Acaricides of Natural Origin, Personal Experiences and Review of Literature (1990-2001)**Dedicated to the memory of Prof. Serena Catalano

Acaricidal and Insecticidal Activities of Essential Oils and Constituents of Tasmannia lanceolata (Poir.) A.C.Sm. (Canellales: Winteraceae) Against Tetranychus urticae Koch (Trombidiformes: Tetranychidae) and Myzus persicae Sulzer (Hemiptera: Aphididae)

The negative side effects of synthetic pesticides have drawn attention to the need for environmentally friendly agents to control arthropod pests. To identify promising candidates as botanical pesticides, we investigated the acaricidal and insecticidal activities of 44 plant-derived essential oils (EOs) against Tetranychus urticae Koch and Myzus persicae Sulzer. Among the tested EOs, Tasmannia lanceolata (Poir.) A.C.Sm. (Tasmanian pepper) essential oil (TPEO) exhibited strong acaricidal and insecticidal activity. Mortality rates of 100% and 71.4% against T. urticae and M. persicae, respectively, were observed with TPEO at a concentration of 2 mg/ml. Polygodial was determined to be the primary active component after bioassay-guided isolation of TPEO using silica gel open-column chromatography, gas chromatography, and gas chromatography-mass spectrometry. Polygodial demonstrated acaricidal activity against T. urticae with mortality rates of 100%, 100%, 61.9%, and 61.6% at concentrations of 1, 0.5, 0.25, and 0.125 mg/ml, respectively. Insecticidal activity against M. persicae was also evident, with mortality rates of 88.5%, 85.0%, 46.7%, and 43.3% at respective concentrations of 1, 0.5, 0.25, and 0.125 mg/ml. Insecticidal and acaricidal activities of TPEO were greater than those of Eungjinssag, a commercially available organic agricultural material for controlling mites and aphids in the Republic of Korea. These findings suggest that TPEO is a promising candidate for mites and aphids control.

Effectiveness of Different Soft Acaricides against Honey Bee Ectoparasitic Mite Varroa destructor (Acari: Varroidae)

Simple Summary

Over the past few decades, the ectoparasitic mite Varroa destructor has been a significant threat to managed honey bee (Apis mellifera) colonies worldwide. Many control methods, including application of synthetic acaricides, have been adopted to control the infestation of varroa mites in honey bee colonies. Synthetic acaricides such as coumaphos and fluvalinate are only effective in reducing susceptible mites. Besides, synthetic acaricides pose multiple threats to honey bee colonies and the environment, necessitating their alteration with non-synthetic options. Naturally occurring compounds are considered an essential alternative control measure for varroa mites. Natural acaricides are derived from plants that contain essential oils or organic acids. The current study investigated the efficacy of formic acid, oxalic acid, and thymol in the control of Varroa mites. These soft acaricides were applied at various concentrations/quantities. Formic acid, oxalic acid, and thymol were all effective at lowering mite population levels. Formic acid, oxalic acid, and thymol can be used in an integrated management plan to control varroa mite populations. This scientific-based information can be shared with the beekeeping community of Pakistan and elsewhere, which will be helpful in managing this parasite that often affects honey bee productivity.

Abstract

Honey bees (Apis mellifera) are essential for their products—honey, royal jelly, pollen, propolis and beeswax. They are also indispensable because they support ecosystems with their pollination services. However, the production and functions of honey bees are hindered by the arthropod pest Varroa destructor, which attacks bees through its feeding activities. Efforts to control varroa mites have been made through the development of various synthetic pesticide groups, but have had limited success because the mites developed resistance and some of these pesticides are harmful to bees. Branded pesticides are rarely used in Pakistan, as beekeepers utilize acaricides from unknown sources. There is a need to create awareness of available naturally occurring acaricides that may serve as an alternative to synthetic acaricides. Although some naturally occurring compounds are considered toxic to the environment, the soft acaricides oxalic acid, thymol, and formic acid 65% are usually safe for honey bee colonies and beekeepers, when handled appropriately. The current study investigated the effectiveness of formic acid (10, 15, and 20 mL/hive), oxalic acid (4.2, 3.2, and 2.1%/hive), and thymol (6, 4, and 2 g/hive) in controlling mite infestation. The results indicated that all treatments significantly reduced the mite population (p < 0.05). The average efficacies of oxalic acid at 3.2% (94.84% ± 0.34) and 4.2% (92.68% ± 0.37) were significantly higher than those of the other treatments. The lowest efficacy was recorded in formic acid 65% at 10 mL (54.13%). Overall, the results indicated that soft acaricides—such as oxalic acid at 3.2% and 4.2% concentrations—are very effective at controlling varroa mites and can be used in broodless conditions without side effects.

Behavioral response of Panonychus citri (McGregor) (Acari: Tetranychidae) to synthetic chemicals and oils

Background

Panonychus citri (McGregor) (Acari: Tetranychidae) population outbreaks after the citrus plantation's chemical application is a common observation. Dispersal behavior is an essential tool to understand the secondary outbreak of P. citri population. Therefore, in the current study, the dispersal activity of P. citri was observed on the leaf surfaces of Citrus reticulata (Rutaceae) treated with SYP-9625, abamectin, vegetable oil, and EnSpray 99.

Method

Mites were released on the first (apex) leaf of the plant (adaxial surface) and data were recorded after 24 h. The treated, untreated, and half-treated data were analyzed by combining the leaf surfaces (adaxial right, adaxial left, abaxial right, and abaxial left). All experiments were performed in open-air environmental conditions.

Results

The maximum number of mites was captured on the un-treated or half-treated surfaces due to chemicals repellency. Chemical bioassays of the free-choice test showed that all treatments significantly increased the mortality of P. citri depending on application method and concentration. A significant number of mites repelled away from treated surfaces and within treated surfaces except adaxial left and abaxial right surfaces at LC₃₀. In the no-choice test, SYP-9625 gave maximum mortality and dispersal by oils than others. No significant differences were observed within the adaxial and abaxial except abaxial surface at LC₃₀. Therefore, the presence of tested acaricides interferes with P. citri dispersal within leaf surfaces of plantations depending on the mites released point and a preferred site for feeding.

Acaricidal activity, mode of action, and persistent efficacy of selected essential oils on the poultry red mite (Dermanyssus gallinae)

In this work, the essential oils (EOs) from Litchi chinensis, Clausena anisata, Heracleum sphondylium, Pimpinella anisum, Lippia alba, Crithmum maritimum and Syzygium aromaticum were tested for their contact toxicity against the poultry red mite, Dermanyssus gallinae, a deleterious ectoparasite of aviary systems. In addition, in order to give insights on their mode of action and effectiveness, the vapor phase and residual toxicity tests were also performed. Results showed that amongst all the tested EOs, that of S. aromaticum demonstrated the highest contact toxicity, with a LC₅₀ value of 8.9 μg/mL, followed by C. maritimum and L. chinensis EOs, with LC₅₀ values of 23.7 and 24.7 μg/mL, respectively. L. chinensis and C. anisata EOs showed higher vapor toxicity than the other EOs. L. chinensis and S. aromaticum EOs showed promising toxic effects up to 4 days post-application. Taken together, these results highlighted L. chinensis and S. aromaticum as two promising sources of biopesticides, able to cause severe contact, vapor and residual toxicity in the poultry red mites. Given the wide plant cultivation and uses in foodstuffs, cosmetics, flavour and fragrances, these EOs may be considered cheap and ready-to-use products as valid, eco-friendly alternatives to pesticides currently used in the aviary systems.

1,4-Naphthoquinone Triggers Nematode Lethality by Inducing Oxidative Stress and Activating Insulin/IGF Signaling Pathway in Caenorhabditis elegans

Plant-parasitic nematodes are destructive pathogens causing enormous economic losses worldwide. With the withdrawal of fumigants, organophosphates and carbamates, pathogenic nematode control is more difficult. Phytochemicals are the plant secondary metabolites and are friendly for men and the environment. For developing new nematocidal candidates, we screened 790 phytochemicals using the model organism Caenorhabditis elegans and found 10 active compounds, 3 of which were further evaluated for their inhibitory activities against egg hatching of C. elegans and J2 Meloidogyne incognita. Among them, 1,4-naphthoquinone (1,4-NQ) was the only compound that could kill more than 50% of targets at 50 μg/mL, prompting us to investigate how 1,4-NQ triggers nematode lethality. In C. elegans, we observed that 1,4-NQ could influence reactive oxygen production, superoxide dismutase activity, and the heat-shock transcription factor (HSF)-1 pathway, which indicated that 1,4-NQ stimulated significant oxidative stress. Furthermore, using quantitative RT-PCR and transgenetic nematodes, we revealed that 1,4-NQ lethality was related to the Insulin/IGF signaling (IIS) pathway, and the effect of 1,4-NQ on IIS pathway related genes indicated that 1,4-NQ could activate this pathway and suppress the expression of DAF-16 target genes. The triggering of oxidative stress and activation of the IIS pathway indicated that 1,4-NQ operates through the generation of oxygen radicals, which can be lethal to C. elegans, thus making it an interesting lead compound for the development of future nematocides.

The field efficacy of Lepidium latifolium and Zataria multiflora methanolic extracts against Varroa destructor

Varroa destructor is the most serious pest of honeybee (Apis mellifera), causing high economic losses in the beekeeping industry worldwide. The intensive utilization of many chemical substances against the mites resulted in resistance development. One of the applicable and alternative treatments being used for their control is plant-derived products (PDSS). The aim of this study was to evaluate the acaricidal activity of Lepidium latifolium and Zataria multiflora leaf extracts on V. destructor in field conditions. Four different concentrations (100, 200, 400, and 500 ppm) of the methanolic extracts were sprayed to treat each colony. The efficacy and side effects on adult bees were compared to Apistan chemical strips (ACSS). The acaricidal activity was the highest (100%) for L. latifolium extract at 500 ppm after 12 days and 86.26% for Z. multiflora. The infestation rate was decreased to 0.0% with L. latifolium and to 13.74% with Z. multiflora. The highest reduction was observed with L. latifolium followed by Z. multiflora extract at 500 ppm concentration. Both of the extracts showed negligible effect on bees, and it can be concluded that these PDSS as biodegradable agents could be used for V. destructor control in honeybee colonies.

The economic importance of acaricides in the control of phytophagous mites and an update on recent acaricide mode of action research

Acaricides are one of the cornerstones of an efficient control program for phytophagous mites. An analysis of the global acaricide market reveals that spider mites such as Tetranychus urticae, Panonychus citri and Panonychus ulmi are by far the most economically important species, representing more than 80% of the market. Other relevant mite groups are false spider mites (mainly Brevipalpus), rust and gall mites and tarsonemid mites. Acaricides are most frequently used in vegetables and fruits (74% of the market), including grape vines and citrus. However, their use is increasing in major crops where spider mites are becoming more important, such as soybean, cotton and corn. As revealed by a detailed case study of the Japanese market, major shifts in acaricide use are partially driven by resistance development and the commercial availability of compounds with novel mode of action. The importance of the latter cannot be underestimated, although some compounds are successfully used for more than 30 years. A review of recent developments in mode of action research is presented, as such knowledge is important for devising resistance management programs. This includes spirocyclic keto-enols as inhibitors of acetyl-CoA carboxylase, the carbazate bifenazate as a mitochondrial complex III inhibitor, a novel class of complex II inhibitors, and the mite growth inhibitors hexythiazox, clofentezine and etoxazole that interact with chitin synthase I.

Comparative toxicity of an acetogenin-based extract and commercial pesticides against citrus red mite

Acetogenins, a class of natural compounds produced by some Annonaceae species, are potent inhibitors of mitochondrial electron transport systems. Although the cellular respiration processes are an important biochemical site for the acaricidal action of compounds, few studies have been performed to assess the bioactivity of acetogenin-based biopesticides on spider mites, mainly against species that occur in orchards. Using residual contact bioassays, this study aimed to evaluate the bioactivity of an ethanolic extract from Annona mucosa seeds (ESAM) (Annonaceae) against the citrus red mite Panonychus citri (McGregor) (Acari: Tetranychidae), an important pest of the Brazilian citriculture. ESAM is a homemade biopesticide which was previously characterized by its high concentration of acetogenins. It caused both high mortality of P. citri females (LC50 = 7,295, 4,662, 3,463, and 2,608 mg l(-1), after 48, 72, 96, and 120 h of exposure, respectively) and significant oviposition deterrence (EC50 = 3.194,80 mg l(-1)). However, there was no effect on P. citri female fertility (hatching rate). In addition, the ESAM efficacy (in terms of its LC90) was compared with commercial acaricides/insecticides (at its recommended rate) of both natural [Anosom(®) 1 EC (annonin), Derisom(®) 2 EC (karanjin), and Azamax(®) 1.2 EC (azadirachtin + 3-tigloylazadirachtol)] and synthetic origin [Envidor(®) 24 SC (spirodiclofen)]. Based on all of the analyzed variables, the ESAM exhibited levels of activity superior to other botanical commercial acaricides and similar to spirodiclofen. Thus, our results indicate that ESAM may constitute a biorational acaricide for citrus red mite integrated pest management in Brazilian citrus orchards, particularly for local use.