Sitophilus Zeamais Research Articles

Toxicity and repellency of essential oils in the management of Sitophilus zeamais

ABSTRACT This study had the following objectives: to identify and quantify the constituent compounds of essential oils from Cymbopogon winterianus Jowitt, Eucalyptus globulus Labill., Eucalyptus staigeriana F. Muell. ex F.M. Bailey, Foeniculum vulgare Mill., Ocimum basilicum L., Ocimum gratissimum L., and Piper hispidinervum C. DC., investigate their toxicity and repellency to S. zeamais and evaluate the toxicity of P. hispidinervum to immature S. zeamais. Individual tests for each essential oil were conducted with a completely randomized design with five concentrations for each oil and four replicates. Gas chromatography-mass spectrometry revealed the presence of citronellal in C. winterianus, 1,8-cineole in E. globulus, limonene in E. staigeriana, limonene in F. vulgare, linalool in O. basilicum, (E)-anethole in O. gratissimum, and safrole in P. hispidinervum. The median lethal concentration required to kill 50% of the insect (LC50) in contact and ingestion toxicity tests ranged from 5.12 to 78.89 μL 40g-1 corn in P. hispidinervum and C. winterianus, respectively. In adult fumigation tests, the LC50 ranged from 2.1 to 19.4 µL L-1 air, and in immature fumigation tests, the egg stage was susceptible to essential oil, whereas larval and pupal phases were tolerant. All of the oils repelled S. zeamais.

Ketahanan Beberapa Genotipe Jagung Hibrida Umur Genjah terhadap Sitophilus zeamais Motschulsky

Sitophilus zeamais is a major pest of cereal products in the storage that can reduce the quality and quantity of the grain. The use of resistant variety is an efficient method to control S. zeamais. This research aimed to evaluate the resistance of 8 early maturing hybrid maize genotypes to S. zeamais. The research was arranged in a single factor completely randomized design with 3 replications, involving 8 genotypes and 4 check varieties. Samples of 25 g seeds were stored in the container covered by gauze, then infested with same-aged 5 males and 5 females of S. zeamais and maintened to 105 days. Observed variables were the number of F1 progenies of S. zeamays, susceptibility index, seed damage, and weight loss. Based on the results, 3 early maturing hybrid maize genotypes (CH-19, CH-18 and CH-20) exhibited high resistance to the S. zeamais as indicated by their susceptibility index, number of progenies, percentage of seed damage, and weight loss. These genotypes had susceptibility index of 1.23-1.80 with low percentage of seed damage of 2.07-4.55%. Correlation tests showed that the susceptibility index of maize seeds had positive correlation with number of progenies and seed damage.Keywords: seed, stored pest, susceptibility index

Role of Maize Weevil, Sitophilus zeamais Motsch. on Spread of Aspergillus section flavi in Different Nepalese Maize Varieties

Experiments were conducted to find out the role of maize weevil, Sitophilus zeamais Motsch. on spread of green fungus, Aspergillus section flavi, in different varieties of stored maize in laboratory in 2016. Lab experiment was conducted to find the role of weevil on spread of A. flavus on five main varieties of maize grown at Nepal in split plot design, namely, Arun-2, Arun-4, Manakamana-1, Manakamana-3, and Rampur composite with three replications at NAST, Khumaltar, from August to September 2016. One hundred grams of each maize variety was exposed to weevil along with fungus and with fungus only to see the spread of the fungus under presence and absence of weevil. Among the tested five maize varieties, the lowest infestation was observed on Rampur Composite (14.99%) while it was the highest on Manakamana-3 (87.70%). The highest mean infestation (75.58%) was found under weevil released condition while it was lower (62.16%) under nonreleased condition. In presence of weevil, the infestation of the fungus increased and in their absence the infestation was low which signifies the role of weevil in fungal spread. All indices indicate that Rampur composite is the best variety among the five tested varieties in terms of storage under the presence of fungus and weevils. This study also indicates ample scope for further study on different varieties of maize under several storage conditions.

Acoustic, Pitfall Trap, and Visual Surveys of Stored Product Insect Pests in Kenyan Warehouses.

Grain production is an important component of food security in Kenya but due to environmental conditions that favor rapid growth of insect populations, farmers and other agricultural stakeholders face ongoing and novel challenges from crop and stored product pest insects. To assist development of methods to reduce economic losses from stored product insect pests in Kenya, acoustic, visual, and pitfall trap surveys were conducted in five grain storage warehouses. Two commercially available acoustic systems successfully detected the pests of greatest economic importance, Sitophilus zeamais (Motschulsky) and Prostephanus truncatus (Horn). Other insects of lesser economic importance also were observed in the visual surveys, including Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), and Tribolium castaneum (Herbst). This study demonstrated that the use of acoustic technology with visual surveys and pitfall traps can help managers to identify and target infestations within their warehouses, enabling them to reduce postharvest losses. With most warehouses being located in relatively noisy urban or peri-urban areas, background noise considerations are being incorporated into the design of future acoustic detectors for stored pest infestations. Kenya must import grain yearly to meet consumption needs; however, if the current yearly postharvest losses of 20–30% in warehouses decreased, import costs could be reduced considerably.

Viabilitas Benih Jagung Lokal yang diberi Tepung Daun Tembelekan (Lantana camara Linn) dalam Pencegahan Serangan Sitophilus zeamais Motsch (Coleoptera:Curculionidae) Selama Penyimpanan

Sitophilus zeamais Motsch (Coleoptera:Curculionidae) sering menyerang benih jagung selama periode penyimpanan sehingga dapat menurunkan viabilitas benih. Tembelekan (Lantana camara linn) memproduksi senyawa metabolit sekunder yang dapat berperan melindungi jagung dari gangguan Sitophilus zeamais. Tujuan penelitian ini adalah mencegah serangan hama Sitophilus zeamais dengan tepung daun tembelekan untuk meningkatkan viabilitas benih jagung selama penyimpanan. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) pola faktorial. Faktor pertama adalah takaran tepung tembelekan, yang terdiri dari empat level yakni T0: tanpa tepung, T1: 10% w/w, T2: 15% w/w, T3: 20% w/w. Faktor kedua adalah lama kontak penyimpanan yang terdiri dari 3 level yakni M0: 1 minggu, M1: 2 minggu, dan M2: 3 minggu. Hasil penelitian menunjukkan bahwa interkasi perlakuan tepung daun tembelekan dan periode simpan mampu mempertahankan viabilitas dan vigor benih jagung lokal pada peubah potensi tumbuh maksimum 97,33%, kecepatan tumbuh 19,06%/etmal, indeks vigor 71% dan berat kering kecambah normal 5,4 gram.

Effects of different concentrations of four spices on the adult mortality and emergence of maize weevil, Sitophilus zeamais Motschulsky (Coleoptera : Curculionidae)

The objective of the study was to evaluate the effects of different concentrations of four spices on the adult mortality and emergence of Sitophilus zeamais Motsch. in maize. The study was carried out in 2017 at the Department of Crop Protection Laboratory, University of Ilorin, Nigeria at prevailing temperature of 28±3°C, relative humidity of 68±3% and photoperiod of L12: D12. The maize variety (SAMMAZ 52) was obtained from Institute for Agricultural Research, Zaria, Nigeria. The seeds were cleaned, stored in air-tight polyethylene bag, kept in domestic deep freezer and later thawed. The experiment consisted of 50 g of seeds weighed into each jar and then treated with African nutmeg Monodora myristica (Gaertn) Dunal, garlic, Allium sativum (L.), cloves Syzygium aromaticum (L.) Merr. and ginger, Zingiber officinale Roscoe powders at the concentrations of 0.00, 1.00, 1.25, 1.50, 1.75, 2.00, 2.25 and 2.50 g and permethrin at 0.12 g against S. zeamais. Five newly emerged adults (2 males: 3 females) of 1–2 day old were used to infest the treated seeds and the untreated control. The experiment was a completely randomized design with four replications. S. zeamais mortality data were taken at 1, 3 and 5 days post-infestation (DPI), anti-oviposition activity was estimated at 6 DPI and adult emergence of S. zeamais was determined at 31, 33 and 35 DPI. Results showed that percentage mortality was significantly (P<0.05) increased compared with the untreated control. At 5 DPI, total mortality (100.0%) of S. zeamais in garlic and clove powders was recorded at highest concentration, suggested their performance in matching the efficacy of permethrin. No adults emerged from the African nutmeg from1.25 to 2.50 g per 50 g seeds at 31 and 33 DPI compared with the control with cumulative mean adult emergence that ranged from 1.25 to 2.25. It could be concluded that the spices had great insecticidal potentials against S. zeamais under small-scale storage. The spices are, therefore, recommended for incorporation in the management of S. zeamais.

No Effect of Bt-transgenic Rice on the Tritrophic Interaction of the Stored Rice, the Maize Weevil Sitophilus Zeamais and the Parasitoid Wasp Theocolax elegans

During Bt transgenic rice storage, Bt Cry1Ab/Cry1Ac fused protein is exposed to the maize weevil Sitophilus zeamais and the parasitoid wasp Theocolax elegans. We have carried out a long-term risk assessment for Bt rice to these non-target organisms in the storehouse. Effects of Bt rice on S. zeamais and T. elegans have been carefully detected in a laboratory experiment of over 5 years. The survival, development, fecundity, and longevity of the maize weevil were compared between Bt rice and non-Bt rice treatments for every 5 generations from generation 1 to 25. Moreover, the development, adult body size and sex ratio of T. elegans were compared between them parasitizing S. zeamais feeding on Bt rice or non-Bt rice. We found that although Bt Cry1Ab/Cry1Ac fused protein exists in the Bt rice grains and S. zeamais digestive tracts, Bt rice is not harmful to the maize weevil S. zeamais and its parasitoid T. elegans.

Effects of host resistance and plant-derived insecticides on mortality of Sitophilus zeamais (Coleoptera: Curculionidae) adults in stored maize

The effect of host resistance and plant-derived insecticides on the mortality of adults of the maize weevil, Sitophilus zeamais, in maize was determined at ambient temperature (30.7 °C) and relative humidity (70.4%) using a 2-factor factorial arrangement in a Randomized Complete Block Design. Powders of pepper fruit (Dennettia tripetala) seeds, mistletoe (Viscum album) leaf, garlic (Allium sativum) bulbs, and clove (Syzygium aromaticum) inflorescence were applied separately to 2000SYNEE-WSTR (highly resistant to S. zeamais), TZBRCOMP.2C1F1 (resistant), ART/98/SW4-OB (moderately resistant), and PVASYN-3F2 (susceptible) maize varieties at the rates of 0.5, 1.0 and 1.5 g per 20 g of grains. The same rate of permethrin (BEST 0.6% D) and an untreated control were included. A similar experiment was conducted using extracts applied at the rate of 0.5, 1.0 and 1.5 ml per 20 g of grains with permethrin (BEST 10% EC) and acetone serving as the control treatments. Denettia tripetala and S. aromaticum at 1.0 and 1.5 g or ml per 20 g grains matched the efficacy of permethrin by the 3rd and 4th day post-exposure, irrespective of maize resistance rating. Across test plants and rates of application, the use of botanicals added value significantly in a progressive way to host resistance. There were no variety or variety x protectant interaction effects on mortality of adult S. zeamais observed for four days at concentrations of 0.5–1.5% w/w or ml/ 20 g grains. There is need for further evaluation of the complementary action of varietal resistance and D. tripetala and S. aromaticum under long-duration storage conditions.

Antennal transcriptome analysis of the maize weevil Sitophilus zeamais: Identification and tissue expression profiling of candidate odorant-binding protein genes.

Our bioassays reviewed that antennae played crucial roles in the responses of maize weevil (Sitophilus zeamais) to food and sex volatiles. In order to identify the maize weevil odorant-binding protein (OBP) genes, we analyzed its antennal transcriptome. In total, 21,587,928 high-quality clean reads were obtained from RNA-seq, 52,206 unigenes were assembled, and 25,744 unigenes showed significant similarity ( E value < 10 -5 ) to known proteins in the NCBI nonredundant protein database. From those unigenes, we identified 41 candidate OBP proteins, which could be categorized into dimeric OBPs subfamily, minus-C OBPs subfamily, and classical OBPs subfamily. Phylogenic analysis indicated that most maize weevil OBPs were closely related to their orthologues in other beetles of the Superfamily Curculionoidea. We further investigated the expression profiles of those candidate OBP genes by quantitative real-time polymerase chain reaction. Twenty-six of forty-one maize weevil OBP genes were highly expressed in the antennae or other parts of the head. The rest were expressed in the legs, wings, or other tested tissues. The antennal transcriptomic data and candidate OBP genes described here provide a basis for the functional studies of the maize weevil chemical perception, which are potential novel targets for pest control strategies.

Weevil pgrp-lb prevents endosymbiont TCT dissemination and chronic host systemic immune activation

Long-term intracellular symbiosis (or endosymbiosis) is widely distributed across invertebrates and is recognized as a major driving force in evolution. However, the maintenance of immune homeostasis in organisms chronically infected with mutualistic bacteria is a challenging task, and little is known about the molecular processes that limit endosymbiont immunogenicity and host inflammation. Here, we investigated peptidoglycan recognition protein (PGRP)-encoding genes in the cereal weevil Sitophilus zeamais's association with Sodalis pierantonius endosymbiont. We discovered that weevil pgrp-lb generates three transcripts via alternative splicing and differential regulation. A secreted isoform is expressed in insect tissues under pathogenic conditions through activation of the PGRP-LC receptor of the immune deficiency pathway. In addition, cytosolic and transmembrane isoforms are permanently produced within endosymbiont-bearing organ, the bacteriome, in a PGRP-LC-independent manner. Bacteriome isoforms specifically cleave the tracheal cytotoxin (TCT), a peptidoglycan monomer released by endosymbionts. pgrp-lb silencing by RNAi results in TCT escape from the bacteriome to other insect tissues, where it chronically activates the host systemic immunity through PGRP-LC. While such immune deregulations did not impact endosymbiont load, they did negatively affect host physiology, as attested by a diminished sexual maturation of adult weevils. Whereas pgrp-lb was first described in pathogenic interactions, this work shows that, in an endosymbiosis context, specific bacteriome isoforms have evolved, allowing endosymbiont TCT scavenging and preventing chronic endosymbiont-induced immune responses, thus promoting host homeostasis.

Impact of storage structures on moisture content, insect pests and mycotoxin levels of maize in Ghana

Insect pests and fungal pathogens can cause extensive product losses and pose health risks in sub-Saharan Africa. In this experiment, maize stored as de-husked cobs or shelled maize in a ventilated crib and a metal bin, and in bags in warehouses, was monitored monthly in Ghana from October of 2015 to December of 2015 (the major season) and from January to April of 2016 (the minor season). Temperature, moisture content, insect pests, and associated damage were assessed monthly, and samples were taken in October, December, January, and April for mycotoxin analyses. Moisture content, which ranged from 9 to 15% during the year was occasionally greater in the bin and warehouse compared to the crib, and greater in months associated with the major season compared to other months. Temperatures varied with season but were generally warmer in the bin compared to the warehouse and crib. The predominant insect collected was Sitophilus zeamais (Motschulsky), with the lowest populations in the crib, but in each structure the populations were about 10x greater in the major season compared to the minor season. Sitotroga cerealella (Olivier) was the second most-prevalent species, but populations of this species were greater in the crib compared to the bin or warehouse. Scattered populations of other stored product insects were collected from the maize samples and in pheromone traps. Percentage insect damaged kernels (IDK) and weight loss were also greater in samples from months where S. zeamais was present. Aflatoxin was above 10 ppb only in the warehouse in December, while fumonisin levels in all the storage structures were <0.5 ppm for all months. Results show that maize stored during the major season in Ghana is at risk from insect damage, and metal bins could be utilized more frequently for storage.

Contact Toxicity of Filter Cake and Triplex Powders From Ethiopia Against Adults of Sitophilus zeamais (Coleoptera: Curculionidae).

Filter cake and Triplex are powdered by-products of aluminum sulfate and soap factories in Ethiopia, respectively. This study was aimed at determining contact toxicity of filter cake and Triplex powders against maize weevil, Sitophilus zeamais Motschulsky. Lethal concentrations for 99% mortality (LC99) against S. zeamais were determined by exposing adults for 12 h to filter cake (0.5-8 g/m2) and Triplex (1-9 g/m2) in concrete arenas. Lethal times for 99% mortality (LT99) were determined by exposing adults over time (1-24 h) in concrete arenas to 3 g/m2 of filter cake and 9 g/m2 of Triplex. Exposed adults were transferred to containers with 30 g of organic wheat and held at 28°C and 65% RH for 14 d to determine mortality. LC99 values for S. zeamais adults were 7.54 and 23.46 g/m2 when exposed to filter cake and Triplex, respectively. The corresponding LT99 values were 21.92 and 39.62 h when exposed to filter cake and Triplex, respectively. Effective concentrations and times for the 99% reduction of progeny production were determined from percentage reduction in adult progeny relative to production in control treatments after 42 d. EC99 values for progeny reduction were 2.48 and 18.59 g/m2 for filter cake and Triplex treatments, respectively. The corresponding ET99 values for progeny reduction were 17.49 and 22.31 h for filter cake and Triplex, respectively. Sitophilus zeamais exposed to filter cake produced lower percentage insect-damaged kernels and weight loss than Triplex. Filter cake was more efficacious against S. zeamais than Triplex.

Overexpression of the ZmDEF1 gene increases the resistance to weevil larvae in transgenic maize seeds.

Plant defensins are divided into 18 groups and are multifunctional proteins. The Zea mays defensin 1 (ZmDEF1) gene encodes the defensin 1 protein, which can inhibit alpha-amylase in the insect gut. In this study, the ZmDEF1 gene was transferred into two maize cultivars, LC1 and LVN99, to improve weevil resistance in maize. The recombinant ZmDEF1 protein was assessed for its ability to inhibit alpha-amylase in the gut of the larvae of the maize weevil (Sitophilus zeamais Motsch.). ZmDEF1 was cloned into a pBetaPhaso-dest vector, which harbours phaseolin, a seed-specific promoter, and the Agrobacterium tumefaciens strain C58 harbouring the pBetaPhaso-ZmDEF1 vector was used to transfer the ZmDEF1 gene into two maize cultivars using immature embryos. Transformed calluses were selected on selection media containing kanamycin. The stable integration of the ZmDEF1 transgene into the transgenic maize plant genome was confirmed using Southern blotting. The recombinant ZmDEF1 protein of approximately 10kDa was expressed in three transgenic maize lines from the LC1 cultivar (C1, C3, and C5) and two transgenic maize lines from the LVN99 cultivar (L1 and L3). The ZmDEF1 transgenic efficiency based on the results of PCR, as well as Southern and Western blotting, was 1.32% and 0.82%, respectively, which depends on the genotypes of LC1 and LVN99. The recombinant ZmDEF1 protein inhibited the alpha-amylase activity of the maize weevil larvae, and its ability to inhibit alpha-amylase is 54.52-63.09% greater than the ZmDEF1 protein extracted from non-transgenic plants.

Identification and Expression Profiling of Odorant Receptor Protein Genes in Sitophilus zeamais (Coleoptera: Curculionoidea) Using RT-qPCR.

This study aimed to identify ORs (odorant receptors) and Orco (odorant receptor coreceptor) genes in Sitophilus zeamais Motschulsky (Coleoptera: Curculionoidea), to explore the relative expression levels of these genes in different adult tissues and obtain information on highly expressed receptor proteins. Putative OR and Orco genes were identified from transcriptomic data previously obtained for S. zeamais using bioinformatics methods. Quantitative real-time PCR was used to compare the differences in expression in seven adult tissues (male antennae, female antennae, heads, thoraxes, abdomens, wings, and legs). The candidate OR and Orco gene sequences were analyzed, and the protein physicochemical properties were predicted. We identified 64 OR genes including the Orco gene. Forty-seven OR genes, including Orco, were over expressed in male or female antennae. Seventeen OR genes appeared to be expressed at elevated levels in male antennae. Twenty-nine genes were expressed at significantly elevated levels in female antennae. In total, 11 OR genes were selected for further sequence analysis. The selected proteins were structurally characterized, and bioinformatics analysis was performed. Overall, in this study, candidate ORs of S. zeamais have been identified for the first time, and these ORs could be molecular targets for interference in the insect olfactory system.

Susceptibility of selected maize seed genotypes to Sitophilus zeamais (Coleoptera: Curculionidae)

Studies were carried out under laboratory conditions of 25 ± 2 °C and 70 ± 5% RH in an incubator to determine the relative susceptibility of eighteen maize genotypes to attack by the maize weevil, Sitophilus zeamais Motschulsky. The experiment was laid out in a Completely Randomized Design (CRD) with three replications. Adult mortality, number of F1 progeny, weevil development time, susceptibility index, percentage seed damage, percentage weight loss, and weight of powder produced were determined after storage period of three months. The susceptibility index was determined using Dobie’s formula and the genotypes were classified into different susceptibility groups. The genotypes exhibited varying degrees of susceptibility to S. zeamais attack. Only Aseda was regarded as resistant and TZE-Y POP STR as moderately resistant to S. zeamais. Kpari-Faako, Tintim, WACCI-M-1215, WACCI-M-1594 and Wang-Dataa were regarded as moderately susceptible to S. zeamais. However, Abontem, Bihilifa, Ewul-Boyu, Sanzal-Sima, TZE-I 17, WACCI-M-1205, WACCI-M-1508 and WACCI-M-1510 were regarded as susceptible genotypes. Furthermore, Aburohemaa, Obaatanpa and Omankwa were regarded as highly susceptible to S. zeamais. Number of F1 progeny, seed damage, seed weight loss, weight of dust produced and seed moisture content had positive relationship with varietal susceptibility while adult weevil mortality, median development period and seed germination after infestation had an inverse relationship with susceptibility in maize. The use of insect resistant genotypes would offer a sustainable way of minimizing postharvest losses of seeds in storage especially for smallholder farmers who keep harvested grains for future use as food and seed.

Efficacy of Combinations of Methoprene and Deltamethrin as Long-Term Commodity Protectants.

Wheat, corn, and brown rice were treated with different combinations of a deltamethrin suspension concentrate (SC) formulation and a new emulsifiable concentrate (EC) formulation, at rates of either 0.5 or 1.0 ppm alone or in combination with 1.25 and 2.5 ppm methoprene (10 treatments in all, including an untreated control). Treated commodities were stored at ambient conditions on the floor of an empty grain bin in Manhattan, KS, USA, in 5-kg lots for individual replicates. The commodities were sampled and bio-assayed every three months for 15 months by exposing 10 mixed-sex parental adults of selected adult stored product insects on 70–80 g of the commodity. For all treatments, there was no regression of declining efficacy with respect to the month. Therefore, the data were combined for analysis. On wheat and brown rice, there was no reproduction of Rhyzopertha dominica (Fabricius) in any of the treatments, and there was no weight loss in either commodity that was caused by feeding of the parental adults or developing progeny. There was reproduction of Sitophilus oryzae (L.) on wheat but, for several combinations, the EC formulation gave better suppression of progeny compared to the standard SC. However, on brown rice, only the combination of 1.0 ppm deltamethrin EC and 2.5 ppm methoprene was different than other treatments with respect to progeny development, sample weight loss caused by feeding, and weight of the feeding damage itself. Progeny production was correlated with grain damage. No progeny of Tribolium castaneum (Herbst) developed on the treated corn, but there was some variation in insect damage, with less damage in those treatments involving the EC formulation. Progeny production of Sitophilus zeamais (Motschulsky) was at the lowest in the combination of 1.0 ppm deltamethrin EC and 2.5 ppm methoprene. The resulting insect damage was the lowest in this combination as well. Results of this study were used by the registrant (Central Life Sciences) in the United States (US) to modify the commercial formulation to replace the deltamethrin SC with the EC, at label rates of either 0.5 ppm EC + 1.25 ppm methoprene, or 1.0 ppm EC + 2.5 ppm methoprene, on wheat, corn, and rice.

Evaluation of the insecticidal potential of leaf extracts of Anadenanthera colubrina var. cebil (Griseb) Altschul against Tetranychus urticae Koch and Sitophilus zeamais Mots

The deterioration and degradation of crops by insects causes economic losses of several billion dollars and affects food security. Sitophilus zeamais and Tetranychus urticae are two economically important species of agricultural crops around the world. The high toxicity of synthetic insecticides and the development of insect resistance to currently used chemicals stimulate the investigation of plant-derived insecticides as new alternatives for pest control. The insecticidal properties of secondary metabolites have been recognized, and have been confirmed scientifically in the last decades. The extract in cyclohexane (Ch) and ethyl acetate (Ea) of the leaves of Anadenanthera colubrina var. cebil collected in the dry and rainy seasons were evaluated for the survival and nutritional physiology of S. zeamais (maize weevil) and for the acaricidal effect front T. urticae (two-spotted spider). All extracts induced mortality of S. zeamais; however, only cyclohexane dry season (Chd) and ethyl acetate in the rainy season (Ear) caused significant mortality (p &lt;0.05), more than 50%, promoting physiological damage to insects in all concentrations tested. In the mortality tests with the spider mite, extracts Chd and Ear showed an LC50 of 52.75 and 156.42 mg.mL-1. Still, in the same test, it can be observed that oviposition was also susceptible to extracts. Therefore, the extracts of A. colubrina are a source of compounds capable of interfering with and impairing the metabolism of the two studied pests.

Comparative Study of the Genetic Variability of Sitophilus Zeamais Subservient to 2 Host Plants (Millet and Maize) in Senegal (West Africa)

Millet and maize, because of the importance of their yields, constitute a reliable alternative to the question of sovereignty and food security. These cereals are exploited in all agroecological zones of Senegal. But their stocks, especially those of maize, are deteriorated by Sitophilus Zeamais, a beetle of the Curculionidae. It is therefore necessary to find natural solutions that are healthier than the use of pesticides which is harmful to living beings and the environment. This article makes a comparative study of the genetic diversity of the populations of this insect individually subservient to maize and to millet. The importance of this study is to find a genetic explanation for the differential vulnerability of these host plants to Sitophilus Zeamais, because the genetic diversity influences the adaptability of the individual and consequently its development. For this, insects Sitophilus Zeamais subservient on the one hand to maize and on the other hand to millet were collected in each agroecological zone. The exploitation of 125 sequences of the Cytochrome B gene corresponding to the individuals, by software of study in population genetics (Bioedit, DNAsp, Mega, Arlequin…) compared to parameters of genetic variability, revealed an approximately similar and high genetic diversity of the 2 populations of millet and maize. Thus, millet and maize genetically have the same effect on the adaptability of Sitophilus Zeamais.

Assessment on Weight Loss of Maize Seeds (Jibat Variety) Caused by Maize Weevil (Sitophilus Zeamais Motsch.) (Coleoptera: Curculionidae) after Treated by Botanical Powder under Laboratory Condition

The present study was emphasized on assessment of weight loss of maize seeds (Jibat variety) caused by maize weevil (Sitophilus zeamais) after treated by botanical powder under Laboratory condition”. Higher percent of weight loss (50.04%) was registered by control at 40 days after application; however, no maize seed was lost under plastics treated by malathion 5% dust; Calpurnia aurea recorded 3.41% of maize seed was lost at rate of 2%; Justice schrimperiana recorded 3.38% of maize seed was lost at rate of 2% and lower maize seed weight loss was recorded under treatment applied by Eucalyptus globules(2.75%), Vernonia amygdalina (2.88%) and Leonotis ocimifolia (2.85%) at 2% of rate respectively. Eighty days after exposure, maize seed weight loss was recorded in Justica schrimperiana (14.67% to 10 %) at a rate of 2% to 11%; Vernonia amygdalina (13% to 9%) at a rate of 2% to 11%; Eucalyptus globules (12.33% to 7.33%) at a rate of 2% to 11%; Calpurnia aurea (6.67% to 3.33%) at a rate of 2% to 11% respectively; malathion 5% dust (no weight loss), However, up to 285 fold weight loss was recorded from the untreated control after 80 days of treatment exposure. Hundred twenty days after exposure, maize seed weight loss was recorded in Justica schrimperiana (7.45% to 5.18 %) at a rate of 2% to 11%; Vernonia amygdalina (4.58% to 2.24%) at a rate of 5% to 11%; Eucalyptus globules (3.75% to 1.33%) at a rate of 2% to 11%; Calpurnia aurea (4.08% to 1.12%) at a rate of 2% to 11% respectively; malathion 5% dust (no weight loss), untreated control 300.79% weight loss was recorded after 120 days of exposure. Generally, maize seed weight loss was increased at lower rate and decreased at higher rate and highly increased under control as the time extended and no any damage in maize seed treated by malathion 5% dust.

Efficacy of Filter Cake and Triplex Powders Against Three Internally Developing Stored-product Insect Species

Filter cake and Triplex powders from Ethiopia were applied to maize and wheat in the laboratory to determine efficacy against the lesser grain borer, <i>Rhyzopertha dominica</i> (Fabricius) (Coleoptera: Bostrichidae); maize weevil, <i>Sitophilus zeamais</i> Motschulsky (Coleoptera: Curculionidae); and rice weevil, <i>Sitophilus oryzae</i> (Linnaeus) (Coleoptera: Curculionidae). These species are major insect pests associated with stored grain in Ethiopia. Efficacy of the two powders was determined by exposing 20 adults of each species to 100 g of maize and wheat treated with 0, 0.3, 0.5, 0.7, 1, 2, 3, 4 and 5 g/kg of filter cake, and 0, 0.5, 0.7, 1, 2, 3, 6, 8 and 10 g/kg of Triplex. Adult mortality was determined 14 d after exposure to untreated and treated grain. Adult progeny production at each species-powder-concentration combination was determined at 42 d. Complete mortality (100%) of <i>R. dominica</i> was achieved on maize treated with 3–5 g/kg of filter cake; however, on maize 100% mortality of <i>S. zeamais</i>, and <i>S. oryzae</i> was not achieved at any of filter cake concentrations. Complete mortality of <i>R. dominica</i> adults was observed on wheat treated with 2–3 g/kg of the filter cake. Complete mortality of <i>S. zeamais</i> and <i>S. oryzae</i> was achieved when adults were exposed to wheat treated with 0.7–3 g/kg of filter cake. Mortality was less than 100% at all Triplex concentrations on maize and wheat for all three species. Adult progeny production of <i>R. dominica</i> was wholly suppressed at filter cake concentrations of 1–5 g/kg on maize, whereas progeny production of <i>S. zeamais</i> and <i>S. oryzae</i> on maize was not entirely suppressed at any of the filter cake concentrations. No progeny of <i>R. dominica</i> was observed on wheat treated with 2–3 g/kg of filter cake. Similarly, progeny production of <i>S. zeamais</i> and <i>S. oryzae</i> was completely suppressed on wheat treated with 3 g/kg of a filter cake. Complete suppression of progeny production of the three species was not achieved at any concentration of Triplex on both maize and wheat. These powders have potential in managing <i>R. dominica</i>, <i>S. zeamais</i>, and <i>S. oryzae</i> infesting maize and wheat.