Effects Of Pyriproxyfen Research Articles

Use of Pyriproxyfen to Induce Oogenesis in Diapausing Megacopta cribraria (Heteroptera: Plataspidae), and Evaluation of Pyriproxyfen-Induced Eggs for Rearing the Parasitoid Paratelenomus saccharalis (Hymenoptera: Scelionidae).

Simple SummaryRearing of many hymenopteran egg parasitoids requires a reliable supply of host eggs. The parasitoid Paratelenomus saccharalis can be reared on eggs produced from field collected kudzu bug, Megacopta cribraria, however field-collected hosts obtained during reproductive diapause do not readily produce eggs and must be reared under a long day-length photoperiod to terminate diapause. In this study we found that an exogenous application of pyriproxyfen was able to terminate diapause, leading to a significant increase in egg production. The eggs produced by pyriproxyfen-treated M. cribraria were accepted by the egg parasitoid Paratelenomus saccharalis, however parasitoid emergence was reduced when compared to eggs from untreated hosts. When the effects of pyriproxyfen treatment on egg production and parasitoid emergence were evaluated together, the net increase in parasitoid yield due to pyriproxyfen treatment was approximately 87%. This method has the potential to increase parasitoid yield and reduce production costs in egg parasitoid rearing programs.The mass rearing of hymenopteran egg parasitoids requires an abundant supply of host eggs. The onset of reproductive diapause and subsequent decline in egg production poses a challenge for parasitoid rearing when using host colonies augmented by field-collected insects. We investigated the application of pyriproxyfen, a juvenile hormone analog, to induce oviposition in diapausing adult kudzu bugs, Megacopta cribraria (Fabricius) (Heteroptera: Plataspidae), and the use of eggs produced by pyriproxyfen-treated kudzu bugs to rear the egg parasitoid, Paratelenomus saccharalis (Dodd) (Hymenoptera: Scelionidae). The effects of pyriproxyfen and photoperiod treatments on host mortality, egg production, and rates of parasitoid eclosion from the eggs were used to calculate the parasitoid yield for the different treatment regimes. A combination of pyriproxyfen and a long-day photoperiod increased the parasitoid yield by 87% compared to acetone and a long-day photoperiod. The general applicability of JH-analog mediated egg production for parasitoid rearing is discussed.

Efficacy of Royal Guard, a new alpha-cypermethrin and pyriproxyfen treated mosquito net, against pyrethroid-resistant malaria vectors

Royal Guard is a new insecticide-treated bed-net incorporated with a mixture of alpha-cypermethrin and pyriproxyfen (an insect growth regulator). We assessed its efficacy and wash-resistance in laboratory and experimental hut studies following WHO guidelines. Mosquitoes that survived exposure to the net were kept in separate oviposition chambers and observed for the reproductive effects of pyriproxyfen. In laboratory assays, Royal Guard induced > 80% mortality and > 90% blood-feeding inhibition of An. gambiae sl mosquitoes before and after 20 standardised washes and sterilised blood-fed mosquitoes which remained alive after exposure to the net. In an experimental hut trial against wild free-flying pyrethroid-resistant An. gambiae sl in Cové Benin, Royal Guard through the pyrethroid component induced comparable levels of mortality and blood-feeding inhibition to a standard pyrethroid-only treated net before and after 20 washes and sterilised large proportions of surviving blood-fed female mosquitoes through the pyriproxyfen component; Royal Guard induced 83% reduction in oviposition and 95% reduction in offspring before washing and 25% reduction in oviposition and 50% reduction in offspring after 20 washes. Royal Guard has the potential to improve malaria vector control and provide better community protection against clinical malaria in pyrethroid-resistant areas compared to standard pyrethroid-only LLINs.

Effects of three conventional insecticides on life table parameters and detoxifying enzymes activity of Pulvinaria aurantii Cockerell (Hemiptera: Coccidae)

The effects of chlorpyrifos, pyriproxyfen and acetamiprid were examined on life table and detoxifying enzymes of Pulvinaria aurantii Cockerell. The LC50 values were 215.1, 92.8 and 126.7 ppm for tested pesticides, respectively. Low lethal concentration (LC30) of pyriproxyfen had the highest severe effect on life table parameters of P. aurantii. The intrinsic rate of increase was reduced to 0.161 day−1 in pyriproxyfen treatment as compared with 0.180 day−1 in the control. The lowest enzymatic activities were recorded for first instar treated with chlorpyrifos. The combination of lethal and sublethal effects of pyriproxyfen can be incorporated in management of this pest.

Susceptibility of immature stages of a biocontrol agent, Cheilomenes sexmaculata, to imidacloprid and pyriproxyfen

Chemical control is one of the important strategies in agricultural pest management because of easy operation, availability and fast control of pests. On the other hand, the environment has been exposed to various types of pesticides and pollutants which are growing daily. The persistent effects of residual pesticides commonly used cause numerous problems for non-target organisms especially parasitoids and predators. In this research, the effects of pyriproxyfen and imidacloprid on Cheilomenes sexmaculata (F.) (Coleoptera: Coccinellidae) were studied. The eggs of the ladybird beetle were treated with each pesticide in three concentrations by dipping method. Maximum field recommended concentration (MFRC=50 mg/L), 2/1 MFRC (to simulate multiple treatments) and 1/2 MFRC (to test the sublethal effects) were used for pyriproxyfen and 1/1 MFRC (140 mg/L), 1/2 MFRC (70 mg/L) and 1/4 MFRC (35 mg/L) were used for imidacloprid. The highest mortality of the first instar larvae was observed in imidacloprid at MFRC and pyriproxyfen at 2/1 MFRC. Also, maximum influence on fertility was observed at 2/1 MFRC of pyriproxyfen and MFRC of imidacloprid with 55% and 44% reduction compared to the control, respectively. Moreover, pyriproxyfen caused significant retardation on larval development at concentrations higher than 1/2 MFRC. Both insecticides initiated a significant effects on adult eclosion compared to the control and the greatest influence was observed by imidacloprid at 1/1 MFRC with 89% reduction in adult eclosion. Although results revealed that imidacloprid has higher acute toxicity to C. sexmaculata, further results obtained from the analysis of on the life cycle parameters of C. sexmaculata also indicated that pyriproxyfen also had toxic effects on this predator.

Effects of pyriproxyfen on wild populations of the housefly, Musca domestica, and compatibility with its principal parasitoids.

The housefly, Musca domestica L., is an important pest of animal agriculture. Effective fly management requires integration of manure management, mass trapping, biological control, and selective insecticide use. Insecticidal control of houseflies is difficult due to the rapidity of resistance development, yet the insect growth regulator pyriproxyfen (PPF) is one of few insecticides that may still be effective. Here, we tested the susceptibility of wild housefly populations in the USA and in Israel to PPF, as well as the effect of PPF on housefly parasitoids of the genera Muscidifurax and Spalangia. Most housefly populations from both countries were completely eliminated at PPF concentrations of 100 mg kg-1 (USA) and 600 mg kg-1 (Israel). One population from each country exhibited initial levels of PPF tolerance. PPF efficacy significantly decreased in cow manure. Emergence rates of parasitoids developing in PPF-treated hosts at concentrations of ≥600 mg kg-1 were significantly affected, whereas other fitness parameters were moderately to non-affected. PPF is still an effective tool for housefly control, but resistance management practices should be employed to avoid resistance. PPF is compatible with principal housefly parasitoids at concentrations <600 mg kg-1 , and is suitable for use in integrated pest management. © 2017 Society of Chemical Industry.

Effects of Pyriproxyfen on Female Reproduction in the Common Cutworm, Spodoptera litura (F.) (Lepidoptera: Noctuidae).

The common cutworm, Spodoptera litura, is a rapidly reproducing pest of numerous agricultural ecosystems worldwide. The use of pesticides remains the primary means for controlling S. litura, despite their negative ecological impact and potential threat to human health. The use of exogenous hormone analogs may represent an alternative to insecticides. Juvenile hormones (JHs) play an important role in the reproductive systems of female insects, but the effects of pyriproxyfen, a JH analog, on reproduction in S. litura were poorly understood. In this paper, we topically treated the newly emerged females with 20, 60, or 100 μg of pyriproxyfen to determine its effects on reproduction. Then, we examined the expression of vitellogenin (Vg) and three hormone receptors, USP, HR3, and EcR, using quantitative reverse transcription and real-time polymerase chain reaction (qRT-PCR), and found that pyriproxyfen up-regulated the expression of Vg, USP, and HR3, whereas the expression of EcR was unaffected. An analysis of fecundity showed that the peak oviposition day, lifespan, and oviposition period were progressively shortened as the pyriproxyfen dosage increased. We also found that pyriproxyfen decreased egg laying amount, whereas the number of mature eggs that remained in the ovarioles of dead females increased as the pyriproxyfen dosage increased. We examined oocytes using transmission electron microscopy and found that treatment with 100 μg of pyriproxyfen increased the metabolism by increasing the amount of rough endoplasmic reticulum and mitochondria in the primary oocytes. Our results suggest that the topical application of pyriproxyfen on newly emerged females can efficiently reduce reproduction in S. litura and may represent an alternative to the use of insecticides for controlling the agricultural pest.

Effects of pyriproxyfen and chlorfluazuron on the external bacteria isolated from Monomorium pharaonis (L.) collected from different cities in Cairo governorate

Effects of pyriproxyfen and chlorfluazuron on the external bacteria isolated from Monomorium pharaonis (L.) collected from different cities in Cairo governorate

Effects of pyriproxyfen and chlorfluazuron on the external bacteria isolated from Monomorium pharaonis (L.) collected from different cities in Cairo governorate

The present study was examined the effect of two IGRs (pyriproxyfen & chlorfluazuron) on the external bacterial flora isolated from the Pharaoh ant workersMonomorium pharaonis (L.). The Pharaoh ant workers were collected from three different cities in Cairo governorate. Different concentrations of 0.1%, 0.5% & 1% pyriproxyfen and 0.001%, 0.01% & 0.1% chlorfluazuron were used. Bacteria associated with Pharaoh ant workers (indoors & outdoors collected samples) were isolated before and after treatment with IGRs. It was found that, the external bacteria isolated from outdoors samples were less counted than those collected from indoors.The presence of some pathogenic bacteria was recorded. The used IGRs cause significant reduction in the count of bacteria in external isolates. Kinds of isolated bacteria were also affected by IGRs treatment and some kinds of them were disappeared in treated samples.

Effects of Pyriproxyfen on Intermediary Metabolism of Rice Striped Stem Borer, Chilo suppressalis Walker (Lepidoptera: Crambidae)

Effects of Pyriproxyfen were determined on intermediary metabolism in the fifth larval instars of Chilo suppressalis via assessments of various enzymatic and non-enzymatic compounds. Bioassay of larvae revealed LC10–50 values of 18, 72 and 190 µg/ml of pyriproxyfen. Results on alanine aminotransferase revealed lower activities in treated larvae versus control for all time intervals while activity of aspartate aminotransferase showed higher activities in treated larvae by 18 and 72 µg/ml of pyriproxyfen. Activities of γ-Glutamyl transferase and aldolase in treated larvae were significantly higher than those of control larvae. Treating of larvae by different concentrations of pyriproxyfen significantly increased lactate dehydrogenase activity for all time intervals although activity of the enzyme after 1 h was not significantly different among control and treated larvae. Activities of acid and alkaline phosphatases in treated larvae were higher than those of control. Amount of high and low density lipoproteins in treated larvae was higher than those of control except for time interval of 3 h of HDL in which control larvae revealed higher amount than 72 and 190 µg/ml treated larvae. Increased activity of the enzyme was noticed in treated larvae versus control in case of general esterases. Similar results were observed in case of glutathione S-transferase. Amount of triacylglyceride, glycogen and protein in control larvae was higher than those of treated larvae for all time intervals indicating their depletion due to energetic costs of pyriproxyfen treatment. These results clearly indicated negative effects of pyriproxyfen on intermediary metabolism of larvae that might lead to desirable mortality in pest population.

Effects of pyriproxyfen and Bacillus thuringiensis in midgut antioxidant enzymes and lipid peroxidation levels of Galleria mellonella larvae exposed to these insecticides singly and mixture

Effects of pyriproxyfen and Bacillus thuringiensis in midgut antioxidant enzymes and lipid peroxidation levels of Galleria mellonella larvae exposed to these insecticides singly and mixture

Effects of Pyriproxyfen on Viability and Increase of Intracellular Lipids in HepG2 Cell Line

Abstract Introduction: Pyriproxyfen, (2-[1-methyl-2-(4-phenoxyphenoxy) ethoxy] pyridine) (PPF) is an insecticidal used in household, agricultural, and horticultural applications to control many insect species. We tested its hepatic toxicity in hepatoma HepG2 cell line, we also evaluate if PPF could induce nonalcoholic fatty liver disease. Materials and methods: The hepatoma HepG2 cell line was exposed for 24-48 hrs with serum-free DMEM to the active principles at different concentrations. The cell viability was assessed by measuring reduction of the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). For the evaluation of in vitro steatosis, the cells were rinsed with cold phosphate buffered saline (PBS) and fixed in 4% paraformaldehyde. Images of cell were captured using an optic microscope and stained lipid droplets were then extracted with isopropanol (60%) for quantification by measuring its absorbance at 510 nm. Results: The MTT-test showed that PPF is cytotoxic at all concentrations tested both at 24 h and 48 h. Cell viability is below 50% for concentrations 1-10 ppm while the viability is less than 10% for the concentration 100 ppm. PPF induces the increasing intracellular lipids from 1 ppm concentration. The maximum effect is observed at 100 ppm. Discussion: In our in vitro study we found a loss of cell viability of about 50% for concentrations from 1-10 ppm by the MTT-Test that measures mitochondrial enzyme activity. Because the mitochondrial enzyme activity affected major changes at the starting/beginning of the apoptotic this condition suggested that PPF is strongly cytotoxic to human hepatocytes in the presented assays. Already at 1 ppm concentration PPF induces the increasing intracellular lipids, in HepG2 in vitro culture.

Toxicological and Biological Effects of Juvenile Hormone Mimic (JHM) Pyriproxyfen Against the Two Spotted Spider Mite, Tetranychus urticae Koch (Acari: Tetranychidae)

The present investigation was carried out to study the effect of Juvenile Hormone Mimic (JHM), Pyriproxyfen 10% EC on toxicological and biological aspects of the two spotted spider mite, Tetranychus urticae Koch under laboratory conditions. The effects of Pyriproxyfen on mortality, life cycle, duration period, adult longevity, ovipositional period and female fecundity were evaluated. Results indicated that the candidate compound exhibited direct contact toxicity against all the different developmental stages of T. urticae, but protonymphs were more susceptible than adult females. The LC50's were 4.21 and 4.36 ppm after 72 hr. post exposure for protonymphs and females, respectively. Also it had contact ovicidal activity influenced by egg age. 48-72 hr. eggs were significantly more sensitive than eggs of the other ages. According to LC50 values LC50's were 117.07, 7.95 and 2.91ppm for the three tested ages (0-24 hr, 24-48 hr and 48-72 hr old), respectively. Also, all the tested concentrations prolongated the incubation, larval, protonymphal and deutonymphal periods, but the maximum conc. level (10 ppm) produced the highest increase. Also, the longevity of males and females were increased, the highest increase was observed with 10 ppm, it produced 23.42 days/♀ and 18.5 days/♂ compared with 15.59 days/♀ and 15.92 days/♂ in the control. On the otherhand, oviposition periods were also influenced as concentration dependant response. The mean number of laid eggs/♀ were highly decreased as conc. increased, the highest decrease was observed with T. urticae females treated with conc. 10 ppm, it gave 14.17 eggs/♀ compared with 124 eggs/♀ in untreated females. Results suggest that JHM, pyriproxyfen could be a good alternative and interesting component in Integrated Pest Management (IPM) for controlling TSSM, T. urticae and minimizing the usage of conventional pesticides.

Effects of pyriproxyfen on some physiological aspects of the pistachio fruit hull borer, Arimania comaroffi Ragonot, pupae

The pistachio fruit hull borer, Arimania comaroffi (Lepidoptera: Pyralidae) is one of the minor pests of pistachio orchards. This pest passes the winter as pupae in silken cocoons in soil beside pistachio trees. In this study, effects of insect growth regulator pyriproxyfen were investigated on some physiological aspects of the pest by measuring glycogen, total sugar, lipid, protein, low-molecular-weight carbohydrates (trehalose and glucose) and polyols (sorbitol and myo-inositol) contents of the pupal body. Last larval instar was treated with 1 μl of the pesticide, and the effects on pupae were measured after one week. Glycogen content in treatment with 3.11 mg/g fresh body weight was significantly different from control with 8.51 mg/g fresh body weight, but no significant differences in protein and lipid contents (p > 0.05) were observed. Glucose content in treated pupae with 1.50 mg/g fresh body weight was significantly different from control with 2.99 mg/g fresh body weight. Trehalose and sorbitol contents in treated pupae with 0.52 and 0.04 mg/g fresh body weight, respectively, were significantly lower than control with 2.07 and 1.5 mg/g fresh body weight, while there were no significant differences in glucose and myo-inositol contents between treated and control pupae.

Biological and molecular effects of pyriproxyfen, insect growth regulator (IGR), on Met gene in susceptible wild type and Met mutant Drosophila

Juvenile hormone (JH) signaling pathway at the molecular level is still not well understood. Methoprene-tolerant (Met) in Drosophila melanogaster fulfills many of the requirements for a hormone receptor gene. However, Met mutant flies are resistant to insect growth regulators (IGRs). In our study, the resistance to juvenile hormone agonist (JHA) in Methoprene-tolerant (Met) mutant flies was studied. Met mutant and susceptible wild type larvae were treated by different concentrations of pyriproxyfen at 0, 0.03, 0.1, 0.3, 1, and 3 ppm. We observed that the mean percentage mortalities in Met mutant were significantly (P<0.05) lower than that in the susceptible wild type. Also, resistance in insects to IGRs due to Met gene was studied using PCR and DNA sequencing analyses. We found that there are no changes in the DNA sequences of Met gene after the treatment with pyriproxyfen.

Toxic effects of pyriproxyfen, neemarin, acetamiprid and Ferula assafoetida essential oil on the common pistachio psylla, Agonoscena pistaciae

The common pistachio psylla, Agonoscena pistaciae, Burckhardt and Lauterer (Hemiptera: Psyllidae) is the key pest of pistachio orchards in Iran. Chemical control is the common method for the control of this pest. In this study, the effects of pyriproxyfen (an insect growth regulator), neemarin (a botanical insecticide), acetamiprid (a neonicotinoid) and Ferula assafoetida essential oil were investigated on the fifth instar nymphs of A. pistaciae. Probit analysis of concentration-mortality data was conducted to estimate the LC50 values. The LC50 values for neemarin, pyriproxyfen, acetamiprid and F. assafoetida essential oil were estimated to be 0.22, 0.52, 290 and 5.62 ppm, respectively. Our results showed that the fifth instar nymphs of A. pistaciae are very sensitive to neemarin and pyriproxyfen.

Sublethal effects of pyriproxyfen, a juvenile hormone analogue, on Plutella xylostella (Lepidoptera: Plutellidae): life table study

The sublethal effects of pyriproxyfen (PYR, a juvenile hormone analogue) were investigated for two consecutive generations on life-history parameters, such as developmental time, pupal weight, fecundity, fertility and longevity of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). After topical application bioassay of third instar larvae, the LC25 and LC50 values (as sublethal doses) were determined to be 1.49 and 2.01 μg/μl, respectively. The results showed that the egg incubation period, larval and pupal duration times and oviposition period were increased in treated groups compared with the control (treated with distilled water). Pupal weight, adult longevity, fecundity and fertility were significantly reduced in the treatment groups compared with the control. Using the age-stage, two-sex life table analysis, we found that the intrinsic rate of increase (r), finite rate of increase (λ), gross reproduction rate (GRR) and net reproductive rate (R 0) significantly decreased while the mean generation time (T) and doubling time (DT) increased in two treatment groups compared with the control. In addition, administration of PYR induced morphogenetic abnormalities including untanned pupae, larval–pupal intermediates and various defective adults. The LC50 value was more effective on all of the above biological characteristics than the LC25 for both generations, although parents were more affected than the offspring. In general, our results revealed that PYR was highly effective against P. xylostella in the laboratory both directly (causing mortality) and indirectly (disruption of normal growth and development). We conclude that PYR is an excellent candidate for suppressing populations of P. xylostella through its sublethal effects.

Effects of pyriproxyfen and buprofezin on immature development and reproduction in the stable fly*

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), is one of the most significant biting flies that affect cattle. The use of traditional insecticides for stable fly control has only a limited success owing to the insect's unique feeding behaviours and immature development sites. A laboratory study was conducted to evaluate the effects of two insect growth regulator (IGR) products, pyriproxyfen and buprofezin, on the development of the immature stages of the stable fly and the effects of pyriproxyfen on oviposition and egg hatch. Both pyriproxyfen and buprofezin had significant inhibitory effects on immature development. The LC(50) s of pyriproxyfen and buprofezin were 0.002 and 18.92 p.p.m., respectively. Topical treatment of adult females with different doses of pyriproxyfen had significant negative effects on both female oviposition and egg hatching when 1- and 3-day-old females were treated, and the effects were dose dependent. A significant reduction in the mean number of eggs laid was observed only at the highest pyriproxyfen dose (8 µg/fly) and egg hatch was unaffected by pyriproxyfen treatment when 5-day-old females were treated. Results from the present study indicate that pyriproxyfen has the potential to be used as part of an integrated stable fly management programme.

Aggressive Interactions Between &lt;I&gt;Solenopsis invicta&lt;/I&gt; and &lt;I&gt;Linepithema humile&lt;/I&gt; (Hymenoptera: Formicidae) Under Laboratory Conditions

The Argentine ant, Linepithema humile (Mayr), and the red imported fire ant, Solenopsis invicta Buren, are natural agonists in their country of origin. Since the first report of L. humile in California in 1907 its range expanded statewide, displacing native ant species wherever it spread. Since the discovery of established populations of S. invicta in southern California in 1998, it has been restricted to discrete areas of southern California. However, as these discrete populations expand, they are encountering large populations of L. humile, which are effective competitors for available resources and are particularly aggressive in their encounters with other ant species such as S. invicta. Most Dolichoderine ants such as L. humile do not prefer to forage on baits made with defatted corn grit and soybean oil typically used in red imported fire ant control programs. Applications of these baits in areas where distributions of these species overlap might selectively affect populations of S. invicta and give L. humile a competitive advantage. Three laboratory experiments were conducted to determine the competitive outcomes between S. invicta pitted against L. humile: 1) agonistic behavior of workers in small arenas, 2) colony interactions with different population ratios, and 3) the effects of pyriproxyfen on the competitiveness of S. invicta against L. humile. Populations of S. invicta consisting of major workers killed more L. humile than did minors or a mixture of majors and minors. When paired against L. humile colonies consisting of 1,100 workers, colonies consisting of 38 S. invicta workers were easily defeated by L. humile. Colonies consisting of 450 S. invicta workers plugged their nest entrances, but they were ultimately defeated by L. humile after 13 d. The S. invicta colonies consisting of 1,100 workers took control of the bridge connecting the colonies, invaded the L. humile colony, killed the Argentine ant queens, and removed their brood. Pyriproxyfen-treated fire ant workers took significantly longer to chase the Argentine ants from a connecting bridge than did untreated fire ants. Thus, fire ant baits may have long-term effects on intercolonial aggression between S. invicta and L. humile, especially when Argentine ant populations are high in the summer.

Aggressive Interactions Between Solenopsis invicta and Linepithema humile (Hymenoptera: Formicidae) Under Laboratory Conditions

The Argentine ant, Linepithema humile (Mayr), and the red imported fire ant, Solenopsis invicta Buren, are natural agonists in their country of origin. Since the first report of L. humile in California in 1907 its range expanded statewide, displacing native ant species wherever it spread. Since the discovery of established populations of S. invicta in southern California in 1998, it has been restricted to discrete areas of southern California. However, as these discrete populations expand, they are encountering large populations of L. humile, which are effective competitors for available resources and are particularly aggressive in their encounters with other ant species such as S. invicta. Most Dolichoderine ants such as L. humile do not prefer to forage on baits made with defatted corn grit and soybean oil typically used in red imported fire ant control programs. Applications of these baits in areas where distributions of these species overlap might selectively affect populations of S. invicta and give L. humile a competitive advantage. Three laboratory experiments were conducted to determine the competitive outcomes between S. invicta pitted against L. humile: 1) agonistic behavior of workers in small arenas, 2) colony interactions with different population ratios, and 3) the effects of pyriproxyfen on the competitiveness of S. invicta against L. humile. Populations of S. invicta consisting of major workers killed more L. humile than did minors or a mixture of majors and minors. When paired against L. humile colonies consisting of 1,100 workers, colonies consisting of 38 S. invicta workers were easily defeated by L. humile. Colonies consisting of 450 S. invicta workers plugged their nest entrances, but they were ultimately defeated by L. humile after 13 d. The S. invicta colonies consisting of 1,100 workers took control of the bridge connecting the colonies, invaded the L. humile colony, killed the Argentine ant queens, and removed their brood. Pyriproxyfen-treated fire ant workers took significantly longer to chase the Argentine ants from a connecting bridge than did untreated fire ants. Thus, fire ant baits may have long-term effects on intercolonial aggression between S. invicta and L. humile, especially when Argentine ant populations are high in the summer.

Effects of pyriproxyfen, a juvenile hormone analog, on development of the mealworm, Tenebrio molitor

Pyriproxyfen, an analog of the juvenile hormone (JH) in insects, has been evaluated in vivo and in vitro on an important stored product pest, the mealworm Tenebrio molitor. On newly ecdysed pupae, this insect growth regulator (IGR) was applied topically (at 0.10 and 0.20 μg/insect). Enzyme immunoassay measurements showed a decrease of the ecdysteroid titer in the hemolymph of treated specimens. In addition, the treatment induced an increase of the protein concentration in the hemolymph, however, there was no significant effect on the protein band pattern. Using in vitro pupal integument explant cultures, pyriproxyfen (at 1 and 10 μM in the medium) caused a significant inhibition of ecdysteroid amounts and of the thickness of new cuticle secreted. These new results are discussed in relation to the physiology of this IGR with a JH action.