Red Imported Fire Ant Workers Research Articles

Exploring bioactive molecules with fumigation toxicity against the red imported fire ant Solenopsis invicta Buren from commercial essential oils by GC–MS combined with chemometrics

Metabolomics approaches are becoming a powerful analytical technique for exploring bioactive molecules in essential oils. The prevalence of imported red fire ants affected the environment, biodiversity of wildlife, infrastructure, and hypersensitivity reactions of people. Due to public health and environmental issues, essential oils as environmentally friendly alternatives to synthetic chemical insecticides in fire ant management have attracted great attention. However, there is a lack of an objective strategy suitable for identifying bioactive molecules that can guarantee the quality of essential oil biopesticides. Therefore, a metabolomics approach with four main steps, including bioassays, GCMS analysis of chemical constitution, construction of multivariate OPLS and univariate Pearson correlation statistical models, and feature selection, was proposed in this study to verify its potential to find bioactive molecules in essential oils that are effective against red imported fire ants. The fumigation mortalities of 20 commercial essential oils ranged from 0 to 100%. A total of 296 mass features were deconvoluted, and 121 of them were identified. Then, 52 potential bioactive molecules were selected by both VIP > 1.0 and P < 0.05. Finally, 6 of these potential bioactive molecules, (+)− 2-bornanone,.beta.-pinene, eucalyptol, isoborneol, linalool, and L-.alpha.-terpineol, have shown good fumigation toxicity against minor and/or major red imported fire ant workers. This study has, in certain aspects, supported the feasibility of this metabolomics approach. It could be helpful for natural molecules to be alternatives to synthetic chemical insecticides, leading to more environmentally friendly and sustainable management policies for red imported fire ants.

Fumigant toxicity and behavioral alterations of six plant essential oils against the red fire ant (Solenopsis invicta Buren).

The red imported fire ant (RIFA), Solenopsis invicta Buren (Hymenoptera: Formicidae), is an invasive species that is considered to be among the 100 most dangerous species to human health and the environment. RIFA is currently controlled primarily by chemical insecticides. However, human health concerns and environmental problems require environment friendly, green insect pest control technology. In this study, the HS-SPME-GC/MS method was used to determine the volatile components of six essential oils, namely Illicium verum Burm, Blumea balsamifera (L.) DC., Citrus limon Burm, Acorus tatarinowii Schott, Mosla chinensis Maxim, and Cinnamomum cassia Presl, as well as their fumigation activity against RIFA. D-Limonene was identified as a core volatile in all six essential oils. The effects of volatile substances from essential oils on the fumigation activity and behavior of RIFA workers were studied by closed fumigation method. Except for C. limon essential oil, all other five plant essential oils exhibit excellent fumigation activity under the treatment of a concentration at 10 μL/ cm3 within 24 h. All plant essential oils are capable of causing the death of all red fire ants, while C. limon essential oil exhibited the lowest fumigation activity at 63.25%. Significant reductions in RIFA aggregation, aggressiveness, and gripping abilities were observed with all plant essential oils, and antenna sensilla appeared to bend or break. Moreover, after treating red ant fire ants with essential oil for 24 h, three protective enzyme activities were assessed. All six plant essential oils were shown to have enhanced enzyme activities for superoxide dismutase (SOD), glutathione S-transferase (GST), and catalase (CAT). It has been shown that plant essential oils have the capability of reducing the viability of red fire ants via receptor and behavioral factors, ultimately causing them to die off. As a conclusion, plant oils were demonstrated to be negatively affecting RIFA and providing a green and environmentally sustainable control method in this study.

Fumigation activity of essential oils of Cinnamomum loureirii toward red imported fire ant workers

Fumigation activity of essential oils of Cinnamomum loureirii toward red imported fire ant workers

Pathogenicity of Beauveria bassiana ANU1 to the red imported fire ant, Solenopsis invicta workers in Korea

• B. bassiana ANU1 (Bb ANU1) showed the pathogenicity to S. invicta workers. • LC 50 s were calculated as major (3.9 × 10 3 ) and minor (4.6 × 10 3 ) at 7 DAT. • Bb ANU1 showed virulence to workers at low temperature, 10 °C. The red imported fire ant (RIFA), Solenopsis invicta , is one of the globalized invasive pests. This study focused on pathogenicity and virulence of entomopathogenic fungi as one of the biological control agents to RIFA workers under different temperatures. The fungal pathogen, Beauveria bassiana ANU1 was isolated from Korea in 2015 and showed the pathogenicity to RIFA workers. A conidial suspension (1 × 10 7 conidia/ml) induced a low mortality from day 2 after treatment and reached to 100% mortality at day 7 and day 8 after treatment for major and minor workers, respectively. The median lethal concentrations of B. bassiana ANU1 were calculated as 3.9 × 10 3 for major and 4.6 × 10 3 for minor workers at day 7 after treatment. Low temperatures decreased a virulence of B. bassiana ANU1 (1 × 10 7 conidia/ml) to RIFA and showed mortality of 26.6% for major and 20% for minor workers. Based on bioassay results, this study provides one of possibilities of effective and successful strategy for controlling RIFA by entomopathogenic fungi.

Colonization by the Red Imported Fire Ant, Solenopsis invicta, Modifies Soil Bacterial Communities.

The long-standing association between insects and microorganisms has been especially crucial to the evolutionary and ecological success of social insect groups. Notably, research on the interaction of the two social forms (monogyne and polygyne) of the red imported fire ant (RIFA), Solenopsis invicta Buren, with microbes in its soil habitat is presently limited. In this study, we characterized bacterial microbiomes associated with RIFA nest soils and native (RIFA-negative) soils to better understand the effects of colonization of RIFA on soil microbial communities. Bacterial community fingerprints of 16S rRNA amplicons using denaturing gradient gel electrophoresis revealed significant differences in the structure of the bacterial communities between RIFA-positive and RIFA-negative soils at 0 and 10 cm depths. Illumina sequencing of 16S rRNA amplicons provided fine-scale analysis to test for effects of RIFA colonization, RIFA social form, and soil depth on the composition of the bacterial microbiomes of the soil and RIFA workers. Our results showed the bacterial community structure of RIFA-colonized soils to be significantly different from native soil communities and to evidence elevated abundances of several taxa, including Actinobacteria. Colony social form was not found to be a significant factor in nest or RIFA worker microbiome compositions. RIFA workers and nest soils were determined to have markedly different bacterial communities, with RIFA worker microbiomes being characterized by high abundances of a Bartonella-like endosymbiont and Entomoplasmataceae. Cloning and sequencing of the 16S rRNA gene revealed the Bartonella sp. to be a novel bacterium.

Fumigant toxicity and biochemical properties of (α + β) thujone and 1, 8-cineole derived from Seriphidium brevifolium volatile oil against the red imported fire ant Solenopsis invicta (Hymenoptera: Formicidae)

The excessive use of chemical insecticides has led to negative effects on human health and the environment. Volatile oils are one of the possible potential alternatives to chemical insecticides. Traditionally Seriphidium brevifolium (Wall. ex DC.) Ling & Y.R.Ling, Asteraceae, powder from its leaves is used to treat gastric problems and expel intestinal worms by local peoples, but yet there is no literature available regarding its insecticidal activity. In this study fumigant toxicity and enzyme inhibition activities of the S. brevifolium volatile oil collected from the highlands of Skardu Baltistan, Pakistan, was evaluated against the red imported fire ant Solenopsis invicta. The phytochemical studies indicated that monoterpenes were the most abundant constituents, accounting for 88% of the total oil. The major dominant constituents were 2-bornanone (28.2%), 1,8-cineole (19.9%), α-thujone (7.5%), β-thujone (6.7%) which accounts for 62.3% of total constituents identified, with volatile oil yield of 4.11% (w/w). The fumigation assay indicated that the volatile oil was acutely toxic to fire ants, with an LC50 of 16.47 µl/l. Among the constituents tested, only (α + β) thujone and 1,8-cineole were toxic, with LC50 of 17.68 and 30.66 µl/ after 12 h of exposure. The volatile oil, (α + β) thujone and 1, 8-cineole showed strong fumigant activity against the red imported fire ant workers in a time- and dose-dependent manner. The volatile oil caused 100% mortality of the red imported fire ant workers, even at the lowest concentration of 20 µl/l after 24 h of exposure. In addition, the volatile oil and 1,8-cineole inhibited acetylcholinesterase activity, while (α + β) thujone inhibited carboxylesterase activity in the fire ant workers. It has been concluded that the volatile oil and some of the compounds from S. brevifolium might be developed as eco-friendly approaches for the control of red imported fire ants.

Insecticidal effect of volatile compounds from plant materials of Murraya exotica against Red Imported Fire Ant Workers

The effect of volatile compounds from the mashed fresh, fallen, and dried leaves of Murraya exotica on the behavior of red imported fire ant (Solenopsis invicta, RIFA) workers was investigated by fumigation toxicity bioassay. The volatile compounds from different mashed leaves (fresh, fallen, and dried leaves) of M. exotica were collected by solid-phase microextraction and identified by gas chromatography–mass spectrometry. β-Caryophyllene, α-cedrene, α-copaene, β-cubebene, and germacrene D were identified as major components of the volatile compounds. In exposure time from 1 d to 9 d, the mortality of RIFA increased from 5.00% to 100.00% (fresh leaves), 11.67% to 93.33% (fallen leaves), and 15.00% to 83.33% (dried leaves) in minor workers, whereas in major workers, the increases were from 13.33% to 93.33% (fresh leaves), 6.67% to 83.33% (fallen leaves), and 10.00% to 60.00% (dried leaves). The volatile compounds reduced the walking and grasping abilities and aggregation rate of RIFA workers. Results indicate that mashed leaves of M. exotica have potential for controlling RIFA.

The Insecticidal and Repellent Activity of Soil Containing Cinnamon Leaf debris against Red Imported Fire Ant Workers

In the study, the amount of cinnamaldehyde and eugenol in soil containing cinnamon leaf debris were determined at different depths by high performance liquid chromatography (HPLC). The insecticidal activity and repellence of the soil was tested separately. Results showed that higher contents of cinnamic aldehyde and eugenol were found in soil at depths of 5 - 10 cm. In the insecticidal toxicity bioassay, the corrected mortality of major workers treated with cinnamon soil at depths of 5 - 10 cm, which was higher than the other soil depths, increased from 13.3% to 80.0% with contact time from 1 - 5 d. Likewise, the corrected mortality of minor workers also increased from 6.7% to 100.0%. In the repellent activity bioassay, the repellency (96.3%) of major and minor workers treated with cinnamon soil at depths of 5 - 10 cm for 24 h were significantly higher than the other treatments. This result revealed ecological value of cinnamon. Soil underneath cinnamon contained cinnamaldehyde and eugenol from fallen leaves, and these components showed insecticidal activity and repellence against red imported fire ants. Perhaps we could control the red imported fire ants by planting cinnamon in some possible regions or by incorporating cinnamon leaves into soil where cinnamon will not grow.

Allergen of the Month—Annual Wormwood

Allergen of the Month—Annual Wormwood

Fumigant Toxicity and Repellence Activity of Camphor Essential Oil from Cinnamonum camphora Siebold Against Solenopsis invicta Workers (Hymenoptera:Formicidae).

The red imported fire ant (RIFA) Solenopsis invicta Buren causes severe damage to humans and animals as well as the environment. Chemical treatment is the main strategy of RIFA management, which also is potentially toxic to the environment. Plant essential oils (EOs) are considered as potential substance that can be used to control insects. This study aimed to identify the chemical composition of camphor EO and investigate the insecticidal activity on RIFAs. The chemical composition of the EO was analyzed by gas chromatography/mass spectrometry and gas chromatography with flame ionization detection. Results revealed that 36.61% camphor and 30.05% cineole were the major components. The insecticidal activity of camphor EO was assessed against RIFA workers by conducting two different bioassays: fumigant toxicity and repellence. Fumigant toxicity assay results showed that the lethal dose (LC50) of the EO at 24 h was 1.67 and 4.28 μg/ml for minor and major workers, respectively; knockdown time (KT50) was 10.82 and 14.73 h. At 2.55 μg/ml, the highest average mortality of the ants was 84.89% after 72 h. Camphor EO exhibited fumigant toxicity against minor and major workers as indicated by the effects on attacking, feeding, and climbing behaviors. This EO was also strongly repellent to the two size workers of the colony as observed in their behavior against Tenebrio molitor treated with 5 µl EO. The fumigant toxicity and repellence of camphor EO against RIFA indicated that this substance could be a potential alternative for the development of eco-friendly products used to control pests.

The Effects of Temperature on the Foraging Activity of Red Imported Fire Ant Workers (Hymenoptera: Formicidae) in South China

In this study, we investigated the effects of temperature of the ambient air, ground surface, and the soil at 5-cm deep on the foraging activity of the workers of red imported fire ant, Solenopsis invicta Buren, in South China with the method of bait traps. Significant correlations were observed between the temperature and the foraging activity of fire ants. Specifically, when the ambient temperature was above 20 °C, the fire ants foraged actively, and the activity reached a maximum when the ambient temperature was between 25 to 33 °C. But the foraging activity decreased as the ambient temperature rose higher than 34 °C. Moreover, fire ants were found to forage at maximal rates with the soil surface temperature between 27 to 40 °C. The ants started foraging when the soil temperature at 5-cm deep was between 16 to 48 °C, while 28~37 °C was the optimal temperature for the foraging activity. The extreme temperature thresholds for foraging of the ambient air, soil-surface, and soil at 5-cm deep were 11 °C/44 °C, 10 °C/57 °C, and 12 °C/48 °C respectively.

Queen Red Imported Fire Ants (Solenopsis invictaBuren) Induce Colony Sororicide to Reduce Competition

Queens of red imported fire ants, Solenopsis invicta Buren, regulate colony dynamics by inducing workers to execute sexual larvae; proteins in the venom glands might be involved. Bioassays of the expressed, isolated queen venom proteins, Sol i 2q and Sol i 4q, did not show an increased rate of execution of sexual larvae compared to the control; however, Sol i 4q had a significantly lower execution rate than Sol i 2q and the control. Ants in the Sol i 4q treatments kept their brood primarily in the foraging chamber, closer to the added protein, and did not move them into the pumice nests; however, no difference in execution of sexual larvae between the colony and brood main locations (nest or tube/chamber) were observed. Identification of the crystal structure of the venom protein of red imported fire ant workers, Sol i 2w, revealed a hydrophobic cavity that binds to a ligand with an overall structure similar to LUSH, a pheromone-binding protein in Drosophila. If the proteins of the queen are structurally similar to the proteins of the worker, the possible cavity in Sol i 2q and Sol i 4q potentially binds to the execution pheromone, masking the protein as the pheromonal source instead of the ligand contained within. These hydrophilic queen venom proteins might act as a transport mechanism for the hydrophobic pheromones in the venom. Identification of the source of the pheromone and transport venom proteins is important in understanding the execution of sexual larvae in this pest species.

Insecticidal, fumigant, and repellent activities of sweet wormwood oil and its individual components against red imported fire ant workers (Hymenoptera: Formicidae).

In total, 29 compounds from sweet wormwood ( Artemisia annua L.) oil were identified using gas chromatography–mass spectrometry. The five active components were d -camphor, linalool, cineole, α-terpineol, and l (−)-borneol. The effectiveness of A. annua oil, as well as d -camphor, linalool, cineole, α-terpineol, and l (−)-borneol, as fumigants, contact insecticides, and repellents, were tested on the red imported fire ant Solenopsis invicta Buren. The results indicated that A. annua oil has no significant topical toxicity; however, the spray contact test revealed that it has strong insecticidal activity and the inhibitory effect is stronger during closed exposure than during open exposure. In the fumigant test, cineole and d -camphor exhibited strong fumigant toxicity on minor and major S. invicta workers. They also caused 100% mortality at 5, 3, 2, and 1 mg/centrifuge tube but not at 0.5 mg/centrifuge tube. The mortality rates of linalool, α-terpineol, and l (−)-borneol exceeded 80% at 5, 3, and 2 mg/centrifuge tube. In the repellent test, cineole and d -camphor showed significant repellency at 100, 10, and 1 mg/kg. However, linalool, α-terpineol, and l (−)-borneol significantly facilitated digging at 10 and 1 mg/kg.

Effect of gland extracts on digging and residing preferences of red imported fire ant workers (Hymenoptera: Formicidae)

There is evidence that ant-derived chemical stimuli are involved in regulating the digging behavior in Solenopsis invicta Buren. However, the source gland(s) and chemistry of such stimuli have never been revealed. In this study, extracts of mandibular, Dufour's, postpharyngeal, and poison glands were evaluated for their effect on ant digging and residing preferences of S. invicta workers from three colonies. In the intracolonial bioassays, workers showed significant digging preferences to mandibular gland extracts in 2 of 3 colonies and significant residing preferences in 1 of 3 colonies; significant digging preferences to Dufour's gland extracts in 1 of 3 colonies and significant residing preferences in 2 of 3 colonies. No digging and residing preferences were found for postpharyngeal and poison gland extracts. In intercolonial bioassays, significant digging and residing preferences were found for mandibular gland extracts in 3 of 6 colony combinations. Significant digging preferences to Dufour's gland extracts were found in 4 of 6 colony combinations and significant residing preferences in all 6 colony combinations. For postpharyngeal gland extracts, significant digging preferences were found only in 1 of 6 colonial combinations and no significant residing preferences were found. For poison gland extracts, no significant digging preferences were found; significant residing preferences were found in 1 of 6 colony combinations. However, a significant residing deterrence (negative residing preference index) was found for 2 of 6 colony combinations. Statistical analyses using data pooled from all colonies showed that mandibular and Dufour's gland extracts caused significant digging and residing preferences in both intracolonial and intercolonial bioassays but not postpharyngeal and poison gland extracts. By analyzing the data pooled from the same three colonies used for gland extract bioassays, it was found that, in no cases, workers showed significant digging and residing preferences to 2-ethyl-3,6-dimethylpyrazine, an alarm pheromone component from mandibular gland.

Efficacy of Beauveria bassiana against the red imported fire ant, Solenopsis invicta (Hymenoptera: Formicidae), in Taiwan

Combining biological control and chemical control could be used for controlling red imported fire ant (RIFA), Solenopsis invicta, more effectively. Beauveria bassiana F256, a local strain from Taiwan, was evaluated for its efficacy in the control of S. invicta under both laboratory and field conditions. The efficacies of different doses of B. bassiana (Bb) using direct application and bait formulation methods were compared. The number of RIFA workers killed by the direct application of Bb or by bait were significantly higher than those of the control, with different rates of efficacy under laboratory conditions. Under field conditions, the direct application of Bb into RIFA mounds was more efficient in inactivating the mounds than the bait application. It was shown that B. bassiana is able to control S. invicta under both laboratory and field conditions and can be used as a biocontrol agent against RIFA in Taiwan.

The major antennal chemosensory protein of red imported fire ant workers

Some chemosensory proteins (CSPs) are expressed in insect sensory appendages and are thought to be involved in chemical signalling by ants. We identified 14 unique CSP sequences in expressed sequence tag (EST) libraries of the red imported fire ant, Solenopsis invicta. One member of this group (Si-CSP1) is highly expressed in worker antennae, suggesting an olfactory function. A shotgun proteomic analysis of antennal proteins confirmed the high level of Si-CSP1 expression, and also showed expression of another CSP and two odorant-binding proteins (OBPs). We cloned and expressed the coding sequence for Si-CSP1. We used cyclodextrins as solubilizers to investigate ligand binding. Fire ant cuticular lipids strongly inhibited Si-CSP1 binding to the fluorescent dye N-phenyl-naphthylamine, suggesting cuticular substances are ligands for Si-CSP1. Analysis of the cuticular lipids showed that the endogenous ligands of Si-CSP1 are not cuticular hydrocarbons.

Significance of Digging Behavior to Mortality of Red Imported Fire Ant Workers, &lt;I&gt;Solenopsis invicta&lt;/I&gt;, in Fipronil-Treated Sand

The effect of fipronil-treated sand on digging behavior and mortality of red imported fire ant, Solenopsis invicta Buren, workers was examined in the laboratory. No-choice digging bioassays where fipronil-treated sand was the only available digging substrate were conducted on two colonies at fipronil concentrations of 0.00, 0.05, 0.10, 0.50, 1.00, 1.50, and 2.00 ppm. Workers dug into the fipronil-treated sand in all cases, even at 2.0 ppm level, which caused 100% mortality in acute toxicity tests for both colonies. At 1.5 and 2.0 ppm, workers from the less sensitive colony had significantly higher mortality than those from the more sensitive colony, which might be explained by the significantly higher digging activity of the less sensitive colony. In two-choice digging bioassays where untreated sand was also available, workers dug into the fipronil-treated sand in 29 of 30 cases, even at 10.0 ppm level. At 1.0 and 10.0 ppm, mortality was positively correlated to digging effort in treated sand; however, such correlation was significant only at 1.0 ppm level. This indicates that digging did affect mortality; however, such effect is concentration dependent.

Significance of Digging Behavior to Mortality of Red Imported Fire Ant Workers, Solenopsis invicta, in Fipronil-Treated Sand

Significance of Digging Behavior to Mortality of Red Imported Fire Ant Workers, Solenopsis invicta, in Fipronil-Treated Sand

Assessment of Repellency of Nine Phthalates against Red Imported Fire Ant (Hymenoptera: Formicidae) Workers Using Ant Digging Behavior

Repellency of nine phthalates against red imported fire ant workers, Solenopsis invicta Buren, was evaluated using ant digging behavior. Test compounds included dimethyl, diethyl, dipropyl, dibutyl, dipentyl, dihexyl, diheptyl, dioctyl, and dinonyl phthalates. The active ingredient was incorporated into sand within a liquid scintillation vial with an entry hole on the cap. Fire ant workers dug and removed sand from the vial through the entry hole. The differences in amount of sand removed from the treated and control vials were used to evaluate chemical repellency. Of the 9 phthalates, dimethyl and diethyl phthalates were most repellant to red imported fire ant workers. The minimum repellant concentration within 24 h was 100 ppm for both dimethyl and diethyl phthalates.

The queen recognition pheromone of [formula omitted], preparation of ( [formula omitted]-6-(1-pentenyl)-2H-pyran-2-one.

The title compound, I , prepared in five steps via four known α-pyrones, is responsible, in part, for “queen recognition” by red imported fire ant workers. IR, NMR and MS data are presented.