Differential consumption of baits by pest blattid and blattellid cockroaches and resulting direct and secondary effects

Consumption was measured of three commercially available cockroach gel baits (0.01 and 0.05% fipronil and 0.6% indoxacarb) by two pest blattellid (German cockroach, Blattella germanica L., and brownbanded cockroach, Supella longipalpa Fabricius) and three pest blattid [oriental cockroach, Blatta orientalis L., American cockroach, Periplaneta americana L., and smokybrown cockroach, Periplaneta fuliginosa (Serville)] species (Dictyoptera), and direct and secondary effects were quantified. All three baits were greatly preferred for consumption over dog food; however, virtually all consumption (ca. 98%) by pest blattids was gel baits containing sugar feeding stimulants and water. Pest blattid greater preference for gel baits was probably due to their greater need for nutrients in baits due to their greater cuticular water permeability and higher metabolism than the pest blattellids. Brownbanded cockroaches had lowest percentage gel bait selection. Pest blattellids consumed greater amounts of bait per g body weight than pest blattids. Cockroaches consumed more active ingredient than needed to cause mortality; however, based on bait consumption, a 30‐g tube of gel bait potentially killed from 394 to 6 966 adult cockroaches, depending on species. Mortality for all cockroach species was faster for adults (≥3 days) than for nymphs (≥7 days); however, most brownbanded cockroaches exposed to indoxacarb survived despite consuming 1.5‐ to >3‐fold more than other baits, suggesting low enzyme production by brownbanded cockroaches and consequently lower conversion of indoxacarb into its toxic form. Besides direct mortality, German cockroaches died from indirect effects: exposure to debris from other cockroaches that had direct access to the gel baits or bait contact without ingestion. Although maximization of bait consumption is important, factors that enhance secondary mortality and contact toxicity should also be considered.     

Attractiveness of insecticide baits for cockroach control (Dictyoptera: Blattellidae): laboratory and field studies.

Several insecticide bait formulations were evaluated for their attractiveness to cockroaches in olfactometer assays in the laboratory and in trapping experiments in the field. Included in the assays were bait stations, gels, pastes, and a powder that contained one of the following active ingredients: abamectin, boric acid, chlorpyrifos, or hydramethylnon. There were significant differences among the baits in their attractiveness to the German cockroach, Blattella germanica (L.). In trapping experiments, Avert powder (abamectin), Maxforce station and gel, and Siege gel (all hydramethylnon) were consistently attractive to B. germanica adults and nymphs. Laboratory olfactometer assays with adult males confirmed these results and showed that nymphs were as responsive as males whereas females were less responsive. Our bioassays also demonstrate that attractiveness of bait can be dramatically affected by the age of the bait. One week of aging significantly reduced the attractiveness of Avert powder in both laboratory and field assays. Aging, however did not diminish the attractiveness of Maxforce gel, indicating that the formulation may be critical for retention of attractiveness of baits. Baits that were most attractive to the German cockroach were also the most attractive to nymphs and adults of the brownbanded cockroach, Supella longipalpa (F.).     

Laboratory and field performance of an indoxacarb bait against German cockroaches (Dictyoptera: Blattellidae)

Experimental indoxacarb powder and gel baits were evaluated in the laboratory, and a gel bait was evaluated in subsequent field studies against the German cockroach, Blattella germanica (L.). In continuous exposure tests, LT50 values were 1.90 and 1.10 d for 0.25 and 1% indoxacarb powder baits, respectively. However, 0.25% indoxacarb gel bait had an LT50 value of 0.68 d, similar to a 0.05% abamectin gel bait formulated with the same bait base. There was no difference in toxicity between fresh and 7-d-old gel bait deposits. A pyrethroid-resistant strain of German cockroaches was significantly resistant to both abamectin and indoxacarb gel baits. Gel bait contained approximately 40% water, desiccated rapidly at 25-28 degrees C and 30-45% RH, but did not rehydrate when held at 56.7% RH for 3 d. Powder indoxacarb baits contained <1% water and did not desiccate or gain water. Indoxacarb gel bait (0.25%) was relatively nonrepellent (approximately 30%) and had positive maximum performance index values (approximately 100) in Ebeling choice box experiments. In field experiments in cockroach-infested kitchens, the 0.25% indoxacarb gel bait significantly reduced visual counts of German cockroaches approximately 74% at 3 d and >95% at 14 d. Indoxacarb baits are toxic, relatively nonrepellent, and can significantly reduce German cockroach populations.     

Contamination affects the performance of insecticidal baits against German cockroaches (Dictyoptera: Blattellidae)

The effects of contamination of insecticidal bait formulations, by using mint oil and silica aerogel, were evaluated in a series of laboratory experiments against the German cockroach, Blattella germanica (L.). Bait consumption at 3 d for uncontaminated baits ranged from 0.01 g for Avert dust to 0.399 g for Combat dry bait with hydramethylnon presented in a station. LT50 values for uncontaminated gel bait deposits ranged from 0.4 d for PreEmpt containing imidacloprid to 4.1 d for Maxforce containing hydramethylnon. As a group, significantly more gel bait was consumed than solid formulations even when both formulations had similar concentrations of the same active ingredient. As a result, gel baits were significantly more toxic than solid formulations. Application of mint oil directly to bait deposits significantly decreased bait consumption and increased overall LT50 values. When bait formulation types were examined individually, there was no difference in consumption or toxicity between contaminated and uncontaminated gel formulations. Contaminated solid baits, however, had significantly greater LT50 values and less consumption than uncontaminated solid baits. Gel formulations probably absorbed the contaminants and removed them from the surface of the bait deposits resulting in normal bait consumption and toxicity. Gel and solid bait deposits, inside plastic exposure stations or alone with no station and placed onto mint oil-contaminated substrates, had significantly lower bait consumption and greater LT50 values than baits placed on uncontaminated substrates. Contamination of a baited area is more likely than contamination of just the bait deposit and therefore a more realistic test of the effects of contamination on bait performance. The importance of contamination to the performance of cockroach baits is discussed.     

Improving liquid bait programs for Argentine ant control: bait station density

Argentine ants, Linepithema humile (Mayr), have a positive effect on populations of mealybugs (Pseudococcus spp.) in California vineyards. Previous studies have shown reductions in both ant activity and mealybug numbers after liquid ant baits were deployed in vineyards at densities of 85-620 bait stations/ha. However, bait station densities may need to be <85 bait stations/ha before bait-based strategies for ant control are economically comparable to spray-based insecticide treatments-a condition that, if met, will encourage the commercial adoption of liquid baits for ant control. This research assessed the effectiveness of baits deployed at lower densities. Two field experiments were conducted in commercial vineyards. In experiment 1, baits were deployed at 54-225 bait stations/ha in 2005 and 2006. In experiment 2, baits were deployed at 34-205 bait stations/ha in 2006 only. In both experiments, ant activity and the density of mealybugs in grape fruit clusters at harvest time declined with increasing bait station density. In 2005 only, European fruit lecanium scale [Parthenolecanium corni (Bouché)] were also present in fruit clusters, and scale densities were negatively related to bait station density. The results indicate that the amount of ant and mealybug control achieved by an incremental increase in the number of bait stations per hectare is constant across a broad range of bait station densities. The results are discussed in the context of commercializing liquid ant baits to provide a more sustainable Argentine ant control strategy.     

Comparisons of toxic baits for controlling the cockroach, Blattella germanica: attractiveness and feeding stimulation

Female German cockroaches, Blattella germanica (L.) (Dictyoptera: Blattellidae) and nymphs (stages 1, 3 and 6) were used to test the attractiveness and the feeding stimulation of several commercial gel formulations of insecticide food baits in laboratory binary choice tests. The four toxic gel baits tested were: 'Avert' (0.05% abamectin=avermectin B1), 'Drax' (33.3% boric acid), 'Goliath' (0.05% fipronil) and 'Maxforce' (2.15% hydramethylnon). The attractiveness of a bait was estimated by the number of cockroaches that chose it first, and by their tendency to change to it secondarily. Feeding stimulation was estimated by the mean duration of feeding bouts and total duration of food intake. Variability of these factors was assessed in relation to age of cockroaches and to age of baits. With a few exceptions, cockroach age did not affect performance in any of these tests. Attractiveness to B. germanica ranked 'Goliath' gel higher than 'Avert', 'Drax' and 'Maxforce' gels, whether or not the active ingredient fipronil was present in 'Goliath' gel. Feeding stimulation ranked 'Avert' and 'Maxforce' gels higher than 'Goliath' gel, and 'Drax' gel was inferior. With ageing up to 3 months, the feeding stimulation power of 'Goliath' and 'Maxforce' gels increased, whereas that of 'Avert' fluctuated. Assuming that all types of bait effectively kill cockroaches once ingested, these results illustrate the importance of behavioural observations on bait efficiency and show that ranking of these different food baits varies in relation to the parameter analysed.     

Use of Rhodamine B to Reveal Patterns of Interspecific Competition and Bait Acceptance in Raccoons

Abstract: Passive treatment of raccoons (Procyon lotor) through distribution of vaccine-laden baits recently has emerged as a potential solution to address health and economic conflicts associated with raccoon rabies and may have applications in the management of other pathogens carried by raccoons if frequent bait deployments are used. Consumption of baits by nontarget species reduces the efficiency in which baits can be used to manage wildlife disease, although no study has explicitly evaluated the influence of bait competitor density on the ability to treat raccoons. Our objectives were to use the biomarker Rhodamine B (RB) to 1) evaluate patterns of raccoon bait acceptance as a function of competition with Virginia opossums (Didelphis virginiana), the dominant bait competitor; 2) characterize attributes of opossum bait acceptance to improve efficiency of raccoon treatment; and 3) evaluate the effect of repeated bait exposure on rates of bait acceptance as may be required in the management of wildlife disease issues beyond rabies. Identifying bait consumption by individuals based on the presence of an RB mark in a sample of whiskers, we used logistic regression to model raccoon and opossum bait acceptance as a function of bait availability, previous exposure to baits, demographic attributes, and an index of time spent in the baited area (residency index). For both raccoons and opossums, the best measure of bait availability was the variable number of baits per opossum. The most parsimonious logistic regression model for raccoon bait acceptance included the variables baits per opossum, exposure history, and residency index. The strength of the variable baits per opossum relative to competing measures of bait availability indicated bait consumption by opossums significantly limited the ability to treat raccoons. The most parsimonious model for opossum acceptance was composed of the variables baits per opossum, sex, weight, residency index, baits per opossum X sex, and weight X sex. Patterns of opossum bait acceptance likely were driven by effects of bait availability and sex-dependent differences in movement. Our results call attention to the importance of bait competition in limiting the ability to effectively treat raccoon populations through distribution of baits and suggest managers incorporate information on density of bait competitors, particularly opossums, in allocation of baits.     

A Behaviorally-Explicit Approach for Delivering Vaccine Baits to Mesopredators to Control Epizootics in Fragmented Landscapes

Despite the widespread use of aerial baiting to manage epizootics among free-ranging populations, particularly in rabies management, bait acceptance and seroconversion rates often are lower than required to eliminate spread of disease. Our objectives in this study, therefore, were to evaluate the performance of stratified bait distribution models derived from resource selection functions (RSF) on uptake of placebo rabies baits by raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana), as well as the probability of bait uptake as a function of proximity to bait distribution areas in fragmented agricultural ecosystems. Among 478 raccoons and 108 opossums evaluated for presence of Rhodamine B (RB) across 8 sites, only 26% of raccoons and 20% of opossums exhibited marking consistent with bait consumption 14–24 days post-baiting. The effective area treated, based on 90% kernel density estimators of marked individuals, ranged from 99–240 ha larger than bait distribution zones, with RB marked individuals captured up to 753m beyond the bait zone. Despite incorporation of RSF data into bait distribution models, no differences in uptake rates were observed between treatment and control sites. These data likely reflect the underlying constraints imposed by the loss and fragmentation of habitat on animal movement in heterogeneous landscapes, forcing individuals to optimize movements at coarse (i.e., patch-level) rather than fine spatial scales in highly fragmented environments. Our data also confirm that the probability of bait acceptance decreases with increasing distance from bait zone interiors, even within the zone itself. Thus, although bait acceptance was confirmed beyond bait zone boundaries, the proportion of vaccinated individuals may comprise a small minority of the population at increasing distances from baiting interiors. These data suggest focal baiting creates a buffered area of treated individuals around bait zones or bait stations, but repeated treatments may be needed to achieve sufficient uptake to eradicate disease.     

Cost-effectiveness of integrated pest management compared with insecticidal spraying against the German cockroach in apartment buildings

This study assessed the cost and effectiveness of an integrated pest management (IPM) program using hydramethylnon gel baits compared with conventional spraying for controlling the German cockroach, Blattella germanica (L.) (Blattodea: Blattellidae), in two residential buildings in Yasuj, Iran. The IPM approach was based on educational programs using pamphlets, posters and lectures, sanitation using vacuuming and application of hydramethylnon gel baits. Conventional approach used cypermethrin (10% EC) on baseboard and cracks-and-crevices. Sticky traps were used as tools for monitoring cockroach population densities. The IPM approach reduced (943%) the rate of insecticide application compared to the conventional spray. Cockroach populations in the IPM treatment were significantly reduced from an average of 12.2 ± 3.01 cockroaches per unit before treatment to zero cockroach per unit by week four and thereafter. Cockroach populations in the conventional spray treatment were reduced from an average of 11.5 ± 4.43 cockroaches per unit before treatment to an average of 3.4 ± 0.99 cockroach per unit after 11 weeks of post treatment. The IPM treatment improved 100% of infested units compared to 78% for spray treatment to obtain a clean level of infestation (< 1cockroach per trap per unit). The results suggest that the intervention by IPM using hydramethylnon gel baits significantly reduced cockroach infestation compared to cypermethrin spray throughout the 11 weeks of post-treatment period. However, within the study period, the IPM system involving gel baits, educational program and sanitation was 363.2% more expensive than the conventional method.     

Acceptance of baits for delivery of oral rabies vaccine to raccoons.

During 1993-96 the Ontario Ministry of Natural Resources (Canada) implemented a research project to evaluate the efficacy of three candidate baits to deliver oral rabies vaccine to wild raccoons (Procyon lotor). Extensive field testing revealed that raccoon acceptance of Sugar-Vanilla baits (SV) at densities of 200/km2 and 400/km2, hand-placed in urban habitats of Scarborough (Ontario) during 1993, was 74% and 82%, respectively. Raccoon density in those areas averaged 11/km2. Aerial placement of SV baits in rural habitats in Barrie (Ontario) during 1993 and 1994, yielded raccoon acceptance levels of 58% with a density of 100 baits/km2, 59% at 75 baits/km2, and 47% at 50 baits/km2. Raccoon acceptance of SV baits was significantly lower in areas baited at the density of 50/km2. Acceptance of Cheese baits (CH) at a density of 75 baits/km2 was 52%. During 1996 trials in Barrie, modified SV baits with blister packs protruding through the matrix yielded raccoon acceptance values of 51% at a bait density of 54/km2, whereas acceptance of regular SV baits was 39% at a density of 51 baits/km2. Pooling of bait acceptance data for all years revealed that bait acceptance was highest for adult male raccoons. Raccoon density in rural habitats (Barrie, Ontario) where the studies took place, averaged 11-13/km2. Puncture and impact testing of blister packs in baits suggested that they would adequately serve as a vehicle to contain oral rabies vaccine for delivery to raccoons via baits.     

The influence of density on frequency-dependent food selection: a comparison of four experiments with wild birds

We compare the results of four experiments, conducted at different times and with different protocols, that explored the relationship between frequency-dependent selection and prey density in wild birds feeding on artificial populations of coloured baits. One (experiment 4) used pastry baits that differed only in the presence or absence of a red stripe, and this experiment provided no evidence for any kind of selective behaviour. The other three experiments used green and brown baits, and they all provided evidence for a trend towards increasing anti-apostatic selection with high densities (>100 baits m^–2). However, one of these (experiment 3) provided no evidence for frequency-dependent selection at low densities (0.5–20 baits m^–2), while the other two experiments concurred in suggesting a trend towards increasing apostatic selection with low densities (down to 2 baits m^–2). Together, these experiments both support and qualify the published findings of experiment 1 that frequency- dependent selection by wild birds on bait populations is modified by density. Experiment 4 indicates that frequency-dependent selection may break down entirely if bait types are too similar, while experiment 3 indicates that some details of this trend with density will depend either on the protocol used or on exogenous changes in the birds’ feeding behaviour. Received: 1 September 1999 / Accepted: 22 March 2000     

Wild carnivore acceptance of baits for delivery of liquid rabies vaccine

A series of experiments are described on the acceptance, by red foxes (Vulpes vulpes) and other species, of two types of vaccine-baits intended to deliver liquid rabies vaccine. The baits consisted of a cube of sponge coated in a mixture of tallow and wax, or a plastic blister-pack embedded in tallow. All baits contained tetracycline as a biological marking agent: examination of thin sections of carnivore canines under an ultraviolet microscope revealed a fluorescent line of tetracycline if an individual had eaten baits. Baits were dropped from fixed-wing aircraft flying about 100 m above ground at approximately 130 km/h. Flight lines followed the edges of woodlots midway between parallel roads. Baits were dropped at one/sec, resulting in one bait/36 m on the ground, or 17 to 25 baits per km2. Crows (Corvus brachyrhynchos) removed many baits, but did not appear to lower the percent of the fox population which took bait. Dropping baits only into corn and woodland to conceal baits, to reduce depredation by crows, reduced acceptance by foxes. Acceptance by foxes ranged between 37 and 68%. Meat added as an attractant did not raise acceptance. Presence, absence, color and perforations of plastic bags did not alter bait acceptance. Dispersal by juvenile foxes probably lowered the estimates of bait acceptance. It took 7 to 17 days for 80% (n = 330) of foxes to eat their first bait. The rapidity with which foxes picked up their first bait appeared more affected by unknown characteristics of years or study areas than by experimental variables. Skunks (Mephitis mephitis) and raccoons (Procyon lotor) also ate these baits, but acceptance was lower. Small mammals contacted baits, but rarely contacted the vaccine, which had the potential for vaccine-induced rabies in some species. Aerial distribution of baits was more cost-effective than ground distribution as practiced in Europe. This system has potential for field control of rabies, although higher acceptance will be desirable.     

Testing baits to control Argentine ants (Hymenoptera: Formicidae) in vineyards

Liquid baits were evaluated for control of the Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae), and associated mealybug and soft scale pests in California vineyards. In 2003, liquid baits with small doses ofimidacloprid, boric acid, or thiamethoxam dissolved in 25% sucrose water resulted in lower ant and mealybug densities and fruit damage, compared with an untreated control. Similar treatments in a soft scale-infested vineyard showed only a reduction of ant density and fruit infestation in only the boric acid and thiamethoxam treatments. In 2004, commercial and noncommercial formulations of liquid baits reduced ant densities in three separate trials, but they had inconsistent effects on mealybug densities and fruit infestation; granular protein bait had no effect. Using large plots and commercial application methodologies, liquid bait deployed in June resulted in lower ant density and fruit infestation, but it had no effect on mealybug density. Across all trials, liquid bait treatments resulted in lower ant density (12 of 14 trials) and fruit damage (11 of 14 sites), presenting the first report of liquid baits applied using commercial methodologies that resulted in a reduction of ants and their associated hemipteran crop damage. For commercialization of liquid baits, we showed that any of the tested insecticides can suppress Argentine ants when properly delivered in the crop system. For imidacloprid, bait dispensers must be protected from sunlight to reduce photodegradation. Results suggest that incomplete ant suppression can suppress mealybug densities. However, after ant populations are suppressed, there may be a longer period before hemipteran populations are effectively suppressed. Therefore, liquid baits should be considered part of a multiseason program rather than a direct, in-season control of hemipteran pest populations.     

Hunger in red imported fire ants and their behavioral response to two liquid bait products

To help manage red imported fire ant, Solenopsis invicta Buren, invasion, several types of pest management systems have been developed, including baits. To accurately test liquid bait effectiveness in the laboratory, we determined that starvation time of 96 h is required for laboratory fire ants to simulate foraging ants in the field. We measured density and viscosity of two commercial baits and 20% sugar water at 25 degrees C and then compared amount of material consumed per ant at these physical properties. Mean densities of 20% sugar water, Dr. Moss, and Terro were 1.051, 1.287, and 1.354 g/ml, respectively, and viscosity of each bait treatment varied in the same order but more drastically (1.7, 32, and 400 centipoises, respectively). Field and laboratory studies demonstrated that bait acceptability may be affected by toxicant and physical properties. Baits that are more dense have more mass per volume and may cause the ant to cease feeding with a lower crop load than when they feed on sugar water. Ants that feed on formulated baits exhibit feeding behaviors different from those that occur when feeding on sugar water. At first glance, one might conclude that the difference is because of the toxicant, but our findings suggest that physical properties of baits may be a factor in this change in feeding behavior.     

Iophenoxic Acid as a Long-Term Marker for Wild Boar

ABSTRACT Chemical markers are increasingly used to investigate consumption of baits used to deliver vaccines, toxicants, and contraceptives. We evaluated whether ethyl-iophenoxic acid (Et-IPA) and propyl-iophenoxic acid (Pr-IPA) can be used as long-lasting systemic bait markers for wild boar (Sus scrofa). We presented captive wild boar with baits treated with either Et-IPA or Pr-IPA at 5 mg/kg (low dose), 10 mg/kg (medium dose), and 20 mg/kg (high dose) of body weight. We collected serum from each boar at 5 time points: 5 days, 3 weeks, 6 weeks, 11 weeks, and 39 weeks following ingestion of iophenoxic acid-treated baits. We detected both Et-IPA and Pr-IPA for ≥39 weeks after ingestion. Throughout the trial, the Et-IPA we found in serum was proportional to the amount eaten. At each time point, animals in the high-dose group had significantly more Et-IPA than animals in the low-dose group. We concluded that both compounds can be used as long-lasting markers in wild boar and that Et-IPA can also be employed as quantitative marker to indicate multiple bait uptake. Both compounds have potential applications in the context of vaccination, fertility, and population control campaigns, where baits are used to deliver pharmaceuticals, and in behavioral studies to establish spatial and temporal patterns of bait uptake.     

Influence of toxic bait type and starvation on worker and queen mortality in laboratory colonies of Argentine ant (Hymenoptera: Formicidae)

The efficacy of toxic baits should be judged by their ability to kill entire ant colonies, including the colony queen or queens. We studied the efficacy of four toxic baits to the Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae). These baits were Xstinguish that has the toxicant fipronil, Exterm-an-Ant that contains both boric acid and sodium borate, and Advion ant gel and Advion ant bait arena that both have indoxacarb. Experimental nests contained 300 workers and 10 queen ants that were starved for either 24 or 48 h before toxic bait exposure. The efficacy of the toxic baits was strongly influenced by starvation. In no treatment with 24-h starvation did we observe 100% worker death. After 24-h starvation three of the baits did not result in any queen deaths, with only Exterm-an-Ant producing an average of 25% mortality. In contrast, 100% queen and worker mortality was observed in colonies starved for 48 h and given Xstinguish or Exterm-an-Ant. The baits Advion ant gel and Advion ant bait arena were not effective against Argentine ants in these trials, resulting in <60% mortality in all treatments. Because of the strong influence of starvation on bait uptake, control efficacy may be maximized by applying bait when ants are likely to be starved. Our results suggest queen mortality must be assessed in tests for toxic bait efficacy. Our data indicate that of these four baits, Xstinguish and Exterm-an-Ant are the best options for control of Argentine ants in New Zealand.     

Exposure time of oral rabies vaccine baits relative to baiting density and raccoon population density

Oral rabies vaccination (ORV) baiting programs for control of raccoon (Procyon lotor) rabies in the USA have been conducted or are in progress in eight states east of the Mississippi River. However, data specific to the relationship between raccoon population density and the minimum density of baits necessary to significantly elevate rabies immunity are few. We used the 22-km2 US National Aeronautics and Space Administration Plum Brook Station (PBS) in Erie County, Ohio, USA, to evaluate the period of exposure for placebo vaccine baits placed at a density of 75 baits/km2 relative to raccoon population density. Our objectives were to 1) estimate raccoon population density within the fragmented forest, old-field, and industrial landscape at PBS: and 2) quantify the time that placebo, Merial RABORAL V-RG vaccine baits were available to raccoons. From August through November 2002 we surveyed raccoon use of PBS along 19.3 km of paved-road transects by using a forward-looking infrared camera mounted inside a vehicle. We used Distance 3.5 software to calculate a probability of detection function by which we estimated raccoon population density from transect data. Estimated population density on PBS decreased from August (33.4 raccoons/km2) through November (13.6 raccoons/km2), yielding a monthly mean of 24.5 raccoons/km2. We also quantified exposure time for ORV baits placed by hand on five 1-km2 grids on PBS from September through October. An average 82.7% (SD = 4.6) of baits were removed within 1 wk of placement. Given raccoon population density, estimates of bait removal and sachet condition, and assuming 22.9% nontarget take, the baiting density of 75/ km2 yielded an average of 3.3 baits consumed per raccoon and the sachet perforated.     

A study of techniques for the distribution of oral rabies vaccine to wild raccoon populations

This study evaluates a technique for delivering an oral rabies vaccine to wild raccoon (Procyon lotor) populations. Various baits and attractants were first tested on caged raccoons and baiting trials were then conducted in two distinct physiographic regions of Virginia (USA), the coastal plain and the Piedmont plateau. Raccoon population density studies preceded the field trials. Each polyurethane sponge bait distributed contained approximately 200 mg tetracycline as a tissue biomarker, and was presented in an outer bag with a fish-based attractant. Baits were frozen until used and distributed from an aeroplane throughout two 4-km2 sites in each region. One site received 450 baits/km2 and the other 120 baits/km2. Postbaiting evaluation included the direct observation of baits in the field and the examination of teeth and bone from trapped and hunted animals for evidence of the biomarker. Between 30% and 73% of the captured animals showed evidence of bait consumption. The proportion of animals with evidence of bait uptake changed when areas adjacent to the actual baiting site were included. The percentage of animals taking baits was not related to the density of baits that were distributed.     

Management of a German cockroach population with a juvenoid bait formulation: an experiment in residential buildings

Baits including 0.1% of ethyl 2-(4-((1,4-dioxaspiro [4.5]dec-6-yl) methyl) phenoxy) ethylcarbamate were applied in two buildings containing 46 apartments with various degrees of infestation of the German cockroach, Blattella germanica (L.). During a yearly experiment, generally 8 baits were placed in each apartment and replenished monthly at which time cockroach population density, demographic structure, and percentage of morphologically deformed adults were determined from specimens captured by stickytrap sampling. Initial growth of the cockroach population observed during the first two months after deposition of the baits was followed by an asymptotical decrease. Only 2.5% of the initial population remained at the end of the experiment. Although adults with twisted wings (sterile) constituted only 70% of the total adult catches, the decrease of the nymph/adult ratio from 2.9 to 0.7 indicated a far more profound inhibitory effect on cockroach reproduction. This study shows that baits might be an efficient alternative to juvenoid formulations currently in use for control of the German cockroach.     

Effectiveness of methoprene-impregnated baits in the control of Monomorium pharaonis ant populations infesting health establishment and households

The use of baits consisting of dried egg yolks and impregnated with 0.5% of methoprene, loosely applied twice within 8-12 days at the rate of 1 g of bait per 3-6 m2 of floor surface area at each application was found to result consequently in a complete eradication of M. pharaonis ant populations in two medium-size health establishments and in one apartment house. Under more favorable conditions in another health establishment the use of methoprene-impregnated baits applied twice at the average dose of 1 g per as many as 46 m2 floor area proved equally effective in ensuring permanent eradication of ants. Providing that all colonies on the premises can be affected by bait a complete eradication of ants can be expected within 100 days after the first application of bait.