Stored-product Pests Research Articles

Bags impregnated with garlic (Allium sativum L.) and parsley (Petroselinum crispum (Mill.) Fuss) essential oils as a new biopesticide tool for Trogoderma granarium Everts, 1898 pest control

Stored product pests can cause significant damages and great economic problems in stored commodities and grain cereal. Using synthetic pesticides in the storage pest control has adverse effects on human health. In our study, the toxicity of garlic (Allium sativum) and parsley (Petroselinum crispum) essential oils (EOs) impregnating with three types of bags were assessed against Trogoderma granarium Everts, 1898 adults after different exposure intervals. GC-MS analysis of the investigated EOs revealed that the major components of parsley and garlic were 1, 3, 8-p-menthatriene (23.34 %) and di-allyl disulfide (27.9 %), with (1.40 %) alpha-terpinene and (1 %) of di-alyl tetra-sulfide as minor components respectively. Additionally, comparison the toxicity among the treated bags was assessed based on the LC50 values and a persistence efficiency of the tested EOs was carried out by the LC90 values for each bag type. In all bag types, garlic and parsley had mortality by 100 % for clothes, and 80 % for both plastic and paper bags after 7 days of exposure, respectively. After two and five days of garlic treatment, plastic bags were the most effective, but after seven days of exposure paper bags was more effective than the other two types. Finally, cloth bags treated with EOs were the most effective packaging for insect control, indicating that this approach could be considered as an additional tool to the concept of stored product management.

The Low-Copy-Number Satellite DNAs of the Model Beetle Tribolium castaneum.

The red flour beetle Tribolium castaneum is an important pest of stored agricultural products and the first beetle whose genome was sequenced. So far, one high-copy-number and ten moderate-copy-number satellite DNAs (satDNAs) have been described in the assembled part of its genome. In this work, we aimed to catalog the entire collection of T. castaneum satDNAs. We resequenced the genome using Illumina technology and predicted potential satDNAs via graph-based sequence clustering. In this way, we discovered 46 novel satDNAs that occupied a total of 2.1% of the genome and were, therefore, considered low-copy-number satellites. Their repeat units, preferentially 140-180 bp and 300-340 bp long, showed a high A + T composition ranging from 59.2 to 80.1%. In the current assembly, we annotated the majority of the low-copy-number satDNAs on one or a few chromosomes, discovering mainly transposable elements in their vicinity. The current assembly also revealed that many of the in silico predicted satDNAs were organized into short arrays not much longer than five consecutive repeats, and some of them also had numerous repeat units scattered throughout the genome. Although 20% of the unassembled genome sequence masked the genuine state, the predominance of scattered repeats for some low-copy satDNAs raises the question of whether these are essentially interspersed repeats that occur in tandem only sporadically, with the potential to be satDNA "seeds".

Population Growth of Three Stored Product Beetle Species on Alphitobius diaperinus (Coleoptera: Tenebrionidae) Meals.

The lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), is an important pest of stored products and at the same time a species with great potential as food and feed that has recently attracted increasing interest as nutrient source. Future predictions show a massive increase of insect meals' production in the near future, therefore, as expected in the case of other durable stored products, insect meals may get infested by insects during their storage. In this context and as a continuance of our previous study on the susceptibility of meal of the yellow mealworm, Tenebrio molitor L. (Coleoptera: Tenebrionidae), to storage insect infestations, the objective of this study was to test the susceptibility of A. diaperinus meals to infestations of three stored products pests, namely A. diaperinus itself, T. molitor, and the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). The population growth of the three species was evaluated on pure A. diaperinus meal, as well as on A. diaperinus meal-based substrates with different percentages of wheat bran (0, 25, 50, 90, and 100% bran). Our results showed that all three insect species tested were able to grow and develop on the A. diaperinus meal-based substrates evaluated, giving in a short time high population densities. This study confirms again our initial theory for insect infestations during storage of insect-based products.

Attraction, mobility, and preference by Lasioderma serricorne (Coleoptera: Ptinidae) to microbially-mediated volatile emissions by two species of fungi in stored grain

Insects and microbes are known to interact in a variety of ways at food facilities, compounding damage. However, little research has explicated how specific common fungal species affect the behavior of the cosmopolitan secondary stored product pest, Lasioderma serricorne. Enhanced knowledge about attraction to microbially-produced volatile organic compounds (MVOCs) may be used to manipulate insect behavior. Aspergillus flavus and Fusarium verticillioides are two common, widespread pre- and postharvest fungi on small cereals that produce aflatoxins and fumonisins, respectively, while directly competing with each other for nutrients. Our goals were to (1) characterize the volatile emissions from grain inoculated by A. flavus or F. verticillioides derived from the cuticle of L. serricorne compared to uninoculated and sanitized grain, and (2) understand how MVOCs from each fungal species affects mobility, attraction, and preference by L. serricorne. Headspace collection revealed that the F. verticillioides- and A. flavus-inoculated grain produced significantly different volatiles compared to sanitized grain or the positive control. Changes in MVOC emissions affected close-range foraging during an Ethovision movement assay, with a greater frequency of entering and spending time in a small zone with kernels inoculated with A. flavus compared to other treatments. In the release-recapture assay, MVOCs were found to be attractive to L. serricorne at longer distances in commercial pitfall traps. There was no preference shown among semiochemical stimuli in a still-air, four-way olfactometer. Overall, our study suggests that MVOCs are important for close- and long-range orientation of L. serricorne during foraging, and that MVOCs may have the potential for inclusion in behaviorally-based tactics for this species.

Mortality of Lasioderma serricorne1 in a Continuously Heated Environment

Heat treatment is a potential alternative to chemicals for controlling stored-product insect pests. During heat treatment, attaining uniform temperature across a facility is not possible because of differential heating rates. Effects of different heating rates of 0 (check), 0.5, 5, and 10°C per hour on life stages of Lasioderma serricorne were studied in a laboratory. Different heating rates killed significantly different numbers of L. serricorne life stages, with more killed with increasing exposure at 50°C. Compared to the check, significantly more L. serricorne larvae exposed to continuous heating of 28 to 50°C at 5 and 10°C per hour were killed after exposure at 50°C for 15, 30, 45, and 60 minutes. However, L. serricorne larvae and eggs exposed to continuous heating of 28 to 50°C at 0.5more at different heating ra per hour significantly increased after exposure at 50°C for 15, 30, 45, and 60 minutes. Maintaining temperature at ≥50°C for >90 minutes in a facility killed almost all life stages of L. serricorne. Pupae were least susceptible to heat.

Molecular identification, life history description and biotic potential of Plodia interpunctella (Lepidoptera: Pyralidae) feeding on amaranth (Amaranthus sp.) products in the state of Morelos, Mexico

The flour moth Plodia interpunctella (Hübner) is considered one of the most significant pests of stored and processed products, its adaptability allowing it to settle on new food hosts. In 2020 in Mexico, the presence of larvae and adults of P. interpunctella in amaranth products stored and processed for export was reported for the first time, causing considerable damage. The objective of this study was molecular identification of the insects found in amaranth products and description of the biotic potential of these pests grown in different amaranth products under laboratory conditions. For this purpose, molecular identification of P. interpunctella was carried out using the mitochondrial gene cytochrome oxidase subunit one (COI). Three cohorts with 200 eggs each, fed with three types of amaranth products (amaranth with chocolate, amaranth with honey and natural amaranth) were implemented, with hatching rates of 75% for amaranth with chocolate, 66.5% for amaranth with honey and 71.5% for natural amaranth. The larval period consisted of five instars and one prepupa, with the shortest life expectancy in the first instar. The life cycle of the insect varied from 51 days in chocolate amaranth, 54 days in honey amaranth and 64 days in natural amaranth. This lepidopteran presented a high fecundity when fed with chocolate amaranth with a mean clutch size of 257.0435.98 eggs per female during her whole life (h/h/v), followed by honey amaranth with 177.3836.23 (h/h/v) and finally by natural amaranth with 157.643.33 (h/h/v), with a mean fertility of 71%. In the population parameters, a generation time (T) of 25.08, 26.69 and 31.41 days and a net reproduction rate (R0) of 405.10, 253.82 and 215.49 were obtained for amaranth with chocolate, with honey and natural respectively, ensuring a high replacement over a short period of time; these values make this species an important pest of stored amaranth products.

Cloning and expression of the mitochondrial cytochrome c oxidase subunit II gene in Sitophilus zeamais and interaction mechanism with allyl isothiocyanate

In the United States, allyl isothiocyanate (AITC) has been registered as an insecticide, bactericide, and nematicide. And it has been confirmed that AITC has significant insecticidal activities against four stored product pests including Sitophilus zeamais Mostchulky (Coleoptera: Curculionidae). This study aimed to verify the mechanism of action of AITC on cytochrome c oxidase core subunits II in S. zeamais. Enzyme - catalyzed reactions and Fourier transform infrared spectrometer (FTIR) analysis revealed that the expressed COX II proteins could competitively bind and inhibit the activity of COX II. Furthermore, molecular docking results showed that a sulfur atom of AITC could form a 2.9 Å hydrogen bond with Ile-30, having a binding energy of −2.46 kcal/mol.

Down to the Wire

“Junior, eat your obsolete computer! Don’t you know that an AppleTM a day keeps the doctor away?” Late last year, I stumbled across a paper by Zhu et al. (2022) and was immediately intrigued by the title—“Feeding Preference of Insect Larvae to Waste Electrical and Electronic Equipment Plastics.” I suppose that, knowing the astonishing ability of insects in general to chew their way through just about anything, I shouldn’t have been surprised that electrical and electronic devices aren’t exempt. Their ability to chew their way out of plastic containers, for example, has been known for about seven decades [and experienced first-hand about a decade ago, when we initially tried to set up a colony of navel orangeworms, Amyelois transitella (Walker), in plastic buckets]. Their ability to digest and thrive on plastic as food, though, is a relatively recent finding, reported initially in Chinese (Miao and Zhang 2010) and four years later in English (Yang et al. 2014). Today, more than a dozen species are known to survive on a diet of plastic (Pivato et al. 2022), the vast majority of which are stored product pests (a pattern consistent with the fact that they are among the insects most likely to encounter plastic, given that the stored products they consume are often stored in plastic containers). But the concept that there are insects that can ingest waste electrical and electronic equipment (yes, there’s an acronym: WEEE), or e-waste, was new to me. It was a challenge to imagine what, over the vast span of insect evolution, might have preadapted insects to consume any of the parts of discarded microwave ovens, cell phones, tablets, computers, keyboards, printers, small servers, fax machines, scanners, televisions, cable boxes, video game consoles, and other once-useful tools fallen victim to hardware upgrades.

Direct competition and potential displacement involving managed Trogoderma stored product pests

The establishment of an exotic pest may require displacing local species with a similar niche. The potential of Trogoderma granarium to displace Trogoderma inclusum was explored in a stored product setting. We performed direct competition experiments varying commodity and temperature over different durations. At nine weeks T. inclusum outproduced T. granarium on all commodities at any temperature. However the proportion of T. granarium versus T. inclusum was greater at 32 °C compared to 25 °C. The nine-week production of T. granarium was best on wheat, while rice was optimal for T. inclusum. After 25 weeks, when adults were used at the start of competition, T. inclusum maintained an advantage in the direct competition. If larvae were used to initiate the competition for 25 weeks, the two species coexisted well at 25 °C, but T. granarium nearly excluded T. inclusum at 32 °C. Thus T. inclusum performs better in competition over shorter intervals when resources are plentiful, but T. granarium can be more successful over longer time periods, particularly when late instar larvae are involved. The finding suggests a real threat of introductions of T. granarium larvae to establish populations within grain storage infrastructure where T. inclusum is common.

Development of an array of molecular tools for the identification of khapra beetle (Trogoderma granarium), a destructive beetle of stored food products

Trogoderma granarium Everts, the khapra beetle, native to the Indian subcontinent, is one of the world’s most destructive pests of stored food products. Early detection of this pest facilitates prompt response towards the invasion and prevents the need for costly eradication efforts. Such detection requires proper identification of T. granarium, which morphologically resembles some more frequently encountered, non-quarantine congeners. All life stages of these species are difficult to distinguish using morphological characters. Additionally, biosurveillance trapping can result in the capture of large numbers of specimens awaiting identification. To address these issues, we aim to develop an array of molecular tools to rapidly and accurately identify T. granarium among non-target species. Our crude, cheap DNA extraction method performed well for Trogoderma spp. and is suitable for downstream analyses including sequencing and real-time PCR (qPCR). We developed a simple quick assay usingrestriction fragment length polymorphism to distinguish between T. granarium and the closely related, congeneric T. variabile Ballion and T. inclusum LeConte. Based on newly generated and published mitochondrial sequence data, we developed a new multiplex TaqMan qPCR assay for T. granarium with improved efficiency and sensitivity over existing qPCR assays. These new tools benefit regulatory agencies and the stored food products industry by providing cost- and time-effective solutions to enhance the identification of T. granarium from related species. They can be added to the existing pest detection toolbox. The selection of which method to use would depend on the intended application.

Effect of temperature on the life table parameters and high-temperature lethality of Tyrophagus putrescentiae

The effects of five constant temperatures (16, 20, 24, 28, and 32 °C) on the development and reproduction of a serious stored products pest, Tyrophagus putrescentiae, fed on wheat bran were evaluated in the laboratory at 75% relative humidity. In addition, the efficacy of high temperatures (lethal temperatures) ranging from 39 to 49°C on the mortality of mobile stages of T. putrescentiae was investigated. The development time of different stages was decreased with increasing temperature, and total immature stages varied from 55.37 to 11.46 days. The pre-oviposition, oviposition, and post-oviposition periods, and female longevity all decreased with the temperature increasing. The longest oviposition period was 46.12 days at 16 °C. The female ratio increased from 52.4 to 68.8%. With the temperature. From 16 to 32 °C, the mean eggs deposited per day were 0.544, 0.994, 2.055, 3.034, and 1.421, respectively. The maximum fecundity (87.69 eggs per female) and the highest intrinsic rate of increase (rm) (0.194) were at 28 °C. In all mobile stages, mortality increased with the increase in temperature and exposure time. When temperatures ranged from 39.0 to 49.0 °C, the half-lethal time (LT50) of adult T. putrescentiae was 347.47, 124.38, 60.01, 33.66, 22.06, and 13.49 min, respectively, and it was shortened by half when the temperature was increased by 2 °C. The larvae were more sensitive to high temperatures than in other stages. Interestingly, the LT50 of adults was almost twice as LT50 of larvae under each temperature. The study suggests that temperature significantly affects the development, survival, and reproduction of T. putrescentiae, and heat treatment is an effective method to control this pest.

The Type of Grain Counts: Effectiveness of Three Essential Oil-Based Nanoemulsions against Sitophilus oryzae

Essential oil (EO)-based nanoemulsions (NEs) are promising grain protectants in the management of stored-product pests. However, the potential impact of the stored-grain species on the green insecticide effectiveness has been poorly studied. In this study, two concentrations of EO-based NEs from Carlina acaulis L., Mentha longifolia (L.) Huds., and Hazomalania voyronii (Jum.) Capuron were evaluated as insecticides against the major stored-product pest Sitophilus oryzae (L.) on barley, oats, and maize kernels. The C. acaulis EO-based NE applied at 1000 ppm on barley achieved the highest mortality, killing 94.4% of S. oryzae adults after a 7-day exposure, followed by 1000 ppm of H. voyronii EO-based NE (83.3%). The lowest mortality (1.1%) was recorded with 500 ppm of M. longifolia EO-based NE on maize after the same interval. All tested NEs exhibited elevated efficacy when applied on barley, while mortalities were lower on oats and maize. Furthermore, C. acaulis EO-based NE was the most effective when applied on all commodities, followed by H. voyronii and M. longifolia EO-based NEs. Overall, our results highlighted the significant impact of the stored cereal on the insecticidal effectiveness of EO-based NE used for stored-product pest control. Sitophilus oryzae adults on barley can be adequately controlled through the application of C. acaulis and H. voyronii EO-based NEs.

Bioefficacy of eight different plant powders applied as fumigants against the adzuki bean weevil, Callosobruchuschinensis

The adzuki bean weevil, Callosobruchus chinensis (L.), is a highly destructive pest of stored legumes. This study aims to evaluate the bioefficacy of eight plant powders applied as fumigants against C. chinensis. Among the evaluated plant powder fumigants, clove, holy basil, lemongrass, and turmeric powder fumigant elicited high mortality up to 100% of C. chinensis and simultaneously showed high oviposition deterrence and F1 progeny inhibition against the pest, which led to a lower percentage of bean damage and weight loss. The antifeedant activity of the plant powder fumigants is reflected by the high feeding deterrence value of up to 82.92%. Additionally, based on a two-choice test assay, it is revealed that clove, holy basil, lemongrass, and turmeric powder fumigant also have adult repellent activity. Analysis of the volatile organic compounds of those four plant powder fumigants indicated that the major constituents responsible for the anti-pest feature were eugenol and caryophyllene for clove; estragole for holy basil; α-Citral and β-Citral for lemongrass; and α-zingiberene and β-sesquiphellandrene for turmeric. However, clove powder was proved to be the most efficacious fumigant in all parameters observed since it showed high bioefficacy even when applied at the lowest dose. Our findings highlight the potential use of plant powder fumigant as an eco-friendly and cost-effective management method of stored product pests, which could be a valuable option for small-hold farmers in developing countries.

A comprehensive review of effective essential oil components in stored-product pest management

A comprehensive review of effective essential oil components in stored-product pest management

Essential oils of Origanum Species from Turkey: Repellent Activity Against Stored Product Insect Pests

Studies on the production of plant-based pest control strategies have been growing in recent years. Origanum (Lamiaceae) species are important medicinal aromatic plants and many studies have been conducted on their biological activities. This study was conducted to determine the repellent effects of plant essential oils extracted from four different Origanum species: O. onites, O. vulgare var. hirtum, O. vulgare var. verticium and O. onites × O. vulgare, against four different stored product pests: Rhyzopertha dominica (F., 1792) (Coleoptera: Bostrichidae), Tribolium confusum Jacquelin Du Val, 1863 (Coleoptera: Tenebrionidae), Sitophilus granarius (Linnaeus, 1875) and Sitophilus oryzae (Linnaeus, 1763) (Coleoptera: Curculionidae), under laboratory conditions. The neo-clavenger apparatus was used to obtain essential oils. As a result of the experiment, O. onites essential oil showed the highest activity at a dose of 0.25 μl cm-2 with 68% on T. confusum after 2 hours. This oil showed the highest activity on S. oryzae with 90% at the lowest application dose of 0.025 μl cm-2. When the results are evaluated generally, the highest activity was found in O. onites essential oil. Other essential oils have varying degrees of activity depending on time and dose. Results of the experiment show that Origanum oils have a significant potential to controlling this pest.

Retrogressive moulting in khapra beetle, Trogoderma granarium (Coleoptera: Dermestidae)

AbstractInsect larvae typically moult to grow, but here we investigate insect larvae that moult to shrink; that is, retrogressive moulting or retrogressive development. We demonstrate this phenomenon in khapra beetle, Trogoderma granarium Everts (Dermestidae), among the world's most invasive pests of stored grains and cereal products, and a quarantine pest of interest for many countries. Larvae survived a 3‐month period of starvation, moulting up to six times and reducing their body mass by about half, on average. When reprovisioned with food, most larvae resumed the normal trajectory of development and pupated within a month. Thus, retrogressive development is a mechanism that may favour species whose resources exhibit feast‐or‐famine dynamics. By enabling survival during periods of privation, retrogressive development contributes to the invasiveness of the khapra beetle by allowing them to persist for long periods in empty storage facilities or empty containers used for international grain shipments.

Insecticidal and Antifeedant Activity of Andrographis paniculata as Rice Grain Protectant against Red Flour Beetle (Tribolium castaneum Herbst)

The red flour beetle (Tribolium castaneum Herbst) is the most common stored-product insect pest infesting rice, which acts as vector for several fungal post-harvest diseases. To eradicate such pest, fumigation with chemicals is often used. As a natural alternative, this study explored the potential of Andrographis paniculata, an indigenous herb in the Philippines, as an antifeedant agent against T. castaneum. Three treatment groups were prepared, consisting of 2kg infected rice with 50 starved unsexed adult red flour beetles. Two grams of A. paniculata crushed leaves were placed inside a teabag (5.5 cm x 7 cm). Different amounts of A. paniculata tea bags (2 g, 4 g, and 6 g) were used for each treatment to determine its toxicity and antifeedant effect. Gathered data were further analyzed by analysis of variance (ANOVA) to compare the significant differences among treatments. Results of the study showed that among the treatments, three teabags (6g) of A. paniculata crushed leaves exhibited the highest percent insect mortality (50%) and lowest percent weight loss (1.87%) of rice. Therefore, this study suggests that three teabags of A. paniculata powder may be used for the efficient management of T. castaneum infestation and reduce the weight loss of rice in storage.

Bioactivity of Essential Oil from Citrus aurantium Peel against the Pulse Beetle Callosbruchus maculatus F. on Chickpea

Plant essential oils (EOs) and their active compounds are recognized as sustainable tools for the management of arthropod pests. The bitter orange, Citrus aurantium L. (Rutaceae), is a widespread tree in the Mediterranean region that is used especially as a rootstock for other Citrus. Although most of this plant’s parts are accredited with medicinal properties, its fruits are not consumable and generally considered as non-valued waste. The aim of this work was to assess the potential use of the EO extracted by hydrodistillation from C. aurantium peel in the fumigation of chickpea seeds against Calloosbruchus maculatus. Analysis of EO of the bitter orange peel by gas chromatography coupled with a mass spectrometer (GC-MS) identified twenty-two compounds with limonene as the major component (86%). EOs of C. aurantium peel exerted toxic effects, in a concentration-dependent manner, on eggs (LC50 = 62.7 µL/L air), larval stages inside the seed (LC50 = 62.8 µL/L air), and adults (females: LC50 = 148 μL/L air and males: LC50 = 109 µL/L air). The C. aurantium EO also negatively affected the biological and demographic performances of the weevil compared to the untreated control. Fecundity and the number of emerged adults were reduced by more than 57 and 71, respectively, while the net reproduction rate and the intrinsic rate of increase were respectively decreased by over 71% and 37%, resulting in the total extinction of the pest at a concentration equal to 100 µL/L air. Our findings suggest the possible valorization of bitter orange peel by using them as a source of bioinsecticide to be integrated within sustainable programs for the management of stored product pests. Further studies are needed to verify similar uses of essential oils extracted from solid wastes from citrus-processing industries.

Screening for Insecticidal Potential of the Chickpea Plant Cicer Arietinum (L.) Against Three Stored Grain Pests Callosobruchus Chinensis (L.), Sitophilus Oryzae (L.) And Tribolium Castaneum (Herbst) Adults Under Laboratory Conditions

Petroleum ether (PE), chloroform (CHCl3), and methanol (CH3OH) extracts of the whole chickpea plant Cicer arietinum (L.) have been tested against adult beetles of Callosobruchus chinensis (L.), Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) through dose-mortality and repellent activity tests. In dose mortality tests, the PE extracts of C. arietinum gave LD50 values of 3.466, 3.292, 2.721, 2.398, 1.887, 1.663 and 1.428 mg/cm2 against C. chinensis and 4.297, 3.415, 2.246, 1.725, 1.384, 0.984 and 0.722 mg/cm2 against S. oryzae both after 12, 18, 24, 30, 36, 42 and 48 h of exposures, respectively. The CHCl3 extracts gave LD50 values of 5.242, 4.844, 3.472, 2.945, 2.540, 1.875, 1.295 and 1.053 mg/cm2 against C. chinensis after 6, 12, 18, 24, 30, 36, 42 and 48 h of exposures, respectively. The CH3OH extracts, on the other hand, yielded LD50 values of 0.923, 0.757, 0.649, 0.515, 0.400, 0.303, 0.247 and 0.197 mg/cm2 against C. chinensis, 4.227, 3.528, 3.454, 2.933, 2.493, 2.187, 1.938 and 1.724 mg/cm2 against S. oryzae and 3.485, 3.176, 2.851, 1.531, 1.113, 0.756, 0.534 and 0.478 mg/cm2 against T. castaneum adults after 6, 12, 18, 24, 30, 36, 42 and 48 h of exposures, respectively. However, the PE extracts of C. arietinum did not show any mortality against T. castaneum and the CHCl3 extracts were inactive against S. oryzae and T. castaneum adults. In repellency tests, all three organic extracts did not show any repellency against the test beetles. According to their intensity of activities, the extracts could be arranged in the following descending order: CH3OH extracts against C. chinensis > CH3OH extracts against T. castaneum > PE extracts against S. oryzae > CHCl3 extracts against C. chinensis > PE extracts against C. chinensis > CH3OH extracts against S. oryzae adults. The present results indicate that the test plant C. arietinum contains bioactive compounds and could be used as a source of control agents for the stored product pests. J Bio-Sci. 30(1): 91-100, 2022 (June)

Demographic characteristics of Cadra cautella on brown rice at different temperatures: Do diapausing individuals contribute to population growth rate?

The almond moth, Cadra cautella (Walker) (Lepidoptera: Pyralidae), is a recognized cosmopolitan pest of stored food products throughout its worldwide distribution. To enable effective control of this pest, a thorough understanding of the effect of temperature on their population growth is required. In this study, we investigated the population growth rate of group-reared C. cautella fed on brown rice at five different temperatures (15–35 °C) using the age-stage, two-sex life table program. At 15 °C, the majority of larvae failed to reach the 2nd instar. At 35 °C, only 5 out of 150 individuals survived to the adult stage. There was no significant difference in fecundity between the three temperature groups (20, 25 and 30 °C), while a dramatic decline occurred at 35 °C (0.5 eggs/female). The intrinsic rates of increase of C. cautella were 0.0566, 0.1149, 0.1429, and −0.0901 d−1 at 20, 25, 30 and 35 °C, respectively, with significant difference between all values. Approximately 16.0% of late instar almond moth larvae showed signs of diapause induction at 20 °C, i.e., wandering behavior and delayed pupation. The developmental times of larvae (74.44 d) and pupae (17.13 d) were significantly longer in the diapausing cohort than in the non-diapausing cohort (54.89 and 15.47 d). At 20 °C, the offspring of the diapausing individuals were still able to contribute 12.98% to the net reproduction rate of the entire cohort – an amount substantial enough to require attention when planning pest management programs. In conclusion, we suggest that 15 °C can effectively limit the damage caused by C. cautella population due to their inability to develop into later instars at this temperature.