Effect of Temperature Gradient of Grain Storage on Migration and Distribution of Three Pests

Temperature gradients were set at the opposite sides of the grain storage: 25°C-30°C, 20°C-30°C, 20°C-35°C, 30°C-30°C. The migration and distribution of imago of Sitophilus oryzae, Rhizopertha dominica and Tribolium castaneum in the grain storage were observed. The results showed significant differences that the distribution trends of imago of Sitophilus oryzae, Rhizopertha dominica and Tribolium castaneum within a certain grain storage temperature gradient (p < 0.05). The temperature gradient of grain storage is 25°C-30°C. Tribolium castaneum tends to gather in the 30°C side area of grain storage, while Sitophilus oryzae has no obvious trend, while Rhizopertha dominica tends to gather in the 25°C. The temperature gradient of grain storage is 20°C-30°C. Both Tribolium castaneum and Sitophilus oryzae tend to gather in the 30°C side area of grain storage, while Rhizopertha dominica tends to gather in the 20°C. The temperature gradient of grain storage is 20°C-35°C. Tribolium castaneum, Sitophilus oryzae and Rhizopertha dominica all tend to gather in the area on the side of grain storage at 35°C. The temperature gradient of grain storage is 30°C-30°C, and there is no obvious trend for Tribolium castaneum. Rhizopertha dominica tends to gather in the 30°C area on the left side of grain storage, while Sitophilus oryzae tends to gather in the 30°C area on the right side of grain storage. After cooling down, it was found that Sitophilus oryzae tended to gather in the center of the grain storage, while the Tribolium castaneum had no obvious trend, and the Rhizopertha dominica tended to gather in the peripheral area of the grain storage.

Comparative analysis of the repellency activity of single compounds and the synthetic blends of semiochemicals from Aframomum melegueta (R.schum) and Dennittia tripetala (Bak.F) against Rhizopertha dominica in Calabar, Nigeria

Bioassay experiments were carried out in Calabar to compare the repellency activity of single compounds and the synthetic blends of Semiochemicals extracted from Afromomum melegueta and Dennittia tripetala. The aim of the experiment was to determine the efficacy of single compounds and the synthetic blends in suppressing the reproductive potential and adult emergence of Rhizopertha dominica, (Fabricius), a primary pest of stored cassava pellets and cereal grains in Sub-Saharan Africa. Insect culture of the adult R. dominica was set up in the laboratory at Federal College of Education Obudu to obtain fresh insects for the bioassay experiments. Dried seeds of A. melegueta (R. Schum) and D. tripetala (Baker f.) Schatz were procured from the main market in Obudu for the purpose of the research work. 100g each of the dried fruits of the spice plants were pounded separately with the laboratory pestle and mortar for the extraction of the essential oils (EOs). The oils extracted were tested for toxicity and reproductive potential deterrence against R. dominica. The chemical constituents of the essential oils were isolated, identified and tested against R. dominica. Synthetic blends of individual compounds were prepared based on their natural ratios and were also tested for toxicity and reproductive potential deterrence against the insect pests in the laboratory. The result showed that both the single compounds and the synthetic blends were toxic and repellent to the insect pest, and could significantly suppress the reproductive potential thereby inhibiting the emergence of adult insect. However, synthetic blends exhibited a stronger efficacy in their toxicity against the pest thereby providing a broad spectrum of insecticidal bioactivity against R. dominica than the single compounds. This action of the synthetic blends of extracts from the spice plants demonstrated their potential for development in stored products protection especially at the small scale resource poor farmer’s level in Nigeria.

Preparation, Characterization and Biological Efficacy of Eucalyptus Oil Nanoemulsion against the Stored Grain Insects

Nanotechnology has enormous potential for developing alternative pest control strategies and reducing the risk of insecticide molecules. The present study aimed to develop a stable nanoemulsion (NE) of eucalyptus oil (EO) by the spontaneous emulsification method and evaluate its insecticidal and repellent effect against Sitophilus oryzae (L.), Rhizopertha dominica (F.) and Tribolium-castaneum (Herbst.). The prepared nanoemulsion formulation having a small particle size 8.57 nm with polydispersity index (PDI) 0.28. The study of the stability and physicochemical properties showed that the prepared formulation had good physical stability without any change in the macroscopic parameters. In addition, results showed that theinsecticidal activity of the prepared NE was higher than the original EO against the three tested insect speciesand the mortality increased with increasing concentrations and extending of exposure time. The contact toxicity of NE film revealed that, adults of R. dominica was more susceptible to all treatments followed by S. oryzae adults, while adults of T. castaneum was the least susceptible one, however, adults of S. oryzae was more susceptible followed by T. castaneum adults while, adults of R. dominica was the least susceptible one according to the fumigant toxicity and repellency. Our results suggested that the prepared formulation may be used in an integrated pest managementprogramfor controlling stored grain insects.

Soil Application of Nano Silica on Maize Yield and Its Insecticidal Activity Against Some Stored Insects After the Post-Harvest

Maize is considered one of the most imperative cereal crops worldwide. In this work, high throughput silica nanoparticles (SiO2-NPs) were prepared via the sol–gel technique. SiO2-NPs were attained in a powder form followed by full analysis using the advanced tools (UV-vis, HR-TEM, SEM, XRD and zeta potential). To this end, SiO2-NPs were applied as both nanofertilizer and pesticide against four common pests that infect the stored maize and cause severe damage to crops. As for nanofertilizers, the response of maize hybrid to mineral NPK, “Nitrogen (N), Phosphorus (P), and Potassium (K)” (0% = untreated, 50% of recommended dose and 100%), with different combinations of SiO2-NPs; (0, 2.5, 5, 10 g/kg soil) was evaluated. Afterward, post-harvest, grains were stored and fumigated with different concentrations of SiO2-NPs (0.0031, 0.0063. 0.25, 0.5, 1.0, 2.0, 2.5, 5, 10 g/kg) in order to identify LC50 and mortality % of four common insects, namely Sitophilus oryzae, Rhizopertha dominica, Tribolium castaneum, and Orizaephilus surinamenisis. The results revealed that, using the recommended dose of 100%, mineral NPK showed the greatest mean values of plant height, chlorophyll content, yield, its components, and protein (%). By feeding the soil with SiO2-NPs up to 10 g/kg, the best growth and yield enhancement of maize crop is noticed. Mineral NPK interacted with SiO2-NPs, whereas the application of mineral NPK at the rate of 50% with 10 g/kg SiO2-NPs, increased the highest mean values of agronomic characters. Therefore, SiO2-NPs can be applied as a growth promoter, and in the meantime, as strong unconventional pesticides for crops during storage, with a very small and safe dose.

Prevalence and abundance of insect pests in stored pulses collected from two local markets of Dhaka city

Prevalence and abundance of stored grain insect pests in four varieties of pulses i.e. Lens culinaris, Pisum staivum, Cicer arietinum collected from two markets of Dhaka city were recorded. Nine species of insect pests, viz. Sitophilus oryzae, Tribolium castaneum, Callosobruchus chinensis, C. maculatus, Rhizopertha dominica, Oryzaephilus surinamensis, Liposcelis entomophila, Sitotroga cerealella, and Formica sp., were recorded throughout the study. The percentage of weight-loss was higher (7.54) in those pulses which were highly infested by pests. Highest pest population was observed during May to June (753). However, Sitotroga cerealella were found only in November to December of the study period. The maximum species richness (7) was observed in Green gram and Chickpeas samples, but the minimum species evenness was observed in Green gram (0.6969) and maximum in Red lentil (0.9886). Jahangirnagar University J. Biol. Sci. 8(1): 75-82, 2019 (June)

Temperature and host dependent functional response of Anisopteromalus calandrae (How.) and Choetospila elegans (Westw.) parasitods in parasitizing wheat infesting Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

Rhizopertha dominica (F.) (Coleoptera: Bostrichidae) is an internal feeder of whole wheat seed, flour, etc. R. dominica is parasitized by two pteromalid ectoparasitoids, Anisoptetromalus calandrae (How.) and Choetospila elegans (Westw.) in the larval and pupal stages. The effects of host density and temperature on the functional response of the parasitoids in parasitizing the larval and pupal stages of the hosts were examined. Four temperatures and five host densities were used. A functional response equation was used in which a quadratic component that included temperature was substituted for handling time. Functional response of parasitization by A. calandrae and C. elegans fit a formula of Hassell et al. (1977) type III model. The maximum rate of parasitization of A. calandrae was 8.6 larvae/24 hrs and 7.2 larvae/24 hrs of C. elegans at 30ºC, respectively. Handling time and instantaneous search rate varied with temperatures. The ability of A. calandrae and C. elegans to find and parasitize R. dominica over a broad range of temperatures demonstrate it as a good candidate for natural control of the pest. Bangladesh J. Zool. 47(1): 41-47, 2019