Rodent behaviour in relation to baiting techniques1

The use of poison baits is still the most important control method against commensal as well as field rodents. The baiting techniques used must be adapted to the ecology and behaviour of the target species. The various aspects of rodent behaviour influencing the effect of a control operation are discussed with emphasis on feeding behaviour, exploratory behaviour, neophobia, bait shyness, transporting, hoarding and territoriality. Advantages and disadvantages of sustained versus pulsed baiting techniques are discussed from a behavioural point of view.     

Development of strategies for monitoring indoxacarb and gel bait susceptibility in the German cockroach (Blattodea: Blattellidae)

BACKGROUND: Advion^® cockroach gel bait (6 g kg^?1 indoxacarb) is in widespread use for Blattella germanica (L.) control in the United States. However, baseline susceptibility levels to indoxacarb in German cockroach field populations are not known. Hence, this research sought to develop monitoring strategies to estimate the susceptibility of German cockroach populations to indoxacarb. RESULTS: Four bioassays were evaluated: topical lethal dose (LD), formulated gel bait lethal time (LT), vial lethal concentration (LC) and gel bait matrix LD. Of these methods, the vial LC and gel bait matrix LD bioassays were the most economical and relevant assessment strategies. For indoxacarb susceptibility monitoring, a two‐tiered approach was developed that utilizes diagnostic concentrations and doses in vial LC (30 and 60 µg vial^?1) and gel bait matrix LD (1.0, 1.5 and 2.5 µg insect^?1) formats. CONCLUSIONS: A two‐tiered susceptibility monitoring strategy was developed that includes testing field populations at diagnostic concentrations and doses in first‐tier vial LC bioassays and second‐tier gel bait matrix LD bioassays. The vial method facilitates rapid identification of field strains with reduced susceptibility. The feeding bioassay effectively simulates field exposure to Advion^® and therefore has utility for secondary confirmation of susceptibility shifts and identification of behavioral resistance (i.e. bait aversion). Copyright © 2010 Society of Chemical Industry     

Methods of testing rodenticides in the field against rats

Poisons used in bait to control rats are of two kinds; single-dose acute poisons and those with a slow or cumulative action lethal only if two or more daily doses are consumed. The two types require different baiting techniques and different methods must be used for testing them in the field. For acute poisons, the relative sizes of rat infestations have to be measured by baiting with unpoisoned bait both before and after poison baiting and the pre-treatment sizes taken into account when analysing the results. When testing possible cumulative or multiple-dose poisons, pre-treatment baiting is unnecessary and the method used was that originally devised for field testing for anticoagulant resistance in rats. Examples of published results of field trials of both types of poison are discussed.     

Short- and long-term control of Vespula pensylvanica in Hawaii by fipronil baiting

BACKGROUND: The invasive western yellowjacket wasp, Vespula pensylvanica (Saussure), has significantly impacted the ecological integrity and human welfare of Hawaii. The goals of the present study were (1) to evaluate the immediate and long‐term efficacy of a 0.1% fipronil chicken bait on V. pensylvanica populations in Hawaii Volcanoes National Park, (2) to quantify gains in efficacy using the attractant heptyl butyrate in the bait stations and (3) to measure the benefits of this approach for minimizing non‐target impacts to other arthropods. RESULTS: The 0.1% fipronil chicken bait reduced the abundance of V. pensylvanica by 95 ± 1.2% during the 3 months following treatment and maintained a population reduction of 60.9 ± 3.1% a year after treatment in the fipronil‐treated sites when compared with chicken‐only sites. The addition of heptyl butyrate to the bait stations significantly increased V. pensylvanica forager visitation and bait take and significantly reduced the non‐target impacts of fipronil baiting. CONCLUSION: In this study, 0.1% fipronil chicken bait with the addition of heptyl butyrate was found to be an extremely effective large‐scale management strategy and provided the first evidence of a wasp suppression program impacting Vepsula populations a year after treatment. Copyright © 2011 Society of Chemical Industry     

An investigation of the parameters of anticoagulant treatment efficiency1

The traditional technique of applying anticoagulant rodenticides, as shaped by long experience in the use of low-toxicity, first-generation anticoagulants such as warfarin, aims to maximize treatment efficiency by maximizing the rate of bait consumption by the target rodents. This is done, somewhat laboriously, by laying surplus amounts of bait initially, and maintaining this surplus throughout the treatment by repeatedly replenishing the bait placements. The suggestion that the high toxicity of the second-generation anticoagulants should enable a more efficient baiting system to be designed is examined experimentally in this field study of the control of Rattus norvegicus on British farms. Bait toxicity, infestation size and the incidence of complete takes of bait were found to be independent and highly significant determinants of treatment duration whilst, in comparison, the size and density of bait points and the frequency with which the bait was replenished were found to be relatively unimportant. However, bait size and, more especially, replenishment frequency had detectable secondary effects, apparently through partial relationships with the incidence of complete takes and infestation size. The results indicate, in relation to the control of commensal infestations of R. norvegicus on British farms, that the use of high-toxicity bait formulations and frequent replenishment schedules increase the speed of control, whilst the number and size of bait placements are relatively unimportant; they also suggest that reductions in the frequency of bait replenishment made in order to save labour could be compensated for by increasing the toxicity of the bait and taking other steps to reduce the incidence of complete takes of bait. The results are discussed in relation to the concept of ‘pulsed baiting'.     

Brodifacoum is effective against Norway rats (Rattus norvegicus) in a tyrosine139cysteine focus of anticoagulant resistance in Westphalia,Germany

BACKGROUND: The tyrosine to cysteine amino acid substitution at location 139 of the vkorc1 protein (i.e. tyrosine139cysteine or Y139C) is the most widespread anticoagulant resistance mutation in Norway rats (Rattus norvegicus Berk.) in Europe. Field trials were conducted to determine the incidence of the Y139C mutation at two rat‐infested farms in Westphalia, Germany, and to estimate the practical efficacy against them of applications, using a pulsed baiting treatment regime, of a proprietary bait (Klerat^?) containing 0.005% brodifacoum. RESULTS: DNA analysis for the Y139C mutation showed that resistant rats were prevalent at the two farms, with an incidence of 80.0 and 78.6% respectively. Applications of brodifacoum bait achieved results of 99.2 and 100.0% control at the two farms, when measured by census baiting, although the treatment was somewhat prolonged at one site, possibly owing to the abundance of attractive alternative food. CONCLUSION: The study showed that 0.005% brodifacoum bait is fully effective against Norway rats possessing the Y139C mutation at the Münsterland focus and is likely to be so elsewhere in Europe where this mutation is found. The pulsed baiting regime reduced to relatively low levels the quantity of bait required to control these two substantial resistant Norway rat infestations. Previous studies had shown much larger quantities of bromadiolone and difenacoum baits used in largely ineffective treatments against Y139C resistant rats in the Münsterland. These results should be considered when making decisions about the use of anticoagulants against resistant Norway rats and their potential environmental impacts. Copyright © 2012 Society of Chemical Industry     

Controlling yellow jackets with fipronil-based protein baits in urban recreational areas

ABSTRACT

The western yellow jacket, Vespula penyslvanica (Saussare), is a serious seasonal pest of outdoor venues in the western United States. In the spring, queens and low numbers of workers were captured in heptyl-butyrate-baited traps until early July, when the number of foragers dramatically increased. Microsatellite data suggest that 18 colonies were actively foraging within the park in 2012. Foragers from 11 different colonies were collected at one trap site. In 2012 and 2013, sufficient numbers of foragers were not captured until early August when baiting trials were initiated. Baits were prepared with canned chicken mixed with fipronil for a final concentration of 0.025%. In 2012, a single baiting provided >96% reduction of foragers for at least two months. A second baiting late in the season provided >80% reductions. In 2013, one baiting trial resulted in a 74% and a 93% reduction. A bait acceptance study was conducted in 2014 to test a bait consisting of the juices from canned chicken and 0.025% fipronil incorporated into a hydrogel, and provided a much longer lasting bait in the field.     

An in-situ baiting bioassay for detecting Phytophthora species in irrigation runoff containment basins

Experiments were conducted in irrigation runoff containment basins to assess the effects of bait species ( Camellia japonica , Ilex crenata or Rhododendron catawbiense ), bait type (whole leaf vs. leaf disc), baiting duration (1, 2, 7 or 14 days), baiting depth and growth media (modified PARP-V8 or PARPH-V8) on the recovery of Phytophthora species. A two-rope, flexible bait-deployment system was compared with a one-rope fixed system for bait stability at designated locations and depths. A total of 907 Phytophthora isolates were subjected to PCR-based single-strand conformation polymorphism (PCR-SSCP) analysis to identify to species level. Seven distinct SSCP patterns representing six morphospecies: P. citricola (Cil I), P. citrophthora (Cip I), P. hydropathica (Hyd), P. insolita (Ins), P. megasperma (Meg I & II) and an unidentified Phytophthora species were identified. Irrespective of culture medium, 7 days of baiting with rhododendron leaves consistently resulted in the recovery of the greatest diversity and populations of Phytophthora species with minimum interference from Pythium species. The flexible bait-deployment system was superior to the fixed system, minimizing the risk of bait loss and dislocation of baiting units and allowing baits to remain at designated depths from the surface under inclement weather.     

Biochemical and histochemical studies on the digestive gland of Eobania vermiculata snails treated with carbamate pesticides

In this study the land snail (Eobania vermiculata), one of the most abundant gastropod of Egyptian farms, was investigated to determine the lethal toxic action of methomyl and methiocarb and to identify the biochemical and histochemical changes as a function of sublethal dose or concentration on the digestive gland of this snail under laboratory conditions, using topical application and baiting techniques. The results showed that methomyl exhibited greater efficacy than did methiocarb against the snails in both techniques. However, higher mortality rates were obtained in the topical application technique than in the poison bait experiments. Biochemical and histochemical examinations revealed that treatment of the snails with methomyl and methiocarb either by topical application or toxic baits caused significant decrease in carbohydrate, lipid and protein contents. This decrease was also more obvious after topical application than after baiting technique, and methomyl was found to be more toxic than methiocarb.     

Effects of quinestrol and levonorgestrel on populations of plateau pikas, Ochotona curzoniae, in the Qinghai-Tibetan Plateau

BACKGROUND: Plateau pikas ( Ochotona curzoniae , Hodgson, 1858) are viewed as a pest in the Tibetan Plateau meadow ecosystem when their population densities are high. Traditional culling using rodenticides often poses a high risk to non‐target species and even to humans. In this study, an investigation was made of the infertility effects of quinestrol (E), levonorgestrel (P) and a combination of the two (EP, ratio E:P = 1:2) on plateau pikas during 2007 and 2008. RESULTS: Treatment with E or EP significantly decreased the pregnancy rate of female pikas in 2007. In 2008, there was a cross‐year effect that still suppressed male reproduction in treated groups. Treatment with E obviously reduced the reproduction of pikas but not their population abundance in 2007; the reduction in population size was significant in 2008. CONCLUSIONS: Single baiting of quinestrol in early breeding season reduced the reproduction and population size of pikas throughout 2007. The effect of infertility lasted into the next breeding season through a cross‐year effect, which resulted in a significant reduction of population size in 2008. Quinestrol is a very promising non‐lethal approach to managing pika populations; however, several factors need to be investigated further to improve the practicality of this method. Copyright © 2012 Society of Chemical Industry     

Laboratory and field cage studies on female‐targeted attract‐and‐kill bait stations for Anastrepha suspensa (Diptera: Tephritidae)

BACKGROUND: Development of attract‐and‐kill bait stations for pest fruit flies has been limited by the water solubility of sugar needed as a feeding stimulant and by the volatility of chemical attractants. A wax‐based matrix was developed that provides the longevity needed for field use and is biodegradable. RESULTS: Laboratory bioassays with the Caribbean fruit fly, Anastrepha suspensa (Loew), confirmed the efficacy of bait stations containing avermectin, methomyl, spinosad and phloxine B. Field cage studies demonstrated that significant mortality occurred with either 1% (w/v) spinosad or 1% (w/v) methomyl bait stations versus pesticide‐free bait stations. Bait stations were exposed to environmental conditions by placing them in trees at the ARS station in Miami, Florida, between tests. There was no loss in efficacy, in spite of exposure to over 360 mm of rainfall over the 56 days of the study, indicating that the bait stations could provide population suppression for at least 1–2 months when used in subtropical environments. CONCLUSION: A long‐lasting, female‐targeted fruit fly bait station, such as the one developed herein, could provide a cost‐effective option for fruit fly population suppression that would be an important tool in tephritid pest management and control. Additional studies are needed to demonstrate efficacy against wild fruit fly populations and determine deployment strategies. Copyright © 2009 Society of Chemical Industry     

Investigation of sodium monofluoroacetate (1080) bait shyness in wild brushtail possum (Trichosurus vulpecula) populations

Bait shyness is a significant threat to the sustainable control of vertebrate pests. New Zealand's foremost vertebrate pest is the introduced brushtail possum (Trichosurus vulpecula). Bait shyness was identified in two wild possum populations by comparing the consumption of two non-toxic bait types before and after each population was presented with one of the bait types containing the toxin sodium monofluoroacetate (1080). Before poisoning, approximately 60% of total bait consumption was of the type which 1080 was later presented in, whereas after poisoning this bait type made up only 2-4% of total consumption. This shyness persisted for at least 11 weeks in one of the populations. No individual component (bait base, cinnamon lure or green dye) of the toxic bait could be isolated as the primary cue eliciting bait shyness as the response. Possible means of overcoming bait shyness are discussed in light of these findings.     

The efficacy of two permanent poison-baiting measures against Mus domesticus living in farm buildings in the UK1

The effectiveness of two poison bait formulations was examined in trials against infestations of Mus domesticus in farm buildings. Treatment was extensive on each of four farms, covering all buildings and lasting 1 year. In the four trials, bait containing calciferol and warfarin in combination, or difenacoum was used. Mouse infestation level was monitored, using the mark-recapture trapping technique, before poison-baiting was begun and every 6 weeks thereafter. Poison bait consumption was high initially and mouse numbers were substantially reduced on all four farms within 6 weeks. Subsequently, the difenacoum treatments were the most effective in keeping infestation levels extremely low. Mice still resident when the treatments were terminated were removed by live and kill traps. Laboratory feeding tests were conducted on the live-caught survivors; all animals died after consuming poison bait of the kind used in the trials. Additional live-trapping, 6 months and 1 year later, produced evidence of recolonization and of renewed population growth. It is concluded that sustained control effort is needed to prevent the build-up of M. domesticus numbers in farm buildings.     

Providing management options to control corn mouse (Calomys musculinus) reservoir populations using a cohort structured model

We evaluate several management options for Calomys musculinus populations through the formulation and validation of a cohort structured model. Initially, a basic model was constructed and validated using field population data. Next, the model was altered to allow us to evaluate different management options. In general, basic model results were in agreement with field data, demonstrating that this model would be useful in describing aspects of corn mouse population dynamics. Restricting control measures to when mouse numbers reach high levels would be inadequate, because population numbers tend to increase in size after some years. In contrast, reducing vegetation cover in spring was more effective in reducing field population abundances. Despite some limitations, the model could be useful for evaluating the relationships between population dynamics and some biotic or physical environmental variables, and thus ensure more efficient use of resources in integrated pest management.     

Effect of hexaflumuron on mortality of the Western subterranean termite (Isoptera: Rhinotermitidae) during and following exposure and movement of hexaflumuron in termite groups

The effects of hexaflumuron consumption on the mortality of workers of the Western subterranean termite, Reticulitermes hesperus Banks, were observed following various exposures to a substrate treated with 14C-labeled hexaflumuron at 5 g kg(-1). Uptake of hexaflumuron by workers was rapid, peaking at approximately 280 ng hexaflumuron per termite 12 days after exposure. The onset of mortality began at day 8, with cumulative mortality reaching approximately 96% by day 45. Excretion of hexaflumuron from worker termites was rapid following various exposure periods, half-lives ranging from 2.1 to 4.7 days. Trophallaxis among worker termites was efficient, hexaflumuron levels in recipient termites approaching two-thirds of levels present in donor termites feeding continuously on hexaflumuron-treated filter paper. The effect of donor-to-recipient group ratios was negligible on the amounts of hexaflumuron transferred from donors to recipients. In laboratory tests, hexaflumuron diffused from a feeding source within 7 days. The presence of additional food sources appeared to inhibit movement of hexaflumuron. Movement of hexaflumuron by cannibalism and coprophagy occurred, but was significant only when termites were starved. Hexaflumuron also appeared to adversely affect egg development by preventing hatch. Hexaflumuron was readily transferred through termite groups, effectively suppressing laboratory populations of R hesperus. Variable efficacy in field situations employing baiting with hexaflumuron in southern California may be a consequence of sporadic feeding at bait stations, the rapid clearance of hexaflumuron from individual termites, and the difficulties in bait presentation (low foraging activity, poor bait station foraging fidelity) inherent in the foraging characteristics of the Western subterranean termite.     

Efficacy and attractiveness of zinc phosphide bait in common voles (Microtus arvalis)

BACKGROUND: Minimising the concentration of active ingredient in rodenticide bait is desirable economically and for the protection of the agroecosystem. This study aimed to identify a zinc phosphide concentration that balances palatability and efficacy for common vole (Microtus arvalis Pall.) management and to compare the attractiveness of two bait carriers. RESULTS: Bait uptake of voles was reduced by 87–98% compared with plain bait when bait contained 0.4–3.2% zinc phosphide. There was an almost 50% decrease in the uptake of zinc phosphide when the zinc phosphide concentration of bait was doubled. Red dye used in commercially available bait decreased bait consumption by 10%. Daily consumption of zinc phosphide bait on days 2 to 5 was half the consumption on the first day of exposure. In bait choice tests, wheat kernels were preferred initially, but within 12 h similar amounts of wheat‐based pellets and wheat kernels were eaten. CONCLUSIONS: According to the results from the laboratory trial, a zinc phosphide concentration of 2.1% seemed to balance uptake/efficacy best and may be most appropriate for the management of common vole populations. This concentration is substantially lower than the concentration used in many registered products. A reduced concentration of active ingredient and the use of pellet bait instead of wheat which is highly attractive for birds may have advantages for agroecosystem health when applying zinc phosphide for rodent control. © Jens Jacob, Mechthild Budde and Angela Leukers, employees of the Federal Research Centre for Cultivated Plants, Germany. Printed with permission.     

Towards a best practice methodology for the detection of Phytophthora species in soils

The genus Phytophthora contains species that are major pathogens worldwide, affecting a multitude of plant species across agriculture, horticulture, forestry, and natural ecosystems. Here, we concentrate on those species that are dispersed through soil and water, attacking the roots of the plants, causing them to rot and die. The intention of this study was to compare the soil baiting protocol developed by the Centre for Phytophthora Science and Management (CPSM) with two other baiting methods used in Australia. The aim was to demonstrate the effectiveness of each protocol for soil baiting Phytophthora species in different substrates. Three experiments were conducted: the first to test the sensitivity of each method to detect Phytophthora cinnamomi, the second to test the effect of substrate type (sand or loam), and the third to test the detection of species (P. cinnamomi, P. multivora, or P. pseudocryptogea). The specificity of different plant species baits was compared within and between the methods. Substrate type influenced isolation in all methods; however, the CPSM method was superior regardless of substrate, albeit slower than one of the other methods for one substrate. Comparing bait species between the three methods, Quercus ilex was the most attractive bait for P. cinnamomi, particularly in the CPSM method. The choice of protocol affected the isolation associated with each bait type. Overall, the multiple bait system used by CPSM was shown to provide the most sensitive and reliable detection of Phytophthora species from soil samples.     

Efficacy of attract‐and‐kill devices for the control of Ceratitis capitata

BACKGROUND: The control of Ceratitis capitata Wiedemann traditionally has relied on chemical control with organophosphate insecticides. The use of many of these substances has been banned by new European directives; therefore, the development of new control methods is essential to manage this pest. Bait sprays with spinosad, mass trapping and lure‐and‐kill techniques have been the base for new integrated pest management programmes. In this study, a 2 year field trial was conducted in two citrus areas to test the efficacy of attract‐and‐kill devices against mass trapping and spinosad‐plus‐bait treatments. RESULTS: The Magnet^® MED attract‐and‐kill device, Spintor^® treatments and mass trapping achieved good control of C. capitata populations, as confirmed by low percentages of damaged fruit in the assessments performed during the harvest period. On the other hand, fly population levels on plots treated with other attract‐and‐kill prototype devices increased more than threefold by comparison with the populations recorded in the rest of the treated plots. The same effect was observed for fruit damage, with 6–8 times less damage with Magnet^® MED and spinosad treatments, respectively, than with the attract‐and‐kill prototype devices. CONCLUSION: By using an effective attractant, conventional trapping systems can be replaced with cheaper and easier‐to‐handle attract‐and‐kill devices. The efficacy of these devices and their advantages over conventional mass trapping systems are discussed. © 2012 Society of Chemical Industry     

Efficacy of noviflumuron gel bait for control of the German cockroach, Blattella germanica (Dictyoptera: Blattellidae)-laboratory studies

The insecticidal activity of a cockroach gel bait containing a chitin synthesis inhibitor, noviflumuron, was evaluated using laboratory and field strains of the German cockroach, Blattella germanica (L.). Noviflumuron gel bait (0.01-5 mg g(-1)) caused > or = 90% nymphal mortality to laboratory and field strains of B. germanica in choice tests after 11 and 19 days of continuous exposure respectively. In 1 m x 1 m bioassay arenas, laboratory strain B. germanica population levels exposed to 5 mg g(-1) noviflumuron bait or 0.1 mg g(-1) fipronil gel bait were significantly lower than untreated population levels after 3 weeks and 1 week of exposure respectively. Various noviflumuron bait exposure periods (2, 4 and 7 weeks) caused similar population reductions, with a mean of 99.3 (+/- 0.3)% at 7 weeks. Fipronil gel bait caused 100% population reduction at 2 weeks post-exposure. The control population increased 89.0% at 7 weeks. In a simulated kitchen experiment with mixed stage laboratory populations, cockroach trap catches decreased 96.8 (+/- 2.0)% at 8 weeks in the 0.5 mg g(-1) noviflumuron bait treatment. The trap catches in the control increased 506.5 (+/- 493.7)% during the same period. Trap catch reduction by 0.1 mg g(-1) fipronil gel bait reached 100% at 4 weeks. Noviflumuron bait caused significantly lower nymph/total ratios to B. germanica populations in bioassay arenas from 2 weeks after exposure, demonstrating its effectiveness as a control agent for B. germanica with a pattern of activity similar to that expected from a chitin synthesis inhibitor.     

Efficacy of lufenuron as chemosterilant against Ceratitis capitata in field trials

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