Stored-product Pests Research Articles

Immediate and Delayed Mortality of Four Stored-Product Pests on Concrete Surfaces Treated with Chlorantraniliprole.

Simple SummaryWe examined the mortality caused by the anthranilic diamide, chlorantraniliprole, at four different doses applied on concrete (0.01, 0.05, 0.1, and 0.5 mg a.i./cm2) in Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) adults and larvae, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) adults, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) adults, and Acarus siro L. (Sarcoptiformes: Acaridae) adults and nymphs. Mortality data were recorded after 1, 2, 3, 4, and 5 days to determine the immediate mortality. Furthermore, after the 5-day mortality counts, still living individuals were conveyed for 7 days to untreated concrete surfaces to estimate the delayed mortality. The highest immediate mortality was recorded for the larvae of T. castaneum, reaching 96.7%, followed by the adults of A. siro (92.2%) after 5 days of exposure to 0.5 mg a.i./cm2. Complete (100.0%) delayed mortality was noticed for T. castaneum (adults and larvae), S. oryzae, and A. siro (both as adults) at 0.5 mg a.i./cm2. Rhyzopertha dominica adults and A. siro nymphs exhibited 98.6% and 96.3% delayed mortality at the same dose, respectively. Overall, our results demonstrate that chlorantraniliprole is effective against all the species tested, causing varying immediate and delayed mortality rates at the developmental stages tested.Chlorantraniliprole is an effective pesticide against a plethora of pests, but its efficacy against stored-product pests is very poorly explored. In this study we treated concrete surfaces with four different doses of chlorantraniliprole (0.01, 0.05, 0.1, and 0.5 mg a.i./cm2) against the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) adults and larvae, the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) adults, the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) adults, and the flour mite, Acarus siro L. (Sarcoptiformes: Acaridae) adults and nymphs, to examine the immediate mortalities after 1, 2, 3, 4, and 5 days of exposure. Additionally, the delayed mortality of the individuals that survived the 5-day exposure was also evaluated after a further 7 days on untreated concrete surfaces. We documented high mortality rates for all tested species and their developmental stages. After 5 days of exposure to 0.5 mg a.i./cm2, T. castaneum larvae and A. siro adults exhibited the highest immediate mortality levels, reaching 96.7% and 92.2%, respectively. Delayed mortality was also very high for all tested species and their developmental stages. Nymphs of A. siro displayed a 96.3% delayed mortality followed by the adults of R. dominica (98.6%) after exposure to 0.5 mg a.i./cm2. All other tested species and their developmental stages reached complete (100.0%) delayed mortality, where even 0.01 mg a.i./cm2 caused ≥86.6% delayed mortality in all species and their developmental stages. Taking into consideration the effectiveness of chlorantraniliprole on this wide range of noxious arthropods, coupled with its low toxicity towards beneficial arthropods and mammals, this pesticide could provide an effective management tool for stored-product pests in storage facilities.

A new monomeric α-amylase inhibitor from the tetraploid emmer wheat is mostly active against stored product pests

A new monomeric α-amylase inhibitor from the tetraploid emmer wheat is mostly active against stored product pests

Repellent Activity of Cymbopogon citratus Essential Oil Against Four Major Stored Product Pests: Plodia interpunctella, Sitophilus oryzae, Acanthoscelides obtectus and Tribolium castaneum

Summary The purpose of this study is to assess the repellent activity of lemongrass (Cymbopogon citratus) essential oil (EO), grown in Serbia under greenhouse conditions, against four prevalent stored product pests: Plodia interpunctella (larvae), Sitophilus oryzae, Acanthoscelides obtectus and Tribolium castaneum (adults). The lemongrass EO repellency was tested using filter paper in Petri dishes and a Y-tube olfactometer. According to the repellency index (RI), the lemongrass EO repellency was divided into 5 classes. Prior to biotesting, the chemical characterization of lemongrass EO was performed and the following main compounds were detected: myrcene (31.0%), geranial (30.0%), and neral (23.6%). The C. citratus EO considered was found to exhibit the Class III repellent activity against P. interpunctella larvae only at the highest concentration (namely 0.5%). This is the very first report on the C. citratus EO repellent activity against this pest. The lemongrass EO examined showed strong repellency (Class IV) against S. oryzae (0.2% and 0.5% of EO), A. obtectus (0.1% and 0.2%), and T. castaneum (0.05-0.1%). Moreover, higher lemongrass EO concentrations (0.5%) were found to exhibit extreme repellency (Class V) against A. obtectus and T. castaneum. The results obtained were confirmed in the bioassays performed, indicating the great potential of lemongrass EO as a bio-repellent when applied in higher concentrations to all the insects considered, regardless of the exposure period.

Origanum vulgare Essential Oil against Tenebrio molitor (Coleoptera: Tenebrionidae): Composition, Insecticidal Activity, and Behavioral Response.

Tenebrio molitor is one of the main stored product pests. This study characterized oregano essential oil (OEO) by gas chromatography (GC/FID and GC/MS) and assessed its insecticidal properties against T. molitor. Mortality, survival, respiration, and behavioral response in larva, pupa, and adult of this insect were determined. The major components of OEO were carvacrol (25.6%), p-cymene (12.3%), linalool (8.71%), thymol (7.22%), γ-terpinene (7.21%), caryophyllene oxide (4.67%), α-pinene (2.71%), and eucalyptol (2.69%). OEO caused high contact toxicity in larvae (LD50 = 3.03 µg insect–1), pupae (LD50 = 5.01 µg insect–1), and adults (LD50 = 5.12 µg insect−1) of T. molitor. Survival rates were 100% in larvae, pupae, and adults of T. molitor not treated with OEO, declining to 65–54%, 38–44%, 30–23%, and 6–2% in insects treated with LD25, LD50, LD75, and LD90, respectively. Low respiration rates of T. molitor at different developmental stages was observed after OEO exposure. Additionally, OEO exposure affects behavioral avoidance response and causes repellency in larvae and adults. These findings show that OEO exerts insecticidal and repellent effects against T. molitor, suggesting a potent alternative to synthetic insecticides for controlling the beetle.

Spatial and Temporal Variation in Stored-Product Insect Pest Distributions and Implications for Pest Management in Processing and Storage Facilities

Abstract Insect infestations can result in a damaged or destroyed product, costing producers and retailers millions of dollars annually. Postharvest insects move through space searching for mates, food, and shelter. Movement of product, sanitation activities, and insecticide applications also drive their spatial distribution patterns. Determining spatial distributions and population density of insects provides important information to develop targeted and cost-effective management programs. Monitoring data collected using traps to capture insect pests have provided information under a range of conditions: in bins of grain, grain elevator silos and their immediate environment, milling and processing facilities, commercial warehouses, and retail stores. In evaluating available data, we identified key influences that may be leveraged to increase the impacts of future monitoring schemes. Species-specific locations of infestation were common among stored product insect pests and seasonal variation was highly influential in population growth patterns. Competition among different species also drives spatial and temporal distributions and overlap among species is rare. Vertical distribution of insects was common in bins, elevators, and silos. More insects were often found in the receiving and storage areas of mills and processing facilities and insects often migrated into facilities from surrounding natural reservoirs. Previously stored grain and spillage can also harbor insect populations, which also reinforces the need for sanitation in and around stored grain products. Continued monitoring research will provide information to develop predictive tools which will use behavioral patterns to further our understanding of these insect pests within these unique facilities and circumstances.

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.

Chemical Composition, Insecticidal and Mosquito Larvicidal Activities of Allspice (Pimenta dioica) Essential Oil.

Essential oils are biologically and environmentally safe pesticidal compounds yielded from aromatic plants. Spices are important sources of essential oils, and they are widely used in the medicine, food, and various other industries. Among the different spices, Allspice (Pimenta dioica) is underexplored in terms of its biological efficacy and a limited number of studies are available on the chemical composition of Allspice essential oil (AEO); thus, the present study evaluated the larvicidal property, the repellency, and the fumigant toxicity against common pests of stored products of AEO. AEO was found to inhibit the survival of larvae of such vectors as Aedis, Culex, and Armigeres species. Further, AEO was found to exert repellant effects against the pests of such stored products as Sitophilus, Callosobruchus, and Tribolium. Similarly, the fumigant toxicity was found to be high for AEO against these species. The contact toxicity of AEO was high against Sitophilus and Callosobruchus. Apart from that, the essential oil was found to be safe against a non-target organism (guppy fishes) and was found to be non-genotoxic in an Allium cepa model. Overall, the results of the present study indicate that the essential oil from Allspice could be used as an environmentally safe larvicidal and biopesticidal compound.

Study on Gas Chromatographic Fingerprint of Essential Oil from Stellera chamaejasme Flowers and Its Repellent Activities against Three Stored Product Insects.

The objective of this study was to establish the chromatographic fingerprints of the essential oil (EO) from Stellera chamaejasme flowers collected from various natural sites by gas chromatography (GC) combined with chemometric methods. The EO was obtained by hydrodistillation, and its chemical composition was analyzed by gas chromatography−mass spectrometry (GC−MS). Most components were identified as ketones and the relatively high-content components were fitone (38.973%), n-hentriacontane (5.807%), myristic acid (4.944%) and phytol (3.988%). In addition, the repellent activities of the EO from S. chamaejasme flowers and its four main chemical compounds were evaluated against three stored product pests (Tribolium castaneum, Lasioderma serricorne, Liposcelis bostrychophila) for the first time. In this work, the EO and the four chemical compounds showed a repellent effect against three storage pests after 2 and 4 h exposure. The experimental method and repellent activity of S. chamaejasme flower EO could provide a basis for the development of botanical pesticide and the utilization of the rich plant resources of S. chamaejasme in the future.

Compatibility of Native and Imported Entomopathogenic Nematodes with Different Applications of Insecticides for Controlling the Cigarette Beetle, Lasioderma serricorne Fabricius (Coleoptera: Anobiidae)

The cigarette beetle, Lasioderma serricorne Fabricius (Coleoptera: Anobiidae), is an important pest of stored products in the world which caused major economic losses that required many strategies for controlling insect pest. This study investigated native entomopathogenic nematodes (EPNs) and imported EPN species alone at different IJs concentrations or in combination with three application rates (recommended, quarter and half recommended concentrations) of lambda-cyhalothrin, emamectin benzoate and indoxacarb against the third and the fourth larval instars of its pest under laboratory conditions. The results showed that The native H.bacteriophora (Ar-4 strain) and the imported H.bacteriophora (HP88 strain) were more effective against the fourth larval instar of L. serricorne than the third instar followed by S.carpocapsae (All strain) while H.bacteriophora (Ba-1 strain) and S. feltiae strain were the least efficacy. According to LT50 of tested EPNs, 100 IJs/larva was the best concentration used against the larvae instars of L. serricorne. As well as, the fourth instar was more susceptible to the tested applications of pesticides than the third larval instar. Moreover, The application with a quarter recommended dose of indoxacarb was the most toxicity application against the fourth instar when compared to lambda-cyhalothrin andemamectin benzoate. On the other hand, the effects of the interactions between native and imported EPNs varied greatly as stated by application rates of tested insecticides and juveniles' concentration of EPNs. It is concluded that the best interaction effect was obtained with quarter recommended application (0.25 RC) of lambda-cyhalothrin when combined with EPNs at 100 IJs/larva, which displayed synergistic effect to overcome incompatibility particularly with heterorhabditid species, the effect that could be beneficial when making progress the integrated program for stored-product pests.

Fumigant toxicity of some essential oils and eucalyptol on different life stages of Tribolium confusum (Coleoptera: Tenebrionidae)

ABSTRACT Essential oils of aromatic plants have a high potential for the development of alternative insect pest management strategies. Especially for the control of stored product pests, alternative methods to replace synthetic insecticides are urgently needed. We evaluate the fumigant toxicity of Myrtus communis, Eucalyptus globulus, Syzygium aromaticum, Thymus saturejoides essential oils, and the main natural compound of two of them, eucalyptol, on different life stages of the confused flour beetle (Tribolium confusum) under laboratory conditions. Whereas eucalyptol and the essential oils of M. communis and E. globulus have rather strong toxic effects on all developmental stages, apart from the eggs of T. confusum, the essential oil of S. aromaticum caused the highest egg toxicity. Our results indicate that eucalyptol or essential oils containing large amounts of this compound might be efficient as potential alternative control agents for T. confusum, but tests under more natural conditions need to be performed.

Efficacy of Saponins Extracted from Yucca schidigera Roezl against the Major Storage Pest, Tribolium castaneum (Herbst)

In the search for biopesticides, increasing attempts have been made to obtain bioactive compounds from plants. In this regard, the insecticidal activity and deterrence of saponins obtained from Yucca schidigera Roezl(Agavaceae) were tested on the major stored product pest, Tribolium castaneum (Herbst) (Coleoptera :Tenebrionidae) via feeding bioassay. Adult beetles were reared on wheat grain dusted with saponins at 1 to 5% concentrations (wt/wt) for 1 to 14 days under optimal development conditions. Our results indicated that the increase of concentration and exposure periods enhanced mortality. The mortality reached 81 and 94% at 1 and 5% saponins, respectively, after 14d of exposure. In the choice test with treated and untreated grains, yucca saponins were able to deter adults immediately after the first 2hr up to the end of the exposure interval after 24hr at 1 and 5% concentrations. The respective deterrent indices were (0.43 - 0.55) and (0.52- 0.78) at the tested intervals. In addition, cellular immune reactions were recorded in adult females as shown by changes in the differential hemocyte counts (DHCs) following the challenge with yucca saponins for 72hr. Finally, the application of yucca saponins at 1 and 5% extensively reduced the grain damage potential by 70 and 80%, respectively, after 7d of application while the reduction increased after 14 d to 73% and 85%, respectively. Due to the combined contact, toxicant and deterrent properties of yucca saponins, they could be considered as a potentially applicable grain protectant against T. castaneum.

Tanacetum vulgare essential oil as grain protectant against adults and larvae of four major stored-product insect pests

In this study the adulticidal and larvicidal effect of tansy, Tanacetum vulgare L. (Asteraceae) essential oil (EO) was estimated against four noxious stored-product insect species; Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae), Tenebrio molitor L. (Coleoptera: Tenebrionidae) and Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae). The EO chemical composition, as determined by GC-MS, was dominated by oxygenated monoterpenes (68.2%), with borneol (13.6%), umbellulone (11.7%), artemisia ketone (9.3%), cis-chrysanthenol (6.9%), camphor (5.9%), and terpinen-4-ol (5.5%) as the major constituents. This profile was quite different from those previously reported from other T. vulgare European accessions which are characterized by high content of the toxic trans-thujone. The T. vulgare EO was applied as wheat protectant at two concentrations of 500 and 1000 ppm. Adult and larval mortality levels were estimated after 4, 8 and 16 h and 1, 2, 3, 4, 5, 6 and 7 days. Tanacetum vulgare EO caused complete mortality (100%) to T. castaneum larvae, but only 25.6% to adults at 1000 ppm 6 and 7 days post-exposure, respectively. The mortality rates of T. confusum larvae and adults were 56.7 and 8.9% on wheat treated with 1000 ppm EO, respectively after 7 days of exposure. The ΕΟ caused moderate mortality to T. molitor adults (52.2%), and low mortality to larvae (8.9%), at 1000 ppm at the end of the experimental period. High mortality of O. surinamensis larvae (93.3%) was noticed at 1000 ppm after 7 days of exposure, while only 13.3% of the exposed adults were dead at the same concentration and exposure interval. Overall, the T. vulgare EO could be considered as a potential wheat protectant for the management of important stored-product insects. However, its efficacy depends on the species and the life stage of the target pest.

Diatomaceous earth low-lethal dose effects on the fitness of entomopathogenic fungus, Beauveria bassiana, against two coleopteran stored product pests

Efficacy of different doses of the Beauveria bassiana-IRAN441C alone (66,125, 250, 500, 1000 mg conidia. Kg−1 grains) and combined with a low-lethal dose (LD25) of diatomaceous earth (DE) SilicoSec® as lethal agents were assessed against the adults of Callosobruchus maculatus (F.) (Chrysomelidae) on mung, and cowpeas, and Oryzaephilus surinamensis (L.) (Silvanidae) on wheat and barley seeds. In both species, mortality reached 60–73% in B. bassiana alone and 83–100% in fungus combined with the DE at the highest dose. A synergistic effect between B. bassiana conidia and the DE was confirmed. The DE low-lethal dose alters fungal mycosis and sporogenesis (conidia mL−1) rates in the infected cadavers. The adult populations of both species were suppressed desirably despite a decrease in the number of cadaver-derived mycosis and their spore production at the highest combination doses (1000 mg kg−1+ LD25 of DE). Seed type had no significant effect on mycosis and sporogenesis on both insects in several combination doses. The cadaver-derived aerial conidia germination rate was increased in the presence of DE low-lethal dose, but it declined by increasing the fungal dose. Type of commodity failed to affect the germination rate of O. surinamensis-derived conidia; however, the mung bean intensified this case for another insect. In both beetles, offspring's emergence was suppressed dose-dependently seven weeks after removing exposed parents to the lethal agents as well it was more in doses mixed with DE. The most significant reduction in progeny production of treated C. maculatus occurred on cowpeas and that of treated O. surinamensis on wheat seeds. Our findings demonstrate that DE's low-lethal dose enhances the virulence of B. bassiana in the various mixtures synergistically, and co-applications of the two substances were feasible. As well, the lethal agents' adverse effects were found to carry over onto both species' offspring during two-month storage time.

English

The saw-toothed grain beetle, Oryzaephilus surinamensis (Linnaeus) is a secondary pest of rice grains and other stored products. Lack of information on the population abundance, spatial, and temporal distribution of O. surinamensis rendered the management control strategy of this pest species less effective. The objective of this study was to investigate the abundance, spatial and temporal pattern of O. surinamensis populations from nine rice warehouses in three zones of Peninsular Malaysia (i.e., the northern, central and southern zones) for three continuous months. The results showed that the abundance of O. surinamensis populations varied significantly (p<0.05, p= 0.00) between zones, with the highest abundance for this species (69%) recorded from the Klang District, in the central zone, followed by Pasir Gudang (27%) in the southern zone, and Seberang Prai (4%) in the northern zone. The patterns of population abundance also showed significant differences between months, p<0.05 (p-value= 0.00-0.011) between all the warehouses. The factors that could be associated with the highest abundance of the pest were attributed to poor sanitation at the warehouses and inconsistency in the fumigation regime. For the spatial distribution analysis, SADIEShell_122 and Surfer8 software were applied. The distribution patterns of O. surinamensis populations varied significantly in all the warehouses, being significantly aggregated at p<0.05 (p=0.0385-0.0513) and Ia>1.0 (1.212-1.579), whilst being non-significantly and randomly distributed at p>0.05 (p=0.1154-0.91032) and Ia>1.0 (0.852- 0.929). The significance of the aggregation might be due to the rapidly changing volume of the rice stock caused by the active and rapid turnover of the storage inventory. The results obtained were very valuable and informative in managing O. surinamensis infestation of stored rice by incorporating the spatial and temporal information of the pest populations in the management strategy for improving the rice and other stored products.

Essential Oil-Based Nano-Biopesticides: Formulation and Bioactivity against the Confused Flour Beetle Tribolium confusum

Post-harvest pest control can rely on few approved pesticides and tools; hence, there is a rising interest in new sustainable, eco-friendly approaches. In this study, eight commercial essential oils (EOs) (anise Pimpinella anisum, artemisia Artemisia vulgaris, fennel Foenicum vulgare, garlic Allium sativum, lavender Lavandula angustifolia, mint Mentha piperita, rosemary Rosmarinus officinalis, and sage Salvia officinalis) were selected for their bioactivity and commercial availability, and then formulated in nano-emulsions. Repellency and acute toxicity of the developed nano-formulations were tested against a key stored product pest, Tribolium confusum (Coleoptera: Tenebrionidae). All the developed nano-emulsions presented optimal physical characteristics (droplet dimension = 95.01–144.30 nm; PDI = 0.146–0.248). All the formulations were repellent over time tested against adult beetles, in area preference bioassays. The best repellent was the anise EO-based formulation (RC50 = 0.033 mg). Mortality values from cold aerosol trials showed that the majority of tested EOs caused immediate acute toxicity, and garlic EO nano-emulsion caused the highest mortality of T. confusum adults (LC50 = 0.486 mg/L of air). EO-based nano-insecticides, used as cold aerosol and gel, are promising control methods against stored product pests, which can be integrated and combined with other sustainable biorational approaches.

On the efficiency of entomopathogenic nematodes (Rhabditida: Heterorhabditidae and Steinernematidae) on rust red flour beetle, Tribolium castaneum (Herbst.) (Coleoptera: Tenebrionidae)

BackgroundThe rust red flour beetle, Tribolium castaneum (Herbst.) (Coleoptera: Tenebrionidae) is a serious pest of stored grains and grain products across the world. This beetle is hold a significant place in Turkey by causing damages on stored products. T. castaneum primarily attacks milled grain and its derivates. Entomopathogenic nematodes (EPNs) are regarded as extremely an important biological control agent. EPNs kills their hosts within 48 h by the bacteria they carry.ResultsEfficacies of 4 isolates of EPNs Steinernema carpocapsae (Tokat Bakisli 05), S. feltiae (Tokat-Emir), Heterorhabditis bacteriophora (TOK-20) and H. bacteriophora (11-KG) against T. castaneum was investigated under laboratory conditions. The experiments were carried out thrice with 10 replicates at 2 different temperatures (15 and 25 ºC). EPNs isolates were tested at 3 different concentrations (250, 500 and 1000 IJs/ml) with a pure water as control. The overall mortality caused by H. bacteriophora (Kg11) was significantly higher than the other EPN species. At 25 ºC, H. bacteriophora (Kg11) at the highest concentration (1000 IJs/ml) caused 87.6% mortality after 120 h., followed by S. carpocapsae and S. feltiae with 79.22 and 75.3% mortality rates, respectively. The mortality percentages exhibited by all nematodes’ species at both temperatures were lowest at the concentration of (250 IJs/ml). At 15 °C, H. bacteriophora (Kg11) caused (55.2%) mortality rate at the highest concentration (1000 IJs / ml) after 120 h.ConclusionThe study suggested that these nematodes were efficient and could be recommended to control T. castaneum in its biological control programs.

Influence of Temperature and Photoperiod on the Fecundity of Habrobracon hebetor Say (Hymenoptera: Braconidae) and on the Paralysis of Host Larvae, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae).

Simple SummaryThis study illustrated the role of optimum temperatures of 25 and 30° in maximizing oviposition by the female H. hebetor. The optimum temperatures for paralysis of P. interpunctella larvae by H. hebetor were shown to be 28 and 30 °C at short exposure periods. However, at long exposure periods, the paralysis rates did not differ significantly. Photoperiod had no impact on oviposition or paralysis of P. interpunctella by the wasp.Studies were carried out in the laboratory to understand the optimum environmental conditions at which the ectoparasitoid, Habrobracon hebetor Say (Hymenoptera: Braconidae), can paralyze and lay eggs when reared on the larvae of the stored product pest, Plodia interpunctella Hübner (Lepidoptera: Pyralidae). At the four temperatures investigated (20, 25, 30, and 35 °C), optimum temperatures for oviposition were found to be 25 and 30 °C, while 35 °C was the least favorable temperature. No significant differences were found between the percentages of diapausing and non-diapausing larvae paralyzed by the wasp at the temperatures of 20, 25, 30, 35 °C within 5 days. However, in another experiment that investigated the effect of photoperiods at different temperatures that included 15, 19 and 28 °C, the number of paralyzed larvae was highly reduced at low temperatures (15 °C) but photoperiods had no significant impact on the number of host larvae paralyzed. In addition, observations at short time intervals also showed that lower temperatures slowed down host larvae paralysis. The results suggest that H. hebetor can paralyze host larvae of P. interpunctella more efficiently and deposit more eggs at temperatures within the range of 20–30 °C.

Isolation, screening and identification of key components having intense insect repellent activity against Plodia interpunctella from four different medicinal plant materials.

Global warming and the indiscriminate use of pesticides have increased the propagation of the stored-product insect pests, leading to enormous losses in the agriculture and food industries. The most used insect repellents are synthetic derivatives; however, these have an adverse effect on human health as well as on the environment. Therefore, we attempted to find materials with insect repellent activity in natural products. The present study aimed to identify the single chemical component with intense insect repellent activity in extracts from four different Oriental medicinal plant materials: (i) Anethum graveolens L. (dill) seeds; (ii) Artemisia capillaris Thunb. (capillary wormwood) leaves; (iii) smoked Prunus mume Siebold & Zucc. (mume) fruits; and (iv) Rhus javanica L. (galls). As a result of the bioassay-guided fractionation of each extract against the Plodia interpunctella, stored-product insect, the n-hexane fraction of dill seeds extract was confirmed as the optimal fraction between all of the fractions. In total, 32 chemical components were identified from the n-hexane fraction of dill seeds by gas chromatography-mass spectrometry analysis, and the two main components were dillapiole (47.51%) and carvone (26.76%). Of the two components, dillapiole was confirmed as the key component playing an essential role in insect repellent activity. Our study suggests that dillapiole has the potential to be used as a natural insect repellent for the control of P. interpunctella infestation in agricultural and food products during distribution and storage. © 2021 Society of Chemical Industry.

Social communication activates the circadian gene Tctimeless in Tribolium castaneum

Chemical communication via pheromones is an integral component in insect behavior, particularly for mate searching and reproduction. Aggregation pheromones, that attract conspecifics of both sexes, are particularly common and have been identified for hundreds of species. These pheromones are among the most ecologically selective pest suppression agents. In this study, we identified an activating effect of the aggregation pheromone of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenibroidae) on a highly conserved circadian clock gene (Tctimeless). Tribolium castaneum is one of the most damaging cosmopolitan pest of flour and other stored food products. Its male produced aggregation pheromone, 4,8-dimethyldecanal (DMD), attracts both conspecific males and females and is used for pest management via monitoring and mating disruption. The Tctimeless gene is an essential component for daily expression patterns of the circadian clock and plays vital roles in eclosion, egg production, and embryonic development. In this study, we demonstrate that constant exposure to the species-specific aggregation pheromone led to Tctimeless up-regulation and a different pattern of rhythmic locomotive behavior. We propose that changing the well-adapted "alarm clock", using DMD is liable to reduce fitness and can be highly useful for pest management.

Behavioral and Antennal Responses of Tribolium confusum to Varronia globosa Essential Oil and Its Main Constituents: Perspective for Their Use as Repellent.

Essential oils of aromatic plants represent an alternative to classical pest control with synthetic chemicals. They are especially promising for the alternative control of stored product pest insects. Here, we tested behavioral and electrophysiological responses of the stored product pest Tribolium confusum, to the essential oil of a Brazilian indigenous plant, Varronia globosa, collected in the Caatinga ecosystem. We analyzed the essential oil by GC-MS, tested the effects of the entire oil and its major components on the behavior of individual beetles in a four-way olfactometer, and investigated responses to these stimuli in electroantennogram recordings (EAG). We could identify 25 constituents in the essential oil of V. globosa, with anethole, caryophyllene and spathulenole as main components. The oil and its main component anethole had repellent effects already at low doses, whereas caryophyllene had only a repellent effect at a high dose. In addition, the essential oil abolished the attractive effect of the T. confusum aggregation pheromone. EAG recordings revealed dose-dependent responses to the individual components and increasing responses to the blend and even more to the entire oil. Our study reveals the potential of anethole and the essential oil of V. globosa in the management of stored product pests.