Effects of Menadione on Survival, Feeding, and Tunneling Activity of the Formosan Subterranean Termite

The Formosan subterranean termite, Coptotermes formosanus Shiraki, is a highly destructive pest and a cosmopolitan invasive species. Sustainable termite management methods have been improving with the search for novel insecticides that are effective, safe, and cost efficient. Menadione, also known as vitamin K3, is a synthetic analogue and biosynthetic precursor of vitamin K with low mammalian toxicity. Menadione has shown insecticidal activity in several insects, presumably due to interference with mitochondrial oxidative phosphorylation. However, little is known about its effectiveness against termites. In this study, we evaluated the toxicity and repellency of menadione in C. formosanus. Our results showed that menadione affected the survival and feeding activity of termites both in filter paper and substrate (sand) treatments, and menadione influenced termite tunneling activity in treated sand. In a no-choice assay, ≥90% mortality after seven days and minimal or no food consumption were recorded when sand was treated with menadione at 6 to 600 ppm. In a two-choice assay with a combination of treated and untreated sand, termites were deterred by menadione at 6 to 600 ppm and exhibited low mortality (≤30%) over seven days, while tunneling activity was prevented with 60 to 600 ppm of menadione treatment. Overall, our study demonstrated dose-dependent toxicity and repellency of menadione in C. formosanus. The potential use of menadione as an alternative termite control agent is discussed.

Transcriptional Responses and GCMS Analysis for the Biosynthesis of Pyrethrins and Volatile Terpenes in Tanacetum coccineum

Natural pyrethrins have been widely used as natural pesticides due to their low mammalian toxicity and environmental friendliness. Previous studies have mainly focused on Tanacetum cinerariifolium, which contains high levels of pyrethrins and volatile terpenes that play significant roles in plant defense and pollination. However, there is little information on T. coccineum due to its lower pyrethrin content and low commercial value. In this study, we measured the transcriptome and metabolites of the leaves (L), flower buds (S1), and fully blossomed flowers (S4) of T. coccineum. The results show that the expression of pyrethrins and precursor terpene backbone genes was low in the leaves, and then rapidly increased in the S1 stage before decreasing again in the S4 stage. The results also show that pyrethrins primarily accumulated at the S4 stage. However, the content of volatile terpenes was consistently low. This perhaps suggests that, despite T. coccineum and T. cinerariifolium having similar gene expression patterns and accumulation of pyrethrins, T. coccineum attracts pollinators via its large and colorful flowers rather than via inefficient and metabolically expensive volatile terpenes, as in T. cinerariifolium. This is the first instance of de novo transcriptome sequencing reported for T. coccineum. The present results could provide insights into pyrethrin biosynthetic pathways and will be helpful for further understanding how plants balance the cost–benefit relationship between plant defense and pollination.

The ameliorative effect of protein hydrolysate on the imazamox-damaged young wheat plants

The plant biostimulants (PBs) are a wide range of microbial and/or organic compounds applied to crops to improve the physiological processes such as nutrition efficiency, plant development and abiotic stress tolerance. Imazamox is a herbicide characterised with a wide spectrum of weed control, low application rates and low mammalian toxicity, but also with a high soil persistence. Therefore, the residual amounts of imazamox may negatively affect subsequent sensitive crops in the crop rotation. In the current study we investigated the effect of a single and combined treatment with imazamox and a plant biostimulant (protein hydrolisate) on the antioxidative defense system and the detoxification metabolism of wheat young plants. The result showed that the seed imbibition with 10 μM imazamox inhibits the growth of the young wheat plants. A slight improvement was found due to the additional treatment with protein hydrolysate of the wheat plants damaged by imazamox herbicide. According to the results, this improving effect on the growth does not ameliorate the plant detoxification metabolism such as glutathione S-transferases or antioxidative defense. However, the improving effect is low and insufficient to restore the plant growth and functioning and its effects on wheat production are not studied yet.

ECOLOGICAL AND HYGIENIC ASSESSMENT OF NEW PESTICIDES FOR GRAIN CEREALS CHEMICAL PROTECTION

Relevance. The use of pesticides in the national economy is to destroy or inhibit the growth of harmful plants and to protect crops from pathogens requires a mandatory assessment of their environmental hygienic hazard. Objective of our study is to assess the hazards of three new pesticides for cereal grains protection: amicarbazone from the chemical class of triazolinone compounds, bicyclopyrone from the class of tricetones and pydiflumetofen from the class of carboxamides, in terms of ecotoxicity and environmental behavior. Materials and methods. Hazard assessment of amicarbazone, bicyclopyrone and pydiflumetofen was performed on the basis of data sources on their physico-chemical characteristics, toxicometry parameters for different species of living things and indicators of environmental behavior. For potential hazards integral assess for terrestrial ecosystems an ecotox was calculated taking into account mammalian toxicity, persistence and maximum rate consumption. To identify the limiting section of migration, the mathematical modeling was performed in the systems "soil-water", "soil-plants" and "soil-atmospheric air". Results. Amicarbazone has been shown to be extremely toxic to algae and highly toxic to higher aquatic plants (HAP) (hazard class I), moderately toxic (class IV) to mammals, mildly toxic (class III) to birds, soil mesofauna and invertebrates, virtually non-toxic to bees and fish; bicyclopyrone - extremely toxic to HAP (class I) and moderately toxic (class II) to the most sensitive algae, mildly toxic (class III) to birds, fish and invertebrates and virtually non-toxic to other terrestrial fauna; pydiflumetofen is highly toxic (class I) to fish and invertebrates, moderately toxic (class II) to algae and HAP, virtually non-toxic to all terrestrial biota. Pydiflumetofen has been shown to be a highly resistant and poorly mobile in soil; amicarbazone is stable and mobile; bicyclopyrone is highly resistant in laboratory experiments and moderately stable in field experiments, its mobility varies in a wide range: from very mobile to less mobile in some soils. The danger for terrestrial biocenoses of all studied pesticides under different soil and climatic conditions is lower by (1–5) orders of magnitude in comparison with DDT; the lowest is the ecotoxicity of bicyclopyrone, the highest – pydiflumetofen. All test substances are highly stable in water. The leading section of their migration in environment is the system "soil – water of ponds" and in case of pydiflumetofen – "soil – plants" as well.

Effects of Bioinsecticidal Aegerolysin-Based Cytolytic Complexes on Non-Target Organisms

Aegerolysin proteins ostreolysin A6 (OlyA6), pleurotolysin A2 (PlyA2) and erylysin A (EryA) produced by the mushroom genus Pleurotus bind strongly to an invertebrate-specific membrane sphingolipid, and together with a protein partner pleurotolysin B (PlyB), form transmembrane pore complexes. This pore formation is the basis for the selective insecticidal activity of aegerolysin/PlyB complexes against two economically important coleopteran pests: the Colorado potato beetle and the western corn rootworm. In this study, we evaluated the toxicities of these aegerolysin/PlyB complexes using feeding tests with two ecologically important non-target arthropod species: the woodlouse and the honey bee. The mammalian toxicity of the EryA/PlyB complex was also evaluated after intravenous administration to mice. None of the aegerolysin/PlyB complexes were toxic against woodlice, but OlyA6/PlyB and PlyA2/PlyB were toxic to honeybees, with 48 h mean lethal concentrations (LC50) of 0.22 and 0.39 mg/mL, respectively, in their food. EryA/PlyB was also tested intravenously in mice up to 3 mg/kg body mass, without showing toxicity. With no toxicity seen for EryA/PlyB for environmentally beneficial arthropods and mammals at the tested concentrations, these EryA/PlyB complexes are of particular interest for development of new bioinsecticides for control of selected coleopteran pests.

Toxicity of 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NKK) in early development: a wide-scope metabolomics assay in zebrafish embryos

The tobacco-specific nitrosamine 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a carcinogenic and ubiquitous environmental pollutant which carcinogenic and cytotoxic activity has been thoroughly investigated in murine models and human tissues. However, its potential deleterious effects on vertebrate early development are yet poorly understood. In this work, we characterized the impact of NNK exposure during early developmental stages of zebrafish embryos, a known alternative model for mammalian toxicity studies. Embryos exposed to different NNK concentrations were monitored for lethality and for the appearance of malformations during the first five days after fertilization. LC/MS-based untargeted metabolomics was subsequently performed for a wide-scope assay of NNK-related metabolic alterations. Our results revealed the presence of not only the parental compound, but also of two NKK known metabolites, 4-Hydroxy-4-(3-pyridyl)-butyric acid (HPBA) and 4-(Methylnitrosamino)-1-(3-pyridyl-N-oxide)-1-butanol (NNAL-N-oxide) in exposed embryos likely resulting from active CYP450-mediated α-hydroxylation and NNK detoxification pathways, respectively. This was paralleled by a disruption in purine and pyrimidine metabolisms and the activation of the base excision repair pathway. Our results confirm NNK as a harmful embryonic agent and demonstrate zebrafish embryos to be a suitable early development model to monitor NNK toxicity.

Risk assessment of secondary metabolites produced by fungi in the genus Stemphylium

The fungal genus <i>Stemphylium</i> (phylum Ascomycota, teleomorph <i>Pleospora</i>) includes plant pathogenic, endophytic, and saprophytic species with worldwide distributions. <i>Stemphylium<i></i> spp. produce prodigious numbers of air-borne spores, so are a human health concern as allergens. Some species also produce secondary metabolites such as glucosides, ferric chelates, aromatic polyketides, and others that function as toxins that damage plants and other fungal species. Some of these compounds also exhibit a low level of mammalian toxicity. The high production of air-borne spores by this genus can result in a high incidence of human exposure. Concern about toxin production appears to be the reason that <i></i>S. vesicarium<i></i>, which is a pathogen of several vegetable crops, was classified in Canada as a potential risk of harm to humans for many years. A detailed assessment of the risk of exposure was provided to the relevant regulatory body, Public Health Agency of Canada. They determined that <i></i>Stemphylium<i></i> spp., in nature or under laboratory conditions, posed little to no risk to humans or animals, and the species was re-assigned as a basic (level 1) risk agent.

Antifungal activities of methanol extracts of some medicinal plants against germination and growth of Colletotrichum destructivum O’Gara in culture

Authors. 2021. Antifungal activities of methanol extracts of some medicinal plants against germination and growth of Colletotrichum destructivum O’Gara in culture. Asian J Nat Prod Biochem 19: 25-29. Cowpea is an important grain and leafy vegetable in many tropical locations. Anthracnose caused by Colletotrichum destructivum O’Gara is one of the several factors constraining the economic production of the crop in warm humid areas. Use of resistant varieties and synthetic pesticides for control of the disease in the crop are disadvantaged for variability of the pathogen, leading to resistance failure of cultivars in many cowpea growing areas; and pesticide residues in the treated crops which ultimately engender mammalian toxicity respectively. This study evaluated the effects of Alchornea cordifolia, Tabernaemontana pachysiphon and Lantana camara as eco-friendly fungicides against the pathogen in culture. The results showed that the extracts inhibited the fungus in a dose-wise manner. At 75 and100 % concentrations, L. camara strongly inhibited the spore germination and radial growth of the fungus better than all concentrations of T. pachysiphon and A. cordifolia; whereas A. cordifolia extracts exhibited the lowest inhibition at all concentrations. Generally, the fungitoxicity of benomyl was found higher which inhibited 90.15 % spore germination and 96.32 % radial growth of the pathogen. However, at 75%, 100% L. camara and 100% T. pachysiphon which significantly (P?0.05) inhibited (80.02%, 84.21 % and 80.91%) spore germination and (87.33%, 90.87 % and 85. %) radial growth of the fungus respectively compared well with inhibition effects recorded from benomyl. Therefore these plants can be used as viable protectants of cowpea against anthracnose (C. destructivum) in small holder farming systems of the humid tropics; to enhance its production and farm economy.

THERAPEUTIC INDICES OF SOME ANTIFUNGAL ORGANIC COMPOUNDS

Objective: The objective of the study was to evaluate the therapeutic indices (TIs) some antifungal organic compounds and to compare their safety. Methods: TIs of 55 organic compounds were evaluated by dividing their mammalian toxicity values given as median lethal doses ([mg/kg] rat, oral) collected from literature by experimentally determined fungitoxicity values evaluated as median effective concentration (EC50 [mg/L]) for the mycelial growth inhibition of Colletotrichum gloeosporioides on potato dextrose agar medium. Results: Large variations in TIs are observed in different classes of compounds, namely, alcohols, carboxylic acids, phenols, esters, and aldehydes. The relationship between carbon chain length of saturated monohydric alcohols and mammalian toxicity shows that toxicity increases from chain length 1 to 5, declines from 5 to 6, increases from 6 to 7, and steadily declines from 7 to 10. Thus, the relationship is by and large parabolic. The relationship between carbon chain length and molar antifungal activity is also parabolic. In spite of this, large differences are found in TIs making 1-decanol (TI=42.1) a very safe antifungal compound and 1-pentanol (TI=0.17) a hazardous antifungal compound. This is because mammalian toxicity reaches a maximum around carbon chain length of 5, while in the case of antifungal activity, it reaches a maximum around carbon chain length of 10. Conclusions: Among the 55 compounds, whose TIs were evaluated, some compounds with high TIs (>10) which can be considered safe as antifungal compounds are citronellol, geraniol, 1-decanol, 1-octanol, phenyl acetaldehyde, methyl anthranilate, 1-naphthol, 2-naphthol, and propionic acid. Some compounds with low TIs (<0.50) which can be considered hazardous as antifungal compounds are resorcinol, hydroquinone, oxalic acid, and acetyl acetone.

Azadirachta indica A. Juss. In Vivo Toxicity—An Updated Review

The Neem tree, Azadirachta indica A. Juss., is known for its large spectrum of compounds with biological and pharmacological interest. These include, among others, activities that are anticancer, antibacterial, antiviral, and anti-inflammatory. Some neem compounds are also used as insecticides, herbicides, and/or antifeedants. The safety of these compounds is not always taken into consideration and few in vivo toxicity studies have been performed. The current study is a literature review of the latest in vivo toxicity of A. indica. It is divided in two major sections—aquatic animals toxicity and mammalian toxicity—each related to neem’s application as a pesticide or a potential new therapeutic drug, respectively.