Fipronil Bait Research Articles

Characterization of insecticide resistance and their mechanisms in field populations of the German cockroach (Blattodea: Ectobiidae) in Taiwan under different treatment regimes.

This study investigated how management strategies influence resistance profiles in German cockroach (Blattella germanica (L.)) populations and their impact on the performance of commercial gel baits containing fipronil, imidacloprid, and indoxacarb. Field populations from premises managed under 3 different strategies: Baiting, random insecticide (RI) used, and insecticide rotation (IR) were tested. Almost all populations under RI and IR were resistant to deltamethrin, but low to moderate resistance was observed under the Baiting approach. Cytochrome P450 monooxygenases (P450) were involved in deltamethrin resistance in these resistant populations. All individuals under Baiting and RI were homozygous for the L993F mutation, but the populations under IR lacked homozygous-resistant individuals. Eighty-three percent of field populations with complete homozygosity for the Rdl mutation displayed low mortality upon exposure to 3× LD95 fipronil. The effect of P450 and the Rdl mutation conferred high fipronil resistance in populations under the Baiting approach, recording moderate performance indices (PI) of 44-67 in fipronil bait. By contrast, those populations under RI and IR, in which involve glutathione S-transferases in fipronil resistance, had high PIs of 78-93. Almost 80% of populations exhibited over 90% mortality at 3× LD95 indoxacarb treatment, accompanied by high PIs of 90-100 in indoxacarb bait. Partial mortality from 1× LD95 imidacloprid occurred across all field populations due to the involvement of P450. PIs of imidacloprid bait ranged 5-57 and 20-94 in populations under RI and IR, respectively. Field populations demonstrate different resistance profiles depending on the treatment regimes, and the resistance mechanisms involved influenced gel bait's effectiveness.

Action mode of fipronil and sulfluramid in baits on Acromyrmex crassispinus (Forel, 1909) (Hymenoptera: Formicidae) in laboratory conditions

The leaf-cutting ants (LCAs) of the genus Atta Fabricius, 1804 and Acromyrmex Mayr, 1865 (Hymenoptera: Formicidae) are major pests in forest plantations, agriculture and livestock. Toxic baits with the active ingredients fipronil and sulfluramid are the main method to manage these insects. The internal hygiene of the ant colony needs to be considered to carry out chemical control of LCA. The baits must act as a true ‘Trojan horse’ deceiving the toxic action during the moment of transport. The objective was to evaluate fipronil and sulfluramid in toxic baits against Acromyrmex crassispinus (Forel, 1909) (Hymenoptera: Formicidae) in the laboratory. The action was observed in the first hours after application. The pick-up of the bait with fipronil was more heterogeneous and more random than that with the sulfluramid. Individuals of A. crassispinus stopped cutting leaves after four and seven days after application (DAA) of fipronil and sulfluramid baits, respectively. The foraging activity tended to zero over time with the sulfluramid bait, but a low carry of leaves was observed on the 11th DAA with the fipronil bait. The fipronil and sulfluramid baits, in laboratory conditions, were toxic and efficient to the ant A. crassispinus. The lethal action of fipronil was faster, an undesired aspect in the management of social insects. A control method that simulates the mythical ‘Trojan horse’ on LCAs nests is desirable.

Foraging Behaviors of Red Imported Fire Ants (Hymenoptera Formicidae) in Response to Bait Containing Different Concentrations of Fipronil, Abamectin, or Indoxacarb.

The red imported fire ant, Solenopsis invicta Buren, is a severe pest with agricultural, ecological, and medical significance. The baiting treatment is one of the main methods to control S. invicta. However, few studies have evaluated the acceptance of fire ant bait. Here, field and laboratory studies were conducted to investigate the foraging behaviors of S. invicta responding to fire ant baits containing different concentrations of active ingredients (fipronil, abamectin, or indoxacarb). Field studies showed that S. invicta transported significantly less 0.0125% fipronil bait than control bait (without toxicant) and 0.0001% fipronil bait. The number of foraging ants significantly decreased with an increase in fipronil concentration. Our previous study showed that S. invicta usually buries the food treated with repellent chemicals, and interestingly, significantly more soil particles were transported into tubes containing 0.0001% fipronil bait than tubes containing control bait or 0.0125% fipronil bait. In addition, S. invicta transported significantly less 0.0005% abamectin bait than control bait, and significantly fewer ants were found in tubes containing 0.0125% abamectin bait than control bait. However, there was no significant difference in bait transport, number of foraging ants, and weight of soil particles relocated in tubes containing different concentrations of indoxacarb bait. In addition, laboratory studies showed that S. invicta transported significantly less 0.0125% fipronil bait than control bait and bait containing abamectin (0.0025% or 0.0125%) or indoxacarb (0.0125% or 0.0625%). In addition, the transport speed for the 0.0125% fipronil bait was the slowest. These results show that specific concentrations of some active ingredients may negatively affect bait acceptance for S. invicta, and should be avoided in fire ant bait production.

Efficacy of a federally approved flea bait, orally administered to white-footed mice (Peromyscus leucopus), against blood feeding Ixodes scapularis larvae under simulated field conditions.

A promising alternative approach to conventional vector control practices is the use of systemic insecticides/acaricides orally administered to relevant mammalian host species to control blood feeding disease vectors. In the United States, Lyme disease continues to be the most prevalent vector-borne disease with the Centers for Disease Control and Prevention estimating approximately 500,000 Lyme disease infections each year. Previous research has demonstrated the potential usefulness of a low dose fipronil bait in controlling Ixodes scapularis larvae feeding on white-footed mice. However, no such acaricide-only product is approved for use in treating white-footed mice to control I. scapularis. The purpose of the study was to evaluate the use of a federally approved fipronil flea control bait (Grain Bait) in controlling I. scapularis parasitizing white-footed mice (Peromyscus leucopus). A simulated field trial was conducted in which Grain Bait was presented to grouped white-footed mice alongside an alternative diet for 168h. Mice were fitted with capsules and manually parasitized with I. scapularis larvae. Replete larvae detaching from each mouse were collected and monitored for molting to nymphs. The inside of each capsule was observed to evaluate tick attachment. Blood was collected from all Treatment group mice via cardiac puncture to determine the fipronil sulfone concentration in plasma (CP) for each animal. Results indicated that Grain Bait would be consumed in the presence of an alternative diet and that bait acceptance was greater for males, relative to females. Treatment with Grain Bait prevented 100% larvae from feeding to repletion at Day 7 post-exposure and prevented 80% of larvae from feeding to repletion and 84% from molting at Day 21 post-exposure, relative to Control groups. Molted nymphs were not recovered from mice that had CP detectable ≥18.4ng/ml. The results suggest that this federally approved flea product could be utilized for tick control and that other medically important vector-host relationships should be considered.

LETHAL EFFECTS ON FLEA LARVAE OF FIPRONIL IN HOST FECES: POTENTIAL BENEFITS FOR PLAGUE MITIGATION.

Plague, caused by the bacterium Yersinia pestis, is a zoonotic disease of mammalian hosts and flea vectors. Fipronil baits have been used to suppress adult fleas for plague mitigation. The degree and duration of flea control may increase if fipronil also kills other stages in the flea life cycle. We fed grain treated with 0.005% fipronil by weight, or nontreated grain, to black-tailed prairie dogs (Cynomys ludovicianus), which excrete fipronil and metabolites in their feces after consuming fipronil in their diet. We presented prairie dog feces to 331 larval Oropsylla montana (Siphonaptera: Ceratophyllidae). When exposed to feces lacking fipronil or metabolites, 84% of larvae survived for 24 h. In contrast, survival declined to 42% for larvae contacting feces from fipronil-treated prairie dogs. Just 7% of larvae consuming feces from fipronil-treated prairie dogs survived. Fipronil and metabolites may persist in host feces for several months or longer in prairie dog burrows where flea larvae dwell and forage. The lethal effects of fipronil on adult and larval fleas (and perhaps other life stages) may help to explain why fipronil baits are capable of suppressing fleas on prairie dogs for ≥12 mo.

Plague mitigation for prairie dog and black-footed ferret conservation: Degree and duration of flea control with 0.005% fipronil grain bait

Sylvatic plague, a primarily flea-borne zoonosis, is a significant threat to prairie dogs (Cynomys spp., PDs) and their specialized predators, endangered black-footed ferrets (Mustela nigripes, BFFs). Host-fed fipronil baits have proven effective in controlling fleas on PDs for the purposes of plague mitigation and BFF conservation. Currently, annual treatments are the norm. We tested the long-term efficacy of fipronil bait treatments with black-tailed PDs (C. ludovicianus, BTPDs) and BFFs in South Dakota, USA. During 2018–2020, we provided BTPDs on 21 sites with grain bait formula, laced with 0.005% fipronil (50 ​mg/kg); 18 non-treated sites functioned as baselines. In 2020–2022, we live-trapped, anesthetized, and combed BTPDs for fleas. Flea control was significant for at least 639–885 days. Flea abundance on the treated sites was < 0.5 fleas/BTPD for ∼750 days. During 2020–2022, we sampled BFFs for fleas on 4 BTPD colonies treated with fipronil grain bait and 8 non-treated colonies. Flea control was significant with BFFs, but flea abundance began to rebound within ∼240 days post-treatment. When feasible, the combination of insecticide treatments, such as fipronil baits, and BFF vaccination against plague provide a “two-pronged” protection approach for these endangered carnivores. If fipronil bait treatments are less effective with predatory BFFs than PDs, as found herein, the “two-pronged” approach might be used to protect BFFs and biennial fipronil bait treatments might be used to protect PDs. If BFF vaccination is not possible, or few BFFs can be vaccinated, annual fipronil bait treatments might be used as a precaution to protect BFFs. Flea densities might be surveyed to determine when/where more frequent treatments seem useful.

Changes over time in activity patterns of Reticulitermes speratus (Blattodea: Rhinotermitidae) fed fast- or slow-acting termiticides

This study aimed to determine the insecticidal effectiveness of commercial fast- and slow-acting termiticides against Reticulitermes speratus by observing the changes in its activity patterns over time. Both the Petri dish and planar arena methods were used to evaluate colony mortality and activity changes over time associated with each termiticide, and the evaluation methods were compared. A colony elimination pattern was observed weekly in R. speratus colonies that ingested fast- or slow-acting termiticides using the planar arena method; however, the results showed that the Petri dish method was not suitable for evaluating slow-acting termiticides with an insecticidal effect that appeared after 3 weeks or more. In the colony-level evaluation, using the planar arena method, termites that ingested fipronil bait became sublethal within 1 week and died inside the 2 m plastic tube connected to the bait feeding site. The dead termites accumulated in the plastic tube and blocked access to the bait feeding site. In contrast, termites that ingested bait treated with bistrifluron or hexaflumuron during the first 3 weeks of the experiment spread throughout the colony. Decreased colony activity and immune mechanism collapse were observed in all screens and subnests, and more than 95% of termites in the colony had died after 10 weeks.

Chemical control of Acromyrmex lundi (Hymenoptera: Formicidae) in anthropic ecosystems.

Leaf-cutting ants are pests in agriculture, forests and pasture and, usually, controlled with toxic baits. The management and control of leaf-cutting ants is complex as a consequence of its sociability and behavior. We tested three toxic baits with abamectin, fipronil and sulfluramid to control colonies of Acromyrmex lundi Mayr, 1865 (Hymenoptera: Formicidae), in two seasons: 'Spring 2020' and 'Summer 2020/21', in Argentina. The percentage of effective bait carried in the spring was similar between treatments with 80%, 80% and 90% for those with abamectin, fipronil and sulfluramid. The ant flow of A.lundi decreased after toxic bait applications compared to the control through time in all treatments. This activity was higher in the spring than in the summer. The baits reduced the foraging activity of A.lundi from 5 to 96 days after application (DAA). Abamectin and fipronil baits controlled 50% and 67% of the nests in the spring, and 20% and 43% at 96 DAA in the summer. Sulfluramid was the best treatment, killing 90% of A.lundi nests. The baits decrease the foraging activity of A.lundi until 96 DAA, with total or partial death of its colonies varying between treatments. The ant symptoms with the sulfluramid bait appeared faster than with fipronil and may be a result of the low level of carry-over or differences in the chemical quality of the active ingredients. © 2022 Society of Chemical Industry.

Efficacy of low-dose fipronil bait against blacklegged tick (Ixodes scapularis) larvae feeding on white-footed mice (Peromyscus leucopus) under simulated field conditions

BackgroundLyme disease, caused primarily by Borrelia burgdorferi sensu stricto, is the most prevalent vector-borne disease in the United States. Treatment of rodent pathogen reservoirs with an oral acaricide may suppress the production of infected host-seeking ticks posing a risk for human infection. A previous study showed that an oral fipronil bait effectively controlled larval Ixodes scapularis ticks on white-footed mice (Peromyscus leucopus) up to 15 days post-bait exposure. The present study expands upon this finding by exposing group-housed white-footed mice to fipronil bait under simulated field conditions prior to tick infestation.MethodsMice (n = 80) were housed in groups of 10 within large enclosures and offered a choice between fipronil bait within a commercial bait station and an alternative diet. The mice were assigned to two treatment groups and two control groups to undergo bait exposure durations of either 24 h (reduced) or 168 h (extended). Groups were further differentiated by the time point post-bait exposure when larval ticks were applied to mice within feeding capsules (reduced day 1, day 15; extended day 21, day 35). For 4 days post-tick introduction, attached larvae were observed by microscopy and replete larvae were recovered. Replete larvae were monitored for molting success. Plasma was collected from all treatment group mice to obtain fipronil plasma concentrations (CP).ResultsThe fipronil bait (0.005% fipronil) was palatable and controlled larval ticks on white-footed mice when presented under simulated field conditions. Efficacy in preventing attached larvae from feeding to repletion was 100% (day 1), 89.0% (day 15), 85.8% (day 21), and 75.2% (day 35). When also considering molting success, the fipronil bait prevented 100% (day 1), 91.1% (day 15), 91.7% (day 21), and 82.5% (day 35) of larvae attaching to mice from molting. The mean CP per mouse was 191.5 ng/ml (day 1), 29.4 ng/ml (day 15), 10.6 ng/ml (day 21), and 1.0 ng/ml (day 35).ConclusionsThe results suggest that fipronil bait will be consumed by white-footed mice in the presence of an alternative diet, and effectively control larval ticks on treated mice. A field trial is needed to confirm the results of this study. Low-dose fipronil bait may provide a cost-effective means of controlling blacklegged ticks to be integrated into tick management programs.Graphical

An organic bait based on Palicourea marcgravii (Rubiaceae) and Tephrosia candida (Fabaceae) does not control nests of Atta laevigata (Hymenoptera: Formicidae) in eucalyptus plantations

AbstractLeaf‐cutting ants of the genus Atta (Myrmicinae: Attini) are the main forest pests in Brazil, due to their economic damage, social complexity and geographical distribution. Chemical control with baits is the most viable and successful method to control these insects; and products with low environmental impact have been researched. The objective of this study was to evaluate the mortality of Atta laevigata (Hymenoptera: Formicidae) nests treated with Bioisca® bait, in different dosages, in eucalyptus plantations compared with those treated with sulfluramid and fipronil baits. Seven treatments were used: Bioisca® (Palicourea marcgravii (Rubiaceae) + Tephrosia candida (Fabaceae)), with 5, 10, 15 and 20 g; Blitz® (fipronil), Atta Mex‐S® (sulfluramid) baits with 6 g/m2 of ant nest loose soil and the control, without ant baits. It took 7 days for the first colony to have its activity stopped using the Blitz® treatment. It happened only at 30 days when treated with Bioisca® and Atta‐Mex‐S® . The mortality of nests treated with Bioisca® was very low with only one controlled out of 20 that received this bait. Bioisca® does not control the nests of A. laevigata in eucalyptus plantations.

Evaluating the use of a low dose fipronil bait in reducing black-tailed prairie dog (Cynomys ludovicianus) fleas at reduced application rates.

Plague is a virulent zoonosis, vectored by fleas, posing danger to black-tailed prairie dogs (BTPDs) (Cynomys ludovicianus), black-footed ferrets (Mustela nigripes), and humans in North America. During prior research, a fipronil grain bait (0.005%) applied at rates of 1-½ cup/burrow, reduced flea abundance by > 95–100% when applied three times February–March in northern Colorado. The objective of the current study was to determine the efficacy of fipronil bait against fleas in northern Colorado at reduced application rates (½ cup/burrow) and frequencies (1–2 applications). The field study was conducted in Larimer county, Colorado USA between June-November 2018. Three test plots were selected: two treatment plots (1 vs. 2 fipronil bait applications) and one untreated control. Fipronil was applied at a rate of ½ cup (~95 g)/burrow. Fleas were collected from captured BTPDs and swabs of active burrows prior to bait application and up to 134-days post-treatment. A total of 203 BTPDs and 210 active burrows were sampled. Within the treatment plots, no fleas were collected from BTPDs up to 134-days post-treatment (100% efficacy). Five fleas were recovered from burrows within the one-application plot (<40-days post-application) with efficacy ranging from 97.1 to 100%. No fleas were recovered from burrows within the two-application plot. We caution that while fleas were present within the control plot throughout the study, abundances were low. The efficacy results are supported by those of prior field research conducted in South Dakota and suggest that fipronil bait may be applied at lower rates and frequencies than initially proposed, with potential to sustain flea removal >4-months.

Efficacy of a low dose fipronil bait against blacklegged tick (Ixodes scapularis) larvae feeding on white-footed mice (Peromyscus leucopus) under laboratory conditions

BackgroundLyme disease is the most prevalent vector-borne disease in the USA with cases continuing to increase. Current control measures have not been shown to be impactful, and therefore alternatives are needed. Treating pathogen reservoirs with low dose systemic acaricides in endemic areas may provide a useful tool for disrupting the cycle of the vector and pathogen. The purpose of this study was to determine the efficacy of a 0.005% fipronil bait, presented orally to white-footed mice, in controlling blacklegged tick larvae (larvae).MethodsSixty mice were assigned to 3 treatment groups and three untreated control groups. All individually housed mice in treatment groups were exposed to 0.005% fipronil bait for 48 hours. Larvae were manually applied to mice within feeding capsules at one of three timepoints: Day 1, Day 9 and Day 15 post-exposure. For 4-days post-tick attachment, replete larvae were collected from water moats underneath each cage and attached larvae were observed by microscopy. Plasma from 4 treated mice at Day-1, Day 13 and Day 19, and 4 control mice (n = 16) was collected to obtain fipronil plasma concentrations (CP).ResultsFipronil bait did not appear to produce neophobia in mice, as the amount of bait eaten at 24- and 48-hours exposure did not differ significantly. The 48-hour fipronil bait exposure prevented 100% of larvae from feeding to repletion at Day 1, Day 9 and Day 15 post-treatment. Within the treatment groups, all larvae observable within the capsules expired and were prevented from detaching by Day 4. In contrast, within the control groups a total of 502 replete larvae were collected from moats and 348 larvae observable within the capsules successfully detached. CP averaged 948.9, 101.2 and 79.4 ng/ml for mice euthanized at Day 1, Day 9 and Day 15, respectively. No fipronil was detected in control mice.ConclusionsWe provide early indication that low dose fipronil bait, orally presented to white-footed mice, can effectively control blacklegged tick larvae. Future research should modify the exposure duration and post-exposure tick attachment timepoints to simulate various field scenarios under which successful efficacy might be obtained. Low dose fipronil bait could provide a cost-effective, practical means of controlling blacklegged ticks and other arthropod vectors.

Development of New Boric Acid Gel Baits for Use on Invasive Ants (Hymenoptera: Formicidae)

The current control measures used against common household ants in urban and agricultural settings include perimeter insecticide applications. These often have the potential to cause problems of poisoning non-target organisms, due to the insecticidal runoff and environmental contamination. A gel-baiting technique is the most effective tool to control ants with less insecticides released into the environment. In this study two commercial gel baits; the Boric acid (2.5% boric acid) and the Fipronil (0.01% fipronil) baits, were evaluated against laboratory made baits (lab baits). The lab baits, consisted of: 1.5% boric + fructose (F1.5), 1.5% boric acid + fructose + molasses (M1.5), 3% boric acid + fructose (F3), and 3% boric + fructose + molasses (M3) were evaluated based on preference and mortality rates of the common household ant species: the Asian needle ant, Monomorium chinensis, Santschi, and the Yellow crazy ant, Anoplolepis gracilipes, Smith, under laboratory conditions. An inconsistent preference was observed between species and different baits; however, the fipronil bait and the lab bait M3, were preferred more by both ant species compared to the other baits tested. Lab bait M3 also had a faster killing speed than the boric acid bait and the lab bait F3.Based on the results it was concluded that lab bait M3 was a more efficient ant bait and is a potential alternative control measure to the current commercial baits.

Development of New Boric Acid Gel Baits Against German Cockroaches, Blatella germanica L (Blattodea: Blattellidae)

The German cockroach, Blatella germanica, is a pest of human habitats distributed throughout the world. Boric acid (BA; H3BO3), in the form of powder, pellets, or blocks, has been used to control German cockroaches. Gel baits are also considered highly effective for controlling German cockroach populations. However, BA is not currently available as a gel bait. Thus, the present study was carried out to determine the best concentration of BA to formulate as a gel bait, and measure its direct effectiveness and the horizontal transfer of the active ingredient (AI) through cannibalism in adult German cockroaches (domino effect). Effectiveness of laboratory-prepared BA gel baits (lab baits) was analysed, and the efficacy and horizontal transfer of the most effective lab bait was compared to four commercial baits. Among three tested lab baits, the bait prepared with 40% BA (lab bait A) resulted in significantly greater cockroach mortality and a lower lethal time (LT50) value than other lab baits. When compared with commercial baits, there was no significant difference between lab bait A and BA baits in the amount of bait consumed and the detection time. Similarly, mortality of cockroaches caused by lab bait A was equal to mortality caused by the commercial BA bait. Percentage of bait unfed adult cockroaches killed by transferred BA from lab bait A fed and dead adult cockroaches (secondary mortality) was significantly greater than that caused by both commercial BA bait and fipronil bait.

Efficacy of gel baits against American cockroaches (Dictyoptera: Blattellidae) under laboratory conditions

This study was executed to measure the efficacy (preference and toxicity) of imidacloprid 3.0%, fipronil 0.05%, and chlorpyrifos 1.0% gel baits for the control of American cockroaches under laboratory conditions. Result revealed that the cockroaches consumed significantly greater amount of fipronil bait than imidacloprid and chlorpyrifos baits. The same bait was detected significantly faster than chlorpyrifos bait. Imidacloprid bait quickly killed the 50% of the tested cockroaches (LT50, 4.64 hours) than fipronil and chlorpyrifos bait. Fipronil bait was detected significantly faster and consumed significantly greater amount than chlorpyrifos. However, chlorpyrifos killed the 50% of tested cockroaches faster than fipronil. Thus, imidacloprid bait was more effective than fipronil and chlorpyrifos baits for the control of American cockroaches under laboratory conditions.

Suppression of female melon fly, Zeugodacus cucurbitae, with cue‐lure and fipronil bait stations through horizontal insecticide transfer

AbstractMelon fly, Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae), is an important quarantine tephritid fruit fly with resident populations established in Hawai'i, USA. In the male‐annihilation approach, male flies are targeted using dispensers with cue‐lure (C‐L) and insecticides, typically organophosphates. The efficacy of the male annihilation approach is thought to be limited to individual male flies, contacting the lure and the pesticide, after which they die. Alternative classes of insecticides, such as fipronil, have been investigated for use in male‐annihilation. We hypothesized that ingestion of fipronil by male flies could lead to horizontal transfer and mortality in female flies. Horizontal insecticide transfer extends pesticide control beyond the individual contacting the toxicant through indirect contact via food sharing or other mechanisms. We tested the possibility for horizontal transfer of fipronil from male to female Z. cucurbitae through field and laboratory studies. Two repeated field trials were conducted to compare the numbers of female flies collected in fields treated with Amulet C‐L (0.34% fipronil active ingredient) bait stations, sanitation, and spot treatments of GF‐120 Fruit Fly Bait to numbers collected in fields where sanitation and spot‐treatments were used without Amulet C‐L. In fields with Amulet C‐L bait stations in conjunction with sanitation and weekly protein bait spot treatments of GF‐120 Fruit Fly Bait, female captures were significantly lower than those in field plots treated with weekly protein bait spot treatments and sanitation. In subsequent laboratory studies, all females died within 6 h after direct exposure to male flies that had access to Amulet C‐L for 1–4 min. The possibility that male regurgitant could be a mechanism for horizontal transfer and subsequent female mortality was determined by collecting regurgitated droplets from fipronil‐fed male flies and feeding them to males and females. Both male and female flies exposed to regurgitant from fipronil‐fed male flies or droplets containing fipronil had higher mortality than the male and female flies that were exposed to regurgitant or droplets with only the C‐L compound or sugar solution. Thus, female flies do experience mortality from exposure to regurgitant from males that have fed on fipronil laced solutions. This provides evidence of at least one mechanism of horizontal transfer of insecticide in tephritid fruit flies. These findings are discussed in the context of Z. cucurbitae integrated pest management programs in Hawai'i.

Unidirectional Cross-Resistance in German Cockroach (Blattodea: Blattellidae) Populations Under Exposure to Insecticidal Baits.

Insect pests, including the German cockroach, Blattella germanica (L.), are prone to the development of physiological resistance when exposed to a number of insecticide sprays, and cross-resistance is frequently observed. Toxic baits are often used as a primary method of controlling German cockroaches, also resulting in heavy selection pressure from insecticidal baits. In response to this pressure, cockroach populations have developed aversion to specific inert ingredients in bait. Here, we examined the effect of exposure to baits containing fipronil, indoxacarb, or hydramethylnon on the development of physiological resistance to the same and other insecticides in a number of German cockroach strains. We found that prolonged exposure to baits containing fipronil or indoxacarb increased physiological resistance to these compounds. However, no increase in physiological resistance against any insecticide was observed in response to exposure to hydramethylnon bait. Additionally, we found that exposure to fipronil bait increased cross-resistance to indoxacarb. On the other hand, exposure to indoxacarb bait did not increase cross-resistance to fipronil. Neither fipronil nor indoxacarb bait exposure increased resistance to hydramethylnon. Interestingly, the development of insecticide resistance in response to bait exposure was strain-dependent and influenced by bait palatability. Our results demonstrate that exposure to toxic baits, particularly those containing fipronil, plays a significant role in the development of insecticide resistance, including cross-resistance, in German cockroaches. Further, although insecticide resistance in response to baits is mediated by exposure through the oral route, the molecular mechanisms at play are likely different for each insecticide.

Evaluation of fipronil baits against Microtermes mycophagus (Blattodea: Termitidae)

AbstractWe evaluated the efficacy of fipronil baits in suppressing or eliminating field colonies of Microtermes mycophagus (Desneux) (Blattodea: Termitidae) an important subterranean termite pest in Pakistan. We tested two doses (10 and 30 ppm) of fipronil in toilet paper baits, chosen from laboratory repellency tests. We monitored four colonies for foraging activity for one month before baiting, and mapped foraging territories with termites marked with Nile Blue A and agonistic tests. Before the fipronil baits were installed there were averages of 782–1938 workers and soldiers per bait station in the four colonies. After baiting, the colonies were eliminated as there were no workers per bait station, whereas the control colony had an average of 1142 workers per bait station. The three possibly eliminated colonies consumed around 47 mg of fipronil formulation (4.7 mg active ingredient) in 45–90 days. Our results suggest that baits containing fipronil could provide an economical and feasible alternative for the management of M. mycophagus in structures and buildings in Pakistan.

Effects of Fipronil Bait on Sugarcane Growth and Yield on Kume Island, Okinawa, Japan

Effects of Fipronil Bait on Sugarcane Growth and Yield on Kume Island, Okinawa, Japan

Different acute toxicity of fipronil baits on invasive Linepithema humile supercolonies and some non-target ground arthropods.

Fipronil is one of the most effective insecticides to control the invasive ant Linepithema humile, but its effectiveness has been assessed without considering the genetic differences among L. humile supercolonies. We hypothesized that the susceptibility of the ant to fipronil might differ among supercolonies. If so, dosage and concentration of fipronil may need to be adjusted for effective eradication of each supercolony. The relative sensitivities of four L. humile supercolonies established in Hyogo (Japan) to fipronil baits were examined based on their acute toxicity (48-h LC(50)). Toxicities of fipronil to seven ground arthropods, including four native ant species, one native isopoda, and two cockroaches were also determined and compared to that of L. humile supercolonies using species sensitivity distributions. Marked differences in susceptibility of fipronil were apparent among the supercolonies (P < 0.008), with the 'Japanese main supercolony' (271 μg L(-1)) being five to ten times more sensitive to fipronil than other colonies (1183-2782 μg L(-1)). Toxicities to non-target species (330-2327 μg L(-1)) were in the same range as that of L. humile, and SSDs between the two species groups were not significantly different (t = -1.389, P = 0.180), suggesting that fipronil's insecticidal activity is practically the same for L. humile as for non-target arthropods. Therefore, if the invasive ant is to be controlled using fipronil, this would also affect the local arthropod biodiversity. Only the 'Japanese main supercolony' can be controlled with appropriate bait dosages of fipronil that would have little impact on the other species.