Toxicity of plant essential oils to acaricide-susceptible and -resistant Tetranychus urticae (Acari: Tetranychidae) and Neoseiulus californicus (Acari: Phytoseiidae)

Lethal and sublethal effects of carlina oxide on Tetranychus urticae (Acari: Tetranychidae) and Neoseiulus californicus (Acari: Phytoseiidae)

BACKGROUND

Tetranychus urticae Koch, is a polyphagous and damaging pest, presenting several resistant populations worldwide. Among new and more environmentally friendly control tools, botanical pesticides represent a valuable alternative to synthetic ones within integrated pest management strategies. Accordingly, we investigated the lethal and sublethal effects of carlina oxide isolated from Carlina acaulis (Asteraceae) roots on T. urticae and its natural enemy, the predatory mite, Neoseiulus californicus (McGregor).

RESULTS

Carlina oxide (98.7% pure compound) was used for acaricidal tests on eggs, nymphs, and adult females of T. urticae (concentrations of 312.5, 625, 1250, 2500 and 5000 μL L-1 ), and eggs and females of N. californicus (1250 and 5000 μL L-1 on eggs and females, respectively). Behavioral two-choice tests were also conducted on phytoseiid females. Carlina oxide toxicity was higher on T. urticae females than nymphs (median lethal dose 1145 and 1825 μL L-1 , respectively), whereas egg mortality and mean hatching time were significantly affected by all tested concentrations. A decreasing daily oviposition rate for T. urticae was recorded with concentrations ranging from 625 to 5000 μL L-1 , whereas negative effects on the population growth rate were recorded only with the three higher concentrations (1250, 2500 and 5000 μL L-1 ). No toxic effect on N. californicus females was found, but a strong repellent activity lasting for 48 h from application was recorded.

CONCLUSION

Carlina oxide reduced longevity and fecundity of T. urticae adults, but not of N. californicus. This selective property allows us to propose it as a novel active ingredient of ecofriendly acaricides for T. urticae management. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Fumigant Toxicity of Essential Oils against Frankliniella occidentalis and F. insularis (Thysanoptera: Thripidae) as Affected by Polymer Release and Adjuvants

Simple Summary

Frankliniella occidentalis is among the most economically significant pests of greenhouse crops. In contrast, F. insularis is a relatively minor pest with a narrower distribution and host range. We conducted a series of fumigation assays to assess the vulnerability of both species to fumigation with essential oils released from hydrogels. These hydrogels contained either (R)-linalool, (S)-linalool, racemic linalool, or a binary mixture of (R)-linalool with one of twelve other essential oils. Solanum lycopersicum seedlings were screened for their sensitivity to the most potent fumigants, as determined from thrips bioassays. The least saturated hydrogels conditioned in essential oils were the most effective, and both species of thrips were more sensitive to (R)-linalool than to (S)-linalool. Frankliniella occidentalis was significantly more resistant to all treatments than F. insularis. Treatment of S. lycopersicum with the same concentrations of oils required to control thrips resulted in reduced root and hypocotyl lengths, most severely in seedlings exposed via foliar sprays than as fumigants. While our study demonstrates that essential oils are a promising alternative to conventional insecticides for thrips control, the resistance demonstrated by F. occidentalis underlines the need for judicious use of essential oils as part of broader pest control programs.

Abstract

Frankliniella occidentalis is among the most economically significant pests of greenhouse crops, whose resistance to conventional insecticides has created demand for biopesticides such as essential oils. We assessed the fumigant toxicity of linalool against F. occidentalis, F. insularis, and Solanum lycopersicum. Thrips were fumigated with polyacrylamide hydrogels containing either (R)-linalool, (S)-linalool, racemic linalool, or a binary mixture of (R)-linalool with one of twelve adjuvants (i.e., peppermint, cedarwood, neem, clove, coconut, jojoba, soybean, olive, α-terpineol, 1,8-cineole, trans-anethole, or (R)-pulegone). Solanum lycopersicum seedlings were exposed to (R)-linalool or a mixture of (R)-linalool and peppermint oil via conditioned hydrogels or foliar spray. For F. insularis, (R)-linalool was more toxic than (S)-linalool, with LC₅₀ values of 11.7 mg/L air and 16.7 mg/L air, respectively. Similarly for F. occidentalis, (R)-linalool was more toxic than (S)-linalool, with LC₅₀ values of 29.0 mg/L air and 34.9 mg/L air, respectively. Peppermint oil and α-terpineol were the only synergists, while the other adjuvants exhibited varying degrees of antagonism. All seedling treatments demonstrated phytotoxicity, but symptoms were most severe for foliar sprays and mixtures containing peppermint oil. While hydrogels conditioned in linalool may be a favorable substitute to conventional insecticides, the cross-resistance demonstrated herein indicates that expectations should be metered.

Acaricidal activity of binary blends of essential oils and selected constituents against Tetranychus urticae in laboratory/greenhouse experiments and the impact on Neoseiulus californicus

The aim of this study was to test the effectiveness of essential oils form Piper aduncum, Melaleuca leucadendra and Schinus terebinthifolius and their blends by fumigation and residual contact on Tetranychus urticae and its natural enemy, Neoseiulus californicus. Bioassays were performed in a greenhouse with the best blend of the oils and compared to the individual oils and Vertimec® (positive control). The main constituents identified by GC-MS were dillapiole, (E)-nerolidol and limonene in the oils from P. aduncum (76.5%), M. leucadendra (87.3%) and S. terebinthifolius (unripe/ripe fruits, 42.5/34.1%). The P. aduncum and M. leucadendra oils were the most toxic to the pest. Among the blends, the greatest toxicity to T. urticae occurred by residual contact with the M. leucadendra + S. terebinthifolius ripe fruit blend (50/50). The evaluation of the effects on N. californicus showed the compatibility of the oils and blends with the predator mite for use in the integrated management of T. urticae. β-Caryophyllene was the most toxic, independent of the method used. Based on toxicities of 11 oil constituents, the structure-activity relationship of these compounds is also discussed. This study showed that the acaricidal effect of the Piper, Melaleuca and Schinus oils can easily be increased by the binary combination of these oils. The binary blend between the oils of the Melaleuca leaves and ripe Schinus fruit in the greenhouse was effective at controlling the mite after 72 h, exhibiting the same level of toxicity as that found for the positive control (Vertimec 18 EC).

Botanicals Against Tetranychus urticae Koch Under Laboratory Conditions: A Survey of Alternatives for Controlling Pest Mites

Tetranychus urticae Koch is a phytophagous mite capable of altering the physiological processes of plants, causing damages estimated at USD$ 4500 per hectare, corresponding to approximately 30% of the total cost of pesticides used in some important crops. Several tools are used in the management of this pest, with chemical control being the most frequently exploited. Nevertheless, the use of chemically synthesized acaricides brings a number of disadvantages, such as the development of resistance by the pest, hormolygosis, incompatibility with natural predators, phytotoxicity, environmental pollution, and risks to human health. In that sense, the continuous search for botanical pesticides arises as a complementary alternative in the control of T. urticae Koch. Although a lot of information is unknown about its mechanisms of action and composition, there are multiple experiments in lab conditions that have been performed to determine the toxic effects of botanicals on this mite. Among the most studied botanical families for this purpose are plants from the Lamiaceae, the Asteraceae, the Myrtaceae, and the Apiaceae taxons. These are particularly abundant and exhibit several results at different levels; therefore, many of them can be considered as promising elements to be included into integrated pest management for controlling T. urticae.

Chemical Variability and Biological Activities of Eucalyptus spp. Essential Oils

Many plant species produce mixtures of odorous and volatile compounds known as essential oils (EOs). These mixtures play important roles in Nature and have been utilized by mankind for different purposes, such as pharmaceuticals, agrochemicals, aromatherapy, and food flavorants. There are more than 3000 EOs reported in the literature, with approximately 300 in commercial use, including the EOs from Eucalyptus species. Most EOs from Eucalyptus species are rich in monoterpenes and many have found applications in pharmaceuticals, agrochemicals, food flavorants, and perfumes. Such applications are related to their diverse biological and organoleptic properties. In this study, we review the latest information concerning the chemical composition and biological activities of EOs from different species of Eucalyptus. Among the 900 species and subspecies of the Eucalyptus genus, we examined 68 species. The studies associated with these species were conducted in 27 countries. We have focused on the antimicrobial, acaricidal, insecticidal and herbicidal activities, hoping that such information will contribute to the development of research in this field. It is also intended that the information described in this study can be useful in the rationalization of the use of Eucalyptus EOs as components for pharmaceutical and agrochemical applications as well as food preservatives and flavorants.

Fumigant toxicity of plant essential oils against Camptomyia corticalis (Diptera: Cecidomyiidae)

The toxicity of 98 plant essential oils against third instars of cecidomyiid gall midge Camptomyia corticalis (Loew) (Diptera: Cecidomyiidae) was examined using a vapor-phase mortality bioassay. Results were compared with that of a conventional insecticide dichlorvos. Based on 24-h LC50 values, all essential oils were less toxic than dichlorvos (LC50, 0.027 mg/cm3). The LC50 of caraway (Carum carvi L.) seed, armoise (Artemisia vulgaris L.), clary sage (Salvia sclarea L.), oregano (Origanum vulgare L.), lemongrass [Cymbopogon citratus (DC.) Stapf], niaouli (Melaleuca viridiflora Gaertner), spearmint (Mentha spicata L.), cassia especial (Cinnamomum cassia Nees ex Blume), Dalmatian sage (Salvia offcinalis L.), red thyme (Thymus vulgaris L.), bay [Pimenta racemosa (P. Mill.) J.W. Moore], garlic (Allium sativum L.), and pennyroyal (Mentha pulegium L.) oils is between 0.55 and 0.60 mg/cm3. The LC50 of cassia (C. cassia, pure and redistilled), white thyme (T. vulgaris), star anise (Illicium verum Hook.f.), peppermint (Mentha X piperita L.), wintergreen (Gaultheria procumbens L.), cinnamon (Cinnamomum zeylanicum Blume) bark, sweet marjoram (Origanum majorana L.), Roman chamomile [Chamaemelum nobile (L.) All.], eucalyptus (Eucalyptus globulus Labill.), rosemary (Rosmarinus officinalis L.),Virginian cedarwood (Juniperus virginiana L.), pimento berry [Pimenta dioica (L.) Merr.], summer savory (Satureja hortensis L.), lavender (Lavandula angustifolia Mill.), and coriander (Coriandrum sativum L.) oils is between 0.61 and 0.99 mg/cm3. All other essential oils tested exhibited low toxicity to the cecidomyiid larvae (LC50, >0.99 mg/cm3). Global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment justify further studies on the active essential oils as potential larvicides for the control of C. corticalis populations as fumigants with contact action.

Fumigant toxicity of lemon eucalyptus oil constituents to acaricide-susceptible and acaricide-resistant Tetranychus urticae

BACKGROUND

This study was aimed at assessing the fumigant toxicity of 14 essential oil constituents from lemon eucalyptus, Eucalyptus citriodora Hook, and another ten known compounds to females of acaricide-susceptible, chlorfenapyr-resistant, fenpropathrin-resistant, pyridaben-resistant and abamectin-resistant strains of Tetranychus urticae Koch.

RESULTS

Menthol (LC(50) , 12.9 µg cm(-3) ) was the most toxic compound, followed by citronellyl acetate (16.8 µg cm(-3) ), against the susceptible females. High toxicity was also produced by β-citronellol, citral, geranyl acetate and eugenol (LC(50) , 21.7-24.6 µg cm(-3) ). The fumigant toxicity of these compounds was almost identical against females from either of the susceptible and resistant strains, indicating that the compounds and acaricides do not share a common mode of action or elicit cross-resistance.

CONCLUSION

Global efforts to reduce the level of highly toxic synthetic acaricides in the agricultural environment justify further studies on materials derived from lemon eucalyptus oil, particularly menthol and citronellyl acetate, as potential acaricides for the control of acaricide-resistant T. urticae as fumigants with contact action.

Acaricidal effect of an isolate from Hoslundia opposita vahl against Amblyomma variegatum (Acari: Ixodidae)

BACKGROUND

Hoslundia opposita Vahl. (Lamiaceae), a common local shrub in Ghana, is traditionally known not only for its pharmacological benefits but also for its insecticidal properties. Its acaricidal property, however, has not been investigated.

OBJECTIVE

To test the acaricidal effects of the crude extract and fractions of H. opposita leaves as well as to isolate and characterize the acaricidal principles.

MATERIALS AND METHODS

The crude methanolic extract, pet. ether, ethyl acetate and aqueous fractions of the leaves of H. opposita were tested against the larvae of the cattle tick, Amblyomma variegatum, using the Larval Packet Test. A bioassay-guided isolation was carried out to identify the acaricidal principle obtained from the ethyl acetate fraction.

RESULTS

The active principle was characterised as ursolic acid, a triterpene previously isolated from the leaves of the same plant. The extract and fractions were less potent than the control, malathion (LC(50) 1.14 × 10(-4) mg/ml). Among the plant samples however the crude methanolic extract exhibited the highest effect against the larvae (LC(50) 5.74 × 10(-2) mg/ml), followed by the ethyl acetate fraction (LC(50) 8.10 × 10(-2) mg/ml). Ursolic acid, pet. ether and aqueous fractions however showed weak acaricidal effects with LC(50) values of 1.13 mg/ml, 8.96 × 10(-1) mg/ml and 1.44 mg/ml, respectively.

CONCLUSION

Ursolic acid was not as potent as the crude methanolic extract and the ethyl acetate fraction from which it was isolated. The overall acaricidal effect of H. opposita may have been due to synergy with other principles having acaricidal properties.

Contact and fumigant toxicity of plant essential oils and efficacy of spray formulations containing the oils against B- and Q-biotypes of Bemisia tabaci

BACKGROUND

The contact + fumigant toxicity of 92 plant essential oils and control efficacy of 18 experimental spray formulations containing nine selected essential oils (0.5 and 0.1% sprays) and six commercial insecticides to females from B- and Q-biotypes of Bemisia tabaci were evaluated using vapour-phase mortality and spray bioassays.

RESULTS

Garlic and oregano (LC50 , 0.15 mL cm(-3) ) were the most toxic oils against B- and Q-biotype females. Strong fumigant toxicity to both biotype females was also obtained from catnip, cinnamon bark, clove bud, clove leaf, davana, savory and vetiver Haiti oils (LC50 , 0.17-0.48 mL cm(-3) ). The 0.5% sprays of these oils (except for thyme red oil) resulted in 90-100% mortality against both biotype females. Only garlic applied as 0.1% spray provided 100% mortality. Spinosad 100 g L(-1) suspension concentrate (SC) treatment resulted in 92 and 95% mortality against both biotype females, whereas acetamiprid 80 g L(-1) wettable powder (WP), imidacloprid 80 g L(-1) SC, thiamethoxam 100 g L(-1) water-dispersible granule (WDG) and pyridaben 200 g L(-1) WP treatments resulted in 89-100% mortality against B-biotype females only.

CONCLUSION

In the light of global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment, the essential oils described, particularly garlic, cinnamon bark and vetiver Haiti, merit further study as potential insecticides for the control of B. tabaci populations as fumigants with contact action.

Adulticidal activity of phthalides identified in Cnidium officinale rhizome to B- and Q-biotypes of Bemisia tabaci

The residual contact toxicity of three benzofuranoids (Z)-butylidenephthalide (1), (3S)-butylphthalide (2), and (Z)-ligustilide (3) identified in the rhizome of Cnidium officinale (Apiaceae) to B- and Q-biotype females of Bemisia tabaci was evaluated using a leaf-dip bioassay. Results were compared with those of eight conventional insecticides. Based on 24 h LC(50) values, (Z)-butylidenephthalide (254 ppm) and (Z)-ligustilide (268 ppm) were more toxic than (3S)-butylphthalide (339 ppm) against B-biotype females, whereas (Z)-ligustilide (254 ppm) and (3S)-butylphthalide (338 ppm) were more toxic than (Z)-butylidenephthalide (586 ppm) against Q-biotype females. Thiamethoxam, imidacloprid, and acetamiprid differ significantly in toxicity between the B- and Q-biotype females (LC(50), 1.7 to 11.6 vs 364.5 to >3000 ppm). This original finding indicates that the phthalides and the neonicotinoids do not share a common mode of action or elicit cross-resistance. Structure-activity relationship indicates that the presence of conjugation rather than aromaticity appeared to play an important role for phthalide toxicities to the B-biotype females. Global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment justify further studies on C. officinale rhizome-derived materials as potential insecticides for the control of B. tabaci populations.

Chemical composition and acaricidal properties of Deverra scoparia essential oil (Araliales: Apiaceae) and blends of its major constituents against Tetranychus urticae (Acari: Tetranychidae)

The essential oil of Deverra scoparia Coss. & Durieu was investigated for its acaricidal activity against the worldwide pest twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). The essential oil was analyzed by fast gas chromatography (GC) and GC-mass spectrometry. The activities of its individual and blended constituents were determined. Our study showed that female mortality increased with increasing D. scoparia oil concentrations, with LD50 and LD90 values at 1.79 and 3.2 mg liter(-1), respectively. A reduction in fecundity had already been observed for concentrations of 0.064, 0.08, and 0.26 mg liter(-1) D. scoparia essential oil. Ten major components, comprising 98.52% of the total weight, were identified; a-pinene was the most abundant constituent (31.95%) followed by sabinene (17.24%) and delta3-carene (16.85%). The 10 major constituents of D. scoparia oil were individually tested against T. urticae females. The most potent toxicity was found with alpha-pinene, delta3-carene, and terpinen-4-ol. The presence of all constituents together in the artificial mixture caused a significant decrease in the number of eggs laid by females, at 0.26 mg liter(-1) (11 eggs), compared with the control (50 eggs). The toxicity of blends of selected constituents indicated that the presence of all constituents was necessary to reproduce the toxicity level of the natural oil.