Lufenuron Treatment Research Articles

Demographic analysis of the biological parameters of Spodoptera frugiperda after sublethal exposure to insecticides

Spodoptera frugiperda (JE Smith) is one of the most destructive pests, causing serious yield losses of corn on all continents except Europe. Low-lethal concentrations of insecticides may affect not only the survival rate but also the demographic parameters of a pest. To understand the effect of low-lethal concentrations of insecticides on S. frugiperda, the developmental parameters after low-lethal concentrations treatment by three different modes of action pesticides tetrachlorantraniliprole, spinetoram, and lufenuron were analyzed. For F0 generation, the pupal length and weight of FAW after insecticide treatment were significantly longer and heavier than that of control. For the F1 generation, the adult longevity and egg hatching rate after spinetoram and lufenuron treated was significantly shorter and lower than that of the control. While no significant effect was observed for the intrinsic rate of increase (r), finite rate of increase (λ), and mean generation time (T) of S. frugiperda, the net reproductive rate (R0) significant decreased after the spinetoram and lufenuron treatment. Results showed tetrachlorantraniliprole, spinetoram, and lufenuron negatively affect larval survival rate, but spinetoram and lufenuron caused early maturity, and all three insecticide treatments increased egg reproduction. The results of this study suggest that low-lethal concentration exposure to insecticides negatively impacts the life table parameters of S. frugiperda, and those three insecticides from different modes of action cannot cause FAW resurgence and can be recommended as insecticides to control FAW. Those results will be helpful for researchers working on S. frugiperda management using chemical pesticides in an integrated pest management program.

Lufenuron treatment temporarily represses gene expression and affects the SUMO pathway in liver of Atlantic salmon.

Lufenuron is a benzoylurea insecticide currently in use to combat sea lice infestation in salmon aquaculture in Chile. With pending approval in Norway, the aim of this work was to study the uptake and toxicity of lufenuron in liver tissue of Atlantic salmon. Juvenile salmon weighing 40 g were given a standard 7-day oral dose, and bioaccumulation and transcriptional responses in the liver were examined 1 day after the end-of-treatment (day 8) and after 1 week of elimination (day 14). Bioaccumulation levels of lufenuron were 29 ± 3 mg/kg at day 8 and 14 ± 1 mg/kg at day 14, indicating relatively rapid clearance. However, residues of lufenuron were still present in the liver after 513 days of depuration. The exposure gave a transient inhibition of transcription in the liver at day 8 (2437 significant DEGs, p-adj < .05), followed by a weaker compensatory response at day 14 (169 significant DEGs). Pathways associated with RNA metabolism such as the sumoylation pathway were most strongly affected at day 8, while the apelin pathway was most profoundly affected at day 14. In conclusion, this study shows that lufenuron easily bioaccumulates and that a standard 7-day oral dose induces a transient inhibition of transcription in liver of salmon.

Effects of lufenuron treatments on the growth and development of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Lufenuron is an effective benzoylurea insecticide that inhibits the synthesis of chitin and regulates the growth of insects. However, little is known about the effects of lufenuron treatment on the development of Spodoptera frugiperda (J. E. Smith). In this study, we assessed the toxicity of lufenuron on S. frugiperda and evaluated the effects of lufenuron treatment on the growth and development of S. frugiperda. The results showed that lufenuron exhibits high insecticidal activity against S. frugiperda, with the LC50 value of 0.99 mg L−1. Lufenuron treatments can significantly prolong the larval developmental duration and reduce the rates of pupation and emergence. To further explore the underlying mechanism of this observation, the expression profiles of the chitin synthase gene (SfCHS) and chitinase gene (SfCHT), two key enzyme genes involved in the molting of S. frugiperda, were determined after exposure to lufenuron for 96 h. The results of qRT-PCR demonstrated that lufenuron treatments can significantly reduce the expression of SfCHT, while the expression of SfCHS remained relatively stable. Furthermore, we found that lufenuron strongly interacted with chitinase (SfCHT) (−10.8 kcal/mol) and chitin synthase (SfCHS) (R1: −9.7 kcal/mol; R2: −10.2 kcal/mol). Our results indicated that lufenuron has significant effects on the development of S. frugiperda that might be attributed to the differential expression of SfCHT and SfCHS.

Ameliorative effect of avocado oil against lufenuron induced testicular damage and infertility in male rats.

Lufenuron is a benzoylurea pesticide that causes significant histological and histochemical damage in mammals. Avocado is a common food in the human diet that contains antioxidant and antitumor properties. In male rats, avocado oil's protection against lufenuron-induced reproductive deterioration, oxidative stress, and DNA damages was investigated. Twenty-eight mature male rats were selected and distributed into four groups: Group 1, control group were administered distilled water orally; Group 2 received 4ml/kg avocado; Group 3 was given lufenuron (1.6mg/kg), and Group 4 was given avocado oil/lufenuron. The findings show that lufenuron treatment reduces reproductive hormone levels, sperm count, motility, viability and causes negative histopathological changes in testicular tissue, such as decreased epithelial height and increased luminal diameter degenerated spermatogenesis. Furthermore, lufenuron reduced the content of antioxidant enzymes while increasing the level of malondialdehyde, nitric oxide and corresponding DNA damage. Results showed that lufenuron is associated with testicular function impairment, which leads to infertility. Treatment with avocado oil improved reproductive hormone secretions, enzymatic activity, histological and DNA damage parameters in testis tissues, reducing the negative effects of lufenuron, proving that it may have a therapeutic role against lufenuron-mediated testicular toxicity.

Knockdown of UDP-N-acetylglucosamine pyrophosphorylase and chitin synthase A increases the insecticidal efficiency of Lufenuron to Spodoptera exigua

Spodoptera exigua (Lepidoptera, Noctuidae) has been responsible for causing considerable and widespread agricultural losses worldwide. Owing to strong selective pressure, S. exigua showed increased resistance to Lufenuron (LUF). Consequently, RNA interference (RNAi)-based insecticides had more benefits than chemical insecticides. Therefore, to enhance the insecticidal activity of LUF to S. exigua, in the present study, we aimed to elucidate the impact of double-stranded RNAs (dsRNAs) on S. exigua larval susceptibility to LUF. First, the transcriptome of S. exigua was sequenced following the treatment with LUF. By comparing the upregulated and downregulated GO enrichment, chitin binding and chitin metabolic processes were the significantly enriched pathways. According to transcriptome sequencing, 8 genes associated with chitin biosynthesis, 8 chitin degradation genes, and 17 cuticle protein genes were obtained. UDP-N-acetylglucosamine pyrophosphorylase (UAP) and Chitin synthase A (CHSA) showed significantly downregulated expression after treatment with different sublethal doses of LUF. Downregulation of UAP increased mortality from 31.97% to 47.91% when the larvae were exposed to LUF. A significant increase in the mortality of S. exigua from 30.63% to 50.19% was observed following LUF administration after dsCHSA. In addition, the expression analysis of genes associated with chitin biosynthesis was significantly changed after LUF treatment, dsRNAs-RNAi, and their combination (LUF-dsRNAs). Significant differences were observed in the chitin content between the control group at 72 h after treatments. Results of the present study can help further elucidate the understanding of the combined effects of RNAi and LUF on S. exigua. Additionally, this research provides a suitable foundation for future studies with the aim to develop an efficient method of delivery for large-scale pest control in the fields.

Bioassay comparative dose efficacy of Lufenuron on the biology of Spodoptera litura (F.) on cauliflower

The common cutworm Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), was first described by Johan Christian Fabricius in 1775, is a nocturnal moth, polyphagous in nature, destructive insect pest, damaging economically important crops, and decreasing the yield completely. The research was conducted to control through sub-lethal doses of Lufenuron under laboratory conditions where mortality was determined. The results indicated that the Lufenuron treatment caused mortality, reduction in larval and pupal weight. The copulation time, fecundity, and fertility decreased as compared to control. The maximum mortality was found on dose one after one week and minimum on dose five after 24 hours. The maximum larval weight reductions were recorded in dose one after one week, and dose three after 24 hours with the longest larval and pupal period in dose one and the shortest in dose five as compared to control. The maximum pupal weight reduction was recorded in dose one and minimum in dose five as the shortest adult longevity of S. litura in dose one and the longest in dose five thus; the longest duration of life-cycle in dose one and the shortest in dose five. The shortest copulation time in dose one and the highest in dose five with the minimum fecundity found in dose one and maximum in dose five whereas; minimum fertility of eggs in dose one and maximum in dose five as compared to control. It is concluded that the Lufenuron (IGR) is effective by their sub-lethal concentrations on S. litura however, the most preference can be given to which caused highly sub-lethal effects on its biology. Keywords: Cauliflower; Different doses; Lufenuron; Laboratory conditions; S. litura http://dx.doi.org/10.19045/bspab.2021.100121

Influence of lufenuron on the nutrient content and detoxification enzyme expression in Aedes aegypti L. (Diptera: Culicidae)

Aedes aegypti is of utmost public health concern transmitting various diseases of human health concern. Employment of chemical-based control interventions has induced immunity in mosquitoes, harmed environment, and adversely affected human health and non-targets diverting the research focus on alternate measures. Current study investigates the efficacy of an Insect Growth Regulator, lufenuron, against early fourth instars of Ae. aegypti. The larvae exposed to lufenuron for 24 h were assessed for the effects on the development and adult emergence. The impact of sub-lethal and median-lethal dose of lufenuron was determined on the nutrients and detoxification enzymes of Ae. aegypti. The larvae exposed to lufenuron showed reduced adult emergence exhibiting the respective IE30 and IE50 as 0.13 μg/L and 0.96 μg/L. Larval treatment with IE30 and IE50 lufenuron reduced the carbohydrate and lipid content in Ae. aegypti. However, the protein levels in the larvae decreased only on exposure to IE30 lufenuron while increased with IE50 lufenuron. Besides, IE30 and IE50 lufenuron treatment elevated α-esterases (1.05-fold; 1.15-fold); β-esterases (1.29-fold;1.62-fold), and Glutathione-S-transferases (1.19-fold; 3.1-fold) expression in the Ae. aegypti larvae. The % acetylcholinesterase inhibition also reduced by 3.75-fold and 2.07-fold, correspondingly, while the cytochrome P450 monooxygenase expression rose (1.15-fold) only with IE50 dosage of lufenuron. It is suggested that lufenuron stress probably ampliflied the catabolism of nutrients and expression of metabolic detoxifying enzymes in Ae. aegypti larvae in order to meet higher energy requirements and counteract the adverse effects of lufenuron. This is the first ever report unravelling the effect of lufenuron on the biochemical parameters of Ae. aegypti larvae.

Lufenuron indirectly downregulates Vitellogenin in the boll weevil females reducing egg viability

AbstractLufenuron, a molecule that belongs to the chitin synthesis inhibitors group of insect growth regulators, has a still unclear mode of action, but probably it affects chitin synthesis at a post‐transcriptional level. In this work, we report the effects of lufenuron on nutrition and reproduction in adult females of Anthonomus grandis, the main neotropical cotton pest and tried to link the effects on peritrophic matrix (PM) with egg viability. After Lufenuron treatment A. grandis females presented weight loss and less accumulation of protein and lipids probably due to PM breakdown. Also, treated females produce the same quantity of eggs as the control, although eggs from lufenuron‐treated females were less viable. After morphological and histochemical analysis, we have noticed that oocytes from lufenuron‐treated females contained less protein. Finally, lufenuron‐treated females produced at least nine times less vitellogenin (AgraVg) RNA than control females. We specifically showed that lufenuron treatment caused PM disruption and it has probably led to vitellogenin (AgraVg) downregulation in females culminating in egg unviability. The effect of lufenuron on PM leads to insect malnutrition, and this malnutrition downregulates vitellogenin among other genes. This is the first work that describes and tries to correlate the lufenuron effects on adult females.

Sterilizing Activity of the Insect Growth Regulator, Lufenuron on Drosohpila melanogaster (Meigen)

Due to the complicated problems coming from excessive applications of insecticides, searching of safe substitutes to these insecticides has become necessity. Thus, the insect growth regulators are candidated to be used in such concern. The insect growth regulator, lufenuron was applied against Drosophila melanogaster (Meigen) as mixed with the diet of the larvae, with concentrations of 5, 10 and 20 ppm to test its efficacy as a sterilizer. Data showed that 5ppm treatment pushed up the larvae to speed pupation by the first two days after treatment. Overall results showed that 20 ppm recorded the highest pupation (94%) followed by 5, 10 ppm and control treatments with values of 87.5, 85.3 and 82.4%, respectively. The top concentration also caused the lowest adult emergence recording 39.4% then, 10, 5 ppm and control with values of 44.8, 71.4 and 85,7%, resp. The mortalities were arranged in descending order as follows 76.9, 35.0, 7.7 and 4.2% at 20, 5, 10 and control respectively. There were no dead adults recorded except on the ninth day at 10 ppm concentration and control. Regarding the sex ratio, it was greatly affected by lufenuron. It tended to increase the number of males. The number of males was four times the number of females at 5 ppm (1:4). There were no females at 20 ppm (0:12). Number of females was similar to that of males at 10 ppm (1:1). According to these results, the number of the output generation recorded 16 and 80 individuals after 10 and 15 days resp., compared to 96 and 220 individuals respectively in control. Females put eggs on the diet surface at 10 ppm, but it did not hatch. Uncompleted emergence was recorded at 5 and 20 ppm (21.4 and 52.9 %, respectively). Adults with deformed wings were recorded at 20 ppm as 11.8%. Total protein analysis and phenoloxidase activity were carried out. The reduction in total protein occurred in females due to lufenuron treatment. The highest reduction was 16.67 mg/ 1000 insects at 10 ppm concentration that affected on female fecundity. Phenoloxidase activity was high in males. It recorded 1153.33 M O.D./1000 insects at 10 ppm, which affected in male fertility. This may explain why the eggs did not hatch.

Field evaluation of two biorational compounds in the control of pear psylla, Cacopsylla pyricola (Förster), on pear trees

Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae) is an important pest of commercial pear in all pear-growing regions of Iran. In the scope of an integrated pest management, a research was carried out on the impact of treatment with biorational compounds in comparison with conventional chemical insecticides for controlling the pear psyllid. The experiments were done with five treatments consisted of diflubenzuron and lufenuron as biorational insecticides and thiacloprid and diazinon as conventional chemical insecticides and untreated check. The trials were set up in a randomised complete block design. The treatments were replicated four times. Samplings were carried out one day before spraying and 3, 7, 15, 30 and 45 days after spraying through clipping 15 leaves in each replicate and counting the number of pear psyllid live nymphs. Mortality percentage was calculated using Henderson–Tilton formula. The data were subjected to analysis of variance (ANOVA) and the means comparison was performed using Duncan’s multiple range test. The results indicated that the highest mortality in diflubenzuron and lufenuron treatments occurred after 15 days, with 82.09% and 71.01% mortality, respectively. In comparison with conventional chemical insecticides, the efficacy of biorational compounds was higher or not significantly different. The results of the trials are discussed in terms of improving management of the populations of pear psylla.

Biological and molecular aspects of the insect growth regulator lufenuron on Spodoptera littoralis (Bosid) (Lepidoptera:Noctuidae)

Article History The cotton leafworm, S. littoralis, is a major pest in Egypt causes severe quantitative and qualitative losses of cotton and other economic crops. This study examined the effect of chitin synthesis inhibitors, lufenuron (match 5%) on the 2 nd instar larvae. The results showed that lufenuron caused not only mortality in larval stages, but also caused effect on pupal and adult duration, adult fecundity and egg fertility. Also lufenuron treatments have resulted in emergence of deformed pupae and adults. PCR-RFLP technique was used in this study to investigate the effect of lufenuron on the vira-like chitinase gene, one of the genes involved in the formation of chitin and concerned with development of insect. The endonucleases Spel, EcoRI and Bbsl were used to detect the molecular changes at different time intervals 6, 12, 24 and 48hrs post treatment with sublethal doses LC25, LC50 and LC90.The results showed significant changes in the sequences of the treated groups which were dose and time dependants. Moreover the number of RNA secondary structure stems was varied in the different studied groups and most of them differed in their nucleotide sequences, positions and free energy.

Lethal and sublethal effects of lufenuron on the Formosan subterranean termite (Isoptera: Rhinotermitidae).

A laboratory study was conducted to understand the effect of low concentrations of lufenuron on termite physiology and behavior. Survivorship, running speed, body water content, food consumption, tunneling, microbial infection, and two behavioral patterns (carcass-burying behavior and particle transport behavior) were compared among Formosan subterranean termites, Coptotermes formosanus Shiraki, fed lufenuron-treated (250, 500, or 1,000 ppm) or untreated (control) filter paper. In 30-32 d, all lufenuron treatments significantly reduced survivorship, running speed, consumption, and tunneling, but had no substantial effect on body water content. In addition, termites fed the three concentrations of lufenuron became infected by opportunistic pathogens. Carcass-burying and particle transport behaviors also were inhibited by lufenuron. Potential application of lufenuron at low concentrations for the control of C. formosanus is discussed.

Comparative Evaluation of Three Chitin Synthesis Inhibitor Termite Baits Using Multiple Bioassay Designs

Use of chitin synthesis inhibitors has revolutionized the potential impact of termite baiting systems. Several chitin synthesis inhibitors have been used or tested against subterranean termites. We evaluated the effect of lufenuron on bait matrix consumption and mortality of Coptotermes formosanus and compared it with 2 other chitin synthesis inhibitors presently used for termite control: diflubenzuron and noviflumuron. Laboratory no-choice and multi-chamber bioassay designs were employed. At the end of 6 weeks, in both the no-choice and multi-chamber tests, mortality was significantly higher in all the chitin synthesis inhibitor treatments as compared to the controls; however, lufenuron treatment had significantly higher mortality than the other chitin synthesis inhibitors. Multi-chamber tests suggested no sign of feeding deterrence with any of the chitin synthesis inhibitors at the concentrations tested. Consumption of lufenuron cardboard or noviflumuron bait matrix was similar to that of control cardboard in the no-choice tests. We conclude that, based on the overall bait consumption and mortality data, lufenuron was at least as effective as noviflumuron and diflubenzuron.

Dietary lufenuron reduces egg hatch and influences protein expression in the fruit fly Bactrocera latifrons (Hendel).

Lufenuron (LFN), a chitin synthase inhibitor, impacts the fertility of Ceratitis capitata, Bactrocera dorsalis, B. cucurbitae, and B. latifrons. We posed the hypothesis that LFN curtails egg hatch in the solanaceous fruit fly, B. latifrons. In this study, newly emerged virgin adults were sexed and fed for 12 days with varying concentrations of LFN-laced agar diets until sexual maturation. Eggs were collected from 12-d-old adults and the egg hatch was assessed. Egg hatch decreased in adults reared on LFN-treated diets. LFN-treated media did not influence fertility after one gender was reared on experimental and the other on control media before mating. Exposure to LFN-treated medium after mating led to reduced egg hatch. We infer that LFN is not a permanent sterilant, and reduced egg hatch depends on continuous exposure to dietary LFN after mating. Proteomic analysis identified two differentially expressed proteins, a pheromone binding protein and a chitin binding protein, between adults maintained on LFN-treated and control diets. Expression of two genes encoding chitin synthase 2, and chitin binding protein, was altered in adults exposed to dietary LFN. LFN treatments also led to increased expression of two odorant binding proteins one in females and one in males. We surmise these data support our hypothesis and provide insight into LFN actions.

Evaluation of two formulated chitin synthesis inhibitors, hexaflumuron and lufenuron against the raisin moth, Ephestia figulilella.

The raisin moth, Ephestia figulilella Gregson (Lepidoptera: Pyralidae), has a nearly cosmopolitan distribution, and causes severe quantitative and qualitative losses throughout the world. The larvae attack various drying and dried fruits, fallen figs, and damaged or moldy clusters of grapes on vines. Control of this pest in storage depends mostly on synthetic pesticides with several adverse side effects. To mitigate the adverse effects of these pesticides, investigations have focused on the development of compounds with more selectivity, and short residual life. In this research, insecticidal effects of two chitin synthesis inhibitors, hexaflumuron and lufenuron, were investigated against E. figulilella. Graded concentrations of each pesticide were prepared with distilled water. One-day-old fifth instar were sprayed by Potter's precision spray tower. Application of hexaflumuron and lufenuron on last instar larvae of E. figulilella caused not only mortality in larval stage, but also caused defects in pupal and adult stages. Larval mortality increased as concentration increased. The longevity of the fifth instars in both hexaflumuron and lufenuron treatments, in comparison with the controls, increased by more than 12 days. The longevity of adults decreased by about 10 days. Probit analysis data revealed that the sensitivity of the test insect to hexaflumuron (EC50 = 95.38 ppm) was greater than lufenuron (EC50= 379.21 ppm).

RESPONSES OF ZOOPLANKTON IN LUFENURON-STRESSED EXPERIMENTAL DITCHES IN THE PRESENCE OR ABSENCE OF UNCONTAMINATED REFUGES

Outdoor experimental ditches were used to evaluate the influence of untreated refuges on the recovery of zooplankton communities following treatment with the fast-dissipating insecticide lufenuron. Each experimental ditch was divided into three sections of the same surface area. The treatments differed in the proportion of ditch (0, 33, 67, and 100% of the surface area) to which the insecticide was applied at the same nominal treatment (3 mug/L). During the first week postapplication, a barrier was placed between treated and untreated ditch sections. The untreated sections were included to provide a source of organisms for recovery of affected zooplankton populations in the treated sections of the ditch after the removal of the barrier. Cyclopoida were the most affected by lufenuron treatment, followed by Daphnia gr. galeata. These and other direct effects of treatment on larvae of the phantom midge Chaoborus spp. resulted in clear indirect effects on populations of Calanoida, Ceriodaphnia, and Rotifera. Overall, faster recovery of the zooplankton community was observed in the treated sections of ditches that were sprayed for a smaller proportion of their surface area. Nevertheless, individual zooplankton populations showed considerable differences in rate of recovery. Cyclopoida showed a relatively slow rate of recovery even in the partially treated ditches. Daphnia gr. galeata recovered more rapidly in treated ditch sections in the presence of unsprayed ditch sections, illustrating the potential influence of unexposed refuges. Furthermore, the presence of refuges most likely dampened the magnitude and duration of indirect effects in the ditches treated with lufenuron.

In Vitro Efficacy of Lufenuron against Filamentous Fungi and Blood Concentrations after PO Administration in Horses

Lufenuron is a benzoylphenyl urea-derived insecticide that has been recently introduced as a novel treatment for fungal infections in horses. The purposes of this study were to determine (1) the in vitro efficacy of lufenuron against Aspergillus and Fusarium spp. and (2) the ability of lufenuron to reach efficacious blood concentrations after PO administration in horses. Fungal colonies isolated from diseased equine corneas were tested against lufenuron solutions up to 700 μg/mL. Twenty-one adult horses received 1 of 3 PO lufenuron treatment regimens: 5 mg/kg body weight (BW) q24h for 3 days, 20 mg/kg BW q24h for 3 days, or 60 mg/kg BW q24h for 1 day. Blood samples were collected up to 96 hours after drug administration and analyzed by high-performance liquid chromatography. Statistical analyses of lufenuron blood concentrations were performed by analysis of variance and Fischer's Least Significant Difference test, with statistical significance set at P < .05. Lufenuron showed no effect on the in vitro growth of Aspergillus or Fusarium spp. Lufenuron was detected in the blood of all but 1 horse and showed no adverse effects. The maximum blood lufenuron concentration (83.5 ± 58.7 μg/L) was lower than the concentrations proven to be ineffective in vitro in this study. Further therapeutic use of lufenuron as an antifungal agent in horses should be based on proven efficacy against specific strains of clinically relevant fungi with pharmacokinetic data demonstrating sufficient lufenuron concentrations in target tissues.

In Vitro Efficacy of Lufenuron against Filamentous Fungi and Blood Concentrations after PO Administration in Horses

Lufenuron is a benzoylphenyl urea-derived insecticide that has been recently introduced as a novel treatment for fungal infections in horses. The purposes of this study were to determine (1) the in vitro efficacy of lufenuron against Aspergillus and Fusarium spp. and (2) the ability of lufenuron to reach efficacious blood concentrations after PO administration in horses. Fungal colonies isolated from diseased equine corneas were tested against lufenuron solutions up to 700 microg/mL. Twenty-one adult horses received 1 of 3 PO lufenuron treatment regimens: 5 mg/kg body weight (BW) q24h for 3 days, 20 mg/kg BW q24h for 3 days, or 60 mg/ kg BW q24h for 1 day. Blood samples were collected up to 96 hours after drug administration and analyzed by high-performance liquid chromatography. Statistical analyses of lufenuron blood concentrations were performed by analysis of variance and Fischer's Least Significant Difference test, with statistical significance set at P < .05. Lufenuron showed no effect on the in vitro growth of Aspergillus or Fusarium spp. Lufenuron was detected in the blood of all but 1 horse and showed no adverse effects. The maximum blood lufenuron concentration (83.5 +/- 58.7 microg/L) was lower than the concentrations proven to be ineffective in vitro in this study. Further therapeutic use of lufenuron as an antifungal agent in horses should be based on proven efficacy against specific strains of clinically relevant fungi with pharmacokinetic data demonstrating sufficient lufenuron concentrations in target tissues.

Disruption of Reproductive Activity of &lt;I&gt;Coptotermes formosanus&lt;/I&gt; (Isoptera: Rhinotermitidae) Primary Reproductives by Three Chitin Synthesis Inhibitors

Effects of the chitin synthesis inhibitors (CSIs) diflubenzuron, hexaflumuron, and lufenuron on the Formosan subterranean termite, Coptotermes formosanus Shiraki, primary reproductives were studied in the laboratory. Incipient colonies were established by collecting and pairing C. formosanus alates and placing them in dishes containing an artificial diet. Three groups of 56 colonies each were fed with a diet containing 10 ppm of one of each of the CSIs and were compared with a control group fed with an untreated diet. All eggs oviposited by treated young queens failed to hatch at the end of 6 mo. Estimated queen fecundity was significantly lower in the lufenuron treatment compared with the control group. Fecundity of hexaflumuron-treated queens did not differ significantly from that of queens from the control group and the other treatments. Adult mortality was significantly higher in the diflubenzuron and lufenuron treatments than in the control group at the end of 6 mo., but not in the hexaflumuron treatment. All the pairs died within 8 mo. in the diflubenzuron and lufenuron treatments, even after treatment was suspended at the end of 6 mo. Mortality in the hexaflumuron treatment was significantly higher than in the control group by the end of 9 mo. The three CSIs tested eliminated reproduction in C. formosanus by preventing egg hatching and induced adult mortality. Possible mechanisms by which CSIs induce termite adult death are discussed.

Efficacy of lufenuron as chemosterilant against Ceratitis capitata in field trials.

Two field trials in citrus orchards in Turis (Valencia, Spain) and Denia (Alicante, Spain) were performed in order to test the sterilant effect of the insect growth regulator lufenuron against wild medfly Ceratitis capitata (Wiedemann) populations. Two application methods for lufenuron were tested: spraying, in spots, an emulsion of lufenuron in a protein bait, and hanging delta traps that contained a proteinaceous gel with lufenuron (solid bait). The sterilant effect was measured as medfly population reduction, reduction of fruit damage in treated fields, and the number of eggs hatching in punctured fruits. In order to assess the efficacy of lufenuron treatments, we recorded results obtained from two different zones in both trial fields: an outer zone, close to untreated fields, and an inner zone, in the centre of lufenuron treated fields. We observed a minimum sterilant effect in the outer zone and a maximum sterilant effect in the inner one. The maximum sterilant effect was in the inner zone, where a reduction of medfly population of 80.4% in the sprayed field and a reduction of 77.6% in the solid bait field was observed. In addition, the greater the distance from the untreated zones of the treated orchard (inwards), the lower the fruit damage and medfly population level. In this inner zone, fruit punctured by medfly developed significantly fewer larvae (38.8%) than punctured fruits from the outer zone (68.6%). In addition, we recorded the decline in the activity of the lufenuron treatments with time. Lufenuron activity persisted in field for at least 2 weeks with spray applications, and for 3 months with bait gels.