2nd Larval Instars Research Articles

Evaluation of fluνalinate, methomyl and kinoprene on the greenhouse whitefly Trialeurodes vaporariorum West. (Homoptera: Aleyrodidae)

The effectiveness of three insecticides, fluvalinate, kinoprene and methomyl (synthetic pyrethrin, juvenile hormone analog and organophosphate, respectively), against the greenhouse whitefly, Trialeurodes vaporariorum West. (Homoptera: Aleyrodidae), was evaluated in commercial greenhouses. The impact of chemicals was studied on isolated whitefly stages in a rearing room (24 ± I”C, 65 ± 5% R.H. and L:D 16:8h). Fluvalinate was the most effective toxicant through its broad activity on whitefly life stages. Kinoprene controlled 2nd and 3rd larval instars but a moderate effectiveness was noticed on eggs, first instar larvae and pupae. Methomyl was effective against first instar larvae and adults but it had no substantial effect on the other stages. Of the three materials tested only fluvalinate approached the total control requirements for a successful whitefly suppression.

Characterization of Juvenile Hormone Related Genes Regulating Cantharidin Biosynthesis in Epicauta chinensis

Cantharidin is a defensive toxin biosynthesized by blister beetles. It is well known for medical applications and toxicity. However, the biosynthesis process of cantharidin is still not well understood. In the present study, three genes (methyl farnesoate epoxidase (EcMFE), juvenile hormone acid O-methyltransferase (EcJHAMT) and juvenile hormone epoxide hydrolase (EcJHEH)) were identified from Epicauta chinensis. The temporal and spatial expression patterns of these three genes revealed that the expression levels of EcMFE and EcJHEH were high in the first instar larval stage of E. chinensis with EcJHEH transcripts highest in the fifth larval instar. The expression level of EcJHAMT was significantly higher in the 2nd and 3rd larval instars. The transcripts of EcMFE, EcJHEH and EcJHAMT showed a similar tendency with the cantharidin production in male blister beetles after mating. We verified the functions of these three genes in cantharidin biosynthesis using the RNA interference method. Interference of EcMFE and EcJHEH significantly inhibited the biosynthesis of cantharidin in male E. chinensis after mating, but interference of EcJHAMT has no apparent influence on cantharidin biosynthesis. We propose that EcMFE and EcJHEH may be involved in the biosynthesis of cantharidin, but JH III might not be the direct precursor of cantharidin.

EFFICACY AND VIRULENCE OF Spodoptera littoralis NUCLEOPOLYHEDROVIRUS on S. littoralis LARVAL FEEDING AND SUSCEPTIBILITY

Entomopathogenic baculoviruses have long been recognized as vital environmentally safe alternatives to chemical pesticides. A study for investigating the virulence and susceptibility of Spodoptera littoralis larvae to S. littoralis nucleopolyhedrovirus (SpliNPV) isolate was carried out. Bioassay experiments on the 1st and 2nd larval instars using droplet feeding method revealed that polyhedral for 50% or 90% mortality of the 2nd larval instar of S. littoralis was significantly lower compared with the 1st instar. While, the 1st instar was killed faster than the 2nd one especially with the higher concentration. The susceptibility of the infected 2nd instar when feeding on different hosts showed that larvae were more susceptible when feeding on eggplant leaves followed by lettuce leaves, artificial diet and tomato leaves as shown by larval weight and reduction in feeding. The reduction in both larval weight and feeding were significantly higher with 1x107 PIB/ml than 1x104 PIB/ml in the majority of cases. S. littoralis larvae showed more than 2 times of tolerant to the 3rd passage of SpliNPV on the level of LC50 and more than 18 times tolerant on the level of LC90. The tolerant levels of S. littoralis larvae for the 3rd passage of virus was associated with more than 20% increase in time taken for kill with no changes in DNA patterns regarding subsequent passages in S. littoralis larvae using a restriction enzyme EcoRI.

Management of the Greater Wax Moth Galleria mellonella with Neem Azal- T/S, in the Laboratory and under Semi-Field Conditions

Abstract Different concentrations of Neem Azal-T/S were used in an artificial diet, to study the mortality of the greater wax moth Galleria mellonella. A Neem formulation and different ages of natural beeswax combs were used for the effective management of the wax moth. While the diet was being prepared, Neem Azal-T/S was directly added ensure that the Neem formulation was distributed evenly in the diet at concentrations of 0.25, 0.5, 1, 2, and 4%. The obtained results showed that the different concentrations of Neem Azal-T/S mixed in the prepared artificial diet had a significant efficacy against the tested 2nd instar larvae. An outstanding elongation of the 2nd larval instar was clear in comparison with the control, even at the least tested concentration (0.25%). Neem Azal-T/S at 4, 2,1, and 0.5% caused 100% mortality for all tested larvae. When using a 4% concentration, all the tested larvae died in the 2nd instar. However, when using a 2% concentration, the larvae died in the fifth instar. When using a decreased concentration of 1.0 and 0.5%, some of the larvae were tolerant and lived till the 6th instar. Feeding the larvae on beeswax combs treated with 2% Neem Azal-T/S, caused 100% mortality when fed on very old wax. When the diet was old wax treated with 2% Neem Azal-T/S, a 91% mortality was recorded. When the diet was new wax treated with 2% Neem Azal-T/S, a 90% mortality was recorded. A 4% Neem formulation caused mortality for all larvae during the first week of treatment on the different tested ages of beeswax combs.

Chemical composition and insecticidal effects of the essential oil of cardamom, Elettaria cardamomum on the tomato leaf miner, Tuta absoluta

Tuta absoluta is one of the key pests of Solanaceae family in the world. This insect is an oligophagous pest and its larva causes damage on the host plants by feeding on leaf, stem and fruit of them. In the current study, chemical composition and insecticidal activities of the essential oil from cardamom, Elettaria cardamomum on egg, the 2nd larval instars and adults of T. absoluta were evaluated. Results indicated that oil is toxic to the T. absoluta. The major components in the oil were as follow: terpinenyl acetate (36.61%), 1,8-cineole (30.42%), linalyl acetate (5.79%) and sabinene (4.85%). LC50 values for eggs, larvae and adults were 351.19, 7.88, 1.55 and 1.88 μl L−1 air, respectively. The tomato leaf miner (TLM), T. absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a important pest on tomato, potato and other Solanaceous with a huge economic importance. TLM can be regarded as a serious threat to tomato production in Iran. TLM larvae cause about 100% losses by attacking tomato leaves, flowers, stems and especially fruits. The discovery of active compounds that are less persistent will be beneficial to both the environment and agricultural product consumers. Management of the pest can be problematic, especially when the infestation pressure is high. The utilization of natural compounds such as plant essential oils is considered as a alternatives to chemical pesticides because of their lower toxicity on the non-target and low persistence in the environment. In the present study, the chemical composition and insecticidal activities of the essential oil from cardamom, E. cardamomum (Maton) (Zingiberales: Zingiberaceae) on egg, the 2nd larval instars and adults of T. absoluta were evaluated. The essential oil was obtained by hydrodistillation method, using a modified clevenger-type apparatus. Experiments were performed at 27 ± 2 °C, 65 ± 5% RH and 16 L:8D h photoperiods. Results showed that the essential oil of E. cardamomum is toxic to T. absoluta. The major components in the oil were α-terpinyl acetate (36.61%), 1,8-cineole (30.42%), linalyl acetate (5.79%) and sabinene (4.85%). Probit analysis showed that the LC50 values for eggs, 2nd larval instar (inside leaf, outside leaf) and adults were 351.19, 7.88, 1.55 and 1.88 μl L−1 air, respectively. The overall results showed that cardamom essential oil has high potential in controlling TLM, especially in protected areas.

EVALUATION OF THE EFFICACY OF TWO BIOAGENTS AGAINST THE COTTON LEAFWORM, SPODOPTERA LITTORALIS (BOISD.), USING MOLECULAR CHARACTERIZATION TECHNIQUES

molecular studies have been carried out on 6th instar larvae of Spodoptera littoralis which treated in 2nd larval instars with LC50 of two bioagents named Viruset and Protecto at 1x103 PIBs/ml and 3.2x102 IU/ml., respectively. Four random primers were used in this study to generate a fragmenting pattern as a tool to investigate the molecular differences between treated samples and control. The numbers of unique and common fragments generated by using these primers (OPO1, OPO2, OPO3 and OPO4) was recorded. It has been found that primer OPO4 was the most powerful one in generating a unique informative fragmenting pattern; it gives 4 specific unique fragments. While the primer OPO1 was the poorest one in generating an informative fragmenting pattern.

Histopathological effects of Diflubenzuron and Chromafenozide (IGRs) on egg development in the cotton leafworm Spodoptera littoralis (Boisd) (Lepidoptera, Noctuidae)

The present study was undertaken to investigate the possible pathogenic impacts of the LC50 of the two insect growth regulators: the chitin synthesis inhibitor, Dimilin® (Diflubenzuron), and the ecdysone agonist, Virtu® (Chromafenozide) on the ovarian tissue of adult female Spodoptera littoralis. Therefore, the LC50 (1.3 & 3 ppm of Dimilin® and 0.1 ppm of Virtu®) were applied to the 2nd and 4th larval instars, respectively. The meroistic polytrophic ovariole of S. littoralis is divided into a terminal filament, a germarium and a vitellarium; the germarium contains the oogonia and the follicular cells that surround the oocytes to form the ovarian follicles in the vitellarium. The ovarian follicles of treated F1 females with Dimilin® exhibited vacuolization, stuffing of follicular sheath, loss of vitellin and degeneration of many cell components of follicular epithelium and oocytes. These obvious signs of damage were increased when using 4th larval instars treatment than the 2nd.Also, damage was pronounced in the ovarioles of the Virtu® treated F1 females. Ovariole growth was stunted and vitellogenesis and chorion formation were inhibited. So, this work shows the high potency and efficacy of the two IGRs on developed ova of S. littoralis

The endophytic fungal entomopathogens Beauveria bassiana and Purpureocillium lilacinum enhance the growth of cultivated cotton (Gossypium hirsutum) and negatively affect survival of the cotton bollworm (Helicoverpa zea)

The effects of two entomopathogenic fungal endophytes, Beauveria bassiana and Purpureocillium lilacinum, were assessed on the growth of cultivated cotton (Gossypium hirsutum) and development of the cotton bollworm (Helicoverpa zea). In two replicate greenhouse trials, cotton plants were inoculated as seed treatments with two concentrations of B. bassiana or P. lilacinum conidia and evaluated for effects on both plant dry biomass, number of nodes and number of developing flowers (squares). We similarly treated cotton plants and evaluated H. zea performance using no-choice in planta assays starting at the 2nd larval instar. Treatment with both fungal endophytes resulted in a significant increases in plant dry biomass (ANOVA, P=0.024). Plant developmental stage and number of squares were also significantly enhanced in the endophyte treated plants (ANOVA, P=0.005 and P=0.027, respectively). The survivorship of H. zea was significantly different among the endophyte treatment groups (Kaplan–Meier, P=0.02), where insects feeding on control plants exhibited higher survival than insects on the endophyte treated plants. There were no significant endophyte treatment effects on larval or pupal weights of H. zea individuals. There was no endophyte effect on days to pupation among treatments, but there was a marginal effect on days to eclosion (Kaplan–Meier, P=0.07). Overall, our results demonstrate (i) the positive plant growth enhancing effects of the target endophyes on cultivated cotton under greenhouse conditions and (ii) the negative effects of endophytic P. lilacinum and B. bassiana on H. zea survivorship and development using whole plant assays.

ROLE OF CERTAIN BEAUVERIA BASSIANA (BALS.) ISOLATE AS BIOLOGICAL CONTROL AGENT AGAINST COWPEA APHID (Aphis craccivora koch) AND ITS EFFECT ON THE PREDATOR Chrysopela carnea (STEPHENS).

The lethal effect of Beauveria bassiana isolateon Aphis craccivora revealed that the least percentage of adult mortality was 11%, which was recorded with the lowest tested concentration (1X103spores/ml), while The highest percentage of adult mortality was (54%) was achieved at (1X107spores/ml). compared with 4% in natural mortality. In a similar trial to evaluate the effect of B. bassiana against the aphid lion Chrysopela carnea (Stephens), exposure of the 2nd larval instar of aphid lion to B. bassiana isolateeither through direct or indirect exposure resulted in adverse effects on the total percent of larval mortality, which was concentration dependent. Whereas the total larval death recorded 3% in control trials, data in case of direct exposure revealed 9 to 41% of larval death at 1X103 and 1X107 spores/ ml, respectively, Comparable trend was recorded with larvae indirectly exposed. A slight increase in larval mortality was recorded by 5 to 15 %, respectively. In case of direct exposure technique the hatchability percentage decreased by increasing fungal concentration. The fluctuation in the indirect exposure technique did not statistically differ from that recorded in case of control trials.

EVALUATION OF ENVIRONMENTAL SAFE NATURAL COMPOUNDS IN CONTROLLING COTTON LEAFWORM Spodoptera littoralis.

The toxicity of azadirachtin, pyridalyl and quercetin compounds were evaluated against the immature stages of the cotton leafworm, Spodoptera littoralis, field strain andlaboratory susceptible strain.The results showed that azadirachtin was the most potent tested compound flowed by pyridalyl and the least one was quercetin. Azadirachtin at 15.0 ppm achieved 30.4% mortality of treated egg masses, while pyridalyl and quercetin at the same concentration caused 28.8% and 21.2% mortality of treated egg masses, for lab strain, respectively, while field strain at the same concentration caused 23.4%; 20.4% and 16.4% mortality of treated egg masses respectively. The toxicity of tested compounds were evaluated against 2nd and 4th larval instar of S. littoralis, cleared that the toxicity of the tested compounds increased with increasing the exposure time, decreased by increasing the stage of larval instars. The larvae stop eating after two days of treatment. Also, the tested compounds shows no pupal mortality after 24; 48, and 72 hrs of treatment, but significantly increased percentages of deformed of adults. Results proved that the three natural compounds (azadirachtin, pyridalyl and quercetin), are potentially potent for control of S. littoralis, as antifeeding. Generally, natural compounds, will produce a new trend to increase toxicity of the newly hatched larvae of S. littoralis, enhance the role of beneficial insects. These compounds could be used in the IPM programmes, in order to minimize the negative effects of conventional insecticides on environment components and to protect the natural enemies.

EFFECT OF BUXUS CHINENSIS, DIPEL 2X AND NUCLEAR POLYHEDROSIS VIRUS (NPV) MIXTURE ON SOME IOLOGICAL ASPECTS OF COTTON LEAFWORM SPODOPTERA LITTORALIS

Effects of Buxus chinensis extract, Bacillus thuringiensis and nuclear polyhedrosis virus (NPV) mixture on certain biological aspects of Spodoptera littoralis were studied against the 2nd and 4th larval instars of S. littoralis. The mixture of the three compounds was the most toxic against the 2nd and 4th instar larvae, where it caused high percentage of mortality, while B. thuringiensis (Dipel 2x) and nuclear polyhedrosis virus (NPV) mixture induced a slight effect against the 2nd and 4th instars. Regarding the ethanolic extract of Buxus chinensis leaves, it was more effective than B. thuringiensis (Dipel 2x) or nuclear polyhedrosis virus (NPV) in respect of pupal mortality and larval , pupal and adult duration. This plant extract also reduced the fecundity and fertility of females emerged from the treated larvae of S. littoralis.

Effects of pyridalyl and emamectin benzoate on some biological and biochemical parameters of Spodoptera littoralis (Boisd.) and Albino rat.

The present investigation aimed to throw light on the efficiency of two novel insecticides, pyridalyl and emamectin benzoate(contact), a semi-synthetic insecticide on two different larval instars (2nd and 4th) of the cotton leafworm, Spodoptera littoralis (Lepidaptera: Noctuidae). Also to study their toxic affects on some biochemical parameters on albino rat. The results clearly showed that pyridalyl was more toxic than emamectin benzoate against the 2nd and 4th larval instar according to LC50 values after all time post exposure (2, 3, 5 and 7 days). In addition the two tested compound decreased pupal weight, pupation and adult emergence percentages resulted from larvae treated with different concentrations of these insecticides as 2nd and 4th larval instars. The present study also animals were treated orally with (1/10 LD50) of each compound done by using sixty male adult albino rats were divided into three groups .First group control was received distilled water daily, second group were received repeated oral administration of 0.07mg/animal/day of pyridalyl and third group were received repeated oral administration of 2.5 mg/animal / day of emamectin benzante for 28 consecutive days. The results showed that there were significant increases of ALT, AST, urea and creatinine in the treatment of Pyridalyl more than emamectin benzante and control. On the other hand there were significant decreases in protein content in the treatment of Pyridalyl more than E. benzante on comparison with control. Conclusion: The results indicated the toxic nature of the insecticide pyridalyl is more than E. benzante on Spodoptera littoralis and albino rats so we suggest that usage of E. benzante although it less toxic to save environment

COMPARATIVE TOXIC ACTIVITY OF FOUR ALGAE, AGAINST THE 2ND AND 4TH LARVAL INSTARS OF BLACK CUTWORM, AGROTIS IPSILON (HUFNAGEL)

The dry biomass of four cyanobacterial microalgal strains Anabaena flos aquae, Anabanea laxa, Anabanea fertilissima and Nostoc muscorum was evaluated in invitro assay as a biopesticides against 2nd and 4th instars of Agrotis ipsilon. Larvae were fed on leaf discs painted with the algal solution for 24h. The 2ndinstar larvae were more susceptible than the 4th ones to the four tested algal treatments. N. muscorum treatment was the most toxic one against the 2nd and 4th larval instars. Where, its LC50values were 45 and 150 mg/ml, respectively while, A. fertilissima was the least one, its LC50 values were 250 and 660 mg/ ml, respectively. All the treated larvae were susceptible to four tested algal treatments and its resistance varied according to the larval instars and tested alga. Marked decrease in pupation for both 2nd and /or 4thinstar by the four algal treatments, whereas, the 2ndinstar treated with N. muscorum alga exhibited the most suppressive decrease to 44%, as compared to control (97%). Significant reduction for pupal weight, where, 4thinstar treated with A. flos aquae alga recorded the highest pupal weight decrease to average 290mg, as compared to 484mg of control. Besides prolonging pupal duration where, treatment for both instar with A. flos aquae and A. laxa algae induced the longest period and increased the pupal malformation percent where, 4thinstar treated with N. muscorum and A. flos aquae algae induced noticeable percent reached to21.3 and20% and increased adult malformation to30 and20% respectively, as respect to control. However, the larval treatment of 2nd instar with N. muscorum and A. fertilissima algae had the strongest effect in larval duration increase to average25 and 25.8day as compared to20.4day of control. In addition, the larval treatment of 4thinstar with the four algae decreased the adult fecundity and fertility. Moreover, N. muscorum and A. flos aquae algae inhibited the adult fecundity and eggs fertility to zero, as compared to505eggs/female of control. Marked declining of adult longevity with N. muscorum, A. flos aquae and A.laxa to average 7day, as compared to11day of control. Also, the treatment with the three algae disorder the sex ratio of males and females, as compared to that of control. While the larval treatment with A. fertilissima alga didn't affect the pupal malformation, eggs fertility, adult longevity and sex ratio.

Insecticidal Efficiency and Latent Effect of certain IGR Compounds on Cotton Leafworm Spodoptera littoralis (Boisd.) in El-Gemmeiza Agricultural Research Station during season 2011

During summer season 2011 an experiment was carried out at El Gemmeiza Agricultural Research Station, Gharbia Governorate to evaluate the efficiency and latent effect of six IGR compounds on 2nd and 4th larval instars of cotton leafworm Spodoptera littoralis (Boisd.). The tested compounds were: Caprice, Kingbo, Leveuron, Steward, Virtu and Dimeuron. The efficiency and residual effect proved that these products induced high efficacy in this respect . The Leveuron compound was the most effective compared with other compounds, while Steward recorded the least toxic product on both 2nd and 4th instars as the initial effect. Reduction percent at end of larval stage of the 2nd and 4th instar larvae ranged between 100% and 50% for Leveuron and Steward; respectively. Also, results obtained indicated that Caprice, Kingbo and Dimeuron compounds induced high level of reductions of insect population. The residual effect of the tested compounds after 7, 14 and 21 days proved that Leveuron treatment had the highest efficacy against cotton leafworm S. littoralis which ranged between 100% to 88%, while Steward treatment gave the lowest one in both larval stages. The biological aspects of These compounds showed that all treatments succeeded in reducing the weights, the instar period of larvae and the leave consumption for the 4th instar larvae.

Gender and timing during ontogeny matter: effects of a temporary high temperature on survival, body size and colouration in Harmonia axyridis.

The ambient temperature experienced during development is a crucial factor affecting survival and adult phenotype in ectotherms. Moreover, the exact response of individuals to different temperature regimes is frequently sex-specific. This sex-specific response can result in varying levels of sexual dimorphism according to the experienced conditions. The majority of studies have investigated the effects of temperature on individuals reared under a constant temperature regime throughout their whole preimaginal development, whereas information on stage-dependent variation in temperature effects is scarce. Here we investigate how the stage at which elevated temperature is experienced influences survival, adult body size and colouration in the harlequin ladybird Harmonia axyridis form succinea. The effects of timing of exposure to elevated temperature on the adult phenotype are assessed separately for males and females. Control individuals were reared at a constant temperature of 20°C. Beetles in other treatments were additionally exposed to 33°C for 48 hours during the following developmental stages: egg, 1st to 2nd larval instar, 3rd larval instar, 4th larval instar and pupa. Exposure to an elevated temperature during the early developmental stages resulted in lower survival, but the adult phenotype of survivors was almost unaffected. Exposure to an elevated temperature during the later developmental stages (4th larval instar or pupa) resulted in the decreased melanisation of elytra, decreased structural body size and increased dry mass. Furthermore, the timing of high temperature exposure affected the degree of sexual dimorphism in elytral melanisation and dry mass. We demonstrate that the effects of elevated temperature can vary according to the developmental stage at exposure. Detailed information on how ambient temperature affects the developmental biology of ectotherms is crucial for modeling population growth and predicting the spread of invasive species such as Harmonia axyridis.

TOXIC AND ANTIFEEDING ACTIVITIES OF CERTAIN PLANT EXTRACTS AND THEIR EFFECTS ON BIOLOGICAL AND BIOCHEMICAL ASPECTS OF THE COTTON LEAFWORM SPODOPTERA LITTORALIS (BOISD.

The present work aimed to study the toxic and antifeeding activities of certain plant extracts against Spodoptera littoralis (Boisd.) The extracts of lantana and lemongrass leaves were applied at 5 & 10% concentrations, against 2nd and 4th instars larvae of S. littoralis under laboratory conditions 27 ± 2 °C and 55 – 65% relative humidity. Results showed that the lemongrass extract in water at 10% conc. on the 2nd larval instar and lantana extract in water at 10% conc. on 4th larval instar were the highest in efficacy as antifeedants. Regarding, conversion of ingested and digested food (ECI) & (ECD) lantana extract in water 10% had the least effect. The highest mortality percentage was attained from the lemongrass extract in acetone 10% and lantana extract in water 5% treatments against both the 2nd and 4th larval instars, respectively. Data showed that all the plant extracts caused significant reductions in respect of larval and pupal durations, pupal weight and % of adult emergence compared with the untreated check. The plant extracts had a clear effect on the carbohydrates hydrolysis enzymes as amylase and trehalse

Age Preference and Fitness ofMicroplitis manilae(Hymenoptera: Braconidae) Reared onSpodoptera exigua(Lepidoptera: Noctuidae)

The larval parasitoid Microplitis manilae Ashmead (Hymenoptera: Braconidae) is a potential biological control agent of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). To understand the preference and fitness of M. manilae on larval instars of S. exigua, we compared host choice, development, and life table parameters when different larval instars of S. exigua were supplied in the laboratory. Results showed that parasitism of 2nd or 3rd instar larvae was significantly higher compared with other instars. The intrinsic rate of increase (r), finite rate of increase (λ), net reproduction rate (R0 ) and mean length of a generation (T) were significantly affected by which larval instars were attacked. The maximum values of r, λ, R0 and T were observed when M. manilae parasitized 2nd instar S. exigua larvae. Therefore, we conclude that the 2nd larval instar of S. exigua represents the optimum host stage and suggest that 2nd larval instar of S. exigua will be the most suitable host stage for mass production of M. manilae as well as the best instar to target for biological control in the field.

Comparative efficacy of certain plant extracts alone and combination with profenofos against Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

Ethyl alcohol, acetone, and petroleum ether extracts of three plant species belonging to three different botanical families [Strychnos nux-vomica (Loganiaceae), Euphorbia lathyrus (Euphorbiaceae), and Datura stramonlum (Solanaceae)], a chemical insecticide; profenofos and their combinations were tested against second and fourth instars of Spodoptera littoralis under lab conditions. Results revealed that the ethanol extract of S. nux-vomica was the most effective among all plant extracts, where the corrected mortality% were 92, 81, 58, and 27% to 2nd instar and 89, 74, 34, and 11% to 4th instar at concentrations 0.5, 0.25, 0.125, and 0.0625%, respectively. Calculated LC50's were 0.11, 0.22, and 0.34% to 2nd instar and 0.17, 0.37, and 0.52% to 4th instar for ethanol, petroleum ether, and acetone extracts, respectively. Acetone extracts of all plants were of lower effect. The chemical insecticide profenofos displayed higher efficacy than plant extracts (LC50 = 0.002 and 0.003% for S. littoralis 2nd and 4th larval instars, respectively). The co-toxicity factor reached 76 and 60 when mixing S. nux-vomica + profenofos and D. stramonlum + profenofos at ratio 1:1 against S. littoralis 2nd instar larvae, thus indicating a potentiating effect. While treatment of the 4th instar larvae by the same mixtures resulted in a co-toxicity factor below 20 at all mixing ratios indicating, only, an additive effect against this instar.

RESIDUAL ACTIVITY OF METHOMYL AND RADIANT INSECTICIDES AGAINST THE LARVAE OF COTTON LEAFWORM, SPODOPTERA LITTORALIS (BOISD.)

The bio-residual activity of two compounds, methomyl and radiant against the 2nd and 4th instars larvae of the cotton leafworm, Spodoptera littoralis was evaluated under laboratory and semifield conditions. The obtained larvae were fed for 24h on cotton leaves treated with methomyl compound and for 48h on the leaves treated with radiant at 0, 3, 7,9 and 12 days after the treatment. The 2nd instar larvae treated with radiant were more susceptible than the fourth ones. While the treatment of both 2nd and 4th larval instars with the methomyl at the three tested leaf residues 0, 3 and 7days had the highest effect, it caused 100 % mortality. Whereas, the larval treatment with radiant was more higher residual effect than the methomyl after feeding on leaves at 12 days post treatment, it caused 70 and 60% larval mortality of both 2nd and 4th instars, respectively, compared to 60 and 50% for the two instars, respectively, treated with methomyl. Methomyl and radiant treatments had a latent effect on the biological activities of this insect when the larvae fed on leaves at 12 days post treatment. The effect was varied according to the larval instar and tested compound. It was found that the treatment of 2nd and 4th instars larvae with radiant had the strongest effect. It caused an increase in the larval duration and pupal malformation and reduced the pupal weight. While, the treatment of 2nd and 4th instar with methomyl was higher reduced the adult emergence and increased the adult malformation percentages. The treatment of the 2nd instar larvae with the two compounds had the highest effect in decrease the pupation percentage to reach 50 and60% compared to control. While the treatment of the 4th instar with radiant at the 12day age leaf residues had the most potent in the fecundityinhibition to reach zero eggs/female in comparison to 569+113.2 eggs/female of control, and it reduced the eggs hatching to reach 0% as compared to 99% of control. While the larval treatment of the 4th instar with the both methomyl and radiant had significant decrease in the adult longevity .Whereas, the larval treatment of the same instar with methomyl had the highest effect in adult sex ratio shifting of both males and females as compared to that of control and the radiant had the next effect in this respect

HOST KIND EFFECT ON ACUTE TOXICITY OF SOME INSECTS GROWTH INHIBITORS ON LARVAL INSTARS OF Plodia interpunctella (Hub.)(Pyralidae : Lepidoptera)

The results of the recent study showed that the host kind and larval instars exhibit a varying response to the insects growth inhibitors ( Buprofezin . Cyromazin and Lufenuron ). And the 1st and 2nd larval instars were more susceptible than the rest larval instars to the insects growth inhibitors the highest toxicity to the 1st and 2nd larval instars reached on casher obtained from Lufenuron and 1st Lc50 reached 0.5% in comparison to Cyromazin and Buprofezin Lc50 values 0.7 and 0.6% respectively the highest relative toxicity value reached 100% for Lufenuron and Cyromazin for the 1st and 2nd larval instars reared on cashew respectively . and the lowest relative toxicity value was obtained from treating 3rd larval instars reached on almond with Lufenuron which reached 27.77 . The highest relative efficiency value reached 36% from treating the 1st and 2nd larval instars reared on cashew by Lufenuron followed by 214.28% for Cyromazin when applied on the same larval instars reared on Pistachio . The lowest relative efficiency value 100% obtained from treating the 3rd larval instars reared on Pistachio by Lufenuron and the 4th larval instars reared on Pistachio by Cyromazin.