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Due to their mutualistic relationship with plant pests, the Argentine ant is considered a major pest in subtropical fruit orchards and vineyards. Besides insecticide sprays, liquid baiting has been demonstrated as an effective method to suppress the Argentine ant populations. To improve the economic feasibility of liquid baiting, hydrogel materials have been recently tested as a carrier for liquid baits containing various insecticidal active ingredients. Here, we tested boric acid as a toxicant in the aqueous sugar bait delivered in a biodegradable calcium alginate hydrogel. Laboratory tests demonstrated that boric acid (1%) liquid bait incorporated in the calcium alginate hydrogel effectively killed Argentine ant workers. Potassium sorbate (0.25%) added to the liquid bait as a preservative did not impact the efficacy of boric acid even though it significantly reduced the degree of swelling of the hydrogel beads in the bait solution. Testing with 2-month-old bait suggested that long-term storage might impact bait efficacy even with potassium sorbate preservative.

New infestations of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), were discovered in southern California, namely in Rancho Santa Fe and La Mesa (San Diego County) and Highland Park (Los Angeles County) in 2021. We investigated whether these new infestations were related to the previous infestations in La Mesa (2018) and Canyon Lake, Riverside County (2020). We used two mitochondrial genes (COI and COII) and seven polymorphic microsatellite markers to infer the genetic relationship between southern California colonies and their breeding systems. The samples collected from seven localities belonged to five colonies (inter-colony distances ranged from ~160 m to 185 km, with an average of 97 km). Of these five colonies, two were simple families, and three were extended families. Structure analyses of microsatellite genotypes grouped the termite samples into three distinct genetic clusters, suggesting at least three independent introduction events in southern California.

Argentine ants are one of the most common nuisance pest ants treated by pest management professionals (PMPs) in southern and western urban residential areas of the United States. Two new technologies (spraying with a pheromone adjuvant and using a biodegradable hydrogel bait delivery method) were used to develop a unique low-impact integrated pest management (IPM) protocol for Argentine ants in urban residential settings. The IPM protocol included a one-time perimeter spray treatment with 0.03% fipronil (mixed with a pheromone adjuvant) at the beginning of the ant season to achieve a quick knockdown. The initial spray application was followed by a biodegradable hydrogel baiting with 1% boric acid as a maintenance treatment. This low-impact IPM protocol was compared with two other conventional methods: (1) one initial fipronil application and one pyrethroid spray application for maintenance, or (2) one initial fipronil application and one essential oil insecticide spray application for maintenance. Based on Argentine ant foraging activity, the protocols were compared for their control efficacy. Insecticide use information and treatment time were also recorded and compared among different treatment protocols. Our results provided empirical data to support the effectiveness and economic feasibility of the low-impact IPM protocol for managing Argentine ants in urban residential settings.

Gel bait insecticides have been extensively used to manage the German cockroach, Blattella germanica (L.) (Blattodea: Ectobiidae), but issues with reduced effectiveness of such formulations are becoming increasingly common. We collected five field strains of German cockroaches in California and evaluated them against five commercial bait products [Maxforce FC Magnum (0.05% fipronil), Maxforce Impact (1% clothianidin), Advion Evolution (0.6% indoxacarb), Optigard (0.1% emamectin benzoate) and Siege (2% hydramethylnon)]. Increased survivorship and incomplete mortality towards all baits were recorded in the field strains. We assessed susceptibility to the active ingredients fipronil, clothianidin, indoxacarb, abamectin, hydramethylnon, and deltamethrin using topical bioassays with diagnostic doses (3 × LD95 and 10 × LD95) developed from the UCR susceptible strain. Low mortality was registered when tested with the 3 × LD95’s of deltamethrin (0%), fipronil (0–3%), and clothianidin (13–27%); low to moderate mortality when treated with the 3 × LD95 of indoxacarb (13–63%), and moderate to high mortality after treatment with the 3 × LD95 of abamectin (80–100%) and hydramethylnon (70–83%). The mortality of all strains remained low after treatment with the 10 × LD99 of deltamethrin (0–20%) and low to moderate with fipronil (20–70%). We found negative correlations (P < 0.05) between Advion Evolution mean survival time and indoxacarb 10 × LD95 mortality and between Maxforce Impact and clothianidin 10 × LD95 mortality. These findings demonstrate multiple resistance towards all tested commercial bait insecticides except Optigard, suggesting the effectiveness of avermectin products in resistance management programs.

Here, we review the literature on the development and application of hydrogel compounds for insect pest management. Researchers have used hydrogel compounds for the past few decades to achieve the controlled release of various contact insecticides, but in recent years, hydrogel compounds have also been used to absorb and deliver targeted concentrations of toxicants within a liquid bait to manage insect pests. The highly absorbent hydrogel acts as a controlled-release formulation that keeps the liquid bait available and palatable to the target pests. This review discusses the use of various types of hydrogel compounds in pest management based on different environmental settings (e.g., agricultural, urban, and natural areas), pest systems (e.g., different taxa), and modes of insecticide delivery (e.g., spray vs bait). Due to their unique physicochemical properties, hydrogel compounds have great potential to be developed into new and efficacious pest management strategies with minimal environmental impact. We will also discuss the future research and development of hydrogels in this review.

Baiting is an effective method to manage Vespula spp. yellowjacket (Hymenoptera: Vespidae) populations without having to locate and treat nests. Here, we assessed the utility of a commercially available polyacrylamide hydrogel as an alternative bait material for yellowjacket baiting. The experimental bait (hereafter referred to as 'hydrogel bait') consisted of diluted chicken juice (from canned chicken meat) and fipronil (0.025%, wt/wt) absorbed into granular polyacrylamide hydrogel particles. Three separate 24-h baiting trials were conducted at two different field sites with the western yellowjacket, Vespula pensylvanica (Saussare), as the target species. The monitoring data from pre- and posttreatment periods indicated that baiting with polyacrylamide hydrogel baits provided ≈74-96% reduction in the foraging activity of V. pensylvanica during its active season. In addition to their ability to absorb large quantities of aqueous bait containing phagostimulants and toxicants, the hydrogels' tactile resemblance to fresh meat upon hydration makes them a promising option as a non-meat material for delivering small amounts of insecticides to yellowjacket populations in a highly targeted manner.

The purpose of this study was to involve pest management professionals in the design of application techniques and strategies that would be efficacious and also reduce insecticide runoff. Our study involved measuring both the efficacy of treatments for the Argentine ant, Linepithema humile (Mayr), and the concurrent runoff of fipronil and pyrethroids. Two collaborating companies used low-impact protocols for controlling ants while minimizing runoff. Protocol 1 involved bimonthly treatments, while Protocol 2 was monthly. Both protocols involved an initial treatment with a fipronil spray around the foundation. At the garage door-driveway interface, the fipronil application was done as a pin stream for Protocol 1, and as a crack and crevice application in the expansion joint near the garage for Protocol 2. Protocol 1 replaced most pyrethroid sprays with bifenthrin granules placed around bushes and away from the driveway. For the next treatment on day 63, Protocol 1 also included cyfluthrin spray treatments around the house foundation and crack and crevice applications around the edge of the driveway. For the first treatment in Protocol 2, the fipronil spray was supplemented with spot treatments of cyfluthrin. For subsequent Protocol 2 treatments, botanical insecticides were applied. For weeks 1 and 2 posttreatment combined, Protocol 1 had significantly higher reductions in ant numbers compared with Protocol 2. Thereafter there were no significant differences between the protocols. Runoff of bifenthrin from the granules used with Protocol 1 was much lower than in previous trials involving bifenthrin sprays. Day 1 fipronil runoff for Protocol 2 was significantly lower than that for Protocol 1. This difference may be because of the crack and crevice application applied in Protocol 2. Cyfluthrin runoff was minimal for Protocol 2, which involved spot treatments to supplement the fipronil on day 1, or the botanical insecticides for subsequent treatments. Protocol 1 had a large peak of cyfluthrin runoff at day 63 corresponding to their house and driveway treatments.

The Turkestan cockroach, Blatta lateralis (Walker), has become an important invasive species throughout the southwestern United States and has been reported in the southern United States. It is rapidly replacing the oriental cockroach, Blatta orientalis (L.), in urban areas of the southwestern United States as the most important peri-domestic species. They typically inhabit in-ground containers such as water meter, irrigation, and electrical boxes, raises of concrete, cracks and crevices, and hollow block walls. On occasion, they will invade dwellings. At 26.7 degrees C, male and female nymphs developed into adults in an average of 222 and 224 d, respectively. Both males and females had five nymphal instars. Adult females deposited up to 25 oothecae. The oothecae averaged 16.8 eggs and 13.9 nymphs emerged per egg capsule, resulting in an 82.7% hatch rate. Adults lived for at least 612 d. Two parameters that might contribute to the success of Turkestan cockroaches compared with oriental cockroaches are that the developmental period of the nymphs of Turkestan cockroaches are shorter and adult female Turkestan cockroaches produce considerably more oothecae than do oriental cockroaches. These may explain the observations by Pest Management Professionals that Turkestan cockroaches are displacing oriental cockroaches in outdoor habitats throughout the southwestern United States.

The spider Holocnemus pluchei (Scopoli) (Araneae: Pholcidae) is a nonnative species commonly found in the southwestern United States. In urban areas around homes and other structures, it is often the dominant spider species on outside surfaces; requests for control of spiders and their cobwebs are common for the commercial pest management industry. We tested two physical (brushing and vacuuming) and two low-impact chemical (permethrin and botanical insecticide) spray control methods for H. pluchei on outbuildings on the University of California-Riverside campus. Forty sites containing at least two H. pluchei spiders along a 5-m section of eave or overhang were chosen for treatment. Treatment was applied within 2 d of a pretreatment census. The number of spiders per section was counted at 2, 4, 8, 12, 16, and 52 wk posttreatment. Untreated sections showed an increase in spiders through summer and a decrease in autumn. Sites treated with permethrin significantly reduced spiders >95% and had strong residual effect throughout the remainder of the sampling period. Compared with untreated controls, the three other treatments did not significantly reduce spiders; these three were similar throughout the season and were intermediate between untreated and permethrin-treated sites. In comparison with the before and 2-wk posttreatments, spiders at the untreated sites showed no difference in body sizes, whereas those in the nonpermethrin treatments showed a decrease, indicating that larger spiders were eliminated. We also tested H. pluchei spiders in the laboratory against the two insecticides used in the field studies to determine the minimum lethal concentrations for controlling H. pluchei.

A novel bait station referred to as a virtual bait station was developed and tested against field populations of the invasive Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae), at White Beach, Camp Pendleton, in Oceanside, CA. White Beach is a nesting habitat for an endangered seabird, the California least tern (Sterna antillarum browni Mearns). The beach is heavily infested with Argentine ants, one of the threats for the California least tern chicks. Conventional pest control strategies are prohibited because of the existence of the protected bird species and the site's proximity to the ocean. The bait station consisted of a polyvinyl chloride pipe that was treated on the inside with fipronil insecticide at low concentrations to obtain delayed toxicity against ants. The pipe was provisioned with an inverted bottle of 25% sucrose solution, then capped, and buried in the sand. Foraging ants crossed the treated surface to consume the sucrose solution. The delayed toxicity of fipronil deposits allowed the ants to continue foraging on the sucrose solution and to interact with their nestmates, killing them within 3-5 d after exposure. Further modification of the bait station design minimized the accumulation of dead ants in the sucrose solution, significantly improving the longevity and efficacy of the bait station. The virtual bait station exploits the foraging behavior of the ants and provides a low impact approach to control ants in environmentally sensitive habitats. It excluded all insects except ants, required only milligram quantities of toxicant, and eliminated the problem of formulating toxicants into aqueous sugar baits.

In a previous experimental study, recluse spiders Loxosceles reclusa Gertsch and Mulaik and Loxosceles laeta (Nicolet) (Araneae: Sicariidae) preferred small cardboard refugia covered with conspecific silk compared with never-occupied refugia. Herein, we investigated some factors that might be responsible for this preference using similar cardboard refugia. When the two Loxosceles species were given choices between refugia previously occupied by their own and by the congeneric species, neither showed a species-specific preference; however, each chose refugia coated with conspecific silk rather than those previously inhabited by a distantly related cribellate spider, Metaltella simoni (Keyserling). When L. laeta spiders were offered refugia that were freshly removed from silk donors compared with heated, aged refugia from the same silk donor, older refugia were preferred. Solvent extracts of L. laeta silk were chosen approximately as often as control refugia when a range of solvents (methylene chloride:methanol, water, and hexane) were used. However, when acetone was used on similar silk, there was a statistical preference for the control, indicating that there might be a mildly repellent aspect to acetone-washed silk. Considering the inability to show attraction to chemical aspects of fresh silk, it seems that physical attributes may be more important for selection and that there might be repellency to silk of a recently vacated spider. These findings are discussed in regard to pest management strategies to control recluse spiders.

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.

This study investigated the effects of the permethrin-impregnated plastic on ant mortality and foraging rates, and tested its potential for preventing ants from colonizing potted soil. Direct exposure to the plastic for as short as 1 min caused significant mortality of both red imported fire ants, Solenopsis invicta Buren, and Argentine ants, Linepithema humile (Mayr); however, red imported fire ants were more susceptible than Argentine ants. Knockdown of virtually all ants initially occurred within 15 min after exposure. However, some moribund ants recovered from the effects within 24 h. For example, after 1 min of direct exposure to the permethrin-impregnated plastic, 70% of Argentine ants and 5% of red imported fire ants recovered from the treatment. In established colonies of Argentine ants, significantly fewer ants foraged for food up posts treated with the plastic compared with untreated posts. In addition, colonies responded to introduction of the treatment by significantly reducing their overall foraging rates, even on untreated posts. When pots filled with moistened soil were introduced into established ant colonies, 82% of Argentine ants and 99% of red imported fire ants moved into the soil. In contrast, when a 1-cm-wide coil of the plastic was placed under the pot, no ants moved into the soil. The potential for use of these materials in nursery production is discussed.

Brief exposures of Argentine ants to four different insecticide treatments, bifenthrin, beta-cyfluthrin, bifenthrin + beta-cyfluthrin, and fipronil, were conducted to determine Kaplan-Meier product limit survivorship percentiles (SPs) at 21-23 and 27-29 degrees C. Bifenthrin, beta-cyfluthrin, and bifenthrin + beta-cyfluthrin provided rapid kill at 21-23 degrees C with SP10 values ranging from 11.2 to 33.7 min. Fipronil provided delayed toxicity at 21-23 degrees C with SP10 values ranging from 270 to 960 min. At 27-29 degrees C, all of the SP10 values significantly decreased. Field tests in which Argentine ants were induced to forage across insecticide-treated surfaces were used to determine the effect that speed of action has on foraging and recruitment ability, and whether these insecticides are repellent. The slower-acting fipronil allowed a greater amount of foraging and consequently a greater fraction of the colony to be exposed, whereas fast-acting bifenthrin, beta-cyfluthrin, and bifenthrin + beta-cyfluthrin inhibited recruitment, resulting in fewer ants being exposed and killed. Implications for controlling ants by using perimeter barrier treatments are discussed.

Horizontal transfer of three contact insecticides, bifenthrin, beta-cyfluthrin, and fipronil, was tested in laboratory colonies. Donor ants were exposed for 1 min to insecticide-treated sand substrates and placed with unexposed ant colonies at two different temperatures. Mortality was monitored to compare the ability of donors to transfer lethal doses of these insecticides to untreated individuals. Treated donor insects, live or dead, were added into colonies to determine the importance of donor behavior on lethal transfer. Fipronil was readily transferable between individuals, resulting in high mortality rates. Bifenthrin and beta-cyfluthrin were less transferable, exhibiting moderate-to-low mortality rates similar to the controls. Greater mortality occurred at 27-29 degrees C than at 21-23 degrees C for bifenthrin, but not the other treatments or controls. Colony mortality did not significantly increase when adding live donors, suggesting that necrophoresis was probably an important donor behavior in addition to grooming and trophallaxis on horizontal transfer.

The foraging range and distribution of Argentine ant, Linepithema humile (Mayr), colonies in urban areas of southern California extended at least 61 m (200 feet) from feeding stations and structures. Ants were fed at 25% sucrose feeding stations containing 0.01% fluorescent brighter (FB28). Within 14 d, from 77-90% of the ants sampled next to the feeding stations were positive for FB28. The percentage of ants with FB28 declined gradually to approximately 55% 61 m away from the feeding station. The percentage of marked ants in the controls didn't change over the 4-wk-test period. There were approximately 290,000 ants visiting the monitored stations each night before treatments. The 0.0001% fipronil baits and 0.06% fipronil SC sprays provided significant reductions in at least 4 wk. The percentage of ants marked with FB28 decreased significantly in both bait and spray treatments over 4 wk suggesting that the resurgence of ants in treated areas were because of immigration from untreated areas. It is likely that much larger areas will need to be treated to control Argentine ants in urban settings, especially if baits are being used.

Appropriate particle size may be a critical characteristic for effective granular ant baits. We examined the particle size preference of six species of pest ants to an anchovy-based bait. We also examined head capsule widths of Argentine ants, Linepithema humile (Mayr) (mean = 0.54 mm), California harvester ants, Pogonomyrmex californicus (Buckley) (mean = 1.63 mm), red imported fire ants, Solenopsis invicta Buren (mean = 0.9 mm), and southern fire ants, Solenopsis xyloni McCook (mean = 0.76 mm) and compared them with the first and second most preferred particle size. There were differences between particle size of which the most mass was removed and of which there were more particles removed by ants. California Argentine ants, southern fire ants, and Alabama Argentine ants removed more 840 to 1,000-microm particle mass of the anchovy diet but had more visits to dishes containing 420 to 590 microm particles. California harvester ants and Allegheny mound ants, Formica spp., removed more2,000 microm particle mass but visited dishes containing 1,000 to 2,000 microm particles more often. Red imported fire ants also removed more2,000 microm particle mass but visited dishes with 590 to 840-microm particles most often. Pharaoh ants, Monomorium pharaonis (L.), removed and visited 420 to 590-microm particles more than any other size. A linear regression model determined that particle size preferred by each ant species relates to forager head width. The majority of particles of commercial ant bait, including Amdro, Ascend, Award, Bushwhacker, Max Force with fipronil, and old and new formulations of Max Force with hydramethylnon, were 1,000 to 2,000 microm, but the majority of Niban particles were420 microm. Altering the size of particles of toxic ant baits to fit the particle size preference of each pest ant species may increase the efficacy of ant baits.

The development of effective baits to control the Argentine ant, Linepithema humile (Mayr), has been problematic because foragers prefer sweet liquids, while many toxicants are insoluble in water and liquid baits are generally difficult to deliver. The incorporation of thiamethoxam and sucrose solutions into a water-absorbing polyacrylamide hydrogel provides a unique and novel carrier and method of application for liquid baits. Formulations of thiamethoxam affected the size of the hydrogels, and sucrose solutions containing 0.0003% technical thiamethoxam provided hydrogels as large as those made with 25% sucrose solution or deionized water. Concentrations of thiamethoxam as low as 0.000075% in the hydrogels provided 50% kill of workers within 3 d in a laboratory setting. In small colony studies, baiting with 0.00015 and 0.000075% thiamethoxam hydrogels provided 100% mortality of workers and queens within 8 d. An enzyme-linked immunosorbent assay indicated that thiamethoxam was absorbed into the interior of the polyacrylamide matrix. The water loss rates of the hydrogels were dependent upon the relative humidity. Polyacrylamide hydrogels with >50% water loss were less attractive to ants. Field studies in highly infested areas indicated that concentrations of 0.0006 or 0.0018% thiamethoxam were more effective than 0.00015%. Hydrogels may provide a cost-effective alternative to providing aqueous baits to control Argentine ants.

Comprehensive laboratory baiting studies with the 4 insecticides abamectin, boric acid, fipronil, and hydramethylnon were conducted against Argentine ant, Linepithema humile (Mayr). Serial dilutions of each insecticide prepared in a 25% sucrose solution were provided for 24 h or 14 d to groups of workers and queens. Sucrose-water baits containing 1 x 10(-5)% fipronil and 0.1% hydramethylnon provided complete mortality of L. humile workers baited for 24 h. Baits containing 1 x 10(-4) and 1 x 10(-5)% fipronil provided 100% kill of queens. In the continuous baiting, 0.5% boric acid, 1 x 10(-6)% fipronil, and 0.025% hydramethylnon provided 100% mortality of workers. The queens and workers provided baits containing 1 x 10(-5)% fipronil and 0.5% boric acid all died within 14 d. Low concentrations of fipronil and boric acid in sucrose may be promising candidates for Argentine ant control.

Structural insect pests may be killed by exposure to freezing temperatures. The critical thermal minimum (CTmin) is the threshold low temperature at which an insect succumbs from momentary exposure to temperatures decreasing at 1°C/min. The CTmin was —21.3°C for the western drywood termite, lncisitermes minor (Hagen); —17.2°C for workers of lncisitermes snyderi (Light); and —13.9°C for workers of the Formosan subterranean termite, Coptotermes formosanus Shiraki. The CTmin for the southern lyctus beetle, Lyctus planicollis LeConte, was —35.6°C for eggs, —26.2°C for small larvae, —30.0°C for medium larvae, and —24.3°C for large larvae. The effectiveness of liquid nitrogen (N2) to chill wall voids below the CTmin values for these structural pests was tested in a mock-up wall. The time to the CTmin was affected by the rate at which liquid N2 was released into the void and the vertical location of the release point. Fiberglass insulation in the wall affected the pattern of cooling by deflecting the liquid N2 around the insulation. Plumbing and electrical fixtures in the wall were not damaged by liquid N2, even though they were exposed to temperatures as low as —50°C. However, liquid N2 cracked vinyl floor tiles adjacent to the wall. The oxygen level in confined spaces where liquid N2 was released rapidly dropped below 19.5%, the minimum acceptable level for worker safety. Consequently, fans probably should be used to circulate fresh air into the areas where liquid N2 is used, and electronic monitoring should be done to ensure safe oxygen level. Because insects survive if they are not exposed to at least their CTmin it is important to monitor accurately the internal temperature of target wood with thermocouples to ensure that the CTmin has been reached where the insect actually occurs. To achieve an effective low temperature throughout a structure, virtually every void would need to be treated. Otherwise, it is unlikely that isolated pockets of termites could survive by escaping exposure to the CTmin Proper placement of thermocouples could be extremely important.

A bioassay was developed to determine the efficacy of insecticides against adult cat fleas, Ctenocephalides felis (Bouché), on turfgrass. Activity was assessed by exposing adult fleas to treated and untreated disks of turf for 24 h, 1 and 7 d after treatment. Filter paper, a representative nonwaxy, porous substrate was bioassayed in similar fashion 1 d after treatment to confirm insecticide activity. Results demonstrated the relative efficacy of insecticides applied to turf at different rates as well as differences among insecticides. Of 10 insecticides tested, chlorpyrifos wettable powder and emulsifiable concentrates consistently provided greatest kill of adult fleas. Although initially active, pyrethroid insecticides and diazinon generally showed significant declines in residual activity by day 7. Possible reasons for differences in activity are discussed.

Insecticide was applied to the perimeter of homes and adjacent areas likely to be visited by Argentine ants, Iridomyrmex humilis (Mayr). Treatment configuration consisted of a 1.8- to 2.4-m-wide band of spray around the exterior of the structure. Margins of sidewalks and pathways and around stepping stones, bases of trees, potted plants, and garbage cans were sprayed with 1.2-to 1.8-m-wide bands. Based on monitoring with traps, significant and relevant control was achieved when the number of ants trapped post treatment declined at least 80%. Barrier sprays of 237 mg (AI)/m2 chlorpyrifos, 14.5 mg (AI)/m2 cyfluthrin and 67.2 mg (AI)/m2 cypermethrin provided >80% reductions in the number of ants trapped at 7 d. Chlorpyrifos provided >82% reductions for at least 30 d. The combination of cyfluthrin spray + granules provided >85% reductions in ant trap counts at day 7. Only the combination treatment provided >80% reductions at 60 d. Cypermethrin and permethrin sprays failed to provide >80% reductions for 30 d. Factors that likely contribute to decreased performance of barrier sprays against ants include heavy irrigation, dense ground cover, exposure to direct sunlight, alkaline nature of the stucco and concrete surfaces, and extremely high temperatures.

Sands treated with solvent systems used to formulate commercially available termiticides, except for isofenphos, were toxic to western subterranean termites, Recticulitermes hesperus Banks, killing 24-86% after a 24-h exposure to sand air dried for 1 d. After air-drying deposits for 7 d, no solvent systems were still toxic. Irrigating solvent-treated sands with the equivalent of 1.27 cm of rainfall removed all toxicity, except for permethrin and cypermethrin solvent systems. After a second irrigation, all sands treated with the solvent systems were not toxic. Sands treated with solvent systems of all termiticides tested were repellent, except for that of isofenphos, and remained repellent after being air dried for 7 d. The loss of toxicity, but not repellency, after air drying suggests different chemical bases for the two effects or a concentration dependent effect. None of the termiticides tested were repellent after two rinses with water (equivalent of 2.54 cm rainfall). The effects of solvents must be considered when evaluating the repellency and toxicity of soils treated with commercially available termiticides.

In a previous experimental study, recluse spiders Loxosceles reclusa Gertsch and Mulaik and Loxosceles laeta (Nicolet) (Araneae: Sicariidae) preferred small cardboard refugia covered with conspecific silk compared with never-occupied refugia. Herein, we investigated some factors that might be responsible for this preference using similar cardboard refugia. When the two Loxosceles species were given choices between refugia previously occupied by their own and by the congeneric species, neither showed a species-specific preference; however, each chose refugia coated with conspecific silk rather than those previously inhabited by a distantly related cribellate spider, Metaltella simoni (Keyserling). When L. laeta spiders were offered refugia that were freshly removed from silk donors compared with heated, aged refugia from the same silk donor, older refugia were preferred. Solvent extracts of L. laeta silk were chosen approximately as often as control refugia when a range of solvents (methylene chloride:methanol, water, and hexane) were used. However, when acetone was used on similar silk, there was a statistical preference for the control, indicating that there might be a mildly repellent aspect to acetone-washed silk. Considering the inability to show attraction to chemical aspects of fresh silk, it seems that physical attributes may be more important for selection and that there might be repellency to silk of a recently vacated spider. These findings are discussed in regard to pest management strategies to control recluse spiders.

Topical toxicity of cypermethrin (LD50 = 1.6 μg/g) was approximately three times greater to Reticulitermes hesperus Banks than chlorpyrifos (LD50 = 4.5 μg/g) and ≈35 times greater than chlordane (LD50 = 56.8 μg/g) after 7 d. Water rinsed from soil treated with chlorpyrifos produced significantly greater kill than did soil treated with an aqueous rinse hom soil h’eated with cypermethrin. The rinse water from soil treated with chlordane did not produce significant kill when redeposited on untreated soil. Termiticidal amounts of chlorpyrifos, chlordane, or cypermethrin moved to soil depths of at least 30,7, and 7 cm, respectively. With cypenrmethrin, sublethal effects were detected to a depth of 42 cm.

The oral toxicity of boron compounds to the Argentine ant, Linepithema humile (Mayr), was evaluated in laboratory tests. The ants were provided 25% sucrose water containing 0.5 and 1% boric acid, disodium octaborate tetrahydrate, and borax. Lethal times of these solutions were a function of the concentration of boron. In field tests, the ants showed no discrimination between disodium octaborate tetrahydrate and boric acid. There was a significant reduction in consumption of sucrose water with >1% boric acid.

Experiments tested the ability of newly emerged spiderlings of a black widow spider, Latrodectus hesperus Chamberlin & Ivie (Araneae: Theridiidae), to crawl through brass screen of various mesh size. The purpose was to determine whether immatures of these medically important spiders could be excluded from buildings. In horizontal orientation, black widow spiderlings were able to easily pass through mesh with openings of 0.83 mm and were prevented from passing in four of five tests with mesh of 0.59-mm openings. Spiderlings also readily pass through 0.83-mm mesh in vertical orientation. Our laboratory studies indicate that the mesh size sufficient for exclusion is too small for practical use in most cases, although there are some specialized situations where such small mesh might be useful. The results are discussed in regard to actual conditions found in typical commercial building situations.

We developed a laboratory method to determine the potential efficacy of baits formulated for control of the Argentine ant, Iridomyrmex humilis (Mayr). Possible effects as insect growth regulators were not examined. Of the 10 formulated baits tested, only mirex applied to granulated silkworm pupae had delayed toxicity. Hydramethylnon applied to granulated silkworm pupae also provided excellent kill of workers but did not exhibit delayed toxicity. In field tests, this bait provided faster control than did a chemical barrier of granular diazinon.

Dichlorvos and chlorpyrifos vapor from dried residual deposits produced significant numbers of moribund workers of the western subterranean termite, Reticulitermes herperus Banks. In some cases, lethal effects were not observed until 7 h after exposure. Tenhour exposure to vapor from deposits of chlordane, chlorpyrifos, cypermethrin, or dichlorvos aged for 12 h produced significantly greater numbers of moribund workers than did the control treatment. Vapor from deposits of chlordane, chlorpyrifos, or cypermethrin aged for 12h produced more moribund insects than did 1-h-old deposits, suggesting that older deposits release more toxicant than fresh deposits. Residual deposits of chlorpyrifos or dichlorvos redeposited from their vapor phase on foil surfaces produced 83–100% moribund termites within 24 h. Redeposition of toxicant or sorption of vapor might be responsible for lethal effects. Regardless of the insecticide used, toxic amounts did not move to dry untreated soil beneath treated soil. Toxic vapor from soil treated with dichlorvos moved down simulated termite tunnels. This phenomenon was not observed for other insecticide treatments.

Western subterranean termites, Reticulitermes Hesperus Banks, did not tunnel in soil with particle sizes ranging from 0.84 to 2.36 mm. Instead, they tunneled at equal rates in soils with particle sizes ranging from 0.15 mm. The latter range of soils was treated with termiticides in the study. In continuous-exposure studies in which termites were placed on soil treated at ≥ 50 ppm with termiticide, bifenthrin, cypermethrin, or permethrin had the greatest activity. Soil treated with chlordane, permethrin ( 50 ppm permethrin. Fenvalerate (< 100 ppm) and isofenphos formulations were the least active treatments. In tunneling studies, termites did not tunnel into soil treated with formulations of bifenthrin or cypermethrin, even at the lowest concentration tested. No tunneling occurred in soil treated with formulated chlordane, chlorpyrifos, fenvalerate, isofenphos, or permethrin at concentrations ≥ 50 ppm. Mortality from the tunneling activities was greatest in tubes filled with soil treated with formulated bifenthrin and chlorpyrifos. Even though termites tunneled only in the untreated soilbelow the soiltreated with chlordane, chlorpyrifos, fenvalerate, isofenphos, or permethrin formulations at concentrations ≥50 ppm, mortality and sublethal effects were observed. Insecticide probably diffused from treated areas to untreated areas in concentrations high enough to produce kill or affect behavior.

Laboratory studies were done to evaluate the repellency and efficacy of 25 insecticides against foraging workers of the Argentine ant, Iridomyrmex humilis (Mayr). The trail pheromone of I. humilis, cis-9 hexadecenal, was used to induce trailing and movement through sections of glass tubing treated with insecticides. General repellency of formulations was ranked as granular < emulsifiable concentrate < dust < wettable powder. As the repellency of the insecticide increased, mortality increased. Potential field efficacy of 25 insecticides as barrier treatments is discussed.

Four different termite control strategies consisting of two soil treatments with cypermethrin and fipronil and two bait treatments with hexaflumuron and sulfluramid were evaluated for their efficacy and potential for controlling the invasive eastern subterranean termite, Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae), in Quillota and Valparaiso, Chile. Monitoring stations were installed at all sites to measure the overall termite activity next to and at distances up to 30 m away from infested structures, most being 3-5 m. Foraging activity was extremely seasonal with the maximum consumption rates occurring from January to April. Termite foraging activity was low from July to September. After treatments in January 2003, there was a significant decrease in wood consumption, percentage of active stations, and numbers of termites in traps for the first 6 mo with hexaflumuron baits. No significant change in R. flavipes foraging activity was observed on wood consumption and percentage of active stations for sulfluramid bait or cypermethrin and fipronil soils treatments. The seasonal pattern of foraging activity remained unchanged for all treatments in 2004 and 2005, except structures baited with hexaflumuron. Feeding activity at the monitors in the area surrounding the hexaflumuron baits declined to 0 after January 2004. Alate flights occurred in approximately 38% of the structures treated with cypermethrin and sulfluramid bait in 2003 and in approximately 40% of the structures treated with cypermethrin, fipronil, and sulfluramid bait in 2004. Sulfluramid baits and cypermethrin soil treatments did not have any impact within a 15-m radius of the structures. Soils treatments of fipronil and cypermethrin prevented termites access in 75% of the homes. The number of active monitoring stations only declined within 2 m of the fipronil-treated zone. Hexaflumuron exhibited a reduction in activity for at least a 15-m radius.

The potential horizontal transfer ofnonrepellent termiticides has become an important paradigm to control termites in recent years. In this study, 14C-radiolabeled fipronil was used in a series of laboratory experiments to demonstrate the extent and ability of termites to transfer lethal amounts of fipronil to unexposed nestmates. Fipronil is an active and nonrepellent termiticide against western subterranean termites, Reticulitermes hesperus Banks, on sand at relevant doses. It exhibited delayed toxicity with the lowest LD50 approximately 0.2 ng/termite expressed between day 4 and 7. Both continuous and brief exposures to fipronil-treated sand seriously impaired the termite's ability to move and respond to a dodecatrienol trail, limiting potential horizontal transfer. In tunneling studies, fipronil prevented termite tunneling at concentrations as low as 0.5 ppm and was nonrepellent even at 500 ppm. Greater than 90% mortality was recorded by day 7 with concentrations ranging from 0.5 to 500 ppm. There was a linear relationship between the time of exposure and uptake of [14C]fipronil when termites were continuously exposed to 0.5, 1.0, and 5.0 ppm for 24 h. However, uptake discontinued when the termites were immobilized. Maximum transfer of fipronil from donors to recipients occurred within the first 24 h. Fipronil was transferred by body contact and trophallaxis did not play a major role in horizontal transfer. In successive transfer studies, there was not enough fipronil on recipients for them to serve as secondary donors and kill other termites. In a linear arena study, there was an inverse relationship between the amount offipronil on dead termites and their distance from the treated zone. Maximum mortality was observed within 1.5 m from the treated zone. Results in our laboratory studies suggest that horizontal transfer was not a major factor contributing to the efficacy of fipronil in the field.

Western subterranean termite, Reticulitermes hesperus (Banks), prefers various mono-, di-, and trisaccharides, total feeding being the greatest on paper disks treated with 5% ribose followed by 3% xylose, 2% maltose, 2% fructose, 2% arabinose, and 2% ribose. In multiple choice tests, termites were not able to discriminate between 2% ribose, 2% fructose, 2% xylose, and 2% maltose. Termites readily take up [14C] sucrose in feeding studies. Most of the sucrose is used as an energy source for respiration (89.2%), a very small proportion remains within the termite (9.3%), and an even smaller amount is excreted as solid waste (1.5%). The amount of 14C label transferred to other colony members via trophallaxis, body contact, or grooming is small and directly dependent upon the time and numbers of donors and recipients. At day 15 postmixing, the percentage of transfer was highest, 14.4 and 15.1% for both 1:1 and 2:1 donor to recipient mixing ratios, respectively. The mean amount of labeled 14C received by recipients increased from seven disintegrations per minute (dpm) on day 2 to 30 dpm on day 15 for 1:1. Overall mean radioactivity recovered from recipient termites when mixed with donor termites at 1:1 ratio (20 dpm) was significantly less than (28 dpm) when mixed with donor termites at 2:1 ratio. Sugars act as phagostimulants to the termites at concentrations much higher to those that termites naturally encounter in wood. Termites readily metabolize carbohydrates such as sucrose, and thus their use in bait matrices may increase consumption and retention at bait stations.

Boric acid, imidacloprid, and thiamethoxam in sucrose aqueous baits had different delayed toxicities to worker Argentine ants, Linepithema humile (Mayr). The concentrations required to produce an LT50 (time required to produce 50% mortality) within 1-4 d were 3.63-0.55% boric acid, 9.2 x 10(-3) to 7.1 x 10(-4)% imidacloprid, and 3 x 10(-4) to 2 x 10(-5)% thiamethoxam. The three toxicants were not repellent. Other laboratory trials showed that 1% boric acid, 5 x 10(-4) to 5 x 10(-3)% imidacloprid, and 1 x 10(-5) to 1 x 10(-3)% thiamethoxam had delayed toxic effects, whereas 0.5% boric acid and5 x 10(-3)% imidacloprid did not. Baits that provided an LT50 between days 1 and 4 were considered to have delayed toxic effects. The utility of aqueous sucrose baits and toxicants soluble in such systems and the negative impact of fast-acting toxicants on trail following, recruitment, trophallaxis, and control of Argentine ants are discussed.

Topical application (LD) and time-mortality response (LT) methods were used to determine resistance levels of field-collected strains of the German cockroach, Blattella germanica (L.). LD50s for chlorpyrifos were determined for seven strams. LT50s and LT90s with eight insecticides were determined for another three strains. Resistance ratios (RR) of >10 to chlorpyrifos (LD50) were directly related to a significant decrease in activity in Ebeling choice-box tests. Using the LT method, the three field-collected strains were shown to possess zero to moderate resistance at the RR50 level (0.9–5.3) to organophosphates, moderate to high resistance to (1.4–>21.0) to carbamates, moderate to high resistance (4.3–20) to cypermethrin, and high resistance (>17–>35) to synergized pyrethrins. When the three field-collected strains were tested in choice boxes, RR50s of 1.2–2.2 for chlorpyrifos and 2.5–5.3 for diazinon directly related to significantly lower efficacy. Low-level propoxur resistance (RR50 of 1.4–2.3) also reduced choice-box efficacy, but an RR50 of 0.9–1.3 for acephate did not reduce its performance. Cypermethrin deposits used in choice tests killed cockroaches exhibiting RR50s as high as 20 in the lethal time test, perhaps because resistance mechanisms could not detoxify the exceptional activity of the active ingredient formulated as a wettable powder. Because they were repellent, residual deposits of pyrethrins resulted in poor efficacy in choice tests with either susceptible or field-collected strains. Strains with low-level physiological resistance as measured by the time-mortality response method survived insecticide exposure in choice-box tests to certain organophosphate and carbamate insecticides, indicating that these compounds would not be effective in the field.

Activities of insecticides against adult cat fleas, Ctenocephalides felis (Bouche), were broadly categorized as follows: organophosphates > carbamates = synergized pyrethrins > pyrethroids. Residues of chlorpyrifos (applied at 127 mg [AI]/m2), propetamphos (127 mg/m2), permethrin (255 mg/m2), diazinon (509 mg/m2), malathion (1,018 mg/m2), and carbaryl (1,222 mg/m2) applied to nylon carpet provided >90% kill of adult cat fleas for at least 21 d. Activities of insecticide sprays were inversely related to increased density or depth of carpet. Vacuuming or simulated wear on treated carpet did not significantly affect residual activity against fleas, but shampooing reduced activity of microencapsulated diazinon and bendiocarb by 30 and 93%, respectively. Propetamphos was not affected by carpet shampoo.

The efficacy and repellency of 6 representative blatticides were tested with and without the addition of extracts of aggregation pheromone of the German cockroach, Blattella gennanica (L.). Efficacy of the toxicants was generally inversely related to its repellency. Avoidance of residues by males was indicated with a Relative Avoidance Index (RAI) in which values > 1.00 indicated repellency greater than diazinon (1.00). Considering the KT-50 of each toxicant, the order of repellency was boric acid < diazinon < chlorpyrifos < Dri-die 68® < Dri-die 67® < propoxur. Toxicants combined with aggregation pheromone against young nymphs significantly increased mortality in choice tests with chlorpyrifos, propoxur, diazinon, and Dri-die 67. With adult males, similar increases were obtained with pheromone and propoxur and diazinon. Aggregation pheromone reduced repellency, and increased the period of time cockroaches contacted each toxicant.

Although laboratory tests indicated that insecticidal laminated tapes containing propoxur, chlorpyrifos or diazinon remained active for long periods, simulated and actual field efficacy against Blattella germanica (L.) was minimal. Effectiveness was related directly with dosage and was dependent on stimuli that increased cockroach movement or foraging.

Chlorpyrifos, diazinon, and propoxur were tested for repellency and efficacy against German cockroaches, Blattella germanica (L.). Repellency of each material was determined by using a relative avoidance index (RAI) and was directly proportional to concentration. Avoidance to each toxicant decreased significantly and mortality increased in choice tests when an extract of aggregation pheromone (AP) was added. Chlorpyrifos (0.25% + AP) and diazinon (0.5% + AP) produced significantly higher mortality than any toxicant alone. In field control tests in apartments infested with German cockroaches, chlorpyrifos (0.5%) and Knox-Out® (1.0%) produced over 90% reductions within 4 wk, but diazinon (0.5%) and flowable microencapsulated diazinon (Knox-Out® 2 FM) (0.5%) failed to produce significant control within 2 wk after treatment; chlorpyrifos (0.25%) produced only partial control. However, similar concentrations of each material + AP produced 78.4, 82.0, and 90.7% reductions at 2 wk, respectively.

Sampling for adult cat fleas, Ctenocephalides felis (Bouche), indoors with a modified vacuum cleaner was more effective than visual inspection. Significantly more fleas were collected from living rooms and bedrooms than from other rooms and more fleas were collected from rooms with carpeted or wooden floors than ones with tile. Fleas were found outdoors at only 8 of 50 residences sampled. Pressurized sprays containing pyrethrins and the pyrethroid tetramethrin provided poor residual activity against adult fleas in the laboratory, but the insect growth regulators fenoxycarb and methoprene provided control by preventing larva development and emergence of adult fleas on deposits aged for at least 56 days. Under field conditions, pressurized sprays containing fenoxycarb or methoprene also provided excellent control for at least 60 days. Total-release aerosols containing no IGR failed to provide adequate control of fleas whereas aerosols with fenoxycarb successfully controlled fleas at least 60 days. Aqueous spray of propetamphos or microencapsulated diazinon provided excellent control for at least 60 days. Bendiocarb sprays failed to control fleas.