis production by honey bee Apis mellifera (Horn) (Hymenoptera: Apidae) and its potential for the management of the larger grain borer (LGB) Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on maize grains. Bee propolis was collected from hives kept on the field for twelve months; they were thereafter diluted with ethanol to obtain 5%, 10%, 15% and 20% concentrations. 5 ml each of the concentrations was applied to 150 g clean maize grains infested with 10 pairs of 1-5 days old LGB in 250 cm3 Kilner jars. The control jars were treated with ethanol. At 90 days post-infestation, data were collected on percentage of weight loss, percentage of grain damage, weight of frass generated (g), number of pupae, larvae and adult LGB. The results indicated that monthly propolis yield was significantly (p < 0.05) lower in the period of honey flow (December-March) relative to other periods. Propolis at all the concentrations tested reduced the population of LGB in propolis-treated maize grains relative to non-propolis treated-ones. The highest effects of propolis was shown at the highest concentration of 20% and it was significantly (p < 0.05) different from its effects at other concentrations. Bee propolis may be integrated with other ecological friendly control methods to manage LGB infestation in maize.
The subject of the study was the lesser grain borer Rhizopertha dominica F. — a dangerous pest of stored grain. The study was carried out in the laboratory at a temperature of 31°C, the optimal temperature for this species, and also in the temperature lowered to 22°C and 60±5% relative humidity. The main aim of the research was to investigate the migration activity of R. dominica in lowered temperature. In addition the population dynamics, mortality and sexual ratio in a population of R. dominica were also analyzed. It was shown that lowering the temperature to 22°C caused an increase in the migration activity of R. dominica in the initial phase of infesting a new habitat. A larger migration and mortality of females were observed. In addition, the population growth was slow and prolonged in time at the temperature of 22°C as compared to the optimal temperature. Lowering the temperature did not influence the mortality of the R. dominica population.
The populations of Rhyzopertha dominica, a dangerous pest in stored grains were investigated. This laboratory study assumed the hypothesis that the introduction of powdered leaves of Salvia officinalis L. and Artemisia absinthium L. containing feeding inhibitors into grain may delay the development and therefore reduce population size of R. dominica. These herbs were powdered and added at 0.5 g of herb per 40 g wheat. The research was conducted in optimum conditions of temperature and humidity (28ºC and relative humidity 60%). The insects used in the experiment were initially obtained from mature individuals of uniform age and were bred in glass containers with base area 28 cm² covered with gauze. The experiments were continued for 310 days and the herb supplements were renewed each month. The results of the study show that the introduction of chemical substances contained in the powdered leaves of S. officinalis and A. absinthium into an optimal substrate (wheat) infested with R. dominica decreases its population size. These substances have properties that inhibit the feeding of this insect species.
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