Untreated Larvae Research Articles

ROLE OF AMINO ACIDS IN PROTECTING PECTINOPHORA GOSSYPIELLA (SAUND.) AGAINST STRONG PROTEIN-DENATURING ACTIVITY OF PHENOLIC COMPOUNDS IN COTTON PLANTS

to test if the generality of glycine secretion in the pink bollworm larvae related to the concentration of phenolic compounds (PCs), a feeding experiment with two concentrations of selected two PCs (pyrocatechol; Pyro & resorcinol; Res) was performed. Then, we determined and compared the lysine and glycine contents in the total body homogenate of treated and untreated 4th instar larvae. Results showed that the lysine and glycine contents recorded were 2.29 & 1.47 mg/100mg of control larval body weight. Lysine content increased at low PCs concentration by 5.68 & 7.42% for Pyro and Res, respectively. On the other hand, its concentration decreased at high PCs concentration by 0.87 & 0.44%, respectively. On the other hand, glycine content generally decreased (except at low concentration of Pyro; 8.84%) by 4.76, 4.08 & 12.24%. Also, it could be noted that the generality of glycine secretion related to the concentration of PCs; whereas the less in glycine content was more notable in high concentration of PCs. And, the loss in glycine content was more than that for lysine. Also, studies extend to other amino acids (AA) and the results indicated that it could be grouped AA in 3 groups: 1. A high AA concentration (more than 3 mg/100mg): GLU and ASP acid. 2. A moderate AA concentration (more than 2 mg/100mg): VAL, LEU, LYS, ARG, ALA and TYR. 3. A low AA concentration (less than 2 mg/100mg): THR, ILE, PHE, HIS, CYS, SER, GLY and PRO.In the control PBW, glutamic acid and aspartic acid were present in high concentration (4.24 & 3.19 mg/100mg, respectively). In the same manner with glycine; the losses in GLU and ASP contents were more than that for LYS. So, it could be used by PBW to overcome PCs toxicity. In addition, generally, at low PCs concentration, AA content increased except in the case of VAL and CYS. In the contrast, at high PCs concentration, AA content decreased except in the case of MET, PHE, HIS and TYR. Commonly, it could be noted that Val, Cys, Gly and Ala had a higher percentage of the reduction. So, it means that other free amino acids may be used by some herbivores as counteractive agents against the denaturing activity of PCs.

Additive Effect of Chitinase Genes in Transconjugants of Entomopathogens Bacillus thuringiensis to Improve Biological Control of Tuta absoluta

This study aimed to evaluate the toxicity of Bacillus thuringiensis (Bt) transconjugants harboring chitinase genes against larval stage of Tuta absoluta . Bacillus licheniformisand Serratia marcescens were used as donors against Bt . Bacillus transconjugants were evaluated for chitinase activity depending on hydrolysis zone appeared on chitin agar medium. Parental strains and their recombinants significantly reduced the number of survived larvae if compared with untreated larvae. Mortality rate was gradually increased to reached a maximum ratio after six days of treatments. Most bioinsecticides including parental strains and their transconjugants significantly losses larval body weight daily if compared with untreated larvae.Bioinsecticides, as well as, bioinsecticide concentrations and the interaction between both factors showed negative significant effect on larval body weight at most time intervals of larval age.In addition, Bt recombinants , as well as, their parental strains has exhibited a great potential effect for controlling and suppress the feeding of larval stage on the host plants.

Larvicidal and Enzymatic Inhibition Effects of Annona muricata Seed Extract and Main Constituent Annonacin against Aedes aegypti and Aedes albopictus (Diptera: Culicidae).

The mosquitoes Aedes aegypti and Aedes albopictus are vectors of arboviruses that cause dengue, zika and chikungunya. Bioactive compounds from plants are environmentally sustainable alternatives to control these vectors and thus the arboviruses transmitted by them. The present study evaluated the larvicidal activity of an acetogenin-rich fraction (ACERF) and its main constituent annonacin obtained from Annona muricata seeds on Ae. aegypti and Ae. albopictus. The larvicidal assays were performed using different concentrations to calculate the LC50 and LC90 values observed 24 h after exposure to the treatment. Annonacin was more active against Ae. aegypti (LC50 2.65 μg·mL−1) in comparison with Ae. albopictus (LC50 8.34 μg·mL−1). In contrast, the acetogenin-rich fraction was more active against Ae. albopictus (LC50 3.41 μg·mL−1) than Ae. aegypti (LC50 12.41 μg·mL−1). ACERF and annonacin treated larvae of Ae. aegypti and Ae. albopictus showed significant differences in the inhibition of their metabolic enzymes when compared to untreated larvae. The results demonstrate the relevant larvicidal action of the acetogenin-rich fraction and annonacin showing the potential to develop new products for the control of Ae. aegypti and Ae. albopictus.

Negative cross resistance of Spodoptera litura Fabricius population of tomato to newer molecule spinetoram

Field population of Spodoptera litura from tomato ( resistant to the majority of the conventional insecticide molecules) were subjected to the in vivo toxicity of spinetoram 12 SC to assess whether cross resistance exists or not. Untreated larvae of both field and laboratory strains showed no mortality during 48 hours of feeding. After 48 hours of feeding on spinetoram 12 SC treated leaves, LC50s of field larvae were 0.28, 0.93, 3.71 and 7.11 ppm for the 2nd, 3rd, 4th and 5th instars of S. litura respectively. However, in the laboratory strain these values were 1.12, 5.86, 36.72 and 91.55 ppm for 2nd, 3rd, 4th and 5th instars of S. litura respectively. Resistance ratio was 0.25, 0.16, 0.10 and 0.08 for the 2nd instar up to the 5th instar of S. litura.

Correction to Influence of Thuja Essential Oil on Untreated Larvae and F1 Generation Larvae of Galleria mellonella Irradiated with Gamma Radiation

Correction to Influence of Thuja Essential Oil on Untreated Larvae and F1 Generation Larvae of Galleria mellonella Irradiated with Gamma Radiation

Biochemical characterization of spiromesifen and spirotetramat as lipid synthesis inhibitors on cotton leaf worm, Spodoptera littoralis

BackgroundTwo lipid synthesis inhibitors compounds (spiromesifen SPM and spirotetramat SPT) were used against the second instar larvae of cotton leaf worm, Spodoptera littoralis under laboratory condition. Toxicity of both compounds was tested. Effect of these insecticides on total lipid also was determined.ResultsThe obtained results showed that both compounds were moderately toxic against the second instar larvae of S. littoralis. The mortality percentages caused by the field rate of spiromesifen and spirotetramat were 51.7 and 60.0%, respectively. The lethal concentrations for 50% of tested insect population (LC50) were 170.1 and 42.2 ppm, respectively. The total lipid content was determined in treated larvae and compared with the untreated. The percentage of total lipid in spiromesifen- and spirotetramat-treated larvae was 2.17 and 2.21%, respectively, compared with 2.42% in untreated larvae. GC/MS also was used in identification of fatty acids composition of S. littoralis larvae.ConclusionThe results cleared that 13 fatty acids were identified in S. littoralis larvae. The obtained results showed significant difference in percentages of fatty acids with both treated and untreated larvae and also, between tested compounds. Some fatty acids were existed in untreated larvae but not existed in treated larvae.

Respiratory analysis as a tool to detect physiological changes in Anisakis larvae subjected to stress.

Human infection due to eating fish parasitized by live Anisakis larvae in the third stage is considered an important health problem, and the application of treatments to ensure their mortality in the fish products is crucial to prevent the risk of infection. Mobility is used to assess viability, but mobile larvae may not always be infective and immobile larvae may be erroneously considered as non-viable. The objective was to establish whether the analysis of respiratory activity by means of the oxygen consumption rate (OCR) of Anisakis could be used to identify subtle differences between larvae that were still considered viable in terms of their mobility but had been subjected to thermal and/or chemical stress. The metabolic modulators FCCP [carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone] and sodium azide were used and the basal, maximum, spare and residual respiration rates calculated. Results showed that maximum respiratory capacity of larvae subjected to freezing significantly decreased immediately after thawing, but after some acclimatization, they recovered their capacity fully. However, when these larvae were stored at 4.6°C, their mitochondria became dysfunctional faster than those of untreated larvae. OCR also showed that mitochondria of larvae were affected by incubation at 37°C in NaCl or gastric juice. To conclude, OCR of Anisakis in the presence of metabolic modulators can help to identify subtle changes that occur in the larva. These measurements could be used to characterize larvae subjected to various stresses so that a broader picture of Anisakis pathogenic potential can be gained.

Influence of Thuja Essential Oil on Untreated Larvae and F1 Generation Larvae of Galleria mellonella Irradiated with Gamma Radiation

The objective of the current study was to determine the fumigant toxicity of Thuja essential oil against 3rd and 5th instar larvae of the greater wax moth, Galleria mellonella. Thuja essential oil was extracted from unripe fruits of Thuja orientalis plant by water distillation. The mortality of larvae at the end of larval period, pupation and adult emergence were tested at different concentrations of Thuja oil after a 24h exposure period ranging from 5 to 25µL for 3rd instar larvae and 80µL for 5th instar. The combined effect of Thuja essential oil and larvae resulting from parents irradiated as pupae of G.mellonella with 80Gy was investigated. The results demonstrated that the mortality increased by increasing oil concentration. The percent mortality of 3rd instar larvae reached 100% when exposed to a higher concentration of Thuja oil (25µL) after 24h, while in the case of 5th instar larvae the mortality was 73.3% at (80µL). Larvae of both instars resulting from parents of G. mellonella irradiated as pupae with 80Gy and exposed to the same concentrations of Thuja oil vapor became more susceptible to the oil as a result of the combined effect of the two agents. The LC50 and LC90 values for each experiment were calculated. The tested plant oil prolonged the larval - pupal periods and reduced both pupation percentage of adult emergence.

Impact of modified atmospheres on respiration of last instar larvae of the rice moth, Corcyra cephalonica (Lepidoptera: Pyralidae)

Effect of modified atmospheres (MAs) containing CO2 at 20, 40, 60 and 80% or containing N2 at 97 and 98% on the mortality of Corcyra cephalonica Stainton (Lepidoptera: Pyralidae) sixth instar larvae was studied to determine the LT values at 30 °C. The respiration rates of untreated and treated larvae with 60% CO2 and/or 98% N2 at LT50 were measured using Q-Box RP1LP low range respirometry package. Total protein and triglycerides of treated and untreated larvae were assayed. Complete larval mortality was recorded after 72 and 144 h of treatment with 60% CO2 and 98% N2, respectively. Calculated LT50 values were 39.3 at 60% CO2 and 87.5 h at 98% N2 MAs. Respiration quotient (RQ) in the light of consumed O2 and produced CO2 of untreated larvae was 1.0 while it was 0.85 at 60% CO2 and 0.72 at 98% N2. Duration time necessary for produced CO2 curve to reach the maximum point (2000 ppm) was significantly shorter at untreated larvae (27.64 min) in comparison with that recorded at CO2 (35.48 min) which also significantly less than that obtained at N2 (98.54 min). At all treatments, total protein was decreased while triglycerides were increased in comparison with control.

Control of Culex pipiens (Diptera: Culicidae), the vector of lymphatic filariasis, using irradiated and non-irradiated entomopathogenic nematode, Steinernema scapterisci (Rhabditida: Steinernematidae)

The goal of this work was to investigate the effect of gamma irradiated entomopathogenic nematode EPN; Steinernema scapterisci on third and fourth larval instars of Culex pipiens under laboratory conditions and its effect on the elemental composition of the treated larvae. Results showed that normal and irradiated tested nematodes differed in their efficacies against third and fourth larval instars. The mortality rates increased with increasing the nematode concentration and the period after treatment, in most cases the mortality in fourth instar larvae was more than in third instar larvae under the same treatments, and the percentage of mortality in irradiated nematodes was more than that in unirradiated ones. Studying the elemental composition showed that phosphorus (P) was the highest concentration in untreated larvae or those treated with normal S. scapterisci, while calcium (Ca) was the highest concentration in gamma irradiated S. scapterisci. The lowest concentration in untreated larvae was zinc (Zn), while copper (Cu) was the lowest concentration in unirradiated and 2 Gy gamma irradiated S. scapterisci. In conclusion, the gamma irradiation of S. scapterisci enhanced its efficacy against C. pipiens, therefore it could serve as safe control method for C. pipiens.

The influence of low temperature and diapause phase on sugar and polyol content in the European corn borer Ostrinia nubilalis (Hbn.)

The European corn borer (ECB, Ostrinia nubilalis Hbn.) is a major pest in temperate regions of Europe and North America. Fifth instar ECB larvae enter diapause before winter and gradually develop cold hardiness. Here we investigated the combined influence of diapause phase and low temperature on sugar and polyol content in ECB larvae. Larvae in mid-diapause or diapause termination were acclimated at 5 °C, −3°C or −16 °C, and sugar and polyol content was measured using GC–MS. Control GC–MS measurements were conducted on untreated non-diapausing larvae. We detected differences in polyol (glycerol, sorbitol, myo-inositol) and sugar (trehalose, fructose, glucose) levels in diapausing versus non-diapausing larvae. Glycerol and trehalose were the most abundant of all analyzed cryoprotective compounds in diapausing larvae. Exposure of diapausing larvae to decreasing temperatures induced changes in polyol and sugar levels that depended on the phase of diapause. In mid-diapause larvae, decreasing temperatures induced a significant increase in glycerol and a decrease in sorbitol and myo-inositol. In larvae at diapause termination, polyol content was lower and less influenced by decreasing temperatures. In contrast, sugar levels were lower in larvae at mid-diapause versus diapause termination. Exposure of larvae to −16 °C induced a significant increase in the levels of all detected sugars. In particular, glucose levels were significantly higher in larvae at diapause termination following exposure to −16 °C. We propose that this shift toward sugar synthesis following low temperature exposure in larvae at diapause termination is a consequence of NADPH dependent polyol synthesis, and may be a mechanism for preservation of carbon reserves needed for post-diapause development.

Appraisal of Positive Pesticides Influence on Pink Bollworm Larvae, Pectinophora gossypiella (Saunders)

Experimentsconducted to study the toxic and biological effects of three chemicalinsecticides (chlorpyrifos, Lambda-Cyhalothrin, and Methomyl), onebiochemical insecticide (spinosad), and two bio-insecticides (Bacillusthuringiensis kurstaki Bt and Nucleopolyhedrovirus, NPV) against neonatelarvae of the pink bollworm, Pectinophora gossypiella (Saund.), were carried out underlaboratory conditions. The highest effect of tested pesticides on larvalmortalities was recorded after four days of feeding these larvae on treateddiet. Spinosad was the effective toxin (LC50=1.84 ppm) to neonatelarvae followed by chlorpyrifos (LC50= 3.06 ppm), Lambda-Cyhalothrin(LC50= 5.99 ppm) then Methomyl (LC50=23.50 ppm) but B.t.(74.84×104 I.U) and NPV (83.5×109 I.U) were the lowestones. LC50 treatments of neonate larvae with all tested insecticidesproduced reduction in larval and pupal weights especially Lambda-cyhalothrintreatment, (31.9 and 24.3 %, resp.) compared with untreated insects. Thedecreasing effect of all treatments observed in fecundity and life span ofadult females which reflected in very high percentages of insect sterility withchlorpyrifos (66.7%) and Methomyl (61%) treatments. Insignificant increase oftotal protein contents and activity of Glutathione-S-transferase enzyme wasdetected in tissues of LC50 treated larvae compared with untreated larvae,but a significant (23.5%) and highly significant (56.9%) increase in enzymeactivity were resulted by Chlorpyrifos and Spinosad treatments. A very highinhibition in activity of Acetylcholinesterase enzyme of larval tissues wasrecorded with NPV (61.3%), B.t. (58.8%), Lambda-Cyhalothrin (55.6%), Spinosad(54.4%), Chlorpyrifos (48.7%), and Methomyl (37.5%)treatments than untreated ones.

Gene expression of serine and cysteine proteinase inhibitors during cereal leaf beetle larvae feeding on wheat: the role of insect-associated microorganisms

Plants and insects have been coexisting for more than 350 million years. During this time, both have evolved many strategies to successfully exploit or respond to reciprocal adaptation and defense reactions. Plants tend to minimize the damage caused by pest feeding, while pests tend to manipulate plant response by suppressing plant defense mechanisms or developing strategies to overcome plant defense systems. Plants recognize insect pests by the wounding that they cause and elicitors present in pest oral secretions (saliva and/or regurgitant). These elicitors or insect-associated microorganisms can modulate plant response to the benefit of their insect hosts. In this article, we have undertaken an analysis of gene expression in serine and cysteine proteinase inhibitors (SerPI and CysPI, respectively) in wheat (Triticum aestivum) plants exposed to cereal leaf beetle (CLB, Oulema melanopus, Coleoptera, Chrysomelidae) larvae feeding, and the impact of microbes associated with CLB on the expression levels of these genes. Using three wheat varieties and antibiotic-treated and untreated CLB larvae, we found that SerPI plays a more important role than CysPIs in plant defense against CLB larvae. Additionally, higher levels of SerPI gene expression were observed in systemic leaves in comparison to the wounded leaves (local response). Each of the tested wheat varieties reacted in a specific way to the particular treatment. Moreover, the presence of microbial components associated with insects influenced plant response to CLB larvae feeding.

Influence of Bacillus thuringiensis toxins on the development and midgut proteases in different larval instars of Helicoverpa Armigera

Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) is one of the most important pest worldwide. Bacillus thuringiensis (Bt) toxins have used as a biopesticide or deployed in transgenic plants for controlling this pest. We examined the biological activity of Cry1Ac, Cry1Ab and Bt formulation in different larval instars of H. armigera with respect to larval development and proteolytic activity to pinpoint the most susceptible instar, and the insect response to ingestion of Bt toxins. In the presence of Bt toxins, the larval mortality and weight loss increased in a dose-dependent manner, and the maximum effect was observed in neonates. Active Cry1Ac toxin resulted in greater mortality and weight loss in all the larval instars. Total protease, trypsin and chymotrypsin activities declined in the presence of Bt toxins as compared to the untreated control in all the larval instars. Ten protease isozymes were observed in the untreated control larvae in second, third and fourth instars. Maximum protease isozymes inhibition was observed in Bt toxin fed neonates. Inhibition of protease activity increased with the concentration of Bt toxins. In presence of Bt toxins, aminopeptidase activity increased from II to IV instar and alkaline phosphatase activity decreased from II to III and then increased in IV instar. The pathogenicity of Bt was greater in early larval instars of H. armigera than the later instars, suggesting that application of Bt formulation or deployment of Bt toxins in transgenic plants should be directed against the early larval instars.

SUBLETHAL EFFECTS OF THE ESSENTIAL OILS OF GARLIC (ALLIUM SATIVUM) AND LEMON (CITRUS LIMON) ON NUTRITIONAL INDICES AND MIDGUT HISTOLOGICAL AND ULTRASTRUCTURAL CHANGES IN THE EGYPTIAN COTTON LEAFWORM (SPODOPTERA LITTORALIS)

The present study was carried out to evaluate the nutritional indices, histological (light microscopy) and ultrastructural (transmission electron microscopy) changes in the midgut of the 4th larval instar of Spodoptera littoralis treated with the LC30 of the essential oil of garlic (Allium sativum) (16.60×104 mg/l) and lemon (Citrus limon) (20.09×104 mg/l) based on leaf–dip method compared to untreated larvae (control). The results of the nutritional metabolism revealed a significant reduction in food consumption index (CI), relative growth rate (RGR), and approximate digestibility (AD) of treated larvae. On the contrary, the efficiency of conversion of ingested food to body mass (ECI) and the efficiency of conversion of digested food to body mass (ECD) increased significantly in treated larvae. The most prominent symptoms revealed by light microscopy on the midgut of the treated larvae were vacuolization of the epithelial layer, clumping of the nuclear chromatin material and degeneration of the peritrophic membrane and microvilli. On the other hand, transmission electron microscopy showed vacuolization and degeneration of the columnar cells, clumping of the nuclear chromatin, breaking of microvilli, loss of the cytoplasmic projections of the goblet cells, appearance of residual bodies, and disintegration of mitochondria. In particular, treatment with lemon oil resulted in the appearance of numerous lysosomes and electron-dense mitochondrial matrices. In conclusion, the reduction of the RGR would result in undersized females in the next generations; in turn this would lead to a reduction of the reproductive potential. Also, the present investigation indicates that the microvilli and/or mitochondria are the probable target site(s) of action of garlic and lemon essential oils.

Toxicity of Cholantraniliprole against Different Developmental Stages of the Cotton Leafworm under Laboratory Conditions

Spodoptera littoralis management has been counted on the application of the synthetic chemical pesticides, but becauseof insecticides resistant problems in the cotton leafworm, the competence of these chemical have been reduced. So, newinsecticides with different action could solve this problem. In this study, the activity of a new insecticide,chlorantraniliprole (Coragen® 20%SC), was evaluated against different stages of S. littoralis. For egg stage of S. littoralis,two different ages, < 24 h and 24-48 h were used and dipped in serial concentrations of chlorantraniliprole. The resultpresented that the young eggs were more sensitive than the old one with LC50 value of 126.6 mg/l in case in the youngeggs while it was 144.81 mg/l in the old one. In addition, the larvae of 2nd instar were exhibited a high susceptibility tochlorantraniliprole after 96 hrs. In contrast, when pupae were dipped in chlorantraniliprole different concentrations, theresult showed no significant pupal mortality (20%) in the lower concentration (200-800 ppm), while the highestconcentration (800 mg/l) showed 43.3% mortality. The letant effect of chlorantraniliprole at LC25 (0.036 mg/l) on 2ndinstar showed that the developmental time of larval and pupal stages has been prolonged and the percentage ofhatchability was reduced as contrasted to untreated larvae. The present results propose that Coragen® could be apotentially effective and likely to be an alternative insecticide that can be used for S. littoralis management in Egypt.

Behavior of detoxifying enzymes of Aedes aegypti exposed to girgensohnine alkaloid analog and Cymbopogon flexuosus essential oil

Because mosquito control depend on the use of commercial insecticides and resistance has been described in some of them, there is a need to explore new molecules no resistant. In vivo effects of girgensohnine analog 2-(3,4-dimethoxyphenyl)-2-(piperidin-1-yl)acetonitrile DPPA and Cymbopogon flexuosus essential oil CFEO, on the detoxifying enzymes acetylcholinesterase (AChE), glutathione-S-transferase (GST), nonspecific esterases (α- and β-), mixed function oxidases (MFO) and p-NPA esterases were evaluated on a Rockefeller (Rock) and wild Aedes aegypti population from Santander, Colombia (WSant). The action was tested after 24h of exposure at concentrations of 20.10, 35.18 and 70.35mgL−1 of DPPA and 18.45, 30.75 and 61.50mgL−1 of CFEO, respectively. It was found that AChE activity of Rock and WSant was not influenced by the evaluated concentration of DPPA and CFEO (p>0.05), while MFO activity was significantly affected by all CFEO concentrations in WSant (p<0.05). GST, α- and β-esterase activities were affected in Rock exposed at the highest CFEO concentration, this concentration also modified β-esterases activity of WSant. DPPA and CFEO sublethal doses induced inhibition of AChE activity on untreated larvae homogenate from 12 to 20% and 18 to 26%, respectively. For untreated adult homogenate, the inhibition activity raised up to 14 to 27% for DPPA and 26 to 34% for CFEO. Elevated levels of detoxifying enzymes, found when CFEO was evaluated, showed a larval sensitivity not observed by the pure compound suggesting that DPPA, contrary to CFEO, was not recognized, transformed or eliminated by the evaluated detoxifying enzymes.

Pine processionary moth (Thaumetopoea pityocampa, Lepidoptera: Thaumetopoeidae) larvae are highly susceptible to the entomopathogenic fungi Metarhizium brunneum and Beauveria bassiana

ABSTRACTThe larvae of the pine processionary moth (PPM), Thaumetopoea pityocampa, feed on the needles of pine and cedar. The urticating hairs of older instars pose a threat to human and animal health. Strains of the entomopathogenic fungi, Metarhizium brunneum (V275, ARSEF 4556) and Beauveria bassiana (KTU-24), were assayed against first to fourth instar T. pityocampa using doses ranging from 1 × 105 to 1 × 108 conidia mL−1. The three strains differed slightly in their virulence but caused 100% mortality of all instars at the highest dose. The newly emerged or first instar larvae were extremely susceptible with 100% mortality being achieved 2–4 days post inoculation with V275 at all but the lowest dose. The fourth instar larvae appeared to be less susceptible than earlier instars. There was good horizontal transmission of conidia from treated to un-inoculated larvae. However, mortality was higher in third and fourth instars and where the ratio of inoculated versus untreated larvae was high. This we presume is due to spores being more readily trapped by the urticating hairs found on third and older instar larvae. Injection of the nests offers a simple and environmentally friendly way of controlling the pest with reduced risk to operators.

Comparative in Vitro Evaluation of Three Geographically Different Isolates of Nucleopolyhedrovirus of Spodoptera littoralis in Egypt

The present study aimed to evaluate the effect of three isolates of Egyptian Nuclearpolyhedrovirus geographically different, namely NPV El-Qalioubia, NPV Al-Fayoum and NPV El-Beheira which isolated in Bio-insectcide Production Unit Plant Protection Research Institute, were evaluated against Spodoptera littoralis larvae under laboratory conditions. Five concentrations of Occlusion Bodies (OBs) from each of the three NPVs isolates (1×106, 1×107, 1×108, 1×109 and 1×1010 PIB/ml) were used against 2nd insters larvae of S. littoralis. The results showed that the percentage mortality of the larvae increased with increasing concentrations of tested pathogens. Also, the isolate NPV Al-Fayoum was the most effective against S. littoralis larvae at different tested concentrations. In biological Studies all tested NPVs isolates decreased the mean larval duration than untreated larvae and decreased of pupation.NPV Al-Fayoum recorded the least Pupation percentage 45.7%. All tested NPVs isolates showed significantly shortening in the mean adult longevity for both males and females. All tested NPVs isolates significantly decreased the mean number of eggs laid and hatched /female.

Susceptibilities of Geographic Populations of Helicoverpa zea (Lepidoptera: Noctuidae) in Mexico to Bt ∂-Endotoxins Cry1Ac and Cry2Ab: An 18-Yr Study.

An insect resistance monitoring program was developed for Mexico to accommodate the commercial introduction and stewardship of Bt cotton. Between 1998 and 2015, field-collected geographic populations of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) were evaluated against Cry1Ac and Cry2Ab proteins of Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) to establish baseline susceptibility data before the commercial use of Bollgard (Cry1Ac) and Bollgard II (Cry1Ac and Cry2Ab) cotton. An annual monitoring program was subsequently established in which a single diagnostic concentration of each Bt protein was used in a diet overlay bioassay. The diagnostic concentration represented the concentration where larvae, evaluated in baseline studies, were reduced in weight by ≥97% relative to untreated controls or failed to molt to third instar after 5 d. In the monitoring study, populations were tested against Cry1Ac from 1998 through 2015, and against Cry2Ab from 2002 through 2004 and again from 2007 through 2015. None of the Cry1Ac-exposed larvae tested during the 18-yr period reached the third larval instar after an exposure of 5 d, and weight reduction relative to untreated control larvae was uniform at about 98-99%. For the 12 yr of Cry2Ab monitoring, no larvae reached third instar, and weight reduction was uniform at >97% relative to controls. These results indicate that H. zea susceptibility to Cry1Ac and Cry2Ab has not changed during the period Bollgard and Bollgard II have been cultivated in Mexico.