Toxicity and horizontal transfer of agricultural insect growth regulators in Coptotermes gestroi (Wasmann) (Blattodea: Heterotermitidae)

The effectiveness of chlorantraniliprole and other insecticides (bifenthrin, fipronil, indoxacarb, imidacloprid and chlorfenapyr) were tested against Coptotermes gestroi (Wasmann). Four experiments were conducted: a topical bioassay, a horizontal transfer study, an insecticide bioavailability test and a feeding bioassay. The topical bioassay showed that chlorantraniliprole was significantly less active to C. gestroi at 24 h post-treatment compared with the other insecticides tested. Nevertheless, it is likely that a lesser amount of chlorantraniliprole was required to cause 50% mortality of C. gestroi at 7 and 14 days post-treatment. The exposure duration and donor:recipient ratio affect the mortality of recipient termites. Mortality after exposure to chlorantraniliprole in sandy clay was significantly lower than in sand; however, by 14 days, > 90% of donor and recipient termites died in both substrates, irrespective of concentration. Fipronil and imidacloprid showed faster action, and high to moderate toxicity to C. gestroi. Termite workers also ceased to feed after exposure for 1 h to 50 mg kg(-1) chlorantraniliprole-treated sandy clay. Chlorantraniliprole demonstrated delayed toxicity at the lowest label rate (50 mg kg(-1) ) in sandy clay. Its slow action will enable greater transfer of toxicant between nestmates, while feeding cessation will promote greater social interaction between healthy and exposed termites.

The Asian subterranean termite,<i>Coptotermes gestroi</i>, baited with insect growth regulators in extended foraging arenas

Biopesticides or biological pesticides refer to the use of living biological organisms or their metabolites for pests, pathogens, weeds, nematodes, rodents, etc. Regarding the field of biopesticides, there is no precise and unified definition. In accordance with the United Nations Food and Agriculture Organization standards, biopesticides are generally natural compounds or genetic modification agents, including biochemical pesticides (pheromones, hormones, plant regulators, insect growth regulators) and microbial pesticides (fungi, bacteria, or genetically modified microorganisms), which do not include antibiotic agricultural preparations. According to their composition and sources, biopesticides can be divided into microbial biopesticides, microbial pesticides, botanical pesticides, and animal pesticides. According to the control object, they can be divided into pesticides, fungicides, herbicides, acaricides, rodenticides, and plant growth regulators. In terms of their use, biopesticides are generally used either directly, in the case of living biological organisms, or indirectly, when using the bioactive substances from organisms. The first category includes bacteria, fungi, nematodes, viruses, and antagonist microorganisms. The latter includes agricultural antibiotics, growth regulators, sex pheromones, feeding inhibitors, juvenile hormones, and herbal physiologically active substances. However, in the practical application of agricultural production, biopesticides generally refer mainly to the large-scale industrial production of microbial pesticides.

The study aimed to control the potato tuber moth Phthorimaea operculella (Zeller) by usingInsect Growth Regulator (Match) and UV-C with a wavelength of 254 nm on adults andincomplete stages (eggs and larvae). The results indicated that (1-2) days old eggs treated byUV-C rays with different exposure times (4,8,12 and 16 min.), from a distance of 50 cm andinsect growth regulator had almost the same effect on the eggs' hatching rates. The highest nonhatchingrates of eggs that sprayed by insect growth regulator was 59.30% at a concentrationof 2 ml /L. While the highest non-hatched rates of eggs that exposed to UV-C rays was 62.20%at a 16-minute exposure period. The results also showed that of (1-2) day old eggs treated withultraviolet rays or treated with the insect growth regulator (Match) were more vulnerable thaneggs at (5-6) days old. As the proportionality was direct between the rates of eggs non-hatchingand the duration of exposure to radiation or the concentration of the insect growth regulator.The results showed that the first instar larvae were more affected than the fourth instar larvaeby both insect growth regulator and UV-C treatments, at different concentrations and exposuretimes. The highest mortality rates for first-stage larvae under the influence of growth regulatorwere 42.20% at a concentration of 2 ml/L and 52.20% under the influence of UV-C rays,exposure time of 16 min., compared with 5.33 and 8.33% in the control treatment, respectively.As for the effect of ultraviolet radiation on the adults of the potato tuber moth, the difference infertility results (number of laid eggs / female) decreased dramatically, as the number of eggs208Academic Science JournalP-ISSN: 4612-2958Volume: 19, Issue: 2Manuscript Code: 675Alaid in the control treatment was 113.00 eggs / female. The lowest number of eggs laid was23.55 eggs / female when insects were exposed to UV rays for 16 min., while the percentagesof hatching, pupation and emergence were 76.33, 68.30 and 60.30% in the control treatment,and decreased to 22.30, 18.10 and 8.00% respectively, when insect exposed to UV-C rays for16 minutes. The results indicate the possibility of using UV-C rays and the insect growthregulator (Match) of chemical pesticides to control potato tuber moth.

The application of conventional pesticides is underlined by many negative externalities including environmental degradation and pest resistance. Consequently, use of biopesticides as alternative agrochemicals is recommended to meet sustainable development goals. Insect growth regulators (IGRs) are biochemical biopesticides. Actually, Biochemical biopesticides are compounds (or exact synthetic analogue) of natural origin possessing active ingredients that control pest in a way that are nontoxic to the target pest, the environment and humans. So, insecticides with growth regulating properties may adversely affect insects by regulating or inhibiting specific biochemical pathways or processes essential for insect growth and development. Ecdysoids and Juvenoids (JH mimics) are among the most promising IGRs. Ecdysoids are synthetic analogues of natural ecdysone and when applied in insects, kill them by formation of defective cuticle. Juvenoids (JH mimics) are synthetic analogues of Juvenile Hormone (JH). Juvenoids have anti-metamorphic effect on immature stages of insect. Along with this, Anti JH or precocenes which act by destroying corpora allata and preventing JH synthesis also act as IGR. In this way, Insect Growth Regulators are potential substitute of insecticides that could be commercially used.

Phytohormones, or plant hormones, are intrinsic organic compounds within plants. These compounds have a significant impact as essential plant growth and development regulators, influencing processes from seed germination to fruit ripening. The exogenous application of these phytohormones, such as gibberellic acid (GA3), indole-3-acetic acid (IAA), and brassinosteroids, has been shown to significantly enhance horticultural productivity, with reported increases in germination, growth, and yield ranging from 10–40%. These signaling molecules are also vital for micro and macroalgae development and functioning. Recognizing their presence within algae presents a fresh perspective for horticultural researchers and cultivators, offering opportunities to enhance the quality and application of horticultural crops. Nevertheless, the challenge arises from the presence of phytohormones in trace amounts, complicating their extraction and identification. This paper will offer a comprehensive overview of phytohormone classification and detection methods and highlight their presence in algae, which may serve as an alternative for promoting plant growth in agriculture.

The first significant use of a chemical to regulate plant growth in agriculture was in 1932, when pineapples were treated with ethylene to induce flowering. Despite a vast research effort in the ensuing years, there have been relatively few important additional applications, though plant growth regulators are used regularly in some specialised cropping situations. For example, following reports of the favourable effects of chlorme-quat chloride on wheat (Tolbert, 1960), the dwarfing properties of this and other synthetic growth retardants have been used commercially in Europe for many years to prevent lodging of cereals. In addition, several growth retardants and the ethylene-generating compound ethephon have been used since the 1970s on agricultural and horticultural crops, including sugarcane. In 1976, Hudson predicted that an increasing range of growth regulators would be found to have a wide spectrum of uses in world agriculture, fully justifying the exciting research and development work of the 1950s and 1960s. However, for most crops, including sugar beet, this prediction has not been fulfilled.

The two-spot cotton leafhopper, Amrasca biguttula (Ishida) (Hemiptera: Cicadellidae), recently detected in the United States, represents an emerging threat to cotton, vegetable, and ornamental crops. Insect growth regulators (IGRs) are considered reduced-risk insecticides. Despite their availability to growers and effectiveness on several piercing and sucking insects, the lethal effects of IGRs on the development of A. biguttula remain poorly understood. Thus, the objective of this study was to determine the effects of common IGRs on various stages of A. biguttula. We evaluated four IGRs: pyriproxyfen, novaluron, azadirachtin, and buprofezin applied at field-recommended rates, alone or combined with nonionic and organosilicone adjuvants, on survival, molting disruption (exuviae production), and longevity of early (1st-2nd), intermediate (3rd-4th), and late (5th) nymphal instars, as well as adults using leaf dip and adaxial leaf smear bioassays. All IGRs induced significant, stage-dependent lethal effects. Mortality of 1st–2nd instars reached over 90% with buprofezin and novaluron, and molting inhibition reached up to 55%, indicating strong effects of the tested insecticides. The chitin biosynthesis inhibitors buprofezin and novaluron caused rapid mortality, strong molting inhibition, and reduced longevity, particularly in early and intermediate instars. Pyriproxyfen and azadirachtin elicited weaker, delayed responses, with limited effects on late instars and adults. Although adding adjuvants slightly enhanced efficacy, their overall impact was marginal. These findings demonstrate that IGRs can profoundly disrupt A. biguttula population development through interference with insect growth and metamorphosis, supporting their use as selective and sustainable tools in integrated pest management programs targeting this invasive leafhopper.

Late-instar German cockroaches, Blattella germanica (L.), were used to evaluate the relative effects of single treatments and combinations of three insect growth regulators (IGRs): pyriproxyfen, fenoxycarb, and diflubenzuron. Groups of 15 males or 15 females were held for 2 wk on food treated with varying amounts of IGRs. After removal, newly mature adults were placed with untreated adults of the opposite sex. Mortality, adult phenotype (normal wings, divergent wings, curly wings, and nymphoids), and reproduction were assessed. Mortality occurred largely in the nymphal stage except when all three IGRs were combined. Neither the average number of nymphs per egg case nor hatch of egg cases from phenotypically normal cockroaches (normal wings, occasional darkening of the body) was affected in single treatments or in combinations of two IGRs, but nymphal numbers were reduced when the three IGRs were combined. Hatch from matings of insects with divergent wings varied. At low concentrations (3-10 ppm), hatch was generally normal; at high concentrations, most mating tests were unproductive. Mating tests of cockroaches with curly wings were almost always unproductive. When males with curly wings were mated, females dropped either unfertilized egg cases (no mating) or partially fertilized egg cases. Curly-wing females either dropped unfertilized egg cases or failed to form egg cases because of deleterious effects on ovarian development. Nymphoids did not mate. Diflubenzuron at 100 ppm had no effect other than causing the appearance of a few insects with divergent wings. Effects on phenotype and reproduction began at 3 ppm of both pyriproxyfen and fenoxycarb and at a comparable concentration in the combination of pyriproxyfen + fenoxycarb (1 ppm each). Female sterility was complete at 100 ppm of pyriproxyfen and fenoxycarb. When pyriproxyfen or fenoxycarb was combined with equal amounts of diflubenzuron, the number of productive matings was not reduced at 6 ppm (3 ppm per each IGR). At 20 ppm (10 ppm per each IGR), a reduction in productive matings coincided with the appearance of curly wings. Complete female sterility occurred only at 600 ppm (300 ppm per IGR). The most severe effects occurred in the experiment with equal amounts of pyriproxyfen, fenoxycarb, and diflubenzuron. In addition to reduced hatch from normal phenotypes, this experiment caused complete male sterility (300 ppm; 100 ppm of each IGR). Female sterility was complete at greater than or equal to 90 ppm (30 ppm of each IGR).

Aim: The aim of this study was to determine the presence, concentrations, dietary intake, and risk of residues of neonicotinoids (NEO) and insect growth regulators (IGR) in commercially available honey in South Africa. Methods: Sample preparation for honey was based on the “dilute and shoot” principle, followed by analysis using an internally validated ultra-high-performance liquid chromatographic coupled to tandem mass spectrometric method. Estimated daily intake and acute and chronic hazard quotients were determined to measure human exposure and health risk to NEO and IGR as well as the risk posed to honeybee. Results: NEO and IGR were detected in 50% and 21% of the 115 honey samples, respectively. The average concentration ranged 0.062-6.50 µgkg-1 and 0.479-1.644 µgkg-1 for NEO and IGR, respectively. While acetamiprid was the most detected (24.35%) NEO, imidacloprid presented the highest concentration (16.945 µg kg-1) in a sample. IGR co-occurred at variable concentrations with NEO in honey samples. The estimated daily intakes (EDI) of NEO and IGR ranged from 9.35 × 10-7 to 4.93 × 10-6 mg kg-1 bwd-1. The chronic hazard quotient (HQc) and acute hazard quotient (HQa) for NEO and IGR were considerably &lt; 1, indicating negligible risk to human health and honeybee population. Conclusion: A UHPLC-MS/MS method was validated for the simultaneous determination of neonicotinoids and insect growth regulators in honey. Overall, the result of the present study confirms the widespread occurrence of NEO and IGR in honey consumed in South Africa. The EDIs, HQc, and HQa indicate that exposure to all target NEO and IGR via honey consumption constitutes negligible human health risk; however, the consequences of multiple routes of exposure to NEO and IGR cannot be overemphasized.

Juvenile hormone (JH) analogs are nowadays in use to control harmful pests. In order to develop new bioactive molecules as potential pesticides, we have incorporated different active structural features like sulfonamide, aromatic rings, amide group, and amino acid moiety to the base structure. We have screened a series of designed novel JH analogs against JH receptor protein (jhbpGm-2RCK) of Galleria mellonella in comparison to commercial insect growth regulators (IGRs) – Pyriproxyfen (T1) and Fenoxycarb (T2). All analogs exhibit the binding energy profile comparable to commercial IGRs. Based upon these results, a series of sulfonamide-based JHAs (T3–T8) as IGRs have been synthesized and characterized. Further, the efficacy of synthesized analogs (T3–T8) and commercial IGRs (Pyriproxyfen and Fenoxycarb) has been assessed against fourth instars larvae of G. mellonella under the laboratory conditions. LC50 values of all the analogs (T1–T8) against the fourth instars larvae were 9.99, 10.12, 24.76, 30.73, 38.45, 34.15, 34.14, 19.48 ppm and the LC90 153.27, 131.69, 112.15, 191.46, 427.02, 167.13, 217.10, 172.00 ppm, respectively. Among these analogs, N-(1-isopropyl-2-oxo-3-aza-3-N-ethyl-pentanyl)-p-toluene sulfonamide (T8) and N-(1-isopropyl-2-oxo-3-aza-3-N-ethyl-pentanyl) benzene sulfonamide (T7) exhibited the good pest larval mortality at different exposure periods (in hours) and different concentrations (in ppm) in comparison to in use IGRs- T1 and T2. Bio assay results are supported by docking at higher concentration. The present investigation clearly exhibits that analog T8 could serve as a potential IGR in comparison to in use IGRs (T1 and T2). The results are promising and provide new array of synthetic chemicals that may be utilized as IGRs.

Aerosol applications of reduced risk insecticides such as pyrethrins, pyrethroids, and insect growth regulators are becoming more commonly used to manage stored-product insects in food facilities. However, these applications have a limited ability to penetrate into hidden refugia, where the majority of the pest population is located. Horizontal transfer of insecticides could occur as individuals directly treated or exposed to treated surfaces move into hidden refugia and encounter untreated individuals. In this series of studies, the potential for horizontal transfer of methoprene from treated Tribolium castaneum , the red flour beetle, to untreated individuals was evaluated. Adding larvae, pupae, or adults treated with methoprene to flour patches with untreated T. castaneum larvae, resulted in increased pupa and adult deformities and higher numbers of dead focal individuals, which suggests the potential for this mechanism. The transfer mechanism might be flour substrate contamination, transfer during contact of individuals, and/or cannibalism of individuals exposed to insecticides. Experiments focused on isolating the impact of contact and cannibalism on horizontal transfer did not detect a significant increase in mortality. Experiments focused on flour substrate contamination resulted in decreased adult emergence as well as lower survival, and higher rates of deformities. These findings suggest that substrate contamination is the more likely mechanism for horizontal transfer, and although horizontal transfer can occur, the impact of this process on populations needs further evaluation. Keywords: Red flour beetle, Tribolium castaneum , Methoprene, Horizontal transfer /* Style Definitions */ table.MsoNormalTable {mso-style-name:Normale Tabelle; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Times New Roman; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Normal 0 21 false false false DE X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:Normale Tabelle; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Times New Roman; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

The key trend for future agricultural growth is efficient, green and sustainable high-quality development, and it is crucial to sort out the factors influencing high-quality agricultural development.Objectives: The purpose of this study is to dissect whether environmental regulation has a catalytic effect on quality rural development, through which paths it is driven and whether there is a threshold effect to be further clarified.Method: In this study, the panel data of 34 provinces in China from 2012 to 2018 are used, and 17 variables are used to construct an evaluation index system, covering four dimensions: agricultural endowment, agricultural output level, agricultural green degree and social sustainability. The high-quality development of agriculture is measured by entropy method. And further, using a baseline regression model and a mediating effects model, we empirically investigated the impact of environmental regulation on high-quality agricultural development and its mechanism of action, and empirically assessed the nonlinear effects of environmental regulation using a threshold regression model.Results: Environmental control, as noted in the study, considerably assists in the establishment of high-quality agriculture; at the same time, large-scale land management plays a role in mitigating the influence of both. There is a single income threshold impact on rural households between high-quality agricultural growth and environmental regulation, and once that threshold is reached, the influence of high-quality agricultural growth grows.Contribution: According to the research findings, recommendations are made for the design of scientific environmental regulation policies, the establishment of a sound service system for large-scale rural land management, and the establishment of a stable mechanism for rural residents to sustain their income, in order to strengthen the effect of environmental regulation and realize high-quality agricultural growth in China. The marginal contribution of this paper is to enrich the study of the relationship between environmental regulation and high-quality agricultural development, which has theoretical and practical implications for promoting sustainable agricultural development.

Insect neuropeptide allatostatins (ASTs) play a vital role in regulating insect growth, development, and reproduction, making them potential candidates for new insect growth regulators (IGRs). However, the practical use of natural ASTs in pest management is constrained by their long sequences and high production costs, thus the development of AST analogs with shorter sequences and reduced cost is essential. Traditional methods for designing AST analogs are often time-consuming and resource-intensive. This study aims to employ new computational methodologies to understand the structure-activity relationship and efficiently discover potent AST analogs. Two machine learning models, utilizing multiple linear regression and support vector machine, were constructed to reveal the key structural factors that influence the juvenile hormone-inhibiting activity of AST analogs. These models suggested that a potent AST analog should contain styrene, hydrophilic, and aromatic groups, and rotatable bonds at positions 1, 2, 3, and 4, respectively. Six analogs (A52-A57) were designed and synthesized, and they exhibited potent juvenile hormone-inhibiting activity (IC50 < 16 nM). Notably, analog A53 showed the best activity (IC50 = 2.07 nM), surpassing that of most natural Dippu-ASTs, making it a potential lead candidate for IGRs. These models promote the efficient design, screening, and prioritization of new or untested AST analogs. The study clarifies how a machine learning-based strategy facilitates the development of AST analogs as novel IGR lead candidates, offering a useful reference for pest management. © 2024 Society of Chemical Industry.

The mortality of fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), larvae was significantly increased when they fed on leaves of southern pea Vignaunguiculata [L.] that had been treated with either of two insect growth regulators (IGRs) (RH-5992 and diflubenzuron), in combination with Konsume@^R, a cottonseed flour based insect feeding stimulant. Larval mortality was increased 2 and 3 days after treatment when Konsume (10% solution) and RH-5992 at 0.001 and 0.01% active ingredient [AI] were applied in combination, respectively. Similarly, a 10% solution of Konsume enhanced the effects of diflubenzuron (0.01% AI) on FAW larvae 4, 6, and 7 days after treatment. A 5% solution of Konsume mixed with diflubenzuron (0.001% AI) resulted in significantly greater fall armyworm larval mortality 2-5 days after treatment compared with diflubenzuron alone. The feeding stimulants Nu-Lure@^R, Coax@^R and Konsume all performed similarly against FAW larvae when mixed with either RH-5992 or diflubenzuron. However, Nu-Lure and Coax mixed with the IGRs did not significantly increase fall armyworm mortality above that caused by the IGRs alone. The simultaneous use of a feeding stimulant, such as Konsume, may provide an effective tool to increase toxicant activity of RH-5992 or diflubenzuron, and decrease the time needed to effect death of fall armyworm larvae.