Fumigant toxicity of Carum copticum L. (Apiaceae) essential oil on Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) adults under greenhouse conditions

Greenhouse whitefly Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) is one of the most injurious pests of greenhouse crops and ornamental plants in worldwide, both outdoor and indoor. This insect, feeding on plant sap, producing honeydew and transmitting plant viruses, causes quantitative and qualitative damages in plants. For controlling this pest in greenhouse, plant essential oils are mentioned instead of chemical insecticidal. So, in this research, fumigant toxicity of Carum copticum L. (Fam.: Apiaceae) plant oil on mentioned adult pest was surveyed. Dry ground seeds were subjected to hydrodistillation using a modified Clevenger-type apparatus and the resulting oil contained Thymol (50.07%), Gama-Terpinene (23.99%), P-Cymene (22.9%), Myrcene (0.51%) and 1,8-Cineole (0.5%). All bioassay tests were conducted at 27?±?2?°C, 65?±?5 RH and a photoperiod of 16:8?h (light: dark). This research was performed with a completely random design with six treatments (five different concentrations of essential oils plus control). Each concentration includes of three replicates and each replicate consisted of 20 adult of pests. The results showed that aforementioned essential oil shows significant mortality of adults 24?h after exposure. The value LC₅₀ of mentioned plant oil on T. vaporariorum was 1.03?μl?L/L air. And mortality percentage shows higher sensitivity of T. vaporariorum against application of essential oil. The value LT₅₀ estimated for T. vaporariorum in concentration of 1.03?μl?L/L air was 7.18?h. Fumigant toxicity this essential oil has had an ordered relationship with the concentration and time exposure. The results of this research showed that mentioned plant oil had appropriate insecticidal effects on these greenhouse pests. The findings showed that C. copticum L. oil has high impact on the above-mentioned pests and it is suggested because of its high potential in fumigant toxicity and its use in integrated pest management programmes in greenhouses is mentioned.     

Towards an understanding of the molecular basis of effective RNAi against a global insect pest,the whitefly Bemisia tabaci

In planta RNAi against essential insect genes offers a promising route to control insect crop pests, but is constrained for many insect groups, notably phloem sap-feeding hemipterans, by poor RNAi efficacy. This study conducted on the phloem-feeding whitefly Bemisia tabaci reared on tomato plants investigated the causes of low RNAi efficacy and routes to ameliorate the problem. Experiments using tomato transgenic lines containing ds-GFP (green fluorescent protein) revealed that full-length dsRNA is phloem-mobile, ingested by the insects, and degraded in the insect. We identified B. tabaci homologs of nuclease genes (dsRNases) in other insects that degrade dsRNA, and demonstrated that degradation of ds-GFP in B. tabaci is suppressed by administration of dsRNA against these genes. dsRNA against the nuclease genes was co-administered with dsRNA against two insect genes, an aquaporin AQP1 and sucrase SUC1, that are predicted to protect B. tabaci against osmotic collapse. When dsRNA constructs for AQP1, SUC1, dsRNase1 and dsRNase2 were stacked, insect mortality was significantly elevated to 50% over 6 days on artificial diets. This effect was accompanied by significant reduction in gene expression of the target genes in surviving diet-fed insects. This study offers proof-of-principle that the efficacy of RNAi against insect pests can be enhanced by using dsRNA to suppress the activity of RNAi-suppressing nuclease genes, especially where multiple genes with related physiological function but different molecular function are targeted.     

Laboratory Evaluation of Isaria fumosorosea CCM 8367 and Steinernema feltiae Ustinov against Immature Stages of the Colorado Potato Beetle

The Colorado potato beetle, Leptinotarsa decemlineata, has developed resistance to most registered pesticides and has become one of the most difficult insect pests to control. Development of new biopesticides targeting this pest might solve the resistance problem and contribute to sustainable crop production. Laboratory experiments were conducted to assess the efficacy of Isaria fumosorosea (syn. Paecilomyces fumosoroseus) strain CCM 8367 against L. decemlineata when applied alone or combined with the entomopathogenic nematode Steinernema feltiae. The last-instar larvae of the Colorado potato beetle showed the highest susceptibility to I. fumosorosea followed by pre-pupae and pupae. The median lethal concentration (LC₅₀) was estimated to be 1.03×10⁶ blastospores/ml. The strain CCM 8367 was more virulent, causing 92.6% mortality of larvae (LT₅₀ = 5.0 days) compared to the reference strain Apopka 97, which caused 54.5% mortality (LT₅₀ = 7.0 days). The combined application of the fungus with the nematodes increased the mortality up to 98.0%. The best results were obtained when S. feltiae was applied simultaneously with I. fumosorosea (LT₅₀ = 2.0 days); later application negatively affected both the penetration rate and the development of the nematodes. We can conclude that the strain CCM 8367 of I. fumosorosea is a prospective biocontrol agent against immature stages of L. decemlineata. For higher efficacy, application together with an entomopathogenic nematode is recommended.     

Enhancing insecticidal efficacy of baculovirus by early expressing an insect neurotoxin, LqhIT2, in infected Trichoplusia ni larvae

LqhIT₂, an insect specific neurotoxin from the venom of Leiurus quinquestriatus hebraeus, has been demonstrated to improve insecticidal efficacy of Autographa californica nuclar polyhedrosis virus (AcMNPV). A polyhedrin-positive recombinant AcMNPVvAcP_hsp70EGFP/P_pag90IT₂ was engineered for larvae to express the enhanced green fluorescence protein (EGFP) and LqhIT₂ under the control of P_hsp70 and P_pag90 promoters, respectively. This would allow a visual observation of the viral infection and an improvement of the insecticidal efficacy. The insecticidal activity of this recombinant baculovirus, a wild type AcMNPV and four other recombinant baculoviruses, was evaluated and compared in terms of mortality, body weight, median lethal time (LT₅₀), and median lethal concentration (LC₅₀). Insecticidal efficacy was unaltered when treated with vAcP_hsp70EGFP, moderately improved when infected by vAcP₁₀IT₂ (a P₁₀-promoted LqhIT ₂ gene), and significantly elevated when treated with vAcP_pag90IT₂ or vAcP_hsp70EGFP/P_pag90IT₂. No apparent difference was observed in insecticidal efficacy when additional EGFP was expressed as a visible marker. These results suggest that recombinant AcMNPV vAcP_hsp70EGFP/P_pag90IT₂ may be used as an effective insecticide against Trichoplusia ni and other lepidopterous insect pests.     

Sharing a predator: can an invasive alien pest affect the predation on a local pest?

Invasive species can strongly affect biotic interactions in ecosystems, interacting both directly and indirectly with local species. In European tomato greenhouses, the invasive alien pest Tuta absoluta may impact the population dynamics of other pests like whiteflies. Besides inducing damages to the host plant and competing for resources with local pests, this alien species may exert a predator-mediated interaction on local pests sharing common natural enemies. Biocontrol agents usually used against whiteflies may also prey upon T. absoluta and this could alter the dynamics of local pest populations. We evaluated possible resource competition and predator-mediated interactions in a system involving one mirid predator Macrolophus pygmaeus and two pests, T. absoluta and a local whitefly, Bemisia tabaci, on greenhouse tomatoes. Results showed that both resource competition and predator-mediated interactions occurred simultaneously. In the presence of the shared predator, there was a short-term positive effect of T. absoluta on B. tabaci [up to 5.9-fold increase of B. tabaci juveniles (egg + larvae) after four weeks]. However, in the long-term there was a negative predator-mediated interaction of T. absoluta on B. tabaci, i.e., after ten weeks the density of B. tabaci was 7.3-fold lower in the presence of the invasive pest. We emphasize the critical role of generalist predators in managing both local and invasive alien pest populations and that the strength and direction of predator-mediated indirect interactions can depend on the time scale considered.     

Development and Field Performance of a Sporeless Mutant of Bacillus thuringiensis Subsp. kurstaki

Commercial formulations of Bacillus thuringiensis subsp. kurstaki (Btk) consisting of insecticidal crystals and endospores are being extensively used by farmers in Karnataka for the control of insect pests on cabbage and cauliflower. The endospores of Btk persist in soil and are infectious to the mulberry silkworm, Bombyx mori. In order to lower the risk of accidental infection to silkworm we have developed sporeless mutants through chemical mutagenesis of a wild type Btk. An isolate of Btk (HR-Px91) was obtained from cadaver of the cabbage pest, Plutella xylostella. Exponential growth phase cells of Btk were exposed to the mutagen N-methyl-N′-nitro, N-nitrosoguanidine and crystalliferous but sporulation-deficient (Spo^? Cry⁺) mutants were isolated. Five oligosporogenous (OS) mutants were selected based on characteristics like autolysis, insecticidal crystal production and toxicity to larvae of P. xylostella, Crocidolomia binotalis and Helicoverpa armigere. Mutagenesis had not affected the quantity of toxins produced on solid medium by the five OS mutants when compared with the wilcitype HR-Px91. Also there was no significant differences in the toxicity of crystals from two OS mutants and those produced by Btks of wild type and a commercial formulation ‘Bactospeine’. Field studies have unequivocally demonstrated the efficacy of OS mutant HR-Pu₇ in protecting cabbage crop against the major insect pests, P. xylostella and C. binotalis. The field efficacy was at-par with ‘Batospeine’ at an equivalent crystal-protein concentration, when evaluated based on marketable yield of cabbage obtained and pest damage. Thus, sporeless mutants of Btk could be generated by chemical mutagenesis and effectively used for plant protection in sericulture tracts with minimum risk to silkworm.     

Insecticidal effect of high carbon dioxide atmospheres on thrips eggs oviposited in plant tissue

Thrips are damaging crop pests, but their eggs are difficult to detect for farmers and agricultural inspectors. We investigated the insecticidal effects of an elevated carbon dioxide atmosphere on thrips eggs oviposited within plant tissues. Percent mortality of Frankliniella occidentalis (Pergande), Frankliniella intonsa (Trybom), Thrips tabaci Lindeman, and Thrips palmi Karny exposed to 60?% CO₂ was evaluated at different temperatures (20, 25, 30, and 34?°C) and durations. Egg mortality of all four species increased with CO₂ exposure duration at each temperature, and the time required to achieve 100?% mortality decreased as the temperature increased between 20?C30?°C. Exposure to 60?% CO₂ at 30?°C for 12?h is considered to be 100?% lethal to most thrips pests of fresh agricultural produce. Our findings suggested that CO₂ treatment could be used to propagate thrips-free plants in horticultural nurseries.     

Water stress and kaolin spray affect herbivorous insects’ success on cotton

Ecological hypotheses of plant–insect herbivore interactions suggest that insects perform better on weakened plants and plants grown under optimal conditions are less damaged. This study tested the hypothesis that the colonization and oviposition rates by pests with different feeding strategies and levels of specialization are affected in different ways by two conditions commonly faced by commercially grown plants–water deficit and application of kaolin sprays, a reducer of abiotic plant stressors. We used four major pests of cotton as insect herbivore models. Three were chewing Lepidoptera: Alabama argillacea (Hüb.), a monophagous pest on cotton; Heliothis virescens (Fabr.), which is polyphagous, but with cotton as a primary host; and Chrysodeixis includens (Walk.), which is polyphagous, with cotton as secondary host. The fourth pest was a sap-sucking species, the polyphagous whitefly Bemisia tabaci (Gen.). In both choice and no-choice trials, the three chewing pests oviposited significantly less upon water-stressed plants; the greatest effect was observed for C. includens (>90 % reduction in oviposition under choice and >58 % under no-choice conditions). In contrast, the sap-sucking B. tabaci exhibited statistically more colonization and oviposition on water-stressed plants. Application of kaolin sprays reduced colonization and oviposition by all herbivore species tested, irrespective of irrigation regime and feeding strategies.     

Lethal and sublethal effects of long‐lasting insecticide‐treated nets on the invasive bug Halyomorpha halys

Halyomorpha halys is a polyphagous insect species with an original eastern Asiatic distribution, which was recently and accidentally introduced in the USA and Europe, where it became a serious agricultural pest. Chemicals have been widely used for its control leading often to failure of IPM programmes. Several approaches aimed at pest monitoring and control are currently under investigation, for example trapping, screening, border management and biological control. In the present work, we investigated the lethal and sublethal effects of the use of a long‐lasting insecticide‐treated net (LLIN with α‐cypermethrin), focusing on the perspective to control H. halys in an integrated approach. All experiments were carried out in the laboratory either in small arenas, at five exposure times (5, 15, 30, 45 and 60 min) or in large cages at 8 hr exposure. In small arenas, the LLIN induced sublethal effects and/or effectively killed the adults. A higher adult mortality was observed after longer exposure times (LT₉₀ was 51.64 min for females and 40.83 min for males). However, several specimens recovered from sublethal effects, with higher recovery rates after shorter exposure times. In the cage experiments, a significantly higher mortality (65% males and 75% of females) was recorded compared with controls. LLINs are physical barriers that can improve crop protection due to their insecticidal activity, and can be reasonably applied in various attract‐and‐kill systems both in glasshouses and in the field.     

印度藏茴香植物精油对温室棉蚜的熏蒸毒性及其成分分析（英文）

【目的】棉蚜Aphis gossypii是世界各地室内和室外果树、蔬菜和观赏植物上最具危害性的害虫之一。这一害虫取食植物汁液,产生蜜露,传播植物病毒,对植物从质和量上产生破坏。为了控制温室中的这一害虫,植物精油可用作化学农药的替代药物。本实验研究了印度藏茴香Carum copticum植物精油对棉蚜成虫的熏蒸毒性。【方法】将研磨的印度藏茴香干种子用改良的挥发油提取器(Clevenger-type apparatus)进行水蒸馏。所有生物测定均在27±2℃,相对湿度65%±5%和光周期16L∶8D条件下进行。研究采用完全随机设计,6个处理(5个不同浓度的精油加对照)。每一浓度3次重复,每一重复20头成虫。【结果】结果表明,棉蚜成蚜接触印度藏茴香精油24 h后出现明显的死亡。该精油对棉蚜成蚜的致死中浓度(LC50)为1.21μL/L空气。棉蚜成蚜的死亡百分率对精油的施用表现出较高的敏感性。精油浓度为1.21μL/L空气时,估计的棉蚜的致死中时(LT50)为11.79 h。这一精油的熏蒸毒性与浓度和接触时间之间具有一定的相关性。GC/MS组分分析结果表明,该精油由18种化合物组成,最重要的是一些化合物引起了熏蒸毒性,如麝香草酚(占50.07%)、γ-萜品烯(占23.99%)和对异丙基苯甲烷(占22.90%)。【结论】本研究结果表明印度藏茴香植物精油对棉蚜具有较好的杀虫效果。印度藏茴香精油对棉蚜产生较大的影响,由于它具有较高的熏蒸毒性潜力,因此可在温室中用于这一害虫的综合治理。     

The effect of simulated seasonal temperatures on Metarhizium brunneum-associated mortality in Agriotes spp. click beetles,and a degree-day infection model

Entomopathogens tend to have a slow speed of kill when used for targeting agricultural insect pests. Relating temperature as a driver of this speed is important to predict pest mortality, and extending this to a degree-day infection model has rarely been studied. Many species of wireworms (Coleoptera: Elateridae), the larvae of click beetles, are subterranean and generalist agricultural pests that can be difficult to control with pesticides. Targeting adult beetles, however, may be an effective method to reduce larval recruitment. Metarhizium brunneum Petch (Hypocreales), an entomopathogenic fungus, kills click beetles but the mortality rate and speed of kill are expected to vary according to temperature. Using a thermal gradient plate to simulate daily oscillating temperatures in Agassiz, British Columbia, Canada, for April, May, and June, the effectiveness of M. brunneum strains LRC112 and F52 in causing mortality to Agriotes obscurus (L.) and Agriotes lineatus (L.) click beetles was studied in the laboratory. Mortality was fastest in beetles exposed to June temperatures and slowest in those exposed to April temperatures, with differences among beetle species × M. brunneum strain combinations. Higher temperatures resulted in more rapid mycelial outgrowth and conidiation in beetle cadavers, with only A. obscurus infected with M. brunneum LRC112 attaining near 100% conidiation. The number of degree days required to kill 50% of the beetles (LDD₅₀) was least for A. obscurus infected with M. brunneum LRC112 (176) followed by A. obscurus × M. brunneum F52 (212), A. lineatus × M. brunneum LRC112 (215), and A. lineatus × M. brunneum F52 (292). Hypothetical calculations showed that M. brunneum exposure earlier in the season resulted in a longer time to kill 50% of the beetles (LT₅₀) but the earliest LT₅₀ calendar date. Later M. brunneum exposure dates resulted in lower LT₅₀'s, but later LT₅₀ dates. This conceptual work demonstrates that daily temperature oscillations, seasonality, and degree days must be considered to predict the efficacy and speed of kill of different fungal entomopathogen strains when targeting different click beetle species.     

Species composition and population dynamics of some arthropod pests in cotton fields of irrigated and semi-arid regions of Punjab,Pakistan

The present study aimed to record seasonal dynamics and diversity of different insect pests in cotton agroecosystems. Two well-known cotton growing districts i.e. district Layyah and Vehari were selected for the study from the cotton belt of Punjab, Pakistan. Sampling was done bi-weekly for two consecutive years from July to October during 2018 and 2019. Sweep netting, visual counting, hand picking, wet finger method, beat sheets, aspirator and pitfall trapping methods were used for collection. Shannon-Wiener and Simpson indices were used to compute diversity while Menhinick and Margalef indices were used for the estimation of species richness. A total of 94,343 individuals representing 43 species, 40 genera, 28 families and 6 orders were recorded. Family Aleyrodidae dominated over other pest families. Bemisia tabaci (Gennadius, 1889) of family Aleyrodidae was the dominant species with 39.68% share among all pest species. Estimated species richness of all arthropod pest species belonging to both districts were about 94%. The densities of pests fluctuated with time. The peaks of sucking pest densities were observed in July and August while densities of chewing pests peaked in late September or early October each year. Population densities of jassids Amrasca biguttula (Ishida), armyworm Spodoptera litura (Fabricius), and pink bollworm Pectinophora gossypiella (Saunders), showed strong negative correlation with temperature, humidity and rainfall while thrips population density showed positive correlation with these parameters. Minor loss due to pests are acceptable everywhere, but it is only possible when their populations remain below their economic threshold levels. Present study will aid to design pest management strategies in cotton growing areas round the globe.     

Economic impact of exotic insect pests in Brazilian agriculture

Agriculture represents one of the major strengths of the economic sector in Brazil. The need to avoid economic losses because of insect pest populations is one of the greatest challenges faced by this sector. Insect pests have caused annual losses of US$12.0 billion to the Brazilian economy, of which approximately US$1.6 billion are because of exotic pest species. Furthermore, exotic insect species often show greater potential to cause harm than native species. In Brazil, since the late nineteenth century, 24 species of insect pests have been introduced into the country, and they have caused significant economic losses. Many of these species, including Bemisia tabaci, Hypothenemus hampei, Ceratitis capitata, Oryzophagus oryzae and Anthonomus grandis, are major crop pests, and they were accidentally introduced during trading of agricultural products. In this review, we present an overview of Brazilian agriculture, a brief history of the introduction of insect pests in the country and the Brazilian legislation on agricultural defence, and we estimate the economic losses caused to the Brazilian economy by the main insect pest species that have been introduced into Brazil over the last 112 years.     

Tolerance of copepods to short-term thermal stress caused by coastal power stations

The tolerance of marine copepods to short-term thermal stress was measured by the median lethal temperature (LT₅₀) tests in laboratory. Experiments on LT₅₀ of copepods from different acclimation and acclimatization conditions collected from the Yueqing Bay were carried out under heat exposure for 15, 30 and 45 min. The LT₅₀ of copepods decreased with increasing exposure time but increased with rising acclimation and acclimatization temperatures. However, the differences in copepod LT₅₀ decreased with rising acclimatization temperatures, which suggested that entrained copepod mortality increased with raised water temperature due to the acute thermal stress of coastal power stations. Results also revealed that the thermal tolerance of Labidocera euchaeta was much higher than that of Calanus sinicus in spring. The thermal tolerances of different copepod species in summer were in the order, Pseudodiaptomus marinus, Acartia spinicauda, Acartia pacifica and L. euchaeta.     

Comparative conventional preventive strategies for insect pest of okra

The use of natural substances for pest control in agriculture is economically viable. It benefits both the human being and the environment due to its low persistence and toxicity. Therefore, the biopesticidal potential of three- plants-derived extracts (clove [Syzygium aromaticum], Hing [Hing (Asafetida)], and Wood Ash [Eucalyptus globulas]) was evaluated against different ' 'insect's pests on five okra varieties. All the treatments were sprayed at two stages, 1st before flowering and 2nd at the fruit-bearing stage. The results of the 24 h pre-spray revealed that the mean density of Aphis gossypii, Erias insulana, and Bemisia tabaci were significantly lower on a Shehzadi variety. However, among the treatments mean density of the A. gossypii and E. insulana after 1st and 2nd treatments were substantially more bass with E. globulas. Moreover, the Mean density of aphids was significantly lower after 72 h and 1-week time intervals. Furthermore, after 1st and 2nd treatments, the B. tabaci was considerably lower with hing on Shehzadi variety. It was found in the present study that the yield of five okra varieties was affected significantly by the application of the three treatments-pesticides. Among the various treatments, the application with E. globulas recorded a considerably higher crop yield. Therefore, clove, hing and E. globulas could be effective as alternative pest management methods. Furthermore, biopesticides generally are encouraged since they can proffer the solution of controlling insect pests without any environmental concern.     

Will the Real Bemisia tabaci Please Stand Up?

Since Panayiotis Gennadius first identified the whitefly, Aleyrodes tabaci in 1889, there have been numerous revisions of the taxonomy of what has since become one of the world''s most damaging insect pests. Most of the taxonomic revisions have been based on synonymising different species under the name Bemisia tabaci. It is now considered that there is sufficient biological, behavioural and molecular genetic data to support its being a cryptic species complex composed of at least 34 morphologically indistinguishable species. The first step in revising the taxonomy of this complex involves matching the A. tabaci collected in 1889 to one of the members of the species complex using molecular genetic data. To do this we extracted and then amplified a 496 bp fragment from the 3′ end of the mitochondrial DNA cytochrome oxidase one (mtCOI) gene belonging to a single whitefly taken from Gennadius'' original 1889 collection. The sequence identity of this 123 year-old specimen enabled unambiguous assignment to a single haplotype known from 13 Mediterranean locations across Greece and Tunisia. This enabled us to unambiguously assign the Gennadius A. tabaci to the member of the B. tabaci cryptic species complex known as Mediterranean or as it is commonly, but erroneously referred to, as the ‘Q-biotype’. Mediterranean is therefore the real B. tabaci. This study demonstrates the importance of matching museum syntypes with known species to assist in the delimitation of cryptic species based on the organism''s biology and molecular genetic data. This study is the first step towards the reclassification of B. tabaci which is central to an improved understanding how best to manage this globally important agricultural and horticultural insect pest complex.     

Horizontally transferred genes as RNA interference targets for aphid and whitefly control

RNA interference (RNAi)-based technologies are starting to be commercialized as a new approach for agricultural pest control. Horizontally transferred genes (HTGs), which have been transferred into insect genomes from viruses, bacteria, fungi or plants, are attractive targets for RNAi-mediated pest control. HTGs are often unique to a specific insect family or even genus, making it unlikely that RNAi constructs targeting such genes will have negative effects on ladybugs, lacewings and other beneficial predatory insect species. In this study, we sequenced the genome of a red, tobacco-adapted isolate of Myzus persicae (green peach aphid) and bioinformatically identified 30 HTGs. We then used plant-mediated virus-induced gene silencing (VIGS) to show that several HTGs of bacterial and plant origin are important for aphid growth and/or survival. Silencing the expression of fungal-origin HTGs did not affect aphid survivorship but decreased aphid reproduction. Importantly, although there was uptake of plant-expressed RNA by Coccinella septempunctata (seven-spotted ladybugs) via the aphids that they consumed, we did not observe negative effects on ladybugs from aphid-targeted VIGS constructs. To demonstrate that this approach is more broadly applicable, we also targeted five Bemisia tabaci (whitefly) HTGs using VIGS and demonstrated that knockdown of some of these genes affected whitefly survival. As functional HTGs have been identified in the genomes of numerous pest species, we propose that these HTGs should be explored further as efficient and safe targets for control of insect pests using plant-mediated RNA interference.