3rd Instars Research Articles

Efficacy of nano-formulated certain essential oils on the red flour beetle Tribolium castaneum and confused flour beetle, Tribolium confusum (Coleoptera: Tenebrionidae) under laboratory and storage conditions

AbtractBackgroundThe confused flour beetles Tribolium confusum (Jacquelin) and red flour beetle Tribolium castaneum (Herbst) are widespread insects found in the stores and homes that attack many stored foods in several commodities. They are controlled by synthetic chemical insecticides. The natural oils give good results in controlling these pests and decreasing its infestations. The natural essential oils have a low effect on the human, non-target insects, and do not pollute the environments. This research is an alternative approach to naturally control these two stored product pests.MethodsNano-formulations of four essential oils, namely, coriander, black seed, caraway oil, and Janesville were tested against T. confusum and T. castaneum in the laboratory and stored conditions. Encapsulation method by the technology of polymerization was followed. The nano-oils were tested at the concentrations of 0.5% against the 3rd larval instars. Cumulative percentages of mortality was determined after 7 days of the first applications. The effect of nano-oils on oviposition was carried out by spraying 2 g of foams of the tested oils and their nano-formulations mixed with 100 g of wheat.ResultsThe results obtained showed that the percentage of larval mortality of T. confusum and T. castaneum increased with an increase in the treatment concentrations. Larvae of T. confusum were more susceptible to the treatments than T. castaneum larvae. Nano Janesville oil was more effective than that of coriander or black seed oil. Fecundity and adult emergence percentage are highly suppressed by nano-formulations of coriander, black seed, or Janesville oils under storage conditions, compared to those of the controls or non-nano-oils.The results suggested that nano Janesville can be used as a valuable tool in pest management programs of T. confusum and T. castaneumConclusionThe results of this work indicate that some essential oils might be helpful management of pests in the stores because of their fumigant and odor action. Essential oils of plant origin contain active ingredients that are effective against many insects. Nano-formulations of essential oils, through controlled release, prevent rapid vaporization and degradation and increase the stability of the oils. Treated foam, using coriander, Janesville, caraway, and black seed (habat al Baraka) oils, gave protection against the red flour beetles Tribolium castaneum and confused flour beetle Tribolium confusum.

Transcriptome analysis of a social caterpillar, Drepana arcuata: De novo assembly, functional annotation and developmental analysis.

The masked birch caterpillar, Drepana arcuata, provides an excellent opportunity to study mechanisms mediating developmental changes in social behaviour. Larvae transition from being social to solitary during the 3rd instar, concomitant with shifts in their use of acoustic communication. In this study we characterize the transcriptome of D. arcuata to initiate sociogenomic research of this lepidopteran insect. We assembled and annotated the combined larval transcriptome of “social” early and “solitary” late instars using next generation Illumina sequencing, and used this transcriptome to conduct differential gene expression analysis of the two behavioural phenotypes. A total of 211,012,294 reads generated by RNA sequencing were assembled into 231,348 transcripts and 116,079 unigenes for the functional annotation of the transcriptome. Expression analysis revealed 3300 transcripts that were differentially expressed between early and late instars, with a large proportion associated with development and metabolic processes. We independently validated differential expression patterns of selected transcripts using RT-qPCR. The expression profiles of social and solitary larvae revealed differentially expressed transcripts coding for gene products that have been previously reported to influence social behaviour in other insects (e.g. cGMP- and cAMP- dependent kinases, and bioamine receptors). This study provides the first transcriptomic resources for a lepidopteran species belonging to the superfamily Drepanoidea, and gives insight into genetic factors mediating grouping behaviour in insects.

The efficacy of seed extract of Tephrosia vogelii and Annona squmosa on larvae of Helicoverpa armigera

Abstract. Nenotek PS, Ludji R. 2020. The efficacy of seed extract of Tephrosia vogelii and Annona squmosa on larvae of Helicoverpa armigera. Trop Drylands 4: 5-9. Corncob borer (Helicoverpa armigera) is important pest of corn, urging the use of insecticide for its eradication. While using chemical insecticides is not sustainable, the use of plant-based insecticides is thus recommended. This study aimed to determine the efficacy of Annona squamosa and Tephrosia vogelii seed extract mixture on the mortality of 3rd instar larvae of Helicoverpa armigera. A range of concentration, as treatments, were evaluated, i.e., 0.05%, 0.11%, 0.28%, 0.65%, 1.5% and a control (water only) applied with three replicates in each treatment. Ten larvae of H. armigera at each treatment were infested in baby corn, using the residue method. Mortality was observed at 24, 48, 72, 96, and 120 hours after treatment (HAT). Percent mortality of the 3rd instar of H. armigera larvae was analyzed using Probit Polo PC, then proceed with mixed activity analysis. The results showed that the mixture of A.squamosa + T. vogelii seeds extracts killed H. amigera larvae with the value of LC50 and LC95 of 0.07% and 2.07%, respectively. A mixture of A. squamosa seeds + T. vogelii seeds extract was synergistic to H. armigera larvae with combined index values at LC50 and LC95 were 0.53 and 0.58, respectively. Thus, the use of a mixture of A. squamosa seed extract and T. vogelii seed is more efficient because the raw materials used were less at low concentrations to control H. armigera larvae than the extract applied separately.

Larvicidal, biochemical and physiological effects of acetamiprid and thiamethoxam against Culex pipiens L. (Diptera: Culicidae).

The resistance of mosquitos to conventional insecticides created an urgent need for using alternative insecticides. In this study, the toxicity of the neonicotinoids (acetamiprid and thiamethoxam) was evaluated against the 3rd larval instar of Culex pipens. In the larvicidal assay, acetamiprid and thiamethoxam showed promising larvicidal activity against Cx. pipiens, with LC50 values of 0.0093 and 0.0305 ppm after 24 hrs, 0.0078 and 0.0206 ppm after 48 hrs and 0.0065 and 0.0137 ppm after 72 hrs of insecticidal exposure. The activity of acetylcholinesterase (AChE), carboxylesterase, (α-esterase), (β-esterase), and glutathione S- transferase (GST) were determined after 72 hrs of insecticidal exposure. Acetamiprid showed a significant increase in the activity level of AChE, GST, carboxylesterase, α, and β- esterases than thiamethoxam. The hemocytes of the treated 3rd larval instar of Cx. pipens were sensitive to both insecticides and showed remarkable deformation compared with control. Therefore, both detoxification enzymes and physiological resistance play a great role in neonicotinoids detoxification.

Morphological, molecular, and pathogenicity characteristics of the native isolates of Metarhizium anisopliae against the tomato leafminer, Tuta absoluta (Meyrick 1917) (Lepidoptera: Gelechiidae) in Ethiopia

The South American tomato leafminer, Tuta absoluta (Meyrick 1917) (Lepidoptera: Gelechiidae), is a newly introduced and a major threat of tomato production in Ethiopia. Laboratory bioassay was conducted to evaluate locally isolated Metarhizium anisopliae (Metsch.) (Sorokin), against larvae of T. absoluta. Twenty-five Metarhizium isolates were isolated from different soil types, using the great wax moth, Galleria mellonella L. baiting method. From these, 13 isolates were prescreened by biological efficiency index model and tested against 2nd and 3rd larval instars of T. absoluta at the concentration of 107 spores ml−1. Sterile water plus Tween 80 (0.1% v/v) was used as a control. Greenhouse reared larvae of T. absoluta were used as experimental organisms. All tested Metarhizium formulations were pathogenic to T. absoluta in all conducted bioassays. Three isolates, AAUM78, AAUM39, and AAUM76, were the most effective and scored 88, 90, and 95% and 90, 93.3, and 95.7% mortality against 2nd and 3rd larval instars of T. absoluta, respectively. The lowest (48.5 and 50%) mortality rate was recorded by isolate AAUM30 against 2nd and 3rd larval instars, respectively, in 7 days post inoculation. However, all isolates showed significant statistical differences with F (24, 50) = 6.825, p < 0.001 and F (23, 15) = 3.97, p < 0.001 of mortality to 2nd and 3rd larval instars, respectively. Molecular analysis categorized these selected isolates under species of M. anisopliae and grouped into 2 different groups. AAUM78 and AAUM39 were recorded LT50 values of 3.93 and 3.5 days at the lowest (104 spore ml−1) concentration and LC50 values of 1.2 × 103 and 2.9 × 103 spore ml−1, respectively. Although AAUM78 and AAUM39 were virulent to the target pest, further field evaluation is required to determine their potential efficacy for T. absoluta control.

Efficacy of entomopathogenic nematodes for the control of white grub, Anomala corpulenta Motschulsky, in laboratory and field

Summary Anomala corpulenta is one of the major white grubs that cause serious damages in peanut production. To develop an environmentally friendly method to control A. corpulenta larvae, the efficacy of species of entomopathogenic nematodes (EPN), application rate and larval stage against A. corpulenta were determined. Results showed that Steinernema longicaudum X-7 and S. glaseri B-4-1 were the most virulent species, which caused 77.8 and 84.4% corrected mortalities of the 2nd instar larvae at 25°C 14 days after treatments. Corrected mortalities of A. corpulenta caused by EPN were significantly affected by EPN application rate. A decrease but no significant difference in susceptibility from the 2nd to the 3rd instar was observed for the test EPN species S. longicaudum, S. glaseri and Heterorhabditis bacteriophora. The field experiments indicated that S. longicaudum and S. glaseri applied at a relatively high rate (⩾5.0 × 103 infective juveniles (IJ) plant−1, i.e., 7.5 × 108 IJ ha−1) were able to provide not only control efficacy against A. corpulenta with ⩾92.7% reduction of larvae and ⩽5.06% of damaged pods, and the peanut yield increase was as good as phoxim, but also gave better control persistency compared to phoxim. Our findings indicated that EPN could be an effective strategy for the management of A. corpulenta in peanut fields.

Intraguild Predation between Chrysoperla carnea (Neuroptera: Chrysopidae) and Hippodamia variegata (Coleoptera: Coccinellidae) at Various Extraguild Prey Densities and Arena Complexities.

Intraguild predation (IGP) is a ubiquitous, important and common interaction that occurs in aphidophagous guilds. The effects of extraguild prey (EGP, i.e., aphids) density, predator life stage combinations and duration of the interaction on the level, asymmetry and direction of intraguild predation between lacewing Chrysoperla carnea and ladybird Hippodamia variegata were examined in simple laboratory arena and more complex microcosm environment. Three initial densities of 50, 150 and 400 Aphis fabae third instar nymphs and a control without aphids were provided to six combinations of predator life stages (2nd and 3rd larval instars of lacewing and 3rd and 4th instars and adult females of ladybird). The remaining aphid density and occurrence of IGP were checked after 24, 48 and 72 h. The IGP intensity (IGP level, IL) was similar in the simple arena (reaching 0.6 between larvae in absence of EGP and 0.3 between lacewing larvae and ladybird females) and microcosm environment (0.3 without EGP). In both environments, increasing EGP density lowered IL according to negative exponential relationship. IGP was asymmetric (general average asymmetry was 0.82 in simple arena and 0.93 in microcosm, the difference was not significant) and mostly in favour of larvae of C. carnea, except in the combination of 2nd larvae of C. carnea with the 4th larvae and adults of H. variegata. The direction of IGP, but not other characteristics, partially changed during the duration of the experiment. The incidence of IGP interactions among aphid predators under real conditions and its consequences on aphid biological control are discussed.

Toxicity of green silver nanoparticles of plant extracts against citrus mealybug Planococcus citri

Planococcus citri is an economically important polyphagous insect pest and is a serious threat to horticultural crops especially mango and citrus. It is mainly controlled by synthetic insecticides which have deleterious effects on humans, livestock and environment. To dispense with the detrimental consequences of insecticides, plant extracts and their silver nanoparticles can be potential alternatives. The present study reports the effectiveness of four plant extracts and their silver based nanoparticles against P. citri. All the plant extracts and their silver nanoparticles caused mortalities of 2nd and 3rd instars of P. citri at all concentrations and exposure durations. The ginger extracts and their silver nanoparticles caused maximum mortality of 2nd and 3rd instars of P. citri (94 and 90% respectively) at the highest concentration after 72 hours followed by neem extracts and their silver nanoparticles. Similarly, the mortalities caused by garlic silver nanoparticles followed the similar pattern. Eucalyptus plant extracts and their silver nanoparticles were found to be the lease effective. It was also observed that with an increase in concentration and exposure period, the mortality also increased showing a direct relationship. Ginger plant extract and their silver nanoparticles gave the best results and lowest LC50 values by a large margin. Neem extracts ranked second followed by garlic and eucalyptus and gave significantly poor results as compared to the first two plants. The required concentration for killing 50% of the nymphal population was observed to decrease with the passage of time.

In Vitro Studies for the Evaluation of Insecticidal Potential of the Venom of Endoparasitic Wasp Aenasius arizonensis (Girault) (Hymenoptera, Encyrtidae)

Aenasius arizonensis (Hymenoptera: Encyrtidae) a nymphal, solitary endoparasitoid is a potent biocontrol agent of cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae). Female wasp injects a blend of secretions in its host during parasitization which alters the host physiology. Insecticidal potential of crude venom of A. arizonensis was evaluated along with its chromatographic fractions by microinjections bioassays in its natural host insect P. solenopsis at 3rd nymphal instars and adult. Host insects were treated with two different volumes of crude venom (0.3 and 0.5 µL) and RP-HPLC fractions of venom, while host insects with saline injections were used as control. Biological activity of the crude venom was also evaluated after heat and protease treatment. Maximum mortality (84.0 ± 2.91) of the host insects was observed at highest dose rate (0.5 µL) of the crude venom; while lowest mortality (71.0 ± 2.31) was recorded at lowest dose (0.3 µL) of venom applied on 3rd instar life stage. On the other hand, significant difference in mortality of four peaks of RP-HPLC venom fractions were recorded against 3rd instar larvae and adult when microinjections containing crude venom and fractionated venom. Our data confirms that crude venom of the wasp induces significant mortality against its host P. solenopsis. Whereas, no significant difference in mortality was observed for heat and protease treated venom, suggesting that bioactive component of the venom secretions of the wasp are proteins in nature, which lost their biological activity upon heat and protease treatments.

Efficacy of entomopathogenic nematodes against the cabbage butterfly (Pieris brassicae (L.) (Lepidoptera: Pieridae) infesting cabbage under field conditions

Experiments were conducted to test the pathogenicity of entomopathogenic nematode, Heterorhabditis pakistanensis alone and in combination with the chemical insecticides, viz., Dichlorvos and Quinalphos and Neem product, viz., Azadirachtin against the cabbage butterfly, Pieris brassicae (L.) (Lepidoptera: Pieridae) infesting cabbage plants under laboratory and field conditions. In laboratory test, inoculum level of 200 infective juveniles (IJs) was most effective causing mortality to both 3rd and 4th instars larvae at 48 h. Nematode multiplication rate in insect cadaver was inversely proportional to the size of initial inoculum level of IJs, whereas IJs yield was directly proportional to the size of larva. The 4th instar larva resulted in a highest yield of IJs, followed by 3rd, 2nd, and 1st instars larvae at all the inoculum levels used in the study. IJs were found compatible with the chemical insecticides and Neem product at lower than half of the optimum single dose. The cumulative mean survival percentage of IJs recorded the highest (77.5%) in the combination of 100 IJs + Azadirachtin (0.25%) and lowest (70.6%) in 100 IJs + Dichlorvos 76 EC (0.05%). Under field conditions, H. pakistanensis (3.0 lakh IJs/m2) + Dichlorvos 76 EC (0.025%) resulted to the highest larval mortality (79.65%), followed by H. pakistanensis (3.0 lakh IJs/m2) + Azadirachtin (0.25%), where it was 76.22%. The larval mortality was the least (61.16%) in case of H. pakistanensis (3.0 lakh IJs/m2) when applied alone. H. pakistanensis + Dichlorvos resulted to the highest increase (31.42%) in cabbage yield over untreated control.

PERFORMANCE OF Metarhizium rileyi APPLIED ON Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae)

This study aimed to evaluate the efficiency of different strains of the entomopathogenic fungus Metarhizium rileyi in the control of Helicoverpa armigera caterpillars in laboratory conditions. Caterpillars between the 2nd and 3rd instar were used, ranging in size from 0.7 to 1.2 cm length. The experimental design used was completely randomized, composed of five treatments and five replications, each one consisting of 50 insects. The treatments T1 - Control (sterile distilled water), T2 - M. rileyi UFMS 02 strain, T3 - M. rileyi UFMS 03 strain, T4 - M. rileyi UFMS 06 strain, and T5 - M. rileyi UFMS 07 strain were evaluated. All treatments were applied (2 mL/insect) in suspensions of the order of 1.0 × 109 conidia mL-1, and Tween 80® was added in all treatments. Evaluations were performed daily to verify mortality and sublethal effects. For emerging adults, Filial Generation (FG), the biological cycle was evaluated. The data referring to larval mortality for the Parental Generation (PG) and GF and pupal for GF were submitted to analysis of variance, and the Scott-Knott test grouped the averages at 5% probability. The strains tested did not provide pathogenicity in the larval phase of H. armigera for PG and FG. However, there was a reduction in oviposition in all treatments regarding the control. There was an effect on the reproductive phase of GF caterpillars exposed to M. rileyi.

English

Chilo partellus (Swinhoe) is the most important destructive pest of sorghum in Africa which results in complete crop loss. Currently the management strategies rely heavily on chemical insecticides, which do not provide effective control. The uses of bio-pesticides are encouraging over chemical pesticides. The study was carried out to identify effective plant and animal products and optimum concentrations against C. partellus. 7 treatments each at 3 concentrations (2.0, 2.5 and 3.0 g and 1.0, 1.5 and 2.0 ml) were applied on 2nd and/or 3rd instars larvae. The untreated check was used for comparison. The experiment was laid out in a completely randomized design with 3 replications for each concentration. Result revealed among the treatments Milletia ferruginea Hochst seed powder and aqua extract caused the highest (100%) mortality at 3 g and 2.0 ml concentration on the 2nd day. Cow urine and the mixture (M. ferruginea+cow urine) were recorded higher efficacy mean mortality (86.7 and 93.3%) at 3.0 ml concentration within 3 days respectively. Phytolacca dodecandra L. seed powder, aqua extract and the mixture (P. dodecandra+cow urine) showed significantly lower efficacy mean mortality. In conclusion, M. ferruginea powder and aqua extract, cow urine and combination of M. ferruginea with cow urine were identified as good alternatives to chemical pesticides against C. partellus. Key words: Chilo partellus, cow urine, Milletia ferruginea, Phytolacca dodecandra, sorghum.

Double-stranded RNA targeting vATPase B reveals a potential target for pest management of Henosepilachna vigintioctopunctata

The development of genetic based techniques, specifically RNA interference (RNAi), has emerged as a powerful tool in novel pest management strategies for pestiferous coleoptera. The 28-spotted ladybird beetle, Henosepilachna vigintioctopunctata, is a dynamic foliar pest of solenaceous plants, primarily potato plants, and has quickly become one of the most important pests attacking many crops in Asian countries. In this study, we demonstrate the efficacy of dietary RNAi targeting vATPase B, which led to significant gene silencing. Downstream effects of vATPase B silencing appeared to be both time- and partial dose-dependent. Our results indicate that silencing of vATPase B caused a significant decrease in survival rate, as well as reduced the food stuffs consumption and inhibited the overall development of H. vigintioctopunctata. Furthermore, results demonstrate expression of insect melanism related genes, TH and DDC, was significantly up regulated under the dsvATPase B (RNAi molecule designed against vATPase B) treatment. The impact of oral dsvATPase B delivery on the survival of 1st, 3rd instars, and adults was investigated through bacterially expressed dsRNA. The effectiveness of RNAi-based gene silencing in H. vigintioctopunctata provides a powerful reverse genetic tool for the functional annotation of its genes. This study demonstrates that vATPase B may represent a candidate gene for RNAi-based control of H. vigintioctopunctata.

Synthesis, molecular docking studies, and larvicidal activity evaluation of new fluorinated neonicotinoids against Anopheles darlingilarvae.

Anopheles darlingi is the main vector of malaria in Brazil, characterized by a high level of anthropophilia and endophagy. Imidacloprid, thiacloprid, and acetamiprid are the most widespread insecticides of the neonicotinoid group. However, they produce adverse effects on the non-target insects. Flupyradifurone has been marketed as an alternative to non-fluorinated neonicotinoids. Neonicotinoids containing trifluoroacethyl substituent reveal increased insecticidal activity due to higher hydrophobicity and metabolic stability.We synthesized novel neonicotinoid insecticides containing fluorinated acceptor groups and their interactions were estimated with the nicotinic acetylcholine receptor (nAChR) binding site by molecular docking studies, to evaluate their larvicidal activity against A. darlingi, and to assess their outdoor photodegradation behavior. New neonicotinoid analogues were prepared and characterized by NMR and mass-spectrometry. The synthesized molecules were modelled by time-dependent density functional theory and analyzed, their interaction with nAChR was investigated by molecular docking. Their insecticide activity was tested on Anopheles larvae collected in suburban area of Manaus, Brazil. Four new fluorinated neonicotinoid analogs were prepared and tested against 3rd instars larvae of A. darlingi showing high larvicidal activity. Docking studies reveal binding modes of the synthesized compounds and suggest that their insecticidal potency is governed by specific interactions with the receptor binding site and enhanced lipophilicity. 2-Chloro-5-(2-trifluoromethyl-pyrrolidin-1-ylmethyl)pyridine 5 showed fast degradation in water maintaining high larvicidal activity. All obtained substances possessed high larvicidal activity in low concentrations in 48 hours of exposure, compared to commercial flupyradifurone. Such activity is connected to a unique binding pattern of the synthesized compounds to insect’s nAChR and to their enhanced bioavailability owing to introduction of fluorinated amino-moieties. Therefore, the compounds in question have a high potential for application as control agents for insects transmitting tropical diseases, and they will be less persistent in the environment.

The Potency of Collecting Larvae of Oryctes rhinoceros L. (Coleoptera:Scarabaeidae) in the Oil Palm Plantation

The intensive and continuous collection of rhinoceros beetles, Oryctes rhinoceros L. (Coleoptera: Scarabaeidae), is an extraordinary strategy in IPM (Integrated Pest Management). This study was intended to evaluate the potency of people in collecting larvae and to determine the age structure of the beetle population. The study was conducted in Asahan Regency, North Sumatera Province. Adult men, adult women, adolescent girls, and adolescent boys collected beetles for 2 hours in each breeding site. Results showed that the beetle was more significant abundant in decomposed trunks at plots of immature and mature palms than at heaps of the empty fruit bunches namely 236, 221 and 93 individuals/2 hours. The population age-structure showed significantly predominant of 2nd and 3rd instars in all breeding sites, i.e. eggs, 1st instars, 2nd instars, and 3rd instars, pupae, adult males, and adult females were 2.02, 23.29, 21.39, 47.06, 3.17, 0.86, and 2.21%, respectively. Adult men, adult women, and adolescent boys had similar potency in collecting 3rd instar larvae while the least amount was collected by the adolescent girls viz. 70, 85, 60, and 38 larvae/2 hours, respectively. It is suggested that the study results support future efforts in the sustainable control of rhinoceros beetle through collecting larvae for commercial utilization.

Evaluation of tansy essential oil as a potential “green” alternative for gypsy moth control

The development of "green" alternatives to chemical pesticides could play a crucial role in integrated pest management (IPM). Their use is considered either as a substitution for or in addition to hazardous synthetic products. We analysed the influence of three concentrations of tansy (Tanacetum vulgare L.) essential oil (EO), previously characterised by GC-MS, on the survival and moulting of the 2nd instar and the nutritional indices of the 4th instar gypsy moth (Lymantria dispar L.) larvae. In a residual contact toxicity assessment, the exposure to tansy EO caused low mortality (< 10%) while larval development was significantly slowed down, i.e., the percentage of larvae that moulted into the 3rd instar was reduced. On the other hand, when tansy EO was incorporated into the diet (digestive toxicity assay), high mortality and a lack of moulting after 120h of eating were recorded for the highest applied concentration of EO. During 48h of feeding on EO-supplemented food at concentrations of 0.5 and 1% (v/v), the relative growth rate (RGR) of the 4th instar larvae significantly decreased, which can be explained by a significant reduction of the relative consumption rate (RCR) and significantly or marginally significantly lower efficiency of conversion of ingested food into insect biomass (ECI). Although the RCR was also reduced with the lowest applied EO concentration (0.1%), the ECI was not affected which meant the RGR was as high as it was for the control larvae. ECI changes, when two higher EO concentrations were applied, were due to a reduction in the efficiency of conversion of digested food into biomass (ECD), while approximate digestibility was unaffected by the presence of EO in the food. Our results on the significant negative effects of tansy EO on gypsy moth larval survival, development time, and nutritional physiology suggest that it could be considered in future designs for botanical insecticides for gypsy moth control.

Evaluation of some pesticides against the tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) under laboratory conditions

The tomato borer, Tuta absoluta (Meyrick) is considered a devastating pest, particularly to the tomato Lycopersicon esculentum. The present study was carried out to determine the efficacy of five pesticides namely, indoxacarb, (abamectin+ thiamethoxam), emamectin benzoate, fipronil and imidacloprid against the 3rd larval instar of T. absoluta under laboratory conditions using the Leaf-dip method. The tested pesticides could be descendingly arranged as follows: emamectin benzoate, fipronil, (abamectin + thiamethoxam), indoxacarb and imidacloprid. The corresponding LC50 values after 72 h. were 0.07, 0.22, 0.28, 0.59 and 2.67 ppm, while LC90 values were 0.56, 3.25, 1.99, 4.69 and 30.29 ppm, respectively. It is clear that emamectin benzoate was the most toxic compound, whereas imidacloprid was the least toxic one. Results indicated that emamectin benzoate can be used as a good element in integrated management program to this pest.

Geometrics of growth in four species of Spodoptera

Four species of Spodoptera (Noctuidae: Lepidoptera) viz., S. litura (F.), S. mauritia Boisduval, S. exigua (Hub.) and S. frugiperda (J.E. Smith) were reared on castor, rice, chickpea and on artificial diet, respectively under laboratory conditions during 2017–2019 at the Department of Entomology, College of Agriculture, PJTSAU, Rajendranagar, Hyderabad. The observations on the geometrics of growth in terms of width of head capsule (widest head width) confirming to Dyar's law were made. In S. litura the linear growth ratio was 1.45 confirming a regular geometrical progression in the consecutive larval instars. In S. mauritia and S. frugiperda it was 1.62 and 1.94, respectively; but in S. exigua it was observed to vary as 1.41 (between 1st and 2nd instars), 2.61 (2nd and 3rd instars), 1.05 (3rd and 4th instars) and 1.64 (4th and 5th), with a mean of 1.68, and slightly deviating from Dyar's law. In specific, it was of the ratio of 2.61 between 2nd and 3rd instars showing the maximum progression factor, and confirming the variation among the four species evaluated.

Biology of Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) on eggplant and tomato

The study mainly focussed on monitoring different life stages viz., egg, nymphal instars, pupae and adults. The present investigation revealed that mean pre-oviposition, oviposition and post oviposition period were 1.50 and 3.70; 3.50 and 4.50 and 1.60 and 3.30 days on eggplant & tomato, respectively. Further, three nymphal instars were observed in the life history of B. tabaci with average duration of 3.50 and 5.70, 2.40 and 4.80 and 3.50 and 5.40 days for 1st, 2nd and 3rd instars on eggplant & tomato, respectively. The total mean nymphal period on eggplant and tomato was observed as 9.40 and 15.90 days respectively. In addition, the mean pupal period and adult longevity of B. tabaci on eggplant and tomato was 3.70 and 6.30 and 4.05 and 8.30 days respectively. The total life cycle from egg to adult ranged amid 16.5 to 22.5 days on eggplant while on tomato it lasted amid 29.5 to 38.0 days.

Biology of the cucurbit fruit fly, Bactrocera cucurbitae (Coq) on host bottle gourd, Lagenaria siceraria

We investigated the biology of the cucurbit fruit fly, Bactrocera cucurbitae (coq) on bottle gourd, Lagenaria siceraria, using variety ‘BARI-Lau 1’. The mean incubation period, larval (1st, 2nd and 3rd instars), pre-pupal, pupal and total developmental periods of B. cucurbitae were 1.69±0.28, (1.72±0.33, 1.41±0.31, 2.31±0.51), 0.74±0.28, 9.2±0.78 and 36±1.69 days, respectively. The mean adult longevity, with food and without food was 14.1±1.28 and 5.0±0.81 days, respectively. The lengths of all three larval instars were 1.1± 0.9, 3.03 ± 0.95 and 6.42 ± 0.90 mm, and the widths were 0.22 ±0.11, 1.12 ± 0.01 and 2.13 ± 0.20 mm, respectively. The length and width of the pre-pupa and the pupa were 5.86 ±0.48, 5.68± 0.26 mm and 1.94 ± 0.23, 2.39±0.20 mm respectively. The length of male and female were 6.61±0.59 and 8.28±0.52 mm. The widths of males and females with wingspan were 10.97 ± 0.43 and 13.02±1.28 mm respectively. The incidence of B. cucurbitae as maggot population in bottle gourd was higher in January during the study period from December 2018 to March 2019.