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Mutualism is a common and important ecological phenomenon characterized by beneficial interaction between two species. Red imported fire ants, Solenopsis invicta Buren, tend honeydew-producing hemipteran insects and reduce the activity of these insects' enemies. Ant-hemipteran interactions frequently exert positive effects on the densities of hemipterans. We tested the hypothesis that ant tending can increase the densities of the mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), and reduce the densities of the mealybug's predatory and parasitic enemies, the lady beetle, Menochilus sexmaculata Fabrieius (Coleoptera: Coccinellidae), and the parasitoid wasp, Aenasius bambawalei Hayat (Hymenoptera: Encyrtidae). We found that more ants foraged on mealybug-infested hibiscus plants than on mealybug-free plants. The number of foraging ants on plants infested with high densities of mealybugs (62.5 ants per plant) was nearly six times that on mealybug-free plants (10.2 ants per plant). Experiment results showed that ant tending significantly increased the survival of mealybugs: if predatory and parasitic enemies were present, the survival of mealybugs tended by fire ants was higher than that in the absence of tending ants. Furthermore, this tending by fire ants significantly decreased the survival of lady beetle larvae. However, no apparent effect was observed on the survival of parasitoid. [ABSTRACT FROM AUTHOR]

In an ant colony, a large number of nestmates with a similar gene pool coexist, making them more vulnerable to pathogenic attacks. These pathogens influence the behavior and physiology of the fire ant Solenopsis invicta Buren. Here, we evaluated the impact of entomopathogenic fungi (EPF) Metarhizium anisopliae on the behavior (locomotion and foraging) and physiology (biological molecules, anti-fungal activity, and survival) of S. invicta. Distance traveled and velocity significantly decreased, while turn angle and angular velocity significantly increased in ants exposed to a higher concentration of M. anisopliae compared to ants exposed to control after 36 h, which showed disturbed locomotion. Fungus infection significantly affected the foraging behavior of ants. Fungus-exposed ants spent significantly less time in the food zone (area with food) than in the inner zone (area without food). The activities of 4 enzymes, peroxidase, glutathione-S-transferase, hydrogen peroxide (H2O2), and carboxylesterase were significantly decreased. In contrast, catalase and anti-fungal activities were increased after fungal exposure compared to the control. The activity of acetylcholinesterase, which hydrolyses the important neurotransmitter acetylcholine, also decreased after fungal application compared to the control. Survival of ants was also significantly reduced after fungus infection compared to the control. Our findings help to understand the influence of M. anisopliae on the behavior and physiology of S. invicta , which will help in the management of S. invicta using the EPF M. anisopliae. [ABSTRACT FROM AUTHOR]

Chemicals, including toxic bait and dusts, are the main means of controlling the red imported fire ant Solenopsis invicta (abbreviation 'RIFA'), which is a serious invasive pest. To identify environmentally friendly chemicals for controlling RIFA, we tested the toxicity and horizontal transfer of three botanical insecticides—matrine, rotenone, and pyrethrin—and their impact on aquatic organisms (i.e. three fish and one shrimp). The LD50 value of matrine, rotenone, and pyrethrin was 0.24, 50.929, and 13.590 ng/ant, respectively. Matrine, rotenone, and pyrethrin had effective horizontal transfer and caused significant secondary mortality. After exposure to donor workers, 90.75%, 90.75%, and 100% of recipient workers in the 0.025% matrine, 1.0% rotenone, and 0.3% pyrethrin dust treatments, respectively, died within 48 h. Furthermore, 0.025% matrine dust caused significant tertiary mortality (49.5%). Tertiary mortality caused by 1.0% rotenone and 0.3% pyrethrin dusts was very low, only 7.75% and 18.5%, respectively. In a field trial, the comprehensive mortality effect of 0.05% matrine, 1.50% rotenone, and 0.375% pyrethrin dust was 74.96%, 30.10%, and 29.27%, respectively, after 14 d of treatment. Matrine had low toxicity to the fish Hypophthalmichthys molitrix , and 37.5 mg/L pyrethrin had low toxicity to the fish Cirrhinus molitorella , H. molitrix , and Oreochromis niloticus. However, rotenone was highly toxic to all three fish. The shrimp Neocaridina denticulate was not sensitive to matrine, rotenone, or pyrethrin. Matrine dust has highly effective horizontal transfer, and 0.05% matrine dust has great potential for managing RIFA in organic farms, aquaculture farms of H. molitrix , and water resource regions. [ABSTRACT FROM AUTHOR]

The use of insecticide remains the frontline method in controlling red imported fire ant (Solenopsis invicta Buren) (Hymenoptera: Formicidae), one of the worst invasive ants in the world. Neonicotinoids are effective ingredients in toxic baits for suppressing S. invicta population. To search for new and effective insecticides, the toxicity and sublethal effects of triflumezopyrim, a novel neonicotinoid analog, were evaluated against S. invicta. No high mortality of ants was observed after they fed on sugar water containing 120 μg/ml triflumezopyrim for 72 h; however, 100% mortality was achieved after ants fed on sugar water containing 10 μg/ml triflumezopyrim for 2 wk. Furthermore, at 10 μg/ml, triflumezopyrim did not inhibit ant food consumption within the 7-d treatment period. These results indicate that triflumezopyrim is a slow acting toxin and may be qualified as bait toxin for managing red imported fire ants. At 1 μg/ml, triflumezopyrim did not cause any significant effect on colony growth within 56 d and did not inhibit the food consumption during the whole trial period. At 10 μg/ml, triflumezopyrim displayed a significant reduction of aggressiveness during confrontation with native ants, resulting in higher mortality than the ants in the control. However, at 1 μg/ml, triflumezopyrim did not show any significant impact on both aggressiveness and mortality of the red imported fire ants. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Although many reports suggested the economic importance of the red imported fire ant, Solenopsis invicta Buren, few attempts to test the hypothesis that the red imported fire ant-aphid mutualism enhances the occurrence of red imported fire ant on crops, thereby interfering with their flowering and fruiting and affecting their output. To address this problem, we compare the effects of red imported fire ant on the flowering and fruiting of self-pollinating and cross-pollinating crops by field investigations and indoor experiments. In the field, our results revealed that regardless of the aphid interaction, red imported fire ant preferred flowering mungbean plants, and their activities decreased the yields of single plants, total pod number, kernel number, and kernel weight. The interaction of red imported fire ant and aphids generated unfavorable effects on rapeseed yields per plant, total pod number, grain number, grain weight, and thousand-kernel weight and stimulated an elevated proportion of malformed seeds. However, the differences were not significant if only red imported fire ant was present. In the laboratory, although red imported fire ant display no apparent preference toward the seedlings of mungbean or rapeseed, the ants clearly favor the flowering plants of mungbeans. Therefore, this study indicated that one of the main mechanisms whereby red imported fire ants affect the crop yield is by compromising the reproduction processes. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effects of environmental factors (temperature, dose, dietary source, and feeding density) on the insecticide tolerance of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). The results indicated that the toxicities of trichlorphon and abamectin to B. dorsalis increased with an increase in temperature. At 15-35°C, the toxicity of β-cypermethrin decreased with an increase in temperature at low doses (0.82 and 1.86 mg/L), but was similar at a high dose (4.18 mg/L). These results demonstrated that the temperature coefficient of β-cypermethrin was related to both temperature and dosage. The insecticide sensitivity of B. dorsalis reared on different dietary sources was significantly different. Trichlorphon sensitivity of B. dorsalis fed on banana was the highest with an LC50, of 1.61 mg/L, followed by on apple, carambola, semiartificial diet, pear, mango, guava, orange, and papaya. With an increasing feeding density, the sensitivity of B. dorsalis adults to trichlorphon increased, while the sensitivities of B. dorsalis adults to abamectin and β-cyper-methrin decreased. The differences between LC50 values of insects reared at densities of 10 and 13 eggs/g of semiartificial diet to trichlorphon, abamectin and β-cypermethrin were not significant. This result suggested that representative toxicity could be obtained by using adults developed at a feeding density between 10-13 eggs/g of semiartificial diet. Adult body weight was positively correlated with the LC50 value of trichlorphon, but was negatively correlated with the toxicities of abamectin and β-cypermethrin. These results suggested that the effects of adult body weight on the toxicity of insecticides were different among different chemicals. [ABSTRACT FROM AUTHOR]