Larvae Of Plodia Interpunctella Research Articles

Effect of critical temperatures on mortality and cuticle composition of Plodia interpunctella larvae: Insights from GC–MS analysis and SEM imaging

The Indian meal moth, Plodia interpunctella Hübner (Lep.: Pyralidae), is a significant global pest of stored products, particularly in temperate regions. This study investigated the impact of various temperatures (25, 50, 55, and 60 °C) over different durations (5, 10, 15 and 20 min) on the mortality and cuticle layer of third instar P. interpunctella larvae. Hexane solvent separated the cuticle layer of 3rd instar larvae treated at critical temperatures; Bis (trimethylsilyl) acetamide and Trimethylsilyl chloride were added for derivatization before injection into the GC–MS. Additionally, SEM imaging was used to observe the epicuticle surface of treated larvae under critical temperatures. The findings showed a direct relationship between increasing temperatures and the mortality rate of 3rd instar larvae, with complete mortality occurring in 20 min at 50 °C, in 15 min at 55 °C, and in just 10 min at 60 °C. Moreover, with an increase in temperature and exposure time, the weight of the larvae decreased significantly. GC–MS analysis unveiled that the waxy layer contained sixteen fatty acids within P. interpunctella cuticles; it was observed that as temperatures increased, there was a significant reduction in fatty acid levels. SEM imaging also revealed that rising temperatures led to a dramatic decrease in cohesion within the epicuticle layer; altering its physical and chemical structure caused dehydration, ultimately leading to death. These results suggest that utilizing critical temperatures for short durations can effectively control P. interpunctella populations.

Insecticidal, antifeedant and acetylcholinesterase inhibitory activity of sesquiterpenoids derived from eudesmane, their molecular docking and QSAR

This work evaluated the insecticidal, antifeedant and AChE inhibitory activity of compounds with eudesmane skeleton. The insecticidal activity was tested against larvae of Drosophila melanogaster and Cydia pomonella, the compounds 3 and 4 were the most active (LC50 of 104.2 and 106.7 μM; 82.0 and 84.4 μM, respectively). Likewise, the mentioned compounds were those that showed the highest acetylcholinesterase inhibitory activity, with IC50 of 0.26 ± 0.016 and 0.77 ± 0.016 μM, respectively. Enzyme kinetic studies, as well as molecular docking, show that the compounds would be non-competitive inhibitors of the enzyme. The antifeedant activity on Plodia interpunctella larvae showed an antifeedant index (AI) of 99% at 72 h for compounds 16, 27 and 20. The QSAR studies show that the properties associated with the polarity of the compounds would be responsible for the biological activities found.

Salvia officinalis, Lavandula angustifolia, and Mentha pulegium essential oils: insecticidal activities and feeding deterrence against Plodia interpunctella (Lepidoptera: Pyralidae)

In this study, the chemical compositions of essential oils obtained from three plants, namely Salvia officinalis, Lavandula angustifolia, and Mentha pulegium, along with their insecticidal activities and feeding deterrence against Plodia interpunctella, were investigated. The chemical composition of S. officinalis essential oil was majorly dominated by α-thujone (26.99%) and camphor (25.50%); on the other hand, limonene (66.12%), eucalyptol (66.12%), and camphor (14.31%) were the major compounds of L. angustifolia essential oil whereas for M. pulegium EO a dominance of pulegone (83.06%) was attained. M. pulegium essential oil showed important contact toxicity (100%) at 3 hours of exposure with the 0.25 μL/cm2 concentration, followed by S. officinalis and L. angustifolia with 90% of mortality reported with the highest concentration of 0.50% within 3 hours. A relative growth rate (RGR) of 0.08 mg/mg/day and -0.31 mg/mg/day was recorded with S. officinalis and M. pulegium oils, respectively, with the highest concentration of 32 μL/pellet. With L. angustifolia the lowest RGR of -0.08 mg/mg/day was attained with the 16 μl/pellet concentration. The food deterrence index experienced an increase to 89% with S. officinalis and L. angustifolia oils for the three concentrations; with M. pulegium, 68.18% was recorded with the 32 μL/pellet. In conclusion, this study suggests that these essential oils could potentially serve as an effective contact toxicant and a potent eco-friendly inhibitory of the feeding behavior of Plodia interpunctella larvae.

Comparison on mortality, pupation, and emergence of Plodia interpunctella (hübner) treated by 2, 4, 6, and 8% carbon dioxide mixed with 2 and 4% oxygen at three temperatures

Low concentration CO2 (e.g., 2–8%) mixed with 2–4% O2 balanced by N2 is more economically feasible than applying 99.99% N2 alone. Mortality, pupation, and emergence of the fifth instar larvae of Plodia interpunctella (Lepidoptera: Pyralidae) were tested in 2 or 4% O2 mixed with 2, 4, 6, or 8% CO2 balanced by N2 at 28, 23, and 18 °C. Mortality of eggs, second instar larvae, and pupae was tested in the mixture of 2% O2, 4% CO2, and 94% N2 at the three temperatures. When fifth instar larvae were exposed in 2% O2 mixed with 0, 2, 4, 6, and 8% CO2 or increasing temperature, the LT50, LT99 value, and time reaching 100% mortality was decreased significantly. Exposing in 4% O2 mixed with 0, 2, 4, 6, and 8% CO2, the pupation and emergence of the surviving fifth instar larvae were also decreased significantly, and reduced more in higher temperatures. This study found 2, 4, 6, and 8% CO2 had additive effect to low O2 on insect mortality, pupation, and emergence at any tested temperature, and higher CO2 concentration or temperature resulted in a higher additive percentage. The fifth instar was the most tolerant stage to the gas mixtures followed by second instar larvae, pupae, and egg; and increasing temperature would sufficiently decrease the lethal exposure time.

Replication of Dengue Virus 4 in Plodia interpunctella (Lepidoptera: Pyralidae) Larvae Under Laboratory Conditions.

Background: Developing methods for the isolation and replication of dengue virus (DENV), based on nonhematophagous insect models to assess virus-host interaction, would contribute, for instance, to the creation of drugs or vaccines and eventually to the control of the disease. In this regard, nonhematophagous mosquitoes have been used as biological hosts for the isolation of DENV because they are specific and sensitive to a low viral load and viral particles with low infectivity. However, implementation of these models is mainly affected by the complexity of the establishment of the entomological colonies. Materials and Methods: In this study, the susceptibility of DENV-4 infection in Plodia interpunctella larvae was evaluated. Ten larvae, previously inoculated with supernatant from DENV-4-infected C6/36 cells, were processed to determine viral replication by the optical density and 2-ΔΔCt methods at different time intervals (1 and 7 days postinoculation). Results: A prospective increase in viral replication was observed, which did not influence the survival and development of P. interpunctella. Conclusion: These results demonstrate the infectivity of DENV-4 in P. interpunctella, thus becoming an option as a biological model for the study of this etiological agent.

Biological performance of Arma chinensis on three preys Antheraea pernyi, Plodia interpunctella and Leptinotarsa decemlineata

Arma chinensis (Fallou) is an important predator of several agricultural and forestry pests. We tested the effects of three different prey species on the biological parameters of the predatory Ar. chinensis under laboratory conditions. These prey species consisted of Antheraea pernyi pupa, Plodia interpunctella larvae and Leptinotarsa decemlineata larvae. The results showed that prey species elicited a significant effect on development times, total survival rate, adult acquisition rate and reproduction. In contrast, the female proportion, survival rates of 3rd instars and 5th instars not significantly affected by prey species. An. pernyi pupa were the most suitable prey among those tested, and led to high survival rates, short development times, and high fecundity of Ar. chinensis. P. interpunctella larvae were also relatively favorable prey, whereas L. decemlineata larvae were less suitable and resulted in reduced development, survival and fecundity. Therefore, P. interpunctella larvae and L. decemlineata larvae can be fed to Ar. chinensis for turning both their harms into benefits and reducing the feeding and breeding costs of Ar. chinensis.

Induced dormancy in Indian meal moth Plodia interpunctella (Hübner) and its impact on the quality improvement for mass rearing in parasitoid Habrobracon hebetor (Say).

A steady supply of hosts at the susceptible stage for parasitism is a major component of mass rearing parasitoids for biological control programs. Here we describe the effects of storing 5th instar Plodia interpunctella larvae in dormancy on subsequent host development in the context of host colony maintenance and effects of the duration of host dormancy on the development of Habrobracon hebetor parasitoids reared from dormant hosts. We induced dormancy with a combination of short daylength (12L:12D) and lower temperature (15°C), conditions known to induce diapause in this species, and held 5th instar larvae of P. interpunctella for a series of dormancy durations ranging from 15 to 105 days. Extended storage of dormant 5th instar larvae had no significant impacts on survival, development, or reproductive potential of P. interpunctella, reinforcing that dormant hosts have a substantial shelf life. This ability to store hosts in dormancy for more than 3 months at a time without strong negative consequences reinforces the promise of using dormancy to maintain host colonies. The proportion of hosts parasitized by H. hebetor did not vary significantly between non-dormant host larvae and dormant host larvae stored for periods as long as 105 days. Concordant with a prior study, H. hebetor adult progeny production from dormant host larvae was higher than the number of progeny produced on non-dormant host larvae. There were no differences in size, sex ratio, or reproductive output of parasitoids reared on dormant hosts compared to non-dormant hosts stored for up to 105 days. Larval development times of H. hebetor were however longer when reared on dormant hosts compared to non-dormant hosts. Our results agree with other studies showing using dormant hosts can improve parasitoid mass rearing, and we show benefits for parasitoid rearing even after 3 months of host dormancy.

Biodegradation of polyethylene by Meyerozyma guilliermondii and Serratia marcescens isolated from the gut of waxworms (larvae of Plodia interpunctella)

The widespread use of polyethylene (PE) causes a large amount of indigestible plastic waste. Waxworms (the larvae of Plodia interpunctella) can eat PE, but the degradation principle of PE under the action of intestinal microorganisms is still unclear, especially the insufficient research on key degradable PE strains. In this study, we fed waxworms with PE. Two strains with high PE degradation efficiency were isolated and purified, and the effects of single and microbial consortia on PE degradation were evaluated by water contact angle (WCA), FTIR, GC–MS, SEM and RT–qPCR. The results showed that Meyerozyma guilliermondii ZJC1 (MgZJC1) and Serratia marcescens ZJC2 (SmZJC2) could degrade PE. However, the degradation efficiency of the microbial consortium was higher, and the weight loss rate of PE was 15.87 %. In addition, the PE degradation products of MgZJC1 were C9H10O, C20H15NO, C28H44O3 and C16H32O2, and the PE degradation products of SmZJC2 were C16H18O, C14H18N2O7 and C31H48O6. The PE degradation products of the microbial consortium were C11H24, C19H10O, C15H32, C14H30, C16H34, C25H52 and C27H56. RT–qPCR results showed that SmZJC2 promoted PE degradation by upregulating the expression of multiple genes, such as multicopper oxidase genes (PiSm-CueO). MgZJC1 responded to carbon deficiency by upregulating the expression of multiple genes, such as key enzyme genes in the tricarboxylic acid (TCA) cycle. This study can be used to develop an efficient microbial consortium for PE degradation and provide a basis for the reuse of PE waste. It can also provide a research basis for the joint degradation of PE by microbial consortia composed of bacteria and fungi.

Development of a multilayer insect-repelling film with trans-anethole for the storage of almond flake cereal.

Trans-anethole (AN), which exhibits strong insect-repellent activity against Plodia interpunctella larvae, was applied on a polyethylene terephthalate (PET) film as an active packaging coating layer. All developed films at different concentrations (25%, 30%, 40%, and 50%) exhibited significant insect repellent activities. However, these films did not significantly differ from the control film in terms of color and transparency. In addition, the developed polypropylene (PP) and PET laminated films containing 25% AN (PP/AN25/PET) exhibited strong and continuous insect-repellent activity for up to 42 days. Finally, the developed film showed 2.86-fold stronger repellent activity than that of the control film when applied to the almond flake cereals packaging. These results suggest that PP/AN25/PET could be used as a potent insect-repelling packaging film in a realistic grain-packaging system. PRACTICAL APPLICATION: A PP/trans-anethole/PET film that exhibited good insect-repellent activity for 42 days was newly developed in this study. As it showed strong insect repellency, especially in almond flake cereals packaging, it is expected to have high potential as an insect-repelling grain-packaging film.

Curing raisins with sulfur dioxide suppresses population growth of Indian meal moth, Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae)

• Curing raisins with SO 2 may help preserve quality and protect against pests. • Fumigation of raisins with 66 g/m 3 or 133 g/m 3 of SO 2 for 3 or 6 h killed 80–90% of Plodia interpunctella larvae. • Fecundity of surviving female moths was reduced to a small fraction of controls. • An inverse dosage-dependent effect rendered 66 g/m 3 SO 2 slightly more effective than 133 g/m 3 SO 2 . A sulfur dioxide treatment is often used to preserve the color and flavor of raisins. We used a life table approach to examine the effects of residual sulfites on Plodia interpunctella (Hubner) when larvae fed on raisins under controlled laboratory conditions. Raisins were fumigated with 66 g/m 3 or 133 g/m 3 SO 2 for either three or six hours, or received no SO 2 exposure (control). A two sex life table was constructed for insects in each treatment (n = 70 per treatment). Total immature mortality exceeded 90% in 66 g/m 3 SO 2 treatments, and 80% in 133 g/m 3 SO 2 treatments, compared to 28.6% in controls. Sulfur dioxide treatments significantly extended developmental time relative to controls, again more so in the 66 g/m 3 SO 2 treatments than in the 133 g/m 3 treatments, but did not affect the adult longevity of survivors. All SO 2 treatments reduced the fecundity of surviving female moths to a small fraction of controls, without significant differences among them. These effects combined to result in significantly diminished life table parameters in all treatments relative to controls, although generation times were increased more in the 66 g/m 3 SO 2 treatments than in the 133 g/m 3 treatments. These inverse dosage-dependent effects may reflect increased feeding avoidance of sulfite residues in the higher dose treatments that resulted in reduced consumption. We conclude that residual sulfur and sulfites deposited on fruit surfaces during SO 2 treatment provide substantial control of P. interpunctella , and should effectively suppress the proliferation of moths within bulk stores of dried raisins.

Application of Ozone against the Larvae of Plodia interpunctella (Hübner) and Its Impacts on the Organoleptic Properties of Walnuts

One of the most important products grown in Iran is walnut (Juglans regia L.), but it can be threatened by storage pests such as insects. Ozonation is an environmentally friendly method for killing pest insects; accordingly, ozone efficacy in the control of a pest species of walnut, Indian meal moth (Plodia interpunctella (Hübner)), was assessed in this research. The selected walnut samples were infested with larvae of Indian meal moth and then subjected to various combinations of ozone concentration (3, 4.5, and 6 ppm) and exposure time (20, 30, 40, and 50 min). After exposure to the treatment combinations, larval mortality rates and changes to the sensory properties (color, taste, smell, crispness, stiffness, and overall acceptability), indicating consumer preference, of the walnuts were evaluated. Our results revealed enhanced mortality rates of P. interpunctella with an increase in both ozone concentration and exposure time: 99% mortality was recorded at the concentration and exposure time of 6 ppm and 50 min, respectively. Sensory assessments of the samples showed that ozone treatments had no significant impacts on the color, taste, crispness, stiffness, and overall acceptability of the product. Also, few changes were recorded for its smell, which could be improved over time after being exposed to the air. We conclude that application of higher ozone concentrations might provide acceptable levels of insect pest control for stored walnuts with no associated reduced trade-off for their quality attributes.

Fumigant toxicity of Haplophyllum tuberculatum (Rutaceae) and Nepeta crispa (Lamiaceae) on the Indian meal moth

The insecticidal activity of essential oil vapors of Haplophyllum tuberculatum (Sapindales: Rutaceae) and Nepeta crispa (Lamiales: Lamiaceae) were evaluated on third instar larvae of Plodia interpunctella (Lepidoptera: Pyralidae) as one of the major insect pests of stored products. Essential oils of the plants were obtained using Clevenger-type water distillation. GC-MS analyses of the oils demonstrated that the main compounds of H. tuberculatum were ρ-menth-2-en-1-ol-cis (20.15 %), ρ-menth-2-en-1-ol-trans (16.92 %), trans-Piperitol (13.23 %), Piperitone (7.34 %) and cis-Piperitol (6.72 %). It is an important plant that has many medicinal properties. 1,8- Cineole (32.98 %), s-Pinene (8.70 %), 4aa,7a,7aa-Nepetalactone (8.08 %) and 4as,7a,7as-Nepetalactone (6.1 %) were detected as the predominant component in N. crispa. The aerial parts of that are used in traditional medicine. The LC50 values were estimated after 24 hours for H. tuberculatum and N. crispa as 4.301 and 5.579 µl L-1 air, respectively. LC50 values were projected using probit analysis. Results on H. tuberculatum showed more toxicity against the Indian meal moth compared to the N. crispa. In conclusion, the essential oil of the two plants could have potential for application to stored grain and agricultural commodities to control of stored crop pests in IPM programs.

Impact of Peanut Depth and Container Size on the Parasitism of Diapausing and Nondiapausing Larvae of Indian Meal Moth (Lepidoptera: Pyralidae) by Habrobracon hebetor (Hymenoptera: Braconidae).

Host mortality and progeny production by the ectoparasitoid, Habrobracon hebetor Say (Hymenoptera: Braconidae) on diapausing and nondiapausing larvae of Plodia interpunctella Hübner (Lepidoptera: Pyralidae) were investigated in response to peanut depths and free space at standard environmental conditions. The free space was created by having four different quantities of peanuts in glass containers of fixed volume or same quantity of peanut in containers of different sizes. Host mortality caused by the parasitoids was significantly higher for diapausing larvae compared with nondiapausing larvae at corresponding peanut depth. Differences in peanut depth affected mortality of nondiapausing larvae exposed to parasitoids but diapausing larvae experienced the same level of mortality. Regardless of container sizes, host mortality was higher than 90.0% for both types of larvae. When equivalent peanut depths were compared, more F1 parasitoids were produced on diapausing larvae than on nondiapausing larvae. Reduced peanut depth affected the sex ratio of parasitoid progeny reared on nondiapausing larvae but not those reared on diapausing larvae. Parasitoid progeny resulting from reduced peanut depth was male-biased and this was more evident with parasitoids that emerged from diapausing host larvae than nondiapausing larvae. Progeny production by H. hebetor was not influenced by container size. This study underscores the fact that host mortality caused by H. hebetor at different peanut depths was significantly different for nondiapausing host larvae, but was not so for diapausing larvae. The container sizes did not affect the performance of H. hebetor in killing P. interpunctella. The entire study emphasizes the potential of diapausing larvae for the rearing of H. hebetor.

Improvement of reproductive performance of Habrobracon hebetor: Consideration of diapausing and non-diapausing larvae of Plodia interpunctella

The major obstacle to the adoption of Habrobracon hebetor (Say) (Hymenoptera: Braconidae) for the management of postharvest moth pests is the short duration of the last instar stage of the hosts, which is the preferred stage by the parasitoid for development. It is postulated that mass rearing of the parasitoid on diapausing larvae is possible due to arrested development of the last instar of Pyralid hosts that offers the parasitoid a wider window to paralyze host larvae. Laboratory studies were conducted to evaluate the rearing of H. hebetor on diapausing and non-diapausing larvae of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) at standard environmental conditions. Host mortality of 100% was observed at nearly all larval densities of diapausing larvae but in non-diapausing larvae, the percentage mortality consistently decreased with increase in host density. More progeny of H. hebetor was produced on diapausing larvae than on non-diapausing larvae. Weights of female parasitoid progeny were highest at host density of 10 for diapausing larvae and not significantly different for males. The number of adults from eggs laid by mated female wasps provisioned daily with fresh diapausing larvae up to 5th day was significantly higher than those by parasitoids provisioned with non-diapausing larvae. The maximum number of adults that completed development from eggs laid daily by H. hebetor provisioned with diapausing larvae was on the 3rd day but those provisioned with non-diapausing larvae was on the 5th day. The results from this study show that diapausing larvae of P. interpunctella will be ideal for mass rearing of H. hebetor for the management of Pyralid populations.

Microbial control using bacteria of the almond moth, Cadra (Ephestia) cautella Walker (Lepidoptera: Pyralidae)

Almond moth, Cadra (Ephestia) cautella (Lepidoptera: Pyralidae) is one of the most serious pests of dried fruits and other stored products. Almond moth is polyphagous pest that is widespread in Turkey and all over the world. Almond moth larvae cause serious damages on trees, warehouse and threshing floor of drying fig. Though various cultural, chemical and biological methods are used to control this pest, it is still effective in Turkey and various part of the world. In order to find a significant microbial control agent against this pest, we isolated 13 bacterial isolates and identified these isolates based on morphological, physiological, biochemical and molecular characteristics. According to these characteristics, isolates were identified as Serratia marcescens (Eca1 and Eca3), Serratia sp. (Eca11), Bacillus thuringiensis (Eca2, Eca4, Eca6, Eca7, Eca8, Eca9, Eca10, Eca12, Eca13) and Bacillus axarquiensis (Eca5). The insecticidal activities of these isolates were performed against three insect species from Lepidoptera group which cause serious damage in warehouses. The highest insecticidal activity is 57% for Eca9 isolate on the 3rd instar larvae of C. cautella, 100% for Eca9 isolate on the 3rd instar larvae of Plodia interpunctella and 100% for Eca10 and Eca3 isolate on the 3rd instar larvae of E. kuehniella. Results indicate that Eca9, Eca3 and Eca10 isolates may be valuable as potential biological control agents for the control of warehouse pests.

CONTACT TOXICITY OF PLOY LACTIC ACID NANOFIBERS LOADED WITH TWO ESSENTIAL OILS AGAINST PLODIA INTERPUNCTELLA HUB. (LEPIDOPTERA: PYRALIDAE)

In the most recent decade, nanoscale materials have received much attention because of their applications in the field of toxicology and biopesticides. Mentha piperita L. and Salvia officinalis L., as green pesticides were incorporated into Poly Lactic Acid (PLA) solution about 14%wt which were successfully electrospun into mats with ∼58 nm fiber diameters. The contact toxicity of essential oils (EOs) was tested on first instar larvae of Plodia interpunctella after 72-h to evaluate the effect of PLA nanofibers loaded with the EOs versus the pure essential oils (PEO)s on the mortality of the larvae over one month. The comparison between LC50 of the formulated essential oils (NFO)s and PEOs showed a significant difference (p< 0.05). The NFOs showed higher contact toxicity than the PEOs to control this pest for a longer time with slow release efficiency. Moreover, M. piperita showed more toxicity than S. officinalis. The nanofibers cause surface tension. Therefore, it is evaluated that this formulation increases the contact toxicity efficiency of essential oils as green contact pesticide. The nanofibers cause surface tension. Therefore, it is inferred that this formulation increases the contact toxicity efficiency of essential oils as green contact pesticide.

Original Article. Efficacy of electrospun bionanofibers as fumigant pesticides in foodstuff storage

Abstract Essential oils as alternative synthetic pesticides for pest management of foodstuffs have recently received increased attention. Controlled and slow release formulations of essential oils are used to enhance their efficiency. Two volatile essential oils of Mentha piperita L. and Salvia officinalis L. were investigated for release rate and mortality percentage by fumigant toxicity against 1st instar larvae of Plodia interpunctella. Electrospinning was used to incorporate various concentrations of essential oils in nanofibers. The essential oils can be released from the nanofibers for long periods of time, from several days to several weeks. Poly(lactic acid) was used as a green polymer carrier and the essential oils were incorporated into the nanofibers (8-15v/v% PLA). Insecticidal bioassay revealed that oil-loaded nanofibers (NFOs) were more toxic than pure essential oils (PEOs) against tested larvae. The LC50 and LT50 of NFOs were 1.2 and 4 times, respectively, more than PEOs. Our results indicated that PEOs completely lost their insecticidal activity after 14 days, whereas at the same period, NFOs had an average of 93% mortality when applied against P. interpunctella. Therefore, it can be concluded that nanofibers improved the persistence of the oil. This study presents S. officinalis has more toxicity and M. piperita had more persistence for controlling the larvae of indian meal moth.

Differential induction of heat shock protein genes to the combined treatments of heat with diatomaceous earth, phosphine or carbon dioxide on Plodia interpunctella

AbstractHeating is one of the many disinfestation methods commonly used in facilities that store and process agricultural products. In this study, we have investigated whether the combination of heat treatment with diatomaceous earth (DE), phosphine (PH3) or CO2 affects the mortality of the wandering larvae of Plodia interpunctella, which is a major pest found in most stored agricultural products. The mortality rate was 35.0% at day 1 after heat treatment at 40°C for 6 h; however, mortality rates increased after combined treatments of heat and 1 ppm DE or 10 ppm PH3, while 10% CO2 had no significant effect. Quantitative real‐time PCR analysis showed that combined treatments involving 1 h of heat treatment with either DE, PH3 or CO2 increased the mRNA levels of four heat shock protein (hsp) genes (hsp25, hsp70, grp78 and hsp90) in wandering larvae, 1 h post‐treatment, although those rates were slightly differentiated in each heat shock protein. Our results demonstrate that combinations of heat and DE or PH3 show increased lethality, although insects produce stress responses at the molecular level.

English

Biochemical and feeding assays were performed in order to assess the bioactivity of trypsin inhibitors from sesame seeds to control Plodia interpunctella larvae. The biochemical assays were based on the ability of protease inhibitors (PI) present in sesame seeds to inhibit bovine pancreatic trypsin and digestive enzymes of insect larvae. The stability of the inhibitors was also assessed at different pH and temperature. The feeding bioassays were carried out in plates containing second instar larvae fed on diet with sesame protein extract. It was observed that all genotypes presented inhibition when tested with BPT, ranging from 51 to 90%, among them BRS Seda, CNPA G3 and CNPA G4 showed average of 69% of inhibitory activity for intestinal homogenate. The FII-fractions in these three genotypes showed thermal and pH stabilities at 40°C and 8.5, respectively. In feeding bioassay, P. interpunctella larvae were susceptible to SPCE of all three genotypes, revealing average mortality of 74% to SPCE and 45% to FII-fractions. Among all genotypes, BRS Seda was more effective to inhibition of digestive enzymes of insects and considered the more suitable genotype for further using in sesame breeding program to resistance to P. interpunctella. Key words: Sesamum indicum L., serine protease, stored grain pest, Lepidoptera.

Effect of some stored insect pest species on biological aspects of the predator, Amphibolus venator Klug (Hemiptera: Reduviidae)

The Reduviid predator, Amphibolus venator Klug (Reduviidae: Hemiptera) was reared on larvae of Plodia interpunctella Hb., Tribolium confusum Duv., Trogoderma granarium Everts, Lasioderma serricorni Fab and Rhizopertha dominica F. under optimum laboratory conditions of 27±1°C and 60±5% R.H. The most preferable host was found to be R. dominica and L. serricorni larvae, followed by T. confusum and P. interpunctella, while the larvae of T. granarium appeared to be unsuitable host for this predator.