We report on our investigations comparing three juvenile hormone (JH) homologs and two synthetic juvenoids to induce caste differentiation in laboratory colonies of Reticulitermes flavipes and R. tibialis. Two laboratory assays were evaluated as model systems for inducing caste differentiation: (1) shorter-term dish assays on groups of 20 individuals and (2) longer-term feeding assays on groups of 500 individuals. Each assay possessed attributes that can be considered advantageous under certain conditions. Specifically, dish assays were most suitable for presoldier and soldier induction, while jar assays provided for the induction of nymphs, presoldiers, soldiers, neotenic reproductives, and intercastes. Differences in response to the JH homologs and synthetic juvenoids were noted between species, suggesting differences in JH physiology may exist between R. flavipes and R. tibialis. Substantial morphological impacts were noted in association with some treatments, including (1) juvenoid-induced mandibular malformation in presoldiers, (2) JH II-induced abdominal elongation in R. flavipes soldiers and workers (associated with a presence of internal reproductive anatomy that is consistent with what would be expected to occur in pseudergates), and (3) JH II-induced soldier-nymph intercastes in R. tibialis that were able to further molt into soldier-alate intercastes. Findings are discussed in relation to the potential differences in JH-related physiology between R. flavipes and R. tibialis, and the use of model systems to induce rare castes and intercastes for molecular investigations of caste differentiation.
Three liquid insecticide formulations were evaluated as barrier treatments against perimeter-invading ants at a multifamily housing complex in West Lafayette, IN. Several ant species were present at the study site, including (in order of abundance) pavement ant, Tetramorium caespitum (L.); honey ant, Prenolepis imparis (Say); odorous house ant, Tapinoma sessile (Say); thief ant, Solenopsis molesta (Say); acrobat ant, Crematogaster ashmeadi (Mayr); crazy ant, Paratrechina longicornis (Latrielle), field ants, Formica spp.; and carpenter ant Camponotus pennsylvanicus (DeGeer). Studies began in May 2001 and concluded 8 wk later in July. Individual replicate treatments were placed 0.61 in (2 feet) up and 0.92 m (3 feet) out from the ends of 46.1 by 10.1-m (151 by 33-foot) apartment buildings. Ant sampling was performed with 10 placements of moist cat food for 1 h within treatment zones, followed by capture and removal of recruited ants for later counting. All treatments led to substantial reductions in ant numbers relative to untreated controls. The most effective treatment was fipronil, where 2% of before-treatment ant numbers were present at 8 wk after treatment. Both imidacloprid and cyfluthrin barrier treatments had efficacy comparative with fipronil, but to 4 and 2 wk, respectively. Odorous house ants were not sampled before treatment. Comparisons of ant species composition between treatments and controls revealed an increase in odorous house ant frequencies at 1-8 wk after treatment in treated locations only. These results demonstrate efficacy for both nonrepellent and repellent liquid insecticides as perimeter treatments for pest ants. In addition, our findings with odorous house ant highlight an apparent invasive-like characteristic of this species that may contribute to its dramatic increase in structural infestation rates in many areas of the United States.
Five selected insecticides were applied to four substrates and evaluated in laboratory studies for repellency and toxicity against the Pharaoh ant, Monomorium pharaonis (L.). We tested both repellent and nonrepellent formulations on outdoor (concrete and mulch) and indoor (ceramic and vinyl) substrates. Repellency was evaluated using a behavioral bioassay in which colonies were given a choice to leave the treated zone and move into empty nests provided in the untreated zone. We used a novel experimental design whereby ants walked on a Slinky coil suspended from a metal support frame, thus permitting a long foraging distance with a minimum use of space and resources. Cypermethrin, a repellent pyrethroid insecticide, resulted in colony budding, although the response was delayed. Toxicity of insecticides was evaluated as worker, queen, and brood mortality. The most effective treatment was fipronil, which provided 100% reduction in pretreatment activity by 2 d posttreatment on both concrete and mulch. Chlorfenapyr was highly effective on both outdoor and indoor substrates. Significant substrate effects were observed with insecticides applied to nonabsorbent substrates (ceramic tile), which performed better than insecticides applied to absorbent substrates (vinyl tile). Other highly absorbent materials (mulch and concrete), however, did not reduce insecticide efficacy. This is because ants relocated nests into and/or under these attractive nesting materials, thus increasing their exposure to toxic insecticide residues. Our results demonstrate efficacy of nonrepellent liquid insecticides as indoor treatments for the control of Pharaoh ants and possibly as exterior perimeter treatments.
Five selected insecticides were applied to four substrates and evaluated in laboratory studies for repellency and toxicity against the Pharaoh ant, Monomorium pharaonis (L.). We tested both repellent and nonrepellent formulations on outdoor (concrete and mulch) and indoor (ceramic and vinyl) substrates. Repellency was evaluated using a behavioral bioassay in which colonies were given a choice to leave the treated zone and move into empty nests provided in the untreated zone. We used a novel experimental design whereby ants walked on a Slinky coil suspended from a metal support frame, thus permitting a long foraging distance with a minimum use of space and resources. Cypermethrin, a repellent pyrethroid insecticide, resulted in colony budding, although the response was delayed. Toxicity of insecticides was evaluated as worker, queen, and brood mortality. The most effective treatment was fipronil, which provided 100% reduction in pretreatment activity by 2 d posttreatment on both concrete and mulch. Chlorfenapyr was highly effective on both outdoor and indoor substrates. Significant substrate effects were observed with insecticides applied to nonabsorbent substrates (ceramic tile), which performed better than insecticides applied to absorbent substrates (vinyl tile). Other highly absorbent materials (mulch and concrete), however, did not reduce insecticide efficacy. This is because ants relocated nests into and/or under these attractive nesting materials, thus increasing their exposure to toxic insecticide residues. Our results demonstrate efficacy of nonrepellent liquid insecticides as indoor treatments for the control of Pharaoh ants and possibly as exterior perimeter treatments.
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