Seed treatment with chlorantraniliprole and carbaryl mixture for managing fall armyworm on maize: systemic synergism, control efficiency and synergistic mechanism.

BACKGROUND: Fall armyworm (Spodoptera frugiperda) is one of the major invasive pests in China, and has been widely controlled by labor-intensive foliar sprays of agrochemicals in maize (Zea mays L.). RESULTS: Systemic bioassay showed that mixtures of chlorantraniliprole (Chlor) and carbaryl (Carb) had dramatically synergistic effect on toxicity to S. frugiperda. Particularly, a mixture of Chlor with Carb at a mass ratio of 2:1 (MCC) exhibited the highest toxicity to S. frugiperda. Therefore, seed treatment of Chlor mixed with Carb was studied as a simple, accurate, efficient and low-cost control technology. Our results showed that MCC treatment shortened the median lethal time and 90% lethal time to S. frugiperda compared to Chlor- and Carb-alone treatments. Meanwhile, smaller leaf consumption by S. frugiperda was recorded under MCC treatment compared to Chlor- and Carb-alone treatments. In field trial, maize-seed treatment with MCC showed efficacy up to 39 days post-emergence in preventing S. frugiperda foliar damage at a low infestation pressure. Moreover, chemical quantification by ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) showed that Chlor residues were more absorbed and concentrated in maize leaves of MCC treatment, compared to that of Chlor-alone treatment. CONCLUSION: These results suggested that seed treatment with MCC can be applied to increase the control efficacy and reduce the cost of Chlor-alone treatment for controlling S. frugiperda. The present study provided evidence of an enhanced translocation and accumulation of Chlor residues in maize leaves under MCC treatment, which likely contributed to a synergistic effect against S. frugiperda. © 2022 Society of Chemical Industry.

Carbon nanomaterial functionalization with pesticide-detoxifying carboxylesterase.

Four carbon materials, spent coffee-ground biochar, carbon black, short CNTs, and nitrogen-doped few-layer graphene (N-graphene) were tested for their functionalization with a commercial carboxylesterase. Their robustness to variations in time and key physicochemical parameters (temperature and pH) was analysed. In general, carbon nanomaterials showed better performance than biochar, both in terms of binding capacity and resilience in harsh conditions, at statistically significant levels. Among the tested materials, functionalized N-graphene also showed the highest level of inhibition of carboxylesterase by pesticide exposure. Therefore, N-graphene was selected for biotechnological application of pesticide scavenging toxicity in T. thermophila, a ciliate bioindicator of water quality. While immobilization of the enzyme was not effective in the case of carbaryl, a methyl carbamate, in the case of the organophosphorus dichlorvos, a 1- or 30-min contact time with a water solution containing 5 times the LC100 - 0.5 mM - allowed 50% and 100% rescue of ciliate survival, respectively. These results suggest that functionalization with carboxylesterase may be of additional benefit compared to bare carbon in water clean-up procedures, especially for highly hydrophilic pesticides such as dichlorvos.

A Simple and Reliable Dispersive Liquid-Liquid Microextraction with Smartphone-Based Digital Images for Determination of Carbaryl Residues in Andrographis paniculata Herbal Medicines Using Simple Peroxidase Extract from Senna siamea Lam. Bark.

A simple and reliable dispersive liquid-liquid microextraction (DLLME) coupled with smartphone-based digital images using crude peroxidase extracts from cassia bark (Senna siamea Lam.) was proposed to determine carbaryl residues in Andrographis paniculata herbal medicines. The method was based on the reaction of 1-naphthol (hydrolysis of carbaryl) with 4-aminoantipyrine (4-AP) in the presence of hydrogen peroxide, using peroxidase enzyme simple extracts from cassia bark as biocatalysts under pH 6.0. The red product, after preconcentration by DLLME using dichloromethane as extraction solvent, was measured for blue intensity by daily life smartphone-based digital image analysis. Under optimized conditions, good linearity of the calibration graph was found at 0.10-0.50 mg·L-1 (r2 = 0.9932). Limits of detection (LOD) (3SD/slope) and quantification (LOQ) (10SD/slope) were 0.03 and 0.09 mg·L-1, respectively, with a precision of less than 5%. Accuracy of the proposed method as percentage recovery gave satisfactory results. The proposed method was successfully applied to analyze carbaryl in Andrographis paniculata herbal medicines. Results agreed well with values obtained from the HPLC-UV method at 95% confidence level. This was simple, convenient, reliable, cost-effective and traceable as an alternative method for the determination of carbaryl.

The biodegradation of carbaryl in soil with Rhodopseudomonas capsulata in wastewater treatment effluent.

In this study, the effects of Rhodopseudomonas capsulata present in wastewater effluent on the biodegradation of carbaryl in soil and improvement of soil fertility were investigated. Compared to control treatment, carbaryl was removed efficiently and soil fertility was remediated with the addition of effluent containing R. capsulata. Molecular analysis revealed that carbaryl induced carbaryl hydrolase gene expression to synthesize carbaryl hydrolase through activating MAPKKKs, MAPKKs, MAPKs genes in MAPK signal transduction pathway. The induction and secretion of carbaryl hydrolase occur after one day in R. capsulata, which can be attributed to its characteristics as an ancient bacteria, which require acclimatization to carbaryl before gene induction. However, lack of organics in soil and control treatment could not maintain R. capsulata growth for over one day. The residual organics in the effluent provided sufficient carbon source and energy for R. capsulata under four effluent treatments. This new method resulted in the remediation of carbaryl pollution and improvement of soil fertility and soybean processing wastewater treatment simultaneously, as well as the reutilization of wastewater and R. capsulata as sludge. Meanwhile, the high-order non-linear mathematical model about carbaryl removal rate was established.

Histopathological analysis of carbaryl-induced toxicity in the spleen of Levantine frog, Pelophylax bedriagae (Anura: Ranidae).

This study describes the histopathological effects of carbaryl in the spleen of Levantine frog, Pelophylax bedriage. Due to its primary role in immune system, it is important to research the toxic effects of pesticides, which play an important role in environmental pollution, on spleen. To that end, adult frogs were exposed to carbaryl for 96 h. Experimental groups contained low dose, (0.05 mg/g), medium dose (0.1 mg/g) and high dose (0.2 mg/g). After following exposure to carbaryl, the frogs were euthanised and dissected. In low-dose group, there were no important changes in spleen tissue. In medium-dose group, prominence in haemorrhage just below the capsule and an increase in the melanomacrophage number were determined. In high-dose group, in addition to increases in the melanomacrophages, separations in capsule, haemorrhage below capsule and within splenic tissue, sinusoidal enlargement, congestion in dilated sinusoid, hypertrophic plasma cells and fibrosis were determined as important histological lesions in exposed frogs. This study clearly showed that carbaryl caused important histopathological damages in splenic tissue of Pelophylax bedriagae. In view of these findings, it can be said that this insecticide has the capacity to disrupt spleen' functions.

Genetically engineered zebrafish liver (ZF-L) cells as an in vitro source for zebrafish acetylcholinesterase (zfAChE) for the use in AChE inhibition assays.

Zebrafish acetylcholinesterase (zfAChE) preparations employed for the evaluation of acetylcholinesterase inhibition are usually extracted from animal tissues, a procedure suffering from both technical and ethical limitations, which may be alleviated using an in vitro expression system for enzyme generation. For this end, a protocol for stable transfection and selection of zebrafish liver (ZF-L) cells using an adapted expression plasmid "ZF-L Exp" was developed. After insertion of zfAChE cDNA, the enzyme was efficiently expressed in transgenic ZF-L cell lines, which were then used as a high yield source of zfAChE activity for acetylcholinesterase (AChE) inhibition assays. An adapted assay protocol was used to demonstrate the effects of carbaryl, dichlorvos and caffeine as model AChE inhibitors towards zfAChE. Dimethyl sulfoxide (DMSO) was also strongly inhibitory towards zfAChE. Finally, we provide data on the stability of zfAChE enzyme preparations. The novel test system provides a promising in vitro test system for the assessment of zfAChE inhibition.

An integrated approach for assessing the migration behavior of chlorpyrifos and carbaryl in the unsaturated soil zone.

Chlorpyrifos (O, O-diethyl O-3,5,6-trichloropyridin-2-yl phosphorothioate) and carbaryl (1-naphthyl methylcarbamate) are often applied concurrently as insecticides in food production. The aim of this study was to research their migration behavior in a real environment. We researched the leaching of both pesticides by setting up field lysimeters on a farm with the typical soil used in fruit production today. In order to analyze the variables involved in this process, we performed complementary adsorption studies, we performed complementary adsorption studies using batches and undisturbed soil laboratory columns for both compounds. The results for pesticide transport through the lysimeters showed that less than 1% of chlorpyrifos was recovered in the leachates, while almost 17% was recovered for carbaryl. Having completed the experiment in undisturbed laboratory columns, soil analysis showed that chlorpyrifos mainly remained in the first 5 cm, while carbaryl moved down to the lower sections. These results can be explained in view of the sorption coefficient values (KD) obtained in horizons A and B for chlorpyrifos (393 and 184 L kg-1) and carbaryl (3.1 and 4.2 L kg-1), respectively. By integrating the results obtained in the different approaches, we were able to characterize the percolation modes of these pesticides in the soil matrix, thus contributing to the sustainable use of resources.

Aged garlic extract ameliorates immunotoxicity, hematotoxicity and impaired burn-healing in malathion- and carbaryl-treated male albino rats.

Malathion and carbaryl are the most widely used organophosphate and carbamate insecticides, respectively, especially in developing countries; they pose a potential health hazard for both humans and animals. Here, we evaluated the protective effects of an odorless (free from allicin) Kyolic aged garlic extract (AGE, containing 0.1% S-allylcysteine; 200 mg/kg body weight) on the toxicity induced by 0.1 LD50 of malathion (89.5 mg/kg body weight) and/or carbaryl (33.9 mg/kg body weight) in male Wistar rats. Doses were orally administered to animals for four consecutive weeks. The present study showed that AGE completely modulated most adverse effects induced by malathion and/or carbaryl in rats including the normocytic normochromic anemia, immunosuppression, and the delay in the skin-burning healing process through normalizing the count of blood cells (erythrocytes, leucocytes and platelets), hemoglobin content, hematocrit value, blood glucose-6-phosphodehydrogenase activity, weights and cellularity of lymphoid organs, serum γ-globulin concentration, and the delayed type of hypersensitivity response to the control values, and accelerating the inflammatory and proliferative phases of burn-healing. In addition, AGE completely modulated the decrease in serum reduced glutathione (GSH) concentration and the increase in clotting time in malathion alone and carbaryl alone treated rats. Moreover, AGE induced a significant increase (P < 0.001) in serum GSH concentration (above the normal value) and accelerating burn-healing process in healthy rats. In conclusion, AGE was effective in modulating most adverse effects induced in rats by malathion and carbaryl, and hence may be useful as a dietary adjunct for alleviating the toxicity in highly vulnerable people to insecticides intoxication. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 789-798, 2017.

Respiratory Allergic Disorders.

Allergic asthma refers to a chronic reversible bronchoconstriction influenced by an allergic trigger, leading to symptoms of cough, wheezing, shortness of breath, and chest tightness. Allergic bronchopulmonary aspergillosis is a complex hypersensitivity reaction, often in patients with asthma or cystic fibrosis, occurring when bronchi become colonized by Aspergillus species. The clinical picture is dominated by asthma complicated by recurrent episodes of bronchial obstruction, fever, malaise, mucus production, and peripheral blood eosinophilia. Hypersensitivity pneumonitis is a syndrome associated with lung inflammation from the inhalation of airborne antigens, such as molds and dust.

Histopathological study of toxic effects of carbaryl on digestive tract of Bufotes variabilis (Anura: Bufonidae).

Due to the negative effects of pesticide usage in environment, i.e., decline in amphibian populations, this study was designed to examine histopathologic changes following carbaryl exposure for 96 h in the digestive tract of variable toad, Bufotes variabilis. After exposure to single doses of carbaryl (low dose 50 µg/g, medium dose 100 µg/g, and high dose: 200 µg/g), the toads were euthanized and dissected and digestive tract samples were quickly removed. Histopathology revealed esophageal vacuolization and necrosis in esophageal cells. Hemorrhage was also observed in the esophagus. In the stomach, necrosis in the glandular epithelium, congested blood vessels, edema among gastric glands, dilated tips of the mucosal epithelial layer, gastric glandular atrophy, and hemorrhage were found. In the intestine, edema within villi, hemorrhage, inflammation, vacuolization, and necrosis in epithelial cells of villi were detected. This study clearly showed that carbaryl caused adverse effects on the digestive tract of B. variabilis in all dose groups.

Carbaryl degradation by bacterial isolates from a soil ecosystem of the Gaza Strip.

Carbaryl is an important and widely used insecticide that pollutes soil and water systems. Bacteria from the local soil ecosystem of the Gaza Strip capable of utilizing carbaryl as the sole source of carbon and nitrogen were isolated and identified as belonging to Bacillus, Morganella, Pseudomonas, Aeromonas and Corynebacterium genera. Carbaryl biodegradation by Bacillus, Morganella and Corynebacterium isolates was analyzed in minimal liquid media supplemented with carbaryl as the only source of carbon and nitrogen. Bacillus and Morganella exhibited 94.6% and 87.3% carbaryl degradation, respectively, while Corynebacterium showed only moderate carbaryl degradation at 48.8%. These results indicate that bacterial isolates from a local soil ecosystem in the Gaza Strip are able to degrade carbaryl and can be used to decrease the risk of environmental contamination by this insecticide.

Carbaryl degradation by bacterial isolates from a soil ecosystem of the Gaza Strip

Abstract Carbaryl is an important and widely used insecticide that pollutes soil and water systems. Bacteria from the local soil ecosystem of the Gaza Strip capable of utilizing carbaryl as the sole source of carbon and nitrogen were isolated and identified as belonging to Bacillus, Morganella, Pseudomonas, Aeromonas and Corynebacterium genera. Carbaryl biodegradation by Bacillus, Morganella and Corynebacterium isolates was analyzed in minimal liquid media supplemented with carbaryl as the only source of carbon and nitrogen. Bacillus and Morganella exhibited 94.6% and 87.3% carbaryl degradation, respectively, while Corynebacterium showed only moderate carbaryl degradation at 48.8%. These results indicate that bacterial isolates from a local soil ecosystem in the Gaza Strip are able to degrade carbaryl and can be used to decrease the risk of environmental contamination by this insecticide.

Histopathologic changes in liver and kidney tissues induced by carbaryl in Bufotes variabilis (Anura: Bufonidae).

The purpose of this work was to investigate for the first time histopathologic effects of carbaryl in liver and kidney tissues of Bufotes variabilis. After 96h following exposure to carbaryl (low dose: 0.05, medium dose: 0.1 and high dose: 0.2mg/g), the toads were euthanized and dissected. In liver tissue, vacuolization in hepatocytes, necrosis, mononuclear cell infiltration, an increase in melanomacrophage number, enlargement of sinusoids, hemorrhage and congestion were determined in exposed toads. In kidney tissue, mononuclear cell infiltration, hypertrophied Bowman's capsule cells, deformation, vacuolization, karyolysis and necrosis of renal tubule epithelium, brush border destruction, glomerular shrinkage, hemorrhage and fibrosis were observed in carbaryl-treated groups. According to this investigation, carbaryl caused histopathologic damages in liver and kidney tissues of B. variabilis.

Identification of polymorphisms in Cyrtorhinus lividipennis RDL subunit contributing to fipronil sensitivity.

As one of the most important predatory enemies, the miridbug, Cyrtorhinus lividipennis, plays an important role in rice planthoppers control, such as Nilaparvata lugens (brown planthopper). In order to compare insecticide selectivity between C. lividipennis and N. lugens, the contact acute toxicities of six insecticides (diazoxon, paraoxon, carbaryl, fenobucarb, fipronil and ethofenprox) were monitored. The results showed that all tested insecticides were more toxic to C. lividipennis than to N. lugens and fipronil had the biggest difference. The RDL subunit (Cl-RDL) was cloned from C. lividipennis and a RDL isoform (Cl-RDL-In) was also found with 31 amino acids insertion in RDL intracellular region. In order to understand the role of the insertion on insecticide sensitivities, three subunits (Nl-RDL, Cl-RDL and Cl-RDL-In) were constructed to obtain the functional receptors in Xenopus oocytes and the fipronil sensitivities were detected by the voltage-clamp technique. Nl-RDL (IC50=32.36 ± 4.07 µM) was more insensitive to fipronil than Cl-RDL (IC50=6.47 ± 1.12 µM). The insertion in Cl-RDL significantly reduced fipronil sensitivity with IC50 value in Cl-RDL-In of 16.83 ± 2.30 µM. Interestingly, after the elution of fipronil, the current response of Cl-RDL-In appeared obvious recovery, which were not observed in Cl-RDL and Nl-RDL. It might imply that the insertion played a special role in fipronil sensitivity.

Enhancement of insecticides against codling moth (Lepidoptera: Tortricidae) with L-aspartate in laboratory and field experiments.

The idea of enhancing insecticide efficacy against phytophagous insects with feeding stimulators was proposed as early as the 1960s, and a number of insect feeding stimulators based on sugars, molasses, and cottonseed extracts, biologically active at relatively high (5% and higher) concentrations, have been advocated. Here, we show that an acidic amino acid, L-aspartate, stimulates feeding in codling moth neonates at much lower concentrations and acts as an effective tank-mixed additive for increasing efficacy of insecticides, reducing fruit damage, and increasing yield of the fruit. In laboratory experiments, 1 mg/ml L-aspartate increased foliage consumption by 40-60% and, when added to Assail 30 SG, Baythroid XL, Delegate WG, or Carbaryl 80S, maintained its feeding stimulatory properties and reduced LD50(s) by approximately 10 times. In a 3-yr field trial, addition of L-aspartate to the aforementioned insecticides at 395 g/ha reduced fruit damage from approximately 6%, on average to < 1% for first-generation codling moth, and from approximately 20 to approximately 5% for the second generation. Interestingly, addition of L-aspartate also increased the average weight of apples by 11-27%, as measured at the time of harvest.

Efficacy of herbal shampoo base on native plant against head lice (Pediculus humanus capitis De Geer, Pediculidae: Phthiraptera) in vitro and in vivo in Thailand.

Head lice infestation (or pediculosis) is an important public health problem in Thailand, especially in children between the ages 5 and 11 years. Head lice resistance is increasing, chemical pediculicides have lost their efficacy, and, therefore, alternative pediculicides such as herbal shampoos have been proposed to treat head lice infestation. Thus, the present study investigated the efficacy of three herbal shampoos based on native plants in Thailand (Acorus calamus Linn., Phyllanthus emblica Linn., and Zanthoxylum limonella Alston) against head lice and compared them with carbaryl shampoo (Hafif shampoo, 0.6% w/v carbaryl), malathion shampoo (A-Lice shampoo, 1.0% w/v malathion), and commercial shampoos (Babi Mild Natural' N Mild and Johnson's baby shampoo) in order to assess their in vitro and in vivo efficacy. For in vitro study, doses of 0.12 and 0.25 ml/cm(2) of each herbal shampoo were applied to filter paper, then 10 head lice were place on the filter paper. The mortalities of head lice were recorded at 5, 15, 30, and 60 min. The results revealed that all herbal shampoo were more effective on pediculicidal activity than chemical and commercial shampoos with 100% mortality at 15 min; LT50 values ranged from 0.25 to 1.90 min. Meanwhile, chemical shampoos caused 20-80% mortality, and LT50 values ranged from 6.50 to 85.43 min. On the other side, commercial shampoos showed 4.0% mortality. The most effective pediculicide was Z. limonella shampoo, followed by A. calamus shampoo, P. emblica shampoo, carbaryl shampoo, malathion shampoo, and commercial shampoo, respectively. In vivo results showed that all herbal shampoos were also more effective for head lice treatment than chemical and commercial shampoos with 94.67-97.68% of cure rate after the first treatment; the second treatment, 7 days later, revealed that the cure rate was 100%. Meanwhile, chemical shampoo showed 71.67-93.0% of cure rate and, unfortunately, commercial shampoos were nontoxic to head lice and showed 0% of cure rate after the first and the second treatments. Our data showed that three herbal shampoos of native plants in Thailand in this study are suitable to be used as pediculicides for Thai children since it is safe for children and there is no side-effect after application.

Molecular and functional characterization of cDNAs putatively encoding carboxylesterases from the migratory locust, Locusta migratoria.

Carboxylesterases (CarEs) belong to a superfamily of metabolic enzymes encoded by a number of genes and are widely distributed in microbes, plants and animals including insects. These enzymes play important roles in detoxification of insecticides and other xenobiotics, degradation of pheromones, regulation of neurodevelopment, and control of animal development. In this study, we characterized a total of 39 full-length cDNAs putatively encoding different CarEs from the migratory locust, Locusta migratoria, one of the most severe insect pests in many regions of the world, and evaluated the role of four CarE genes in insecticide detoxification. Our phylogenetic analysis grouped the 39 CarEs into five different clades including 20 CarEs in clade A, 3 in D, 13 in E, 1 in F and 2 in I. Four CarE genes (LmCesA3, LmCesA20, LmCesD1, LmCesE1), representing three different clades (A, D and E), were selected for further analyses. The transcripts of the four genes were detectable in all the developmental stages and tissues examined. LmCesA3 and LmCesE1 were mainly expressed in the fat bodies and Malpighian tubules, whereas LmCesA20 and LmCesD1 were predominately expressed in the muscles and hemolymph, respectively. The injection of double-stranded RNA (dsRNA) synthesized from each of the four CarE genes followed by the bioassay with each of four insecticides (chlorpyrifos, malathion, carbaryl and deltamethrin) increased the nymphal mortalities by 37.2 and 28.4% in response to malathion after LmCesA20 and LmCesE1 were silenced, respectively. Thus, we proposed that both LmCesA20 and LmCesE1 played an important role in detoxification of malathion in the locust. These results are expected to help researchers reveal the characteristics of diverse CarEs and assess the risk of insecticide resistance conferred by CarEs in the locust and other insect species.

Subchronic neurotoxicity of chlorpyrifos, carbaryl, and their combination in rats.

Anticholinesterase pesticides have been widely used in agricultural and domestic settings and can be detected in the environment after long-term use. Although the acute toxic effects of chlorpyrifos and carbaryl have been well described, little is known about the chronic toxicity of the pesticides mixture. To investigate their chronic neurotoxicity, Wistar rats were exposed to chlorpyrifos, carbaryl, and their mixture (MIX) for 90 consecutive days. The activities of serum cholinesterase (ChE) as well as acetylcholinesterase (AChE) and neuropathy target esterase (NTE) in nerve tissues were determined. Furthermore, the histopathological examination was carried out. The results showed that ChE activity significantly decreased in all treated rats except the rats treated with low dose carbaryl. Treatment with middle- and high-dose chlorpyrifos and MIX in rats significantly inhibited AChE activity in the central nervous tissues, whereas treatment with carbaryl alone did not. In sciatic nerve, AChE activity was significantly inhibited by high-dose carbaryl and MIX, but not by chlorpyrifos alone. No significant NTE inhibition was observed in all treatment groups. Histopathological examination revealed that both chlorpyrifos and MIX treatment induced hippocampal damage. However, no obvious hippocampal damage was found in carbaryl-treated rats. Carbaryl and MIX, but not chlorpyrifos alone, induced pathological damage of sciatic nerve. Taken together, all of the results indicated that chlorpyrifos and carbaryl have different toxicological target tissues in nervous system and showed corresponding effects in the nervous tissues, which may reflect the different sensitivity of central and peripheral nervous tissues to different pesticides individually and in combination.

Carbaryl-induced histopathologic alterations in the digestive tract of the Levantine frog, Pelophylax bedriagae (Anura: Ranidae).

In this study, histopathologic changes following carbaryl exposure for 96 hr were investigated in the digestive tract of Levantine frog, Pelophylax bedriagae. Adult frogs were exposed to carbaryl once by oral gavage in concentrations of 0.05, 0.1, and 0.2 mg/g. Histopathological changes were more prominent in medium- (0.1 mg/g) and high-dose (0.2 mg/g) groups than in the low-dose (0.05 mg/g) group. Esophageal cells showed vacuolization, cellular swelling, nuclear pyknosis, karyolysis, and necrosis. Additionally, esophageal glandular atrophy and infiltration of inflammatory cells around esophageal glands were observed at medium and high doses. In the stomach, there were prominent histopathologic defects such as cellular swelling and necrosis in gastric glands, necrotic cells within the interstitial spaces, separation of epithelial cell layer, congested vessels, and hemorrhage at medium and high doses. In the intestine, detachment of epithelial layer, epithelial cell disorganization, inflammation, and necrosis were detected at medium and high doses. The results of this study showed that carbaryl caused adverse effects on the digestive tract of the Levantine frog, P. bedriagae.

Insect herbivores change the outcome of plant competition through both inter- and intraspecific processes.

Insect herbivores can affect plant abundance and community composition, and theory suggests that herbivores influence plant communities by altering interspecific interactions among plants. Because the outcome of interspecific interactions is influenced by the per capita competitive ability of plants, density dependence, and intrinsic rates of increase, measuring herbivore effects on all these processes is necessary to understand the mechanisms by which herbivores influence plant communities. We fit alternative competition models to data from a response surface experiment conducted over four years to examine how herbivores affected the outcome of competition between two perennial plants, Solidago altissima and Solanum carolinense. Within a growing season, herbivores reduced S. carolinense plant size but did not affect the size of S. altissima, which exhibited compensatory growth. Across seasons, herbivores did not affect S. carolinense density or biomass but reduced both the density and population growth of S. altissima. The best-fit models indicated that the effects of herbivores varied with year. In some years, herbivores increased the per capita competitive effect of S. altissima on S. carolinense; in other years, herbivores influenced the intrinsic rate of increase of S. altissima. We examined possible herbivore effects on the longer-term outcome of competition (over the time scale of a typical old-field habitat), using simulations based on the best-fit models. In the absence of herbivores, plant coexistence was observed. In the presence of herbivores, S. carolinense was excluded by S. altissima in 72.3% of the simulations. We demonstrate that herbivores can influence the outcome of competition through changes in both per capita competitive effects and intrinsic rates of increase. We discuss the implications of these results for ecological succession and biocontrol.