Prostephanus Truncatus Research Articles

Effect of Storage Technologies on Postharvest Insect Pest Control and Seed Germination in Mexican Maize Landraces.

Simple SummaryIn Mexico, smallholder farmers produce locally adapted maize varieties, generally called landraces, for food. They participate in the conservation of landraces by selecting and storing their seeds from one production cycle to another, but are facing challenges such as storage losses caused by insects (mainly Sitophilus zeamais and Prostephanus truncatus) and climate change. In the current study, the effectiveness of the conventional storage practices of farmers in the highlands of Mexico (polypropylene woven bags) in minimizing storage losses and maintaining seed germination was compared with hermetic storage technologies. After six and three months of storage, the percentage of insect damage and weight loss was highest in samples stored in polypropylene woven bags, reaching 61.4% and 23.4% after six months of storage. On the contrary, with hermetic technologies, storage losses were minimal, with maximums of 4.1% and 2.2% for insect damage and weight loss, respectively. Overall, the germination rate of samples stored in these airtight containers was greater than 90%. The results of this study demonstrate the potential of hermetic technologies in preserving the biodiversity of maize seed landraces and strengthening smallholders’ food security.Smallholder farmers who grow maize landraces face important challenges to preserve their seed biodiversity from one season to another. This study was carried out in the central highlands of Mexico to compare the effectiveness of two seed storage practices—specifically, polypropylene woven bags (farmers’ conventional practice) vs. hermetic containers—for minimizing seed losses and maintaining germination. Four Mexican landraces were stored for three and six months. Data on moisture content and kernel damage were collected at the beginning and the end of the storage period. Pest-free samples collected were also analyzed for seed germination. Moisture content was below 13% overall and was not significantly affected by storage technology or storage time. Samples from the polypropylene woven bags suffered significant damage from Sitophilus zeamais and Prostephanus truncatus, with the percentages of insect damage and weight loss reaching 61.4% and 23.4%, respectively. Losses were minimal in seed stored in hermetic containers, with a maximum insect damage of 4.1% and weight loss of 2.2%. Overall, the germination rate of samples stored in these airtight containers was greater than 90%. This study provides additional evidence on the effectiveness of hermetic containers at maintaining Mexican landraces’ seed quantity and quality during storage in smallholder conditions in central Mexico.

Maize seeds storage systems and post-harvest losses in Benin: diversity, efficiency, storage insects, and implications for better products conservation

Background: Storage pests cause extensive damages to stored products and are responsible for huge post-harvest losses affecting the quality, quantity, and germination potential of stored grains and seeds. This study aimed to investigate the variability of traditional methods of storage and conservation of maize seeds practiced by farmers to propose alternative measures for a significant reduction of post-harvest losses of seeds. Methods : Using participatory research approaches, we surveyed farmers from 21 randomly selected villages in 5 districts in southern Benin. Data were collected on the storage structures of the 3 certified and most produced maize seeds varieties. The forms under which maize seeds are stored, as well as the damage caused by the major storage insects, were determined. Results: Results showed that most farmers store maize seeds in the form of grains and spathe. Following the laboratory observation of the three maize varieties studied, the DMR / QPM variety produced only in the district of Zagnanado has a low abundance of storage insects and a low rate of post-harvest losses. Sitophilus zeamais is the most abundant pest of the three maize seed varieties followed by Prostephanus truncatus. The variety 2000 SYN EE was the most attacked by storage insects. The most promising post-harvest agricultural practice is the storage of maize with spathe saved in jute bags, in granaries or cribs. Conclusions: Storage insects contribute to the depreciation of the quality of grains, loss of grain and reduction of their germinability in stock. Improving farmers' awareness of these post-harvest practices could help to reduce the damage of storage insects.

Competition between Prostephanus truncatus and Sitophilus oryzae on maize: the species that gets there first matters

AbstractLaboratory tests were carried out in order to examine the population growth of Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) and Sitophilus oryzae (L.) (Coleoptera: Curculionidae) on maize. These two species were placed either simultaneously or one species was allowed to colonize the kernels 7 days earlier than the other, at two temperatures, 26 and 30 °C for 65 days. Apart from progeny production, grain quality parameters, such as insect-damaged kernels (IDK) and undamaged kernels (NDK), the weight of frass and kernel weight were measured. Our data confirms that temperature plays a key role in the competition of these two species; P. truncatus seems to perform better at the higher temperature (30 °C), regardless of the presence of an additional species. Moreover, the results of the present study demonstrates that P. truncatus outcompetes S. oryzae. Sitophilus oryzae produced fewer progeny than P. truncatus in all combinations. Given the outcome of a competition, we hypothesize that most of the kernel damage was due to feeding by P. truncatus. Based on these data, we surmise that P. truncatus has a competitive advantage as an invasive species in new areas with stored maize, even in the presence of S. oryzae.

Exposure to a Novel Insecticide Formulation on Maize and Concrete Reduces Movement by the Stored Product Pests, Prostephanus truncatus (Horn) and Sitophilus zeamais (Motschulsky)

Two major stored products pests of maize are the Prostephanus truncatus (Horn) (larger grain borer) and Sitophilus zeamais (Motschulsky) (maize weevil). Under climate change, P. truncatus may be expected to shift its distribution northward farther into the United States (US). Thus, there is a critical need to develop diversified chemical control tools in the post-harvest supply chain for these two species. In this study, we investigated the efficacy of a novel insecticide formulation, containing the insect growth regulator, S-methoprene, combined with the pyrethroid, deltamethrin and the synergist piperonyl butoxide (Central Life Science, Schaumberg, IL, US), compared to the existing commercial standard formulation without synergist, and controls at inducing direct mortality and sublethal changes in movement on treated grains as a grain protectant, and on concrete as a surface treatment. Mortality of adults was assessed visually, while movement was tracked with a network camera coupled with Ethovision software that automatically recorded velocity and distance moved by both species, after continuous exposure on treated material for 4–168 h. The novel formulation significantly induced mortality while reducing distance and velocity moved by multiple-fold compared to controls for exposed adults even after relatively brief exposure periods. In fact, the novel formulation was just as effective as the older formulation, but used only a fraction of the active ingredients, thus it may be more cost-effective. Overall, the novel insecticide formulation is a promising tool for controlling S. zeamais and P. truncatus in bulk storage and around other food facilities.

Effectiveness of Tick Berry (Lantana camara) in Controlling Larger Grain Borer (Prostephanus truncatus) in Stored Maize

The larger grain borer, Prostephanus truncatus is a devastating storage pest of maize and cassava which was introduced in Africa from America in the early 1980s through imports of maize. An experiment was carried out to determine the effectiveness of tick berry, Lantana camara in controlling the larger grain borer in stored maize. The experiment was laid out in a Completely Randomized Design with 6 treatments replicated 3 times. The treatments were; 1 control, 2 Actellic gold, 3. 10g Lantana camara, 4. 7.5g Lantana camara, 5. 5g Lantana camara and 6. 2.5g Lantana camara applied to 200g maize. Significant differences (p<0.001) were observed amongst all treatments with respect to mortality. The highest mortality of 100% was observed in the Actellic gold followed by 83.3% from 10g of Lantana camara at 21days after application. A significant difference (p<0.001) was also noted amongst treatments with respect to frass accumulation which translates to grain damage. At 21 days of observation, the control treatment had the highest grain damage (10.05%) followed by 2.5g Lantana camara (1.70%). No significant differences (p>0.05) were observed between 10g Lantana camara (0.18) and Actellic gold (0). Reproduction was significantly (p<0.001) inhibited by Lantana camara with failure of adults to emerge between day 21 and 42 after removal of adults. The control treatment had the highest number of adults emerging (177) followed by 2.5g Lantana camara (84) at 42 days in storage, no adults emerged in the Actellic gold treatment and no significant differences (p>0.05) were observed between 10g Lantana camara and Actellic gold. Lantana camara effectively controlled P. truncatus and the effectiveness was correlated to concentration and period of exposure. Lantana camara is recommended as a control option against P. truncatus.

Fertilizer Effects on Endosperm Physicochemical Properties and Resistance to Larger Grain Borer, Prostephanus truncatus (Coleoptera: Bostrichidae), in Malawian Local Maize (Zea mays L.) Varieties: Potential for Utilization of Ca and Mg Nutrition

Maize grain hardness influences storage pest resistance, a key characteristic valued by smallholder farmers. The structural changes in the endosperm determine grain hardness and are influenced by agronomic practices. The purpose of this study was to establish whether supply of calcium and magnesium based fertilizers can alter physicochemical properties of local and hybrid maize varieties and reduce the infestation by larger grain borer (Prostephanus truncatus (Coleoptera: Bostrichidae)) during storage. Two local and one hybrid maize varieties commonly grown by smallholder farmers in Malawi were cultivated under three fertilizer treatments (NPK (nitrogen, phosphorous, potassium), NPK plus gypsum, and NPK plus dolomite). After harvest, the grains were classified into flint and dent types, followed by P. truncatus infestation and determination of their physicochemical properties. The addition of gypsum and dolomite fertilizers led to higher levels of amylose, total zein and β-14 zein, traits associated with kernel hardness, compared to the application of NPK fertilizer. Moreover, local maize varieties showed higher resistance to P. truncatus infestation, hardness and biochemical properties associated with hardness (total zein, α-19 and β-14 zein, starch lysophosphatidylcholine, and non-starch free fatty acid) compared to hybrid variety. Our study suggests the potential for utilizing Ca and Mg nutrition in maize to improve kernel hardness, thus adoption of gypsum and dolomite by smallholder farmers may be beneficial against P. truncatus during storage.

Insecticidal activities of indigenous plants from Volta Region, Ghana in managing Sitophilus zeamais and Prostephanus truncatus in stored maize

Abstract. Ankutse DK, Eziah VY, Afreh-Nuamah K. 2021. Insecticidal activities of indigenous plants from Volta Region, Ghana in managing Sitophilus zeamais and Prostephanus truncatus in stored maize. Intl J Trop Drylands 5: 48-60. The rising rate of pest resistance, and the high expense and health risks associated with insecticide use, have become a source of public concern. This study aimed to discover and evaluate plant species used by farmers in the Volta Region to control Sitophilus zeamais (Motschulsky, 1855) and Prostephanus truncatus (Horn, 1878) in stored maize grains. In a survey, Azadirachta indica, Clausena anisata, Phyllanthus amarus, Picralima nitida, Vernonia amygdalina, Nauclea latifolia, and Momordica charantia were discovered to be grain protectants against stored insect pests. All of the plants indicated above were employed in the experiment, except for A. indica, which has a long history of being used to combat grain storage pests. The insecticidal activity of dried powders (5 and 10%) and aqueous extracts (0.1 and 0.2 g/mL) of plants against P. truncatus and S. zeamais was examined. Plant species and dose rate influenced repellency. In the V. amygdalina treatment, plant powders and methanol extracts were the most poisonous to insects. The toxicity of V. amygdalina to P. truncatus and S. zeamais was 83.3 and 86.7%, respectively, at higher concentrations of 0.2 g/mL. At 0.2 g/mL, all plant extracts exhibited a significant difference in Actellic repellent (P0.05); nevertheless, C. anisata had the highest repellent action against P. truncatus and S. zeamais, with 80.0 and 66.7%, respectively. As grains were treated with plant extracts, oviposition and egg emergence were reduced compared to the control. When embryonic stages of insects were treated with methanol extracts of botanicals, the number of adult insects decreased. These findings show that the studied plants have the potential to aid in the development of post-harvest protection technology against the principal pests of stored grains, P. truncatus and S. zeamais. As a result, farmers should use it to control P. truncatus and S. zeamais in stored maize grains.

Modeling the Influence of Abiotic and Biotic Factors on Spatial and Temporal Fluctuations of Prostephanus truncatus (Coleoptera: Bostrichidae) Populations in Mozambique

The larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), is a serious pest of stored maize in Mozambique and in other African countries. This study investigated the influence of abiotic and biotic factors on populations of P. truncatus at four sites over a two-year period (2013-2014) in Mozambique. Fourteen 250 × 250 m quadrants were selected at each site. Plant species diversity, temperature, precipitation, and relative humidity data were recorded. Pheromone-baited Uni-traps were used to monitor P. truncatus inside each quadrant. In addition, plant species were identified using visual observation and measurement of morphological features of leaves and fruits, and quantified, after which the percentage of host plant species of P. truncatus was determined out of all species in each quadrant. Multiple regression analysis and generalized linear models showed that host plant species dominance, maximum and minimum temperature, relative humidity, and rainfall influenced the variations in P. truncatus abundance. The development of these models of P. truncatus flight activity provides a baseline for further studies predicting dispersal and potential areas of invasion by this pest.

Etofenprox as grain protectant for the management of five key stored-product insect pests.

Etofenprox is a broad spectrum pyrethroid insecticide with low toxicity to mammals, fishes, and honeybees. In the present study it was evaluated as grain protectant against Ephestia kuehniella (Lepidoptera: Pyralidae) larvae,Prostephanus truncatus (Coleoptera: Bostrychidae) adults,Rhyzopertha dominica (Coleoptera: Bostrychidae) adults, Sitophilus oryzae(Coleoptera: Curculionidae) adults, and Tribolium confusum (Coleoptera: Tenebrionidae) larvae and adults. Etofenprox was applied at 0.1, 1, 5, and 10 ppm on wheat, or maize in the case of P. truncatus, and tested at different combinations of temperatures (20, 25, and 30 °C) and relative humidity (RH) levels (55 and 75%). Progeny production of the tested coleopteran adult species was also assessed. For E. kuehniella, after 21 days of exposure 75.6% of the exposed larvae were killed at 20 and 30 °C/55% RH. Mortality of P. truncatus adults reached 99.4 and 97.8% at 10 ppm of 55 and 75% RH, respectively, at 30 °C. For S. oryzae, after 21 days of exposure, mortality was moderate at both RH levels, even at the elevate doses, reaching 66.7% at 10 ppm at 20°C/75% RH. All R. dominica adults died 21 days post-exposure at 30°C/55% RH and 25 or 30°C/75% RH at 10 ppm. For T. confusum adults, mortality was 81.1% 10 ppm 21 days post-exposure at 20°C/75% RH. Etofenprox killed 99.4% of the exposed T. confusum larvae at 10 ppm respectively 14 days post-exposure at 25°C/55% RH. Concerning progeny production, complete suppression was recorded for P. truncatus, R. dominica, and T. confusum in various combinations of temperature/RH. Our findings indicate that etofenprox is a well-promising insecticide for the protection of stored grains. However, its performance differs among insect species and abiotic conditions.

Effect of Processing Methods on Proximate Composition of Cassava Varieties Manihot esculenta (Crantz) Before and After Infestation by Prostephanus truncatus (Horn)

In Africa, Prostephanus truncatus is a destructive pest of economic importance which has assumed a serious pest status on stored maize and dry cassava chips. This study investigates the effect of processing methods of cassava varieties Manihot esculenta on the proximate composition before and after exposure to P. truncatus. The four cassava varieties used for this study were; TMS 0505, TME 419, NR 8082 and TMS 0581 subjected to two processing method parboiling and plain sun-drying at temperature 28-34oC and relative humidity of 65-75%. The experiment was carried out in a Complete Randomized Design. Proximate composition was carried out to determine the Moisture, Ash, Crude fibre, Fat, Crude Protein and Carbohydrate of the different samples. Analysis of Variance was used for the statistical analysis of the data obtained. The result reveals that the proximate composition of the sundried chips are significant at P<0.05%. All the proximate contents of the sample were significant at P<0.05% before the introduction of P. trucatus. After the introduction of P. truncatus and the storage period of 30days, the sundried sample had a higher reduction in the moisture contents of TMS 0505 with 13.05±0.00a and carbohydrate contents of NR 8082 with 50.0±0.00a. The activity of P. truncatus also has a negative impact on some of the nutritional components of cassava chips.

Periodic disturbance time interval for suppression of the maize weevils, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) in stored maize (Zea mays L.)

Sitophilus zeamais Motschulsky threaten maize (Zea mays L.) storage in the tropical regions of low-income countries where maize is a staple. Disturbance of maize during storage can be an alternative to chemical treatment in suppressing populations of S. zeamais. Disturbance has been successful against insect pests of stored products, i.e. bean weevils, Acanthoscelides obtectus (say) (Coleoptera: Chysomelidae: Bruchinae) and lesser grain borers Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae). Prior research has not established a standard disturbance interval. This study tested various disturbance intervals to see determine suppression of S. zeamais populations in stored maize with four treatments: stationary jars (control) and jars disturbed at intervals of 8, 12 and 24 h. Jars contained 1 kg of 16 ± 0.7% wet basis moisture maize and 234 ± 51 adult S. zeamais stored at 27 °C, 70% r. h. and 12 h light and dark phases. Periodically, electric motors rotated jars through about 1.25 revolutions in 3 s. Three jars were selected randomly from each treatment every 40 d up to 160 d for analysis. Reduction in S. zeamais populations was 75%, 95% and 94% for 8, 12 and 24 h disturbance intervals, respectively, compared to the stationary jars after 160 d. The average quality of maize in all disturbed jars was better than in stationary jars, respectively, for moisture content (13 ± 1.1% vs. 21 ± 1.0%), bulk density (553.5 ± 1.1 kg/m3 vs. 231.7 ± 1.2 kg/m3), broken corn and foreign material (9 ± 1.2% vs. 68 ± 3.9%), insect damage (70 ± 4.5% vs. 100 ± 0.0%), and mold damage (0.4 ± 0.2% vs. 27 ± 17.2%). Disturbances of 12h and 24 h (once per day) proved the best intervals in suppressing S. zeamais populations and maintaining the quality of maize, much longer than previously reported. Of these two intervals, the less frequent 24 h disturbance interval may be an effective non-chemical approach to control S. zeamais in maize stored by smallholder farmers, requiring less effort.

Phytosanitary risk associated with illegal importation of pest-infested commodities to the South African agricultural sector

We evaluated the phytosanitary risk associated with illegal importation of pest-infested plant commodities into South Africa. Samples were collected from different South African ports of entry over 8 years (2011 to 2019) and data were analysed descriptively using Statistical Software Package. Pests were frequently detected on commodity species such as Citrus (18.31%), Zea mays (13.22%), Phaseolus vulgaris (12.88%), Musa spp. (9.15%) and Fragaria ananassa (5.08%). The highest number of pests intercepted occurred on fresh fruits (44.06%), followed by grains (26.44%) and vegetables (14.23%). The most intercepted organisms were Callosobruchus rhodesianus (7.79%), Dysmicoccus brevipes (7.11%), Callosobruchus maculates (6.10%) and Phyllosticta citricarpa (4.74%). The majority of intercepted organisms were non-quarantine organisms (70.50%), followed by pests of unknown status (17.28%), quarantine pests (10.84%) and potential quarantine pests (1.35%). Phyllosticta citricarpa, Bactrocera dorsalis, Spodoptera frugiperda and Prostephanus truncatus were the only quarantine pests intercepted in terms of South African regulatory status. The interception was mainly from southern African countries, particularly Mozambique, Zimbabwe and Eswatini. The findings present the level of phytosanitary risk associated with illegal importation and/or non-compliance in regard to plants and plant commodities from different countries through South African ports of entry. Crop production, biodiversity, food security, existing export markets, and access to new export markets could be threatened as importing countries may impose stringent phytosanitary measures to limit the chances of introduction and establishment of quarantine pests into their territories. Significance
 
 Illegal importation of plant commodities may lead to the introduction, establishment and spread of pests that are of quarantine significance to South Africa.
 Introduction of pest species such as Phyllosticta citricarpa, Bactrocera dorsalis, Spodoptera frugiperda and Prostephanus truncatus into South Africa could result in undesirable impacts on the ecosystem, agriculture, biodiversity and economy of the country.
 Access to new export markets of plant commodities could be threatened as importing countries may impose stringent phytosanitary measures to limit the chances of introduction and establishment of these quarantine pests into their territories.

Insecticidal effect of thiamethoxam against seven stored-product beetle species

Bioassays were carried out in order to assess the insecticidal value of the neonicotinoid thiamethoxam in different concentrations against seven important beetle species that are major pests of stored grains. These species were Prostephanus truncatus (Horn), Rhyzopertha dominica (F.), Sitophilus oryzae (L.), Sitophilus granarius (L.), Oryzaephilus surinamensis (L.), Tribolium confusum Jacquelin du Val, and Cryptolestes ferrugineus (Stephens). Adults of these species were exposed to grains treated with thiamethoxam at dose rates of 0 (control), 0.01, 0.1, 0.5, 1, 2, 5 or 10 ppm. Our results indicate that with the increase of the insecticide concentration, there was also an increased adult mortality and a reduction in progeny production. To illustrate the relative sensitivity to thiamethoxam of the seven insects, starting with the most susceptible, we can classify them as P. truncatus > R. dominica = S. granarius = S. oryzae > T. confusum = O. surinamensis > C. ferrugineus. The findings of the present research show that thiamethoxam can be recommended for its efficacy at a rate of 10 ppm and duration of 14 days that could be used to control all insects and their progeny.

Residual efficacy of an insecticide-coated net for the control of stored product beetles

In the present study, the residual efficacy of an alpha-cypermethrin-coated net (Carifend®, BASF AG, Ludwigshafen, Germany) was evaluated in laboratory studies against four species of stored product insects. The insecticide-treated net was fitted into the bottom of plastic petri dishes, whereas two other sets of dishes (without net, with net without insecticide) served as controls. The insects used in the bioassays were Sitophilus oryzae, Tribolium confusum, Oryzaephilus surinamensis and Prostephanus truncatus. Adults of these species were exposed every 30 d for a total of 90 consecutive days in total. Based on the results, the insecticidal effect of the net remained at high levels during the entire experimental period, indicating its high residual effect. Among the species tested, T. confusum was the least susceptible. Carifend® can be a valuable tool for the protection of stored products against storage insects, and its use can be further examined towards this direction.

Desiccation and temperature resistance of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae): pedestals for invasion success?

AbstractThe larger grain borer, Prostephanus truncatus (Horn) is an invasive insect pest species of global economic concern. It however remains unknown how P. truncatus succeeds under increasing temperatures and desiccation effects associated with projected climate change. Here, we investigated the effects of desiccation and high‐temperature stress on physiological fitness of P. truncatus larvae and adults. Specifically, we measured critical thermal maxima, heat knockdown time and water loss rates following heat and desiccation acclimation. Results showed beneficial heat acclimation effects on heat tolerance (critical thermal maxima and heat knockdown time). Similarly, desiccation acclimation significantly improved both heat tolerance traits, indicating cross‐tolerance effects, not for heat knockdown time in larvae. In all cases, adults exhibited more improved heat tolerance than larvae. Conversely, heat acclimation increased water loss rates, and more so in larvae than adults. Improved heat tolerance plus abiotic stress cross‐tolerance of P. truncatus may explain its enhanced physiological and ecological fitness in dry tropical and changing climate environments. These results are important in explaining the role of physiology in insect invasions and may inform pest management and forecasting.

Evaluation of Two Formulations of Chlorantraniliprole as Maize Protectants for the Management of Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae).

Simple SummaryProstephanus truncatus (Horn) (Coleoptera: Bostrychidae) is a major insect pest of stored maize and dried tubers of cassava, but also a wood-boring species. In the current study, we evaluated two chlorantraniliprole formulations, WG (wettable granule) and SC (suspension concentrate), as maize protectants against P. truncatus adults at 20, 25 and 30 °C. Both formulations performed similarly. The highest mortality was noted in chlorantraniliprole WG, at 10 ppm and 30 °C (98.9%), followed by chlorantraniliprole SC (96.1%), at the same dose and temperature. WG formulation was more effective at 10 ppm and 25 °C (92.8%) than SC formulation (89.4%). No progeny production was noted on maize treated the WG formulation at 20 and 30 °C. The SC formulation caused complete offspring suppression at 10 ppm at all three tested temperatures. The results indicate that chlorantraniliprole is an effective compound with a high insecticidal activity against T. truncatus that depends on temperature, dose and exposure.The larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) is one of the most destructive insect pests of stored maize and dried tubers of cassava, and a wood-boring species. In the present study, we examined two chlorantraniliprole formulations, WG (wettable granule) with 350 g/kg active ingredient (a.i.) and SC (suspension concentrate) with 200 g/L a.i., as maize protectants against P. truncatus adults. Chlorantraniliprole formulations were applied as solutions at 0.01, 0.1, 1 and 10 ppm, and tested at 20, 25 and 30 °C. Both formulations performed similarly. After 7 days of exposure, the overall mortality provided by both formulations was very low (<17%). Seven days later, mortality was remarkably increased on maize treated with 1 and 10 ppm at 25 and 30 °C for both formulations. The highest mortality was noted in chlorantraniliprole WG, at 10 ppm and 30 °C (98.9%), followed by chlorantraniliprole SC (96.1%), at the same dose and temperature. WG formulation was more effective at 10 ppm and 25 °C (92.8%) than SC formulation (89.4%). No progeny production was noted on maize treated with the WG formulation at 20 and 30 °C. The SC formulation caused complete offspring suppression at 10 ppm at all three tested temperatures. The results of the present work indicate that chlorantraniliprole is an effective compound with a high insecticidal activity against T. truncatus on stored maize that depends on temperature, dose and exposure interval. The fact that chlorantraniliprole is a broad-spectrum insecticide, exhibiting low toxicity to mammals and beneficial arthropods, could be a valuable management tool in storage facilities.

Chemical composition and repellent potentials of two essential oils against larger grain borer, Prostephanus truncatus (Horn.) (Coleoptera: Bostrichidae)

Abstract Larger grain borer {Prostephanus truncatus (Horn.) (Coleoptera: Bostrichidae)} is a polyphagous pest which infests timber products, cereals, legumes, dried yam and cassava chips. Its infestation causes quantitative and qualitative losses, leading to food insecurity and reduced income generation for farmers. Essential oils (EOs) were obtained from fresh leaves of Cymbopogon citratus (DC.) Stapf and Lantana camara Linn. via hydrodistillation using Clevenger type apparatus. Each EO was assayed for repellent properties against P. truncatus using area preference methodology while pure acetone served as control. The percentage of oil yield from C. citratus and L. camara was 0.263% and 0.221% v/w, respectively. A total of 29 compounds were identified in C. citratus EO, dominated by oxygenated monoterpenes (92.58%), with citral (44.92%) and verbenol (34.97%) being the major compounds. A total of 47 compounds were identified in L. camara EO, dominated by sesquiterpenes hydrocarbons (49.96%), with gamma-cadinene (21.93%) and delta-cadinene, (+)- (9.88%) being the major compounds. When applied at 0.16 μL/cm2, L. camara exhibited a significantly (p

Assessment of four plant extracts as maize seed protectants againstSitophilus zeamaisandProstephanus truncatusin Ghana

Sitophilus zeamais and Prostephanus truncatus can cause weight loss of about 20 to 90% of untreated stored maize seeds. This study assesses four plants (Lantana camara, Moringa oleifera, Citrus sin...

Insecticidal Drimane Sesquiterpenes from Warburgia ugandensis against Maize Pests

Sitophilus zeamais and Prostephanus truncatus, the destructive pests of maize in Africa, cause extensive tunneling in maize grain leading to conversion of maize grain into flour within a very short time. Small-scale farmers are often forced to sell maize shortly after harvest to minimize losses during storage, thereby attract low prices and compromising food security. Most available pesticides have adverse effects on environment and humans. The aim of this study was to evaluate efficacy of extracts and compounds of Warburgia ugandensis in controlling of S. zeamais and P. truncatus. Chromatographic fractionation of extracts from W. ugandensis afforded 7α-acetylugandensolide (1), ugandensolide (2), polygodial (3), warbuganal (4), ugandensidial (5), mukaadial (6) and muzigadial (7). The structures of the compounds were determined using spectroscopic and physical methods. n-Hexane extract was the most repellent among the extracts while polygodial (3) was the most repellent compound against the two pests. n-Hexane and ethyl acetate extracts caused 76.3-78.3% and 71.1-75.0% deaths of the insects respectively. Polygodial (3) and warbuganal (4) caused 64.3-70.0 and 61.7-65.0% deaths respectively. n-Hexane and ethyl acetate extracts, polygodial (3) and ugandensolide (2) significantly inhibited the emergence of the insects. The findings from this study show that extracts from W. ugandensis are effective in controlling maize insect pests.

English

The aim of this study was to establish the attributes of kernel type based on kernel hardness and its interrelationship with maize endosperm chemical components, which are essential during storage. Three local varieties and one hybrid variety commonly grown by smallholder farmers in central Malawi were used. For storage experiment, the maize samples were infested with Prostephanus truncatus, larger grain borer (LGB) for eight weeks. Due to the high propensity of maize to cross-pollinate, the kernels were classified into flint and dent kernels to establish the physicochemical properties of the kernel type and variety independently. Local variety (L-3) exhibited the lowest number and weight of damaged grains and the highest adult LGB cadavers. Local variety, L-1 and L-3 had significantly the highest proportion of flint kernels type. Moreover, flint kernels of local varieties showed significantly the highest hardness, and the highest content of protein, total zein, α-zein and zinc (p < 0.05). Furthermore, hardness was significantly and positively correlated with total zein and 14 kDa β-zein content (p < 0.05). Zein in the endosperm, particularly 19 and 22 kDa α-zein mainly contributed to distinct hardness of the local varieties hence may contribute to physical barrier of the kernels against storage pests. Key words: Maize, local variety, kernel type, hardness, chemical properties, larger grain borer.