2nd Instars Research Articles

Efficacy and Residual Analysis of Three Insecticides against Spodoptera littoralis (Boisd.) on Field-grown Tomatoes

Spodoptera littoralis (Boisd.) is among the most destructive insect pests in Egypt, the field study was conducted at El-Beheira Governorate, Egypt to evaluate the toxicity of three insecticides against 2nd and 4th larval instars of these insect and residual effect in tomato fruit into open field application. The outcomes demonstrated that spinosad, methoxyfenzide and diflubenzuron proved to be very toxic. Semi-field application showed that spinosad was the most effective with 91.38 % and 100% insect pest mortalities at initial and residual effects against second instar larvae, respectively. The initial effect manifested higher morality (90.25%) for fourth instar larvae when treated with diflubenzuron followed by spinosad (86.50%), then methoxyfenzide (84.25%), while the residual effects of all tested insecticides were 100% mortality. The findings additionally demonstrated that the pre-harvest intervals (PHI) for diflubenzuron, spinosad, and methoxyfenzide were 3,7 and 10 days, respectively, for tomato fruits. Following this PHI, the products are considered safe for export and local consumption, as the residue level satisfies the maximum residue limit, which is the level documented by the European Union.

An effective way to monitor the population of juvenile horseshoe crabs in the Beibu Gulf of China

Population conservation of horseshoe crab is urgently required in China as their population is declining dramatically. However, conservation efforts are severely constrained by the lack of information on the population dynamics of the species. Here, a citizen science-based investigation was conducted to continuously monitor the population dynamics of juvenile Tachypleus tridentatus and Carcinoscorpius rotundicauda in the Beibu Gulf of China over five years. A low abundance of horseshoe crabs was observed at all stations. T. tridentatus was primarily observed in the eastern of Beibu Gulf, with an abundance (0.179 ind/100 m2) larger than that of C. rotundicauda (0.007 ind/100 m2). The prosomal width range of T. tridentatus was between 9.0 and 138.0 mm while that of C. rotundicauda was between 20.0 and 111.0 mm, representing their different age distribution patterns. A continuous distribution pattern from 3rd to 14th instar was observed in the T. tridentatus population, whereas a discontinuous distribution pattern from 6th to 16th instars was observed in the C. rotundicauda population. This instar distribution pattern implies that these areas are crucial nursery habitats for the two species. No horseshoe crab within the 1st to 2nd instars (for T. tridentatus) or before 6th instar (for C. rotundicauda) were observed within five years, indicating a declining age structure with few natural births. It was concluded that the declining population would exacerbate the risk of endangered horseshoe crab. There is an urgent need to strengthen the protection of horseshoe crab in the Beibu Gulf, particularly to protect their nursery habitats. The value of long-term citizen science based-monitoring was highlighted, which greatly increased public awareness of horseshoe crab protection.

Toxicity and fitness evaluation of Chrysoperla carnea resistant strains on cotton mealy bug Phenacoccus solenopsis Tinsely

Research was conducted to select chlorantraniliprole and bifenthrin resistant strains of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) at Bahauddin Zakariya University, Multan, Pakistan. Moreover, fitness parameters of resistant C. carnea were evaluated after feeding on 2nd instars nymph of Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae). Two to three day old C. carnea larvae were used in each topical bioassay. The raw data of biological parameters were analysed using an age stage, two sex life table. After 16 and 13 rounds of selection, the Chlo-Sel and Bife-Sel strains of C. carnea developed 91- and 2.19-fold resistance level, respectively compared with the UN-Sel strain. Biological parameters such as larval duration (days), pupal duration (days), female longevity (days), male longevity (days), adult pre-oviposition period (APOP) (days), total pre-oviposition period (TPOP) (days), oviposition (days), reproductive female ratio (RepF/Fn), and fecundity/female (F) were significantly different while pre-adult female (days), pre-adult male (days), and female ratio (Nf/N) was not significantly different among all strains. Demographic parameters such as finite rate of increase (λ), mean generation time (T), intrinsic rate of increase (r), net reproductive rate (Ro), and gross reproductive rate (GRR) were significantly different while doubling time (DT) was significantly similar among all strains of C. carnea. This information could be helpful in developing and promoting the use of insecticide resistant strains of C. carnea for the management of P. solenopsis under field conditions. Moreover, knowledge of fitness advantages will be helpful in IPM for the development of control strategies against P. solenopsis. In order to explore the practical relevance of our findings, more research ought to be conducted.

Inducible defense phytohormones in annual bluegrass (Poa annua) and creeping bentgrass (Agrostis stolonifera) in response to annual bluegrass weevil (Listronotus maculicollis) infestation.

The annual bluegrass weevil (Listronotus maculicollis) is the most damaging insect pest of short-mown turfgrass on golf courses in eastern North America. Listronotus maculicollis larvae cause limited visible damage as stem-borers (L1-3), compared to the crown-feeding (L4-5) developmental instars. Prolonged larval feeding results in discoloration and formation of irregular patches of dead turf, exposing soil on high-value playing surfaces (fairways, collars, tee boxes, and putting greens). Annual bluegrass (Poa annua) is highly susceptible to L. maculicollis compared to a tolerant alternate host plant, creeping bentgrass (Agrostis stolonifera). This study explored whether defense signaling phytohormones contribute to A. stolonifera tolerance in response to L. maculicollis. Concentrations (ng/g) of salicylic acid (SA), jasmonic acid (JA), jasmonic-isoleucine (JA-Ile), 12-oxophytodienoic acid (OPDA), and abscisic acid (ABA) were extracted from turfgrass (leaf, stem, and root) tissue samples as mean larval age reached 2nd (L2), 3rd (L3), and 4th (L4) instar. Poa annua infested with L. maculicollis larvae (L2-4) possessed significantly greater SA in above-ground tissues than A. stolonifera. Levels of constitutive JA, JA-Ile, OPDA, and ABA were significantly higher within non-infested A. stolonifera aboveground tissues compared to P. annua. Inducible defense phytohormones may play a role in P. annua susceptibility to L. maculicollis but are unlikely to provide tolerance in A. stolonifera. Additional studies in turfgrass breeding, particularly focusing on cultivar selection for increased constitutive JA content, could provide a non-chemical alternative management strategy for L. maculicollis for turfgrass managers.

Cloning and characterization of the histone variant gene H2A.Z in Bombyx mori.

H2A.Z, the most evolutionarily conserved variant of histone H2A, plays a pivotal role in chromatin remodeling and contributes significantly to gene transcription and genome stability. However, the role of H2A.Z in the silkworm (Bombyx mori) remains unclear. In this study, we cloned the BmH2A.Z from B. mori. The open reading frame of BmH2A.Z is 390 bp, encoding 129 amino acids, with a confirmed molecular weight of 13.4 kDa through prokaryotic expression analysis. Sequence analysis revealed that BmH2A.Z has a conserved H2A.Z domain and is closely related to the systemic evolution of other known H2A.Zs. The expression profile of BmH2A.Z at various developmental stages of the B. mori exhibited the highest expression level in the 1st instar, followed by the grain stage and the 2nd instar, and the lowest expression level in the moth. The highest transcript level of BmH2A.Z was observed in the head, with relatively lower levels detected in the blood than in the other tissues under consideration. In addition, the upregulation of BmH2A.Z resulted in the amplified expression of B. mori nucleopolyhedrovirus (BmNPV) genes, thus facilitating the proliferation of BmNPV. This study establishes a foundation for investigating the role of BmH2A.Z in B. mori and its participation in virus-host interactions.

Substantially altered bacterial diversity associated with developmental stages of litchi stink bug, Tessaratoma javanica (Thunberg) (Hemiptera: Tessaratomidae)

The mutualistic symbiotic relationship between insects and bacteria greatly influences the growth and development of host insects. Tessaratoma javanica (Thunberg) (Hemiptera: Tessaratomidae), also referred to as the litchi stink bug, has recently been established as an important insect pest of Litchi chinensis Sonn. and causes substantial yield loss in India. To design effective and environmentally safe management strategies, an understanding of the diversity and functions of microbiota harbored across the development stages is very important. The assessment of the diversity of development-associated bacteria in T. javanica and their predicted functions was conducted using 16S rRNA gene sequences obtained by the Illumina MiSeq technology. The result showed that taxonomic analysis of associated bacteria in different developmental stages includes a total of 46 phyla, encompassing 139 classes, 271 orders, 474 families, and 893 genera of bacteria. All developmental stages of T. javanica shared a total of 42.82 percent of operational taxonomic units (OTUs), with a 97 % similarity threshold. Alpha diversity indices showed maximum species richness in the egg and adult stages. The phyla Proteobacteria followed by Firmicutes, Bacteriodetes, and Actinobacteria, exhibited the highest levels of abundance across all the developmental stages of T. javanica. Microbiota were most different between the egg and the 4th nymphal stage (χ2 = 711.67) and least different between the 2nd and 4th nymphal instars (χ2 = 44.45). The predicted functions of the microbiota associated with T. javanica are mainly involved in amino acid metabolism, cell motility, cellular processes and signaling, glycan biosynthesis and metabolism, lipid metabolism, and membrane transport. The present study documentation and information on symbiotic bacteria across T. javanica life stages will prompt the development of novel biological management strategies.

Biological Control of Aphid by using Beetle (Coccinella septempunctata)

Development and reproductive potential of the Coccinella septempunctata L. CSL was conducted under normal conditions to determine its fecundity and longevity on natural diet. Tests were made on normal temperature rearing materials and all development stages were carefully recorded. Diet quality is related to egg production, so CSL fertility is affected by diet type. CSL consumed highly significant (Rhopalosiphum maidis) approximately 28 aphids per day as compared to other treatments. The insect has the largest Oviposition, feeding on the 1st and 2nd instar of Macrosiphum rosae. Biological control (BC) of seven-spotted ladybirds emphasizes evaluating specific livestock for maximum efficiency, understanding agriculture in a new environment, and evaluating social interactions.

Age-Stage, Two-Sex Life Table of an Alarming Quarantine Pest Trogoderma granarium on Stored Products

Trogoderma granarium (Coleoptera: Dermestidae) is a polyphagous pest of stored products and an alarming threat to food security around the globe. The current study is designed to construct the life table of T. granarium on four stored products, i.e., wheat, barley, rice, and maize at controlled conditions (33±1°C, 65% RH, and a photoperiod of 14 : 10 (L:D) h). The incubation period of T. granarium was longer (5.13 d) on maize and shorter (4.30 d) on wheat. The developmental period of 1st, 2nd, 3rd, and 4th larval instars of T. granarium was longer on maize than the other three hosts were significant. Statistical difference between the longevity of females and males was recorded, while no statistically significant difference was found in the preoviposition period. The mean fecundity values observed on wheat, barley, rice, and maize were 31.33±1.62, 26.21±1.49, 28.00±1.35, and 25.58±1.13, respectively. The highest fertility was observed in wheat and the lowest in maize. The net reproductive rate (R0) of T. granarium ranged from 8.66±2.86, 13.16±2.65, 12.53±2.27, and 10.23±2.32 offsprings on wheat, barley, rice, and maize, respectively. The highest gross reproductive value (GRR) was for T. granarium reared on barley (18.31±4.10/d), and the lowest was for maize (15.35±2.95/d). To complete the development, T. granarium took 48.97±0.68 d on maize, significantly higher than on other treatments (p<0.05). The mean generation time (T) of T. granarium was considerably affected by tested products. Based on the results of the present study, maize is a less favorable diet for the development and reproduction of T. granarium and may be considered for the management of this detrimental pest.

Characterization of the serosal cells surrounding Cotesia kariyai larvae and their role in host immunosuppression

About half of the serosal cells (Scs) of Cotesia kariyai (Ck) eggs are released as teratocytes into the host body cavity after hatching, and another half remain attached to the larval epidermis until the 1st instar larvae of Ck ecdysis to 2nd instars. To investigate the role of the serosal cells surrounding Ck 1st instar larvae (1st Scs) in immune avoidance, Ck 1st instar larvae with and without Scs removed using dispase were transplanted into Mythimna separata larvae (MsLrv), respectively. As a result, Ck 1st instar larvae surrounded by Scs were less susceptible to the MsL encapsulation than Ck 1st instar larvae without the Scs, suggesting that the Scs are involved in suppressing the encapsulation of the MsL. Furthermore, when the granular cells and plasmatocytes of the MsL involved in the encapsulation were incubated in a medium supplemented with proteins extracted from 1st Scs, the plasmatocytes failed to adhere to glass slides, and did not spread their filopodium and lamellipodium. These findings suggest that 1st Scs express proteins that inhibit filopodium and lamellipodium spreading to prevent the MsL plasmatocytes from adhering to Ck larvae.

Biology of Fall Armyworm Spodoptera frugiperda (J.E. Smith) on Maize under Laboratory Conditions

Maize is a important cereal harvests developed for food, fodder and raw material throughout the country. It is rich source of proteins, carbohydrates and vitamins. Corn production is decreasing day by day due to attack of more than 353 insect species and mites. Among insect pests, Fall armyworm, Spodoptera frugiperda is best destructive pest for corn production. The rearing of Fall armyworm, Spodoptera frugiperda was conducted under laboratory conditions in Department of Entomology, Acharya Narendra Deva University of Agriculture & Technology, Kumarganj, Ayodhya, U. P. during 2023. The complete metamorphosis (egg, larva, pupa and adult) was certified in Spodoptera frugiperda. The average fecundity was 2.59 ± 0.40 days. There were 6th instar larval of Spodoptera frugiperda and total larval period was 15-20 days. The growth period of 1st, 2nd, 3rd, 4th, 5th and 6th larval instar was 2-3, 2.5-3, 2.2-3, 2-2.5, 2.5-3, 4-6 days respectively on corn leaves. The average period of pupa was 10.33 ± 1.07 days. The female was long lived than male. The total evolved period from egg to adult was 45-47 days.

Toxicity of Ocimum basilicum L. leaf extract against Spodoptera exigua Hübner (Lepidoptera: Noctuidae)

The beet armyworm Spodoptera exigua Hübner (Lepidoptera: Noctuidae) is one of the most significant shallot pests worldwide, which affects agricultural production by approximately 100% in Indonesia. The growing awareness of sustainable agriculture encourages the search for natural alternatives to synthetic pesticides that promote resistance and contaminate the environment. Therefore, this study aims to evaluate the efficacy of basil (Ocimum basilicum L) leaf extract against the 2nd and 3rd instar larvae of S. exigua. The extracts were prepared using maceration and hydrodistillation and the pathogenicity was carried out against the 2nd and 3rd instar of S. exigua using three replicates with several doses of extract ranging from 0- 2.0%. The extracts were applied to the larvae using contact and topical methods. The results showed that maceration extraction yields a greater extract with different types compared to those of the hydrodistillation method. Maceration extract of basil leaves with the contact application method to 2nd instar showed better results than the topical application with the highest mortality rate of 75% (F=24.464; P< 0.001) and LC50 of 0.007%. This indicated that basil leaf extract with the contact application method has great potential to be developed as a botanical insecticide to control S. exigua in the field as part of Integrated Pest Management (IPM).

Molecular characterization of the camel nasal botfly, Cephalopina titillator (Diptera: Oestridae)

BackgroundLarval stages of the camel nasal botfly, Cephalopina titillator (Diptera: Oestridae), rank among the top obligate endoparasites causing nasopharyngeal myiasis. Such infestations have adverse effects on camel health, reducing their economic value. The current study’s objective is to assess the applicability of PCR using partial regions of the COI mtDNA and 28S rRNA gene sequences to identify, classify, and reveal the phylogenesis of C. titillator.ResultsLarvae of the 2nd and 3rd instars of C. titillator were collected from the El-Bassatin abattoir in Egypt, extracted from the nasopharyngeal passage of the Arabian camel (Camelus dromedarius) during postmortem inspection. Genomic DNA was successfully isolated from 10 samples of 3rd instar larvae of C. titillator and amplified using primer pairs targeting partial mitochondrial COI (916 bp) and ribosomal 28S rRNA (830 bp) gene fragments. Nucleotide sequences from five samples have been sequenced and submitted to GenBank under accession numbers OP482168 to OP482172 for the COI gene and OP482160 to OP482164 for the 28S rRNA gene fragments. The COI gene exhibited 97.3% nucleotide identity across all specimens, while the 28S rRNA gene displayed 99.74% identical nucleotides. Maximum likelihood trees were constructed based on the generalized time-reversible (GTR) model. The resulting COI phylogenetic tree demonstrated that the subfamily Oestrinae does not exhibit monophyly. Additionally, it revealed that C. titillator is a sister group to the subfamily Gasterophilinae. Despite the scarcity of data available for the 28S rRNA gene, the phylogenetic analysis utilizing 28S rRNA revealed one distinct lineage for the Egyptian camel nasal bot fly.ConclusionsMolecular phylogenetic analysis was conducted using molecular markers of distinct origins (both mitochondrial and nuclear) to elucidate the evolutionary relationships within the family Oestridae. This analysis is particularly significant following the inclusion of C. titillator, a first-time discovery in Egypt.

Assessment of Relative Toxicity of Common Insecticides against Adult and Grubs of Coccinella septempunctata under Laboratory Settings

One of the significant aphid-eating predators that are natural is the ladybird beetle Coccinella septempunctata. C. septempunctata is a biological control agent and effective in integrated pest management strategies (IPM). In the development of IPM, chemical insecticides are routinely utilized, to boost crop protection and support the activity of biological control agents. Research on the relative toxicity of multiple insecticides on seven spotted ladybird beetle C. septempunctata L. instars was conducted in a lab environment to gauge the C. septempunctata’s reaction to powerful insecticides. Six insecticides were treated as Spinetoram 120SC (0.4%/0.5L), Steward 150EC (0.86/0.5L), Coragen 200ml (0.4%/0.5L), Siphtoram 120SE (0.8/0.5L), Chlorfenapyr 36% (1.25/0.5L), and Lufenuron 50% (1.0/0.5L) to the 1st, 2nd, 3rd, and 4th instars of C. septempunctata. After 4, 12, 24, 48, and 72 hours of the treatment, the results of the proportional death were determined. Ongoing investigation was done at 60±5% RH and 25+2oC. When administered on adult ladybird beetles, Lufenuron was detrimental in 99.4 % cases, Chlorfenapyr in 88.4% Steward in 85.5% of cases, Coragen in 83.2%, and Siphtoram in 77.6%, Spinetoram was very little hazardous substance based on the death rate, followed by, Coragen, Steward, Chlorfenapyr, and Lufenuron.

Toxicity and residual effects of spinetoram on adults and larvae of Anastrepha fraterculus and Ceratitis capitata (Diptera: Tephritidae)

The use of organophosphate insecticides is one of the main strategies for the chemical control of Anastrepha fraterculus and Ceratitis capitata (Diptera: Tephritidae) in Brazil. Although organophosphate insecticides are effective in population suppression, their constant use (up to 5 applications/harvest) may favor pest resistance. Nevertheless, some organophosphate insecticides are highly toxic to natural enemies and thus their use has been banned. In this study, we investigated acute and residual toxicity of different doses of insecticide spinetoram for the control of larvae and adults of A. fraterculus and C. capitata under laboratory and field conditions. Spinetoram (Delegate 250WG™) showed high toxicity to adults and larvae of A. fraterculus and C. capitata (mortality>80%), based on topical application and ingestion bioassays. At the highest dose evaluated, 5.0 g a.i. (active ingredient) per 100 L of water, spinetoram was statistically similar to organophosphate (Lorbans 480BR™), but superior to neonicotinoid (Eleitto™), standard products for fruit fly control in Brazil. In addition, at doses 3.75 and 5 g a.i.100 L-1, spinetoram showed significant toxicity (mortality>70%) via tarsal contact for both species. Furthermore, toxic effects at depth were observed on larvae of 1st, 2nd, and 3rd instars of fly species in apple and peach fruits, reducing adult emergence by up to 90%. In the field, the highest dose evaluated (spinetoram 5 g a.i.100 L-1) reduced infestation of A. fraterculus by 90%. The results show that spinetoram could be used in the management of A. fraterculus and C. capitata, also as an alternative control for insect resistance management programs.

Risk of resistance and the metabolic resistance mechanism of Laodelphax striatellus (Fallén) to cyantraniliprole

Cyantraniliprole is a highly effective diamide insecticide used to control of Laodelphax striatellus (Fallén). This study aimed to assess the insecticide resistance risk of L. striatellus and its metabolic resistance mechanisms. After 25 continuous generations of selection, the resistance of L. striatellus to cyantraniliprole increased by 17.14-fold. The realistic heritability of resistance was 0.0751. After successive rearing for five generations without exposure to insecticides, the resistance ratio for the resistant strain of L. striatellus decreased by 3.47-fold, and the average resistance decline rate per generation was 0.0266. Cyantraniliprole-resistant strains did not exhibit cross-resistance to triflumezopyrim, pymetrozine, flonicamid, sulfoxaflor, dinotefuran, clothianidin, thiamethoxam, nitenpyram, or imidacloprid. Compared to those of the sensitive strain, the 2nd, 3rd, and 4th instars, nymphal stage durations, total preoviposition period, and average generation time of the resistant strain were markedly reduced. Furthermore, the activity of cytochrome P450 monooxygenase (P450) and carboxylesterase (CarE) were markedly increased. The upregulation of CYP419A1v2 expression was most evident among the P450 genes, with a 6.10-fold increase relative to that in the sensitive strain. The CarE gene LsCarE5 was significantly upregulated by 1.94-fold compared with that in the sensitive strain. With the continuous use of cyantraniliprole, L. striatellus may develop resistance to this insecticide. This resistance may be related to the increase in metabolic enzyme activities regulated by the overexpression of P450 and CarE genes.

Laboratory evaluation of selected botanicals and insecticides against invasive Spodoptera frugiperda (Lepidoptera: Noctuidae)

BackgroundMaize is an economical crop of China, and its production has been severely affected by the invasive Spodoptera frugiperda in recent year. Application of synthetic pesticides are one of the most effective practices against FAW as an emergency control. This pest causes serious damage to the maize crop worldwide in recent decade, especially in China. MethodsTo find an alternative to synthetic insecticides there were total 16 different chemicals were used including ten botanical insecticides comprising of seven botanicals, azadirachtin, pyrethrin, nicotine, osthole, rotenone, Celastrus angulatus, matrine, and three insect growth regulators, diflubenzuron, lufenuron and buprofezin. Six synthetic insecticides, including emamectin benzoate, indoxacarb, imidacloprid and thiamethoxan, chlorantraniliprole, chlorfenapyr, were evaluated against 2nd instar of S. frugiperda larvae using leaf-dip method. ResultsThe results revealed that osthole, azadirachtin, buprofezin and pyrethrin were showed the significant larval mortality of 98.0, 96.7, 94.0 and 90.7%, in 120 h observation and exhibiting minimum LC50 (39.04, 35.58, 61.45 and 48.46 mg/L, respectively) and LT50 (48.91, 68.85, 58.67 and 58.57 h, respectively) values. Among tested synthetic insecticides, emamectin benzoate, chlorantraniliprole and chlorfenapyr were showed significant higher mortality against larvae of S. frugiperda (99.3, 96.0 and 89.3%, respectively) in 72 h observation by exhibiting minimum LC50 (0.26, 0.39 and 0.72 mg/L, respectively) and and LT50 (10.18, 10.57 and 13.42 h, respectively) values. More study is needed to test the laboratory findings in the field, although the efficient biorational pesticides might be utilized as part of integrated pest management against S. frugiperda. ConclusionThe effective chemicals could be used in the management for S. frugiperda. The highest discriminating concentrations of tested botanical insecticides, insect growth regulators and insecticides caused significant mortality of S. frugiperda larvae.

Predatory potential and functional response of Coccinella undecimpunctata Linnaeus (Coleoptera: Coccinellidae) on Brevicoryne brassicae (Linnaeus) (Homoptera: Aphididae)

The determination of functional response provides the foundation to determine the efficiency of a natural enemy for its use against a specific crop pest. The results indicated that the number of prey eaten by 1st, 2nd, 3rd and 4th instars, male and female adults of C. undecimpunctata increased significantly with increasing prey density. Prey consumption increased with development of larvae, i.e. the 4th instar consumed more number of aphids at each prey density than the 3rd, 2nd, and 1st instars. Female adults consumed more aphids than the male adults. All stages of C. undecimpunctata exhibit a Type II functional response curve (a curvilinear rise to plateau) as B. brassicae densities increase, and the curve predicted by Holling’s disk equation did not differ significantly from the observed functional response curve. The attack rate was highest with the lowest handling time, when adult females fed on B. brasicae, followed by adult males and 4th instar larvae. However, further field experiments are needed to confirm its potential.

Effect of low-temperature stress on the survival of Meloidogyne incognita and its application in greenhouse of northern China.

We examined the effects of low temperature on egg hatching and killing rate of the 2nd instars of Meloi-dogyne incognita (J2) in the laboratory. We further evaluated the effects of two soil treatment methods on the survival rate of M. incognita in northern China in a field experiment. The results of laboratory experiment showed that survival rate of J2 was 0 after being subjected to -7 ℃ for 24 hours, and that egg hatching was completely inhibited 24 hours after being subjected to -9 ℃. The survival rate of J2 was 0 after being subjected to -1, -2, -3, and -4 ℃ for 8, 5, 3, and 1.5 d, respectively. Egg hatching was completely inhibited after being subjected to -2, -3, -4, and -5 ℃ for 9, 6, 4, and 1 d, respectively. Results of the fitting analysis showed that both the relationships between the temperature and the lethal time of J2 as well as the temperature and the non-hatching time of the eggs followed exponential functions. The results of field test showed that death rate of M. incognita in 0-50 cm soil layer after ridging treatment and 0-30 cm soil layer after leveling treatment could reach 100%, while the disease index of the former in 30-40 cm and 40-50 cm was 84.9% and 75.8%, respectively, which was lower than that in the greenhouse. Our results suggest that preventing and controlling M. incognita in greenhouses through low-tempe-rature in winter could achieve a better control effect in Yulin City and the northward region. The proposed technique is convenient and has high potential for popularization.

Impact of insect growth regulators on reproduction and life stages of Tribolium Castaneum (Coleoptera: Tenebrionidae)

Tribolium castaneum is devastating cosmopolitan insect pest of stored grain. The present study investigated the impact of three insect growth regulators on different life stages of T. castaneum. Percent mortality (%) induced was observed at 0.75. 1.25, 2.5, 5, 10, and 20 ppm doses of each IGR after 7, 14 and 21 day exposure. In addition to larval and parental mortality, progeny suppression data was also recorded. The larvae of the 2nd instar were more susceptible to lufenuron, with mortality reaching 100% at 10ppm even after a 14-day interval. In the case of pyriproxifen, 2nd instar did not responded to all dose rates until 14 days however 21 days, statistically corresponding 2.5 to 10 ppm dose rates was detected. At 20 ppm, methoxy fenazide resulted in 92 percent mortality of 2nd larval instar mortality, and the larvae responded to all dose rates at all exposure intervals that varied significantly among themselves. The mean mortality of the 4th instar larvae at 20 ppm for lufenuron after a 21-day interval was 90%, which was not significantly different from the mortalities (62 and 80%) at the same dose rate after 7 and 14 days, respectively. All the IGRs were very effective in progeny suppression (>80%) and complete progeny suppression (100%) was observed in adults treated with methoxyfenazide and lufenuron at 2.5 and 10 ppm doses, respectively. It is concluded that all the screened IGRs were effective in progeny suppression and in some cases, complete progeny suppression was achieved

In Vitro and In Vivo Toxicity of Selected Insecticides Against 2nd Instar Larvae of Spodoptera Frugiperda

In Vitro and In Vivo Toxicity of Selected Insecticides Against 2nd Instar Larvae of Spodoptera Frugiperda