Insecticidal Activity of Four Medicinal Plants against Stored Grain Borer, Rhyzopertha dominica (Fabricius)

Simple SummaryEucalyptus essential oils have shown promising insecticidal effects on several insect pests. The lesser grain borer, Rhyzopertha dominica (F.), causes economically significant damage to stored grains as an internal primary insect pest. In this study, the chemical compositions of essential oils isolated from four Eucalyptus species. E. microtheca, E. procera, E. spatulata, and E. torquata were detected and identified using a gas chromatography-mass spectrometer, and their lethal and sublethal insecticidal effects were evaluated against the adults of R. dominica. Although all essential oils have significant fumigant toxicity, due to the high relative potency, R. dominica was more susceptible to the E. procera essential oil than the others. The total protein, glycogen, and lipid contents and digestive amylase and protease enzyme activities of the treated insects were reduced. The nutritional indices consumption index, relative consumption rate, and relative growth rate were also reduced in the treated adults. The findings of this study reveal that E. microtheca, E. procera, E. spatulata, and E. torquata essential oils can be potentially used for the development of eco-friendly natural agents for the management of R. dominica. The lesser grain borer, Rhyzopertha dominica (F.), causes damage to stored grains resulting in both quantitative and qualitative losses. The use of synthetic fumigants in the management of stored-product pests resulted in undesirable side effects such as environmental contamination and threat to human and animal health. In this study, the lethal and sublethal effects of essential oils from four Eucalyptus species, E. microtheca, E. procera, E. spatulata, and E. torquata were studied against R. dominica adults. Gas chromatographic–mass spectral analysis of the essential oils was carried out, in which terpenes such as 1,8-cineole and globulol were abundant in essential oils. The pest was susceptible to the fumigation of the essential oils and, considering concentrations and exposure times (24, 48, and 72 h), had significant effects on the pest mortality. The total protein, glycogen, and lipid contents and digestive amylolytic and proteolytic activities of the adults treated with tested essential oils were reduced. The consumption index, relative consumption rate, and relative growth rate were also reduced in the treated adults. According to the insecticidal effects on the adults of R. dominica, the essential oils of E. microtheca, E. procera, E. spatulata, and E. torquata can be candidates for further investigations as grain protectant agents.

Essential oils and plant dusts from the Croatian aromatic plants Lavandula officinalis [L. angustifolia] (dust from ground leaves, flowers and stems), Laurus nobilis (dust from ground leaves), Rosmarinus officinalis (dust from ground leaves and stems), and Thymus vulgaris (dust from ground leaves, flowers and stems) were evaluated for insecticidal activity against the lesser grain borer R. dominica infesting market and seed wheat under laboratory and storage conditions. Up to 100% mortality of adults was obtained over the exposure period. The efficacy of the plant material was compared to a control with no treatment. The rates of essential oils and plant dust recalculated on 5-kg wheat samples were 3.75 ml per sample of oils, and 37.5 g per sample of dust. In general, all essential oils exhibited strong insecticidal effect (100% mortality of adults after 24 h). L. nobilis was the most effective in dust form (100% mortality of adults after 7-10 days of exposure) under storage conditions. In the control samples, no mortality of adults was recorded. Over the 5-month period, damage on wheat was 30%, while insect population increased up to 190%. No changes in quality, colour or flavour of the commercial wheat flour were recorded during the treatment; however, each sample retained the scent of the plants tested. On seed wheat, no negative effect on germination or energy of germination was recorded. These aromatic plant products proved to be partial substitutes for synthetic insecticides if applied to smaller stocks of stored wheat.

The uncontrolled use of synthetic insecticides is a great hazard for the environment and consumers. Essential oils were introduced as low toxic agents against mammals and non-targeted insects. In this study, essential oil from aerial parts of blue giant hyssop (Agastache foeniculum [Pursh] Kuntze) (Lamiaceae) was isolated by the water steam distillation method with a Clevenger apparatus, and its chemical composition was studied by gas chromatography mass spectrometry. The toxicity of A. foeniculum essential oil against red flour beetle, Tribolium castaneum (Herbst), and lesser grain borer Rhyzopertha dominica (F.) was evaluated by fumigation at 24, 48, and 72 h exposure times. Estragole and 1,8-cineole were identified as major constituents of the A. foeniculum oil. Fumigation bioassays revealed that A. foeniculum oil had strong insecticidal activity on experimental insects. Rhyzopertha dominica was more susceptible than T. castaneum for all exposure times. Insecticidal activity varied with essential oil concentration and exposure time. Probit analysis showed that increased exposure time and essential oil concentration increased mortality. These results indicated that A. foeniculum essential oil can be applied in the management of stored-product insects to decrease the detrimental effects of synthetic insecticides.

Observations on stored grain, products from its manufacture and materials from plant origin in the storage-silo bases in Bulgaria were conducted from 2000 till 2019 to establish the damage and weight losses from the lesser grain borer Rhyzopertha dominica F. (Coleoptera: Bostrichidae). It was found that the grain beetle adults consumed 0.905 ± 0.00374 mg of food per day. With an average adult lifespan of 130 days, an adult consumes 117.678 mg of dry matter from the grain. In experiments aimed to determine the weight losses caused by the larvae of the grain beetle during their development, it was found that they amounted to 13.7861 ± 0.04632 mg per individual. Thus, losses for the development of individual amount to an average of 131.6647 mg. A test for the presence of mycotoxins (fumonisins - FB1 and FB2 total in ng/g) was done on maize attacked up to 5% and 25% with latent infection by the grain beetle. The results showed that at 5% latent infection the quality of mycotoxins was almost 5 times higher -lower than that at 25% corn infestation - 693.9 ± 69 ng/g and 3436.1 ± 34 ng/g, respectively. This shows that the development of the species in the grain stocks also leads to secondary processes of decay accompanied with an increase of mycotoxins consentrations. Keywords: Rhyzopertha dominica, the lesser grain borer, damage, stored cereals

Control failure and insecticides resistance in populations of Rhyzopertha dominica (Coleoptera: Bostrichidae) from Colombia

Lesser grain borer Rhyzopertha dominica (F.) is a destructive insect pest of stored grains. Both larvae and adults of the pest attack whole, sound grain and cause extensive damage. Larvae are internal feeders whereas adults are free living and bore into the commodity and can fly. Fumigation is the most useful and effective method to manage this insect pest. There are several insecticides available in the market to manage this pest but some insecticides have been banned because of environmental pollutions and for some insecticides this insect pest has developed resistance. Therefore efforts are required to find safe, effective and viable alternatives. Natural products are well known to have a range of useful biological properties against insect pests. Recently, there has been considerable interest in essential oils and extracts of medicinal and edible plant and herbs for the development of alternative insecticides and fumigants. This research was initiated to evaluate the fumigation toxicity and repellent action of Eucalyptus globulus Labill essential oil against adults of R. dominica. GC/MS analysis showed the major components of E. globulus essential oil as 1,8-cineole (22.35%), α-pinene (12.58%) limonene (4.01%), aristolene (3.35%), p-cymene (3.25%), trans-verbenol (3.02%), isosativene (2.85%), α-myrcene (2.15%) and terpinen-4-ol (2.10%). Fumigation toxicity and repellent activity showed that as the concentration and exposure time increased the mortality and repellency also increased. Maximum repellency of 62.0% was observed at 0.32μl/cm2 concentration after 36 hours of exposure.

Store grain insect pests such as Lesser grain borer (Rhyzopertha dominica) is a key feeder and cause substantial weight loss of wheat during storage. Present study was planned to evaluate insecticidal, repellent and growth regulator potential of botanical extracts of two plants Jatropha curcas and Linum usitatissimum along with Spinetoram against Rhyzopertha Dominica. This study was conducted at the Department of Entomology, University of Agriculture, Faisalabad (UAF) Grain Research, Training, and Storage Management Cell. Each treatment with three replication of 5%, 10%, and 15% concentrations of plant extracts and 100ppm, 200ppm, and 300ppm concentrations of insecticide were used against the adults of R. dominica by using Complete Randomized Design. Insect mortality was taken after 24, 48, and 72 hours after treatment. Data of growth regulation data was observed after 30 and 60 days. Data was analyzed by statistic 8.1 software for analysis of variance at 5% level of significance and treatment means was compared with the help of Tukey's Honestly Significant Difference (THSD) test. After 72 hours, Spinetoram showed maximum percent mortality (84%) followed by J. curcas (19.17%) and L. usitatissimum (12.28%) at their higher concentrations rate. Among treatments, after 60 days of exposure, Spinetoram was proved to be more effective against the R. dominica with maximum growth inhibition (70%) as compared to J. curcas (44%) and Linseed (28%). Overall the results indicated that these plant extracts and Spinetoram can be used as efficient alternatives of synthetic chemicals for management of stored grains insect pests.

Stored product beetles that are resistant to the fumigant phosphine (hydrogen phosphide) have been reported for more than 50 years in many places worldwide. The high levels of phosphine resistance in lesser grain borer Rhyzopertha dominica (F.) have been noted from several countries including Bangladesh. This study was designed to evaluate the status of resistance to phosphine in Bangladeshi R. dominica and to verify the possible comparison among other phosphine resistant strains from tropical countries viz. Burkina Faso and Malaysia. The data reported and summarized here showed varied levels of resistance compared to the laboratory phosphine susceptible strain (RDLAB). Rhyzopertha dominica strains originating from Bangladesh (RDBGD) and Burkina Faso (RDBKF) exhibited higher levels of resistance to phosphine compared to the Malaysian strains (RDMAL). Analysis of dose–response data indicated that the RDBGD and RDBKF strains were the most resistant to phosphine under different exposure periods. At LC50, these two strains were more than 80-fold more resistant at all exposures compared to the susceptible strain. Results also revealed that RDBGD and RDBKF strains required a relatively high concentration of 334.94 and 240.081 mg L-1 for 99% mortality. The mean survival time (MST) for the phosphine resistant and susceptible also varied significantly. The maximum MST was recorded for RDBGD and RDBKF strains. The present findings further confirmed that the Bangladeshi originated R. dominica strain contained higher resistance to phosphine compared to strains from other countries. This study could be useful in developing management strategies to prevent stored grain from being infested by resistant strains of R. dominica in tropical countries.

Pulses and Cereals have great nutritional value in the daily human diet. Infestation of Stored grain is a serious issue since different life stages of several types of insects can cause it. Insect degrade the quality of stored grains and product, resulting in economic losses. The storage of grains has been linked to a high number of insect infestations. Almost all stored grain insect pests have remarkably high multiplication rates and may destroy 10-15 % of grains. The major pest of stored grains includes Weevil (Sitophilus oryzae, Sitophilus zeamais, Sitophilus granaries), Tribolium species (Tribolium castaneum and Tribolium confusum), Khapra beetles (Trogoderma granarium), lesser grain borer (Rhyzopertha dominica), Pulse beetles (Callosobruchus maculatus), Rice moth (Corcyra cephalonica), etc. Continuous and indiscriminate over use of insecticides are responsible for the development of resistance against these insect pesticides. Accumulation of synthetic chemical pesticide residues on pulses and cereals are unfortunately consumed by human. Recently, in agricultural practices in different areas of the world, attention has been given towards the exploitation of plant biochemical as a new approach in stored grain protection. Various scientific literature already documented the efficacy of plant derivatives against storage grain pests. Biopesticides kill and repel the insect pests, affect insect growth, development and metamorphosis. Farmers have used higher plants, medicinal plants, various herbs and traditional spices for stored grain insect pest management, but majority of farmer use chemical insecticide to increase productivity but it causes adverse effect on environment and non-target animal including human also, so there is more need for scientific research regarding the plant Biopesticides efficacy against stored grain pests.

Fumigant effects of the essential oils from Laurus nobilis L., 1753 (Laurales: Lauraceae), Mentha piperita L., 1753 and Lavandula x intermedia Emeric ex Loisel, 1828 (Lamiales: Lamiaceae) were determined using the lesser grain borer [Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrychidae)], an important pest species of stored grains. The experiments were conducted in the 2021 in the Department of Crop Protection, Faculty of Agriculture, Malatya Turgut Özal University. The experiments were conducted in a controlled-climate chamber at 27 ± 1°C, 50 ± 10% RH and in the dark. The fumigant effects of essential oils were determined at five concentrations (1, 5, 20, 50 and 200 μl/L air) with larva, pupa and adult stages of R. dominica. The highest fumigant effect was with R. dominica larvae was complete mortality with 200 μl/L L. nobilis essential oil and for the adults, 200μl/L of either L. nobilis and M. piperita essential oil also caused complete mortality. However, the complete mortality of pupal stage was not obtained and the highest mortality was 49% with L. nobilis. As a result, it is considered that both L. nobilis and M. piperita essential oils have the potential to be used as effective biofumigants for stored product pests.

Rhyzopertha dominica (Bostrichidae: Coleoptera) is one of the most serious devastating insect pests attacking stored wheat grains in Nigeria. The most common strategy adopted in controlling this insect pest is the application of synthetic pesticides which is costly, toxic to non-target organisms and is non eco-friendly. Botanical pesticides are recently used as alternatives to synthetic pesticides due to their non-hazardous effect on the environment and non-target organisms, cost effectiveness and direct impacts on the target organisms. This study was carried out to determine the toxicity of leaf powders obtained from three species of plants: Ageratum conyzoides, Momordica charantia and Tephrosia vogelii in the control of R. dominica infestation on stored wheat grains. Five doses (0.50, 1.00, 2.00, 4.00 and 8.00 g) per 20.00 g were measured from the powdered leaves of the tested plants with ethanol treatment as the control (0.00 g 20.00 g-1). The powdered doses were applied onto wheat grains before the insects were introduced. The experiment was laid down in completely randomized design (CRD) with three replications. The data obtained was analyzed using analysis of variance at 5% probability level with Least Significant Difference used to separate the means. The results showed significant (p ≤ 0.05) differences in the magnitude of toxicity imparted by various doses of the powders on R. dominica. The treatments influence high rate of mortality, reduced number of laid eggs and emerged adults when compared with the control. The toxicity of the powders increased with increase in dosage. It was concluded that 8.00 g 20.00 g-1 of the powders were more toxic to R. dominica, inducing 28.00-77.30% insects’ mortality thereby protecting grain damage to as low as 1.04% at 6th month of storage. T. vogelii leaf powders were recommended for use against R. dominica in stored wheat grains.
 Key words: botanicals, dose, lesser grain borer, wheat

Environmental safety and agricultural sustainability are important for survival on the Earth. Spedoptera littoralis and Rhyzopertha dominica are among the most destructive pests for economic crops in Egypt. Indiscriminate use of chemical pesticides called for safe alternatives. seaweeds are among these alternatives Hence, it is imperative to evaluate the efficacy of (Sargassum acinarium, Turbinaria turbinata, Petrocladia capillacea, and Cystoseira myrica ) extracts against S. littorlais third and fifth instar larvae and R. dominica adults. The seaweed extracts-insect contact method was used. Also the antifeediant activities of the tested sea weeds were recorded. All tested seaweeds exhibited insecticidal and antifeediant activities with S.littoralis third instar larvae being more susceptible. T. turbinata and P. capillacea exhibited the highest insecticidal and antifeddiant effects, respectively. C. myrica showed the lowest insecticidal and antifeediant activities at all. There was a direct relationship between the percent mortalities and seaweed concentrations. Sea weeds gas chromatogra¬phy-mass spectrometry analyses revealed different bioactive compounds, which might be responsible for their insecticidal properties.. finally the tested seaweeds can be used as ecofriendly and safe biopes¬ticides for control of S. littoralis and R. dominica and we recommend them to be involved in integrated pest management program.

Recently, essential oils have received much attention as pest control agent because of their insecticidal properties, antifeedant and repellent activity. Fumigant toxicity and repellency effect of essential oil of orange leaves Citrus sinensis (L.) were tested on adults of two coleopteran stored product pests, lesser grain borer Rhyzopertha dominica, and cigarette beetle Lasioderma serricorne. The essential oil of orange leaves was obtained by Clevenger-type apparatus. The bioassays were conducted by using 40 ml glass vials as container and Whatman filter paper (1×2 cm) as the essential oil release source. Repellency effect of four concentrations 0.1, 0.2, 0.41 and 0.83 μl/cm2of the essential oil was evaluated by comparing the number of adults in both treated and non-treated portions. Based on probit analysis of data, the LC50 valued were 90.15 and 235/75 μl/l air respectively after 24 h post-treatments. The adult of lesser grain borer were more sensitive than cigarette beetle to this oil. Average repellency, were 49.99 and 58.33% respectively, at three hours post-treatments which are grades of III consisting of the sextet classification.

Medicinal and aromatic plants (MAPs) have become a part of traditional system of medicines and have gained importance, more so in today’s world. According to the estimate of World Health Organization (WHO), about 80% of the population of developing world are making use of traditional medicines. The medicinal plants have been used for widespread purposes since ancient times in countries particularly India, China, Greece, Persia etc. In India, according to a report of AICEP, Anthropological Survey of India, 1994, it is estimated that over 7,500 species of medicinal plants are used for therapeutic uses. The major floral species which are widely used as medicinal and aromatic plants (MAPs) include Ephedra gerardiana Wall., Rauvolfia serpentina, Swertia chirata, Aconitum heterophyllum Wall. ex Royle, Rhododendron anthopogon D. Dun., Peganum harmala L. etc. The widespread use of these medicinal plants for both internal consumption and export purposes have led to their large-scale exploitation, resulting in loss of biological diversity (both at genetic and species level). Most of the medicinal plants like Rauvolfia serpentina, Gentiana kurro, Alpinia galanga, Saussurea lappa have become endangered and threatened. Overexploitation along with lack of initiatives from government bodies, absence of proper management systems and loss of traditional knowledge are some of the factors responsible for rapid biodiversity loss. Indigenous people and biodiversity complement each other and the former has played an important role in conservation of biodiversity since time immemorial. The rural communities over the period of time have gathered a pool of indigenous knowledge/know-how for cultivation of the medicinal plants and their propagation. In the meantime, the importance of local knowledge systems in conservation and preservation of the germplasm of medicinal plants have also attained global significance. In India, various programmes on medicinal plants and their conservation based on traditional knowledge are being carried out by the local people, Non Government Organizations (NGOs), Community Based Organizations (CBOs) at various grass root levels such as the districts and villages. Though an unorganized sector, the local people are playing their role in the propagation as well as conservation of the medicinal plants through the application of the concepts of herbal gardens and local “mandis” (markets). There is a need to strengthen these linkages and build upon the indigenous knowledge base of the local people through proper documentation and building of a strong database. This paper deliberates upon the importance (therapeutic, ecological and economic) of medicinal plants and threats to their biodiversity. The communication also describes the details of some of the local efforts, which are being carried out at local levels in India for conservation of medicinal plants through the use of indigenous knowledge of traditional medicines. The paper also highlights the need to integrate indigenous knowledge into national policies and strengthen the participation of the indigenous communities in order to harness maximum potential of medicinal plant biodiversity along with sustainable management of these resources.

Mitochondrial response of the lesser grain borer Rhyzopertha dominica (F.) to modified atmospheres