Biodegradable hydrogel insect bait formulation

Abstract

An insect bait includes a hydrogel substrate and a formulation on the hydrogel substrate. The formulation includes glycerol and boric acid. Preparing an insect bait includes preparing a conditioning solution with an active ingredient and hydrating a hydrogel substrate with the conditioning solution.

Description

BIODEGRADABLE HYDROGEL INSECT BAIT FORMULATIONCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 631,704 filed on April 9, 2024, which is hereby incorporated by reference herein in its entirety.STATEMENT OF GOVERNMENT SUPPORT

[0002] This invention was made with government support under NR233A750011G023 awarded by the Natural Resources Conservation Service. The government has certain rights in the invention.TECHNICAL FIELD

[0003] This invention relates to a biodegradable hydrogel insect bait formulation.BACKGROUND

[0004] Ants are common insect pests in urban, agricultural, and natural settings. In agricultural areas, ants can interfere with natural biocontrol by tending honeydew-producing pests such as aphids, whiteflies, mealybugs, and scales, protecting them from their natural enemies to more fully benefit from the honeydew they secrete, thereby promoting pest outbreaks that can negatively affect tree health and crop production. In natural areas, invasive ants, often facilitated by these mutualisms with honeydew-producing hemipterans, are frequent threats to native invertebrate and vertebrate biodiversity. Insecticide sprays, liquid baits, and hydrogels are among the most common control options for ants around structures and agricultural areas.SUMMARY

[0005] This disclosure describes a biodegradable hydrogel insect bait formulation that includes a sugar and an active ingredient (e.g., boric acid) and can optionally include a humectant or moisturizing agent (e.g., glycerol). One example of a suitable sugar is sucrose. In some cases, the formulation includes a surfactant. The surfactant can help solubilize an oil-based substance (e.g., an essential oil or other substance that functions as an herbicide or insect repellant). This hydrogel insect bait formulation is effective for sugar-loving ants (e.g., ants ofgenera Pheidole, Nylanderia, Brachymyrmex, Solenopsis, Paratrechina, Cremcitogaster), nonsugar-loving ants, and fire ants. Examples of ants that respond to the bait include the outdoor- occurring longlegged ant, Anoplolepis gracilipes. and the indoor-occurring ghost ant, Tapinoma melanocephahim .

[0006] In a first general aspect, an insect bait includes a hydrogel substrate and a formulation on the hydrogel substrate. The formulation includes glycerol and boric acid.

[0007] Implementations of the first general aspect can include one or more of the following features. In some cases, the hydrogel substrate includes alginate. In certain cases, the hydrogel substrate includes polyacrylamide. The formulation can include 10% to 30% vol / vol of glycerol or 20% to 30% vol / vol of glycerol. In some implementations, the formulation includes 1 wt% to 5 wt% of the boric acid. The formulation can further include a sugar. In some cases, the sugar includes sucrose. In certain implementations, the formulation includes 20% to 30% w / vol sucrose. The formulation can further include a surfactant. In one example, the formulation further includes an oil-based substance. The oil-based substance can include an essential oil.

[0008] In a second general aspect, an insect bait station includes the insect bait of the first general aspect.

[0009] In a third general aspect, preparing an insect bait includes preparing a conditioning solution with an active ingredient and hydrating a hydrogel substrate with the conditioning solution.

[0010] Implementations of the third general aspect can include one or more of the following features. In some cases, the conditioning solution includes sucrose and glycerol. The conditioning solution can include 20% to 30% w / vol sucrose. In certain implementations, the conditioning solution includes 10% to 30% vol / vol glycerol or 20% to 30% vol / vol glycerol. The active ingredient can include boric acid. Suitable materials for the hydrogel substrate can include alginate, polyacrylamide, or both.

[0011] The details of one or more embodiments of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.BRIEF DESCRIPTION OF DRAWINGS

[0012] FIGS. 1A-1F show number (mean ± standard error of the mean; n = 4) of longlegged ants feeding on hydrogel beads containing different concentrations of glycerol over time (minutes). FIG. 1 A uses fresh hydrogels. FIG IB uses hydrogels aged for 3 days. FIG. 1C uses hydrogels aged for 7 days. FIG. ID uses hydrogels aged 14 for days. FIG. IE uses hydrogels aged for 28 days. FIG. IF uses hydrogels aged for 98 days. For each time point, symbols labeled with same letters are not significantly different at p = 0.05 (Tukey’s honestly significant difference (HSD) test).

[0013] FIG. 2 shows an example of a replicate of hydrogel attractiveness assessment using solid calcium alginate hydrogel beads aged for 28 days, showing variation in water retention, texture, and attractiveness to longlegged ants among formulations containing 0%, 10%, 20%, or 30% glycerol. Photo is taken 30 minutes post introduction to test arena.

[0014] FIG. 3 shows an example of a replicate of hydrogel attractiveness assessment using solid calcium alginate hydrogel beads aged for 28 days, showing variation in water retention, texture, and attractiveness to ghost ants among formulations containing 0%, 10%, 20%, or 30% (vol / vol) glycerol. The image was taken 30 minutes after introduction to the test arena.

[0015] FIG. 4 shows a diurnal course of longlegged ant foraging activity (mean number of ants ± standard error of the mean attracted to hydrogels) and air temperature for the period of 0700h to 21 OOh.

[0016] FIG. 5 A shows longlegged ant foraging activity (mean ± standard error of the mean number of ants in monitoring traps) at field plots treated with standard hydrogel sucrose baits containing 2% boric acid (wt %). FIG. 5B shows longlegged ant foraging activity (mean ± standard error of the mean number of ants in monitoring traps) at field plots treated with improved hydrogel sucrose baits containing 20% glycerol and 2% boric acid. Arrows indicate the timing of the hydrogel bait treatment. Data with different letters within a treatment are significantly different at p = 0.05 (Tukey’s honestly significant difference (HSD) test). “Pre” indicates pre-treatment and “Wk” indicates week post-treatment.

[0017] FIG. 6A shows ghost ant foraging activity (mean ± standard error of the mean number of ants in monitoring traps) at domestic sites treated with standard hydrogel sucrose baits containing 2% boric acid. FIG. 6B shows ghost ant foraging activity (mean ± standard error of the mean number of ants in monitoring traps) at domestic sites treated with hydrogel sucrosebaits containing 20% glycerol and 2% boric acid. Arrows indicate the timing of the hydrogel bait treatment. Data with different letters within a treatment are significantly different at p = 0.05 (Tukey’s honestly significant difference (HSD) test). “Pre” indicates pre-treatment and “Wk” indicates week post-treatment.DETAILED DESCRIPTION

[0018] This disclosure describes hydrogel insect baits including a hydrogel substrate and a formulation on the hydrogel substrate. In one example, the formulation includes glycerol and boric acid. In some examples, the formulation includes a sugar (e.g., sucrose). The hydrogel substrate can include alginate (e.g., alginate beads). The hydrogel insect bait is a controlled- release matrix delivering liquid baits for longer periods, which can in turn attract and manage higher numbers of ants. These hydrogel insect baits demonstrate strong efficacy in ant reduction for longlegged ants and ghost ants throughout 8-week assessment periods when compared to pretreatment levels. These baits maintained lower ant populations for a longer period when compared to other hydrogel baits. Furthermore, if reapplication of hydrogels is needed for heavily infested sites, these hydrogel baits can extend the suppression period between applications. They are also cost-effective and are more convenient than other liquid bait stations, as they do not require frequent maintenance. Thus, these hydrogels provide an effective and sustainable approach in sugar-feeding ant integrated pest management programs in both urban and outdoor settings.

[0019] Alginate beads hydrated in conditioning solutions are used to produce hydrogel baits containing 20% to 30% (e.g., 25%) (w / vol) of sucrose and either no glycerol (standard hydrogel bait) or 10% to 30% (e.g., 10%, 20%, or 30%) (vol / vol) of glycerol (improved hydrogel baits). As used herein, “standard” formulations (e.g., hydrogel beads or bait) refer to formulations without glycerol, and “improved” formulations (e.g., hydrogel beads or bait) refer to formulations with glycerol. Other suitable hydrogel beads include polyacrylamide hydrogels (e.g., synthetic polyacrylamide). The hydrogel can be in the form of beads (e g., in a range of sizes). The hydrogel can be produced in a dry powder form, treated with the insect bait formulation, and rehydrated before use (e.g., to reduce product shipping rate). In some cases, the hydrogel can be a potential nutrient source and a carrier for an herbicide or insect-repellent carrier. In one example, the hydrogel is impregnated with one or more volatile compounds (e.g.,one or more essential oils) that function as a repellant. The hydrogel can be used with or without bait stations.

[0020] The baits are evaluated to determine water loss rates, attractiveness towards the two ant species, and field efficacy against the two species when formulated with 1% to 5% boric acid (e g., 2%) (wt %) and deployed at peak foraging times. Improved hydrogel baits containing 20% glycerol have lower water loss rates as compared to standard baits starting at 72 hours and 12 hours for indoor and outdoor conditions, respectively. In the laboratory, standard hydrogel baits lose their attractiveness to ants after day 14, whereas the hydrogel baits described herein remain attractive to ants after day 98. Due at least in part to their greater water retention and extended palatability, a single application of the hydrogel baits described herein reduce ant activity relative to pre-treatment levels from week 2 through week 8 post-treatment, indicating substantial residual activity. In comparison, a single application of standard hydrogel baits also reduce ant activity by 2 weeks post-treatment, but ant numbers gradually rebound by 4 and 6 weeks posttreatment for both the longlegged ant and the ghost ant, respectively. Hydrogel baits containing sucrose, glycerol, and boric acid can effectively target and manage sugar-feeding ants with fewer applications, reducing cost and insecticide in the environment.

[0021] Assessments in Examples 1 and 2 are conducted to evaluate an alginate hydrogel bead containing glycerol by determining its water loss rate under outdoor and laboratory conditions and its attractiveness to longlegged ants and ghost ants. Another strategy for enhancing hydrogel performance in the field includes applying the baits at the ants’ peak foraging time. Assessments in Example 3 are conducted to determine the peak foraging time of field populations of longlegged ants. Assessments in Example 4 are conducted to compare the field efficacy of a boric acid active ingredient delivered with standard (no glycerol) or improved hydrogel baits (glycerol added) against longlegged ants in natural environments (treated at their peak foraging time) and ghost ants in urban environments.

[0022] Rates of water loss measured under indoor and outdoor conditions indicate statistically significant, but modest, differences between standard and improved hydrogels. However, this metric does not fully capture the differences in hydrogel behavior that accompanies the addition of glycerol. In some cases, as water evaporates from aging hydrogels, ants can take a longer time to feed from them and ingest less bait solution. With enough desiccation, standard hydrogels become hard, opaque, and unattractive to ants. This occurs withthe standard alginate beads after aging approximately 7 days to 14 days under laboratory conditions. In contrast, hydrogels containing glycerol retain a flexible, gelatinous consistency, as well as a clear appearance, even after losing approximately 90% of their water content. As a result, alginate beads with glycerol remain attractive to ants, and continue to elicit feeding, even after aging for 98 days under laboratory conditions. Glycerol concentrations of 30% or higher may reduce palatability to ants in fresh hydrogel beads, but hydrogels formulated with 20% or less glycerol exhibit little to no reduction in palatability relative to fresh standard beads, as shown, for example, in FIG. 1A.

[0023] Rates of water loss can be further reduced by deploying hydrogels in shaded locations when possible, and by coordinating treatment times with peak foraging activity of the target species. Longlegged ants are a largely nocturnal species whose activity increases with higher relative humidity and lower temperature. Foraging peaks at sites in the morning and evening hours. Deploying hydrogels at these times increases the probability that more ants will discover and feed on them, and share consumed bait with nestmates through trophallaxis before they lose their attractiveness. Early morning or late evening treatment of nocturnal ant species also takes advantage of the more humid environmental conditions occurring at these times.

[0024] The longer duration of attractiveness of improved hydrogel beads translates into better suppression of both longlegged ants and ghost ants in field and domestic settings, respectively. In both cases, the efficacy of improved hydrogels containing 20% glycerol to standard hydrogels containing no glycerol is compared, using 25% sucrose as the attractant and 2% boric acid as the active ingredient. No apparent repellency to this formulation by either ant species is observed. The assessments show that for both species, a single treatment of improved hydrogel baits is sufficient to provide statistically significant reductions in ant numbers at 2 weeks post-treatment and substantial (e.g., 64%) reductions at 3 weeks to 4 weeks post-treatment relative to pre-treatment levels, despite the high densities of ants at some sites. Ant numbers remained at similarly reduced levels until at least 8 weeks post-treatment. In comparison, standard hydrogels lacking glycerol also reduces ant numbers by 2 weeks post-treatment, but ant numbers begin rebounding by 4 weeks to 6 weeks post-treatment and, especially in the case of longlegged ants, became similar to pre-treatment levels by 8 weeks post-treatment.

[0025] The results suggest that one application of improved hydrogel baits formulated with boric acid can be sufficient to achieve lasting control of pest ants, depending on the level ofinfestation. The reductions in longlegged ant numbers obtained are likely conservative, as only relatively small areas within moderate to heavily infested sites are treated, resulting in continuous and high reinvasion pressure from surrounding areas. The extended activity of improved hydrogels containing glycerol, which act as miniature controlled-release bait dispensers, can therefore be well suited for a boric acid active ingredient and compatible with other insecticidal active ingredients in ant-baiting systems. Avoidance of multiple treatments also reduces the amount of insecticide applied to the environment, as well as cost. Both standard and improved hydrogel beads disintegrate into the soil or biodegrade on the floor at 4 weeks to 8 weeks post-treatment.EXAMPLESExample 1 : Water loss of hydrogel beads

[0026] Assessment was conducted to determine the effects of glycerol (Sigma Aldrich, St. Louis, MO, USA) on the hydrogel water loss rate under laboratory and outdoor conditions. Alginate hydrogels were used at least in part because they could easily bind with divalent cations like Ca2+, resulting in stable calcium alginate beads. Alginate beads were produced and subsequently hydrated for a 24-hour period in sucrose and glycerol conditioning solutions to produce hydrogels containing 25% sucrose (w / vol) and 0 (standard), 10%, 20% or 30% glycerol (vol / vol). To prepare the conditioning solutions, glycerol, which is miscible with water, was mixed into water at the stated concentrations, after which a constant weight of sugar was dissolved in the respective glycerol solutions.

[0027] The water loss dynamics of improved alginate hydrogel beads were studied over the course of 3 days both in the laboratory and in an outdoor setting (under a tree on the University of Hawaii (UH) at Manoa campus) to reflect field temperature and moisture conditions.Individual beads were weighed and placed on the surface of moistened sand (play sand, The Quikrete International Inc., GA, USA) containing 10% water (w / w) in an uncovered Petri dish. For the laboratory test, the dishes were placed on a laboratory bench with ambient air conditions of 22 °C to 23 °C and 60% to 65% relative humidity. Conditions for the outdoor test were approximately 21 °C to 30 °C and approximately 45% to 72% relative humidity throughout the entire 72 hours, with no significant rainfall. Temperature and humidity levels in both locations were continuously recorded with a data logger (UX100-011A, Onset Computer Corp., MA,USA). The hydrogel beads were weighed at 2 hours, 4 hours, 8 hours, 12 hours, 24 hours and 72 hours using an analytical balance (PR series, Ohaus Corp., NJ, USA) after carefully removing sand particles. The assessment was replicated four times. After 72 hours, all the hydrogel beads were placed in a desiccator with 0% relative humidity, and the beads were weighed daily until there was no further weight reduction, indicating all water had been lost. The weight difference between the initial hydrogel bead and the completely dehydrated bead was used to calculate the percent water loss at each time point. One-way analysis of variance (ANOVA) and Tukey’s honestly significant difference (HSD) test at the 0.05 level of significance were used to compare percent water loss at each time point across different concentrations of glycerol (SPSS Inc, 2022).

[0028] In the laboratory, hydrogel beads containing 20% and 30% glycerol had lower water loss rates when compared with standard beads containing no glycerol starting at 72 hours and 24 hours, respectively (2h, F = 0.106, df = 3, 12, P = 0.955; 4h, F = 0.067, df = 3, 12, P = 0.976; 8h, F = 0.278, df = 3, 12, P = 0.840; 12h, F = 1.119, df= 3, 12, P = 0.380; 24h, F = 4.308, df = 3, 12, P = 0.028; 72h, F = 8.030, df = 3, 12, P = 0.003), as seen in Table 1. At the outdoor site, hydrogel beads containing 20% and 30% glycerol had lower water loss rates when compared with standard beads starting at 12 hours and 8 hours, respectively (2h, F = 2.731, df = 3, 12, P = 0.090; 4h, F = 2.983, df = 3, 12, P = 0.074; 8h, F = 3.838, df = 3, 12, P = 0.039; 12h, F = 18.582, df = 3, 12, P = 0.000; 24h, F = 10.570, df = 3, 12, P = 0.001; 72h, F = 32.591, df = 3, 12, P = 0.000), as seen in Table 2. Example 1 showed that hydrogel beads formulated with at least 20% glycerol should be sufficient to retain higher moisture in hydrogel beads.Table 1 : Weight percent water loss (mean ± standard error of the mean) over time under laboratory conditions for hydrogel beads formulated with different concentrations of glycerol.Concentration of Time (h) glycerol 2 4 8 12 24 7213.95 ± 26.31 ± 49.28 ± 68.23 ± 92.37 ± 1.45 96.02 ±U / o1.02 a 1.74 a 3.05 a 3.92 a a 0.47 a13.55 ± 27.45 ± 51.91 ± 70.00 ± 91.74 ± 1.86 95.55 ± iU / ° 1.15 a 2.21 a 3.93 a 4.75 a a 0.28 a13.16 ± 27.36 ± 48.72 ± 62.75 ± 87.31 ± 1.94 87.74 ±2U / ° 0.76 a 2.03 a 2.92 a 2.24 a ab 0.88 b0 / 13.82 ± 26.68 ± 47.98 ± 61.73 ± 81.03 ± 4.01 86.30 ± jU / o1.26 a 2.44 a 2.92 a 3.98 a b 3.45 b a Means followed by same letter within a column are not significantly different (P > 0.05) ANOVA and Tukey’s HSD.Table 2: Weight percent water loss (mean ± standard error of the mean) over time under outdoor conditions for hydrogel beads formulated with different concentrations of glycerol.Concentration of Time (h) glycerol 2 4 8 12 24 7218.10 ± 50.02 ± 82.77 ± 2.16 88.86 ± 93.93 ± 0.62 95.63 ± 0.36U / o2.69 a 3.22 a ab 1.46 a a a19.94 ± 54.78 ± 83.49 ± 2.32 87.65 ± 88.06 ± 2.44 95.27 ± 0.76 1.68 a 1.81 a a 1.27 a ab ab16.13 ± 46.51 ± 79.15 ± 1.21 81.79 ± 83.13 ± 1.26 93.17 ± 0.072U / o1.04 a 2.04 a ab 1.11 b b b13.29 ± 47.62 ± 75.45 ± 1.67 77.46 ± 82.30 ± 1.71 89.36 ± 0.55JU / o0.87 a 0.54 a b 1.03 b b c a Means followed by same letter within a column are not significantly different (P > 0.05) and Tukey’s HSDExample 2: Attractiveness tests with fresh and aged standard vs. improved hydrogel beads

[0029] The attractiveness of fresh and aged alginate hydrogels formulated with 25% sucrose and 0%, 10%, 20%, or 30% glycerol was tested with laboratory colonies of longlegged ants and ghost ants. In each trial, approximately 150 worker ants were introduced into an arena, which included a polyethylene container (e.g., 20 cm x 15 cm) whose inner sides were coated with a film of Teflon (polytetrafluoroethylene suspension; BioQuip, CA, USA) to prevent escape. Ants were starved for 1 day before the tests. For assessments testing fresh hydrogels, hydrogels were prepared following the methods in Example 1 and used immediately. To prepare the agedhydrogels, fresh hydrogels were left exposed at ambient room conditions for 3 days, 7 days, 14 days, 28 days, and 98 days. In each assessment, four individual beads of the same age formulated with 0%, 10%, 20% and 30% glycerol were simultaneously placed 2 cm apart in a square configuration on a petri dish cover at the center of the arena. Digital pictures of the arena were taken at 5 minutes, 10 minutes, 20 minutes and 30 minutes after beads were introduced, and numbers of ants feeding on individual beads at each time interval were subsequently counted. The assessments were replicated four times using four different ant colonies of each species. At least in part because the count data were not normally distributed and exhibited heterogeneity of variance, the data were logio (x+1) transformed prior to analysis. One-way ANOVA and Tukey’s HSD test at the 0.05 level of significance were used to compare the ant counts among the different concentrations of glycerol at each time point.

[0030] For fresh hydrogel beads, no significant differences (P > 0.05) were found between numbers of longlegged ants attracted to standard hydrogel beads and any of the formulations containing glycerol at 5 minutes and 10 minutes post-introduction. At 20 minutes postintroduction, fewer ants were attracted to beads containing 30% glycerol compared to all other formulations. At 30 minutes post-introduction, however, numbers of ants attracted to 30% glycerol were significantly lower than numbers attracted to standard beads with no glycerol, as shown in FIG. 1A (5 min, F = 1.626, df = 3, 12, P = 0.235; 10 min, F = 0.196, df = 3, 12, P = 0.897; 20 min, F = 11.817, df = 3, 12, P = 0.001; 30 min, F = 4.815, df = 3, 12, P = 0.020).

[0031] For hydrogels aged for 3 days, there were no significant differences in mean numbers of longlegged ants attracted to any of the formulations at any point in time, as shown in FIG. IB (5 min, F = 0.105, df = 3, 12, P = 0.955; 10 min, F = 0.178, df = 3, 12, P = 0.910; 20 min, F = 0.673, df = 3, 12, P = 0.585; 30 min, F = 0.205, df = 3, 12, P = 0.891).

[0032] For hydrogels aged for 7 days, more longlegged ants were attracted to the hydrogel beads containing 10%, 20%, and 30% glycerol compared to the standard hydrogel beads at 30 minutes post-introduction, as shown in FIG. 1C (5 min, F = 3.655, df = 3, 12, P = 0.044; 10 min, F = 0.086, df = 3, 12, P = 0.967; 20 min, F = 4.412, df = 3, 12, P = 0.026; 30 min, F = 9.126, df = 3, 12, P = 0.002). The standard beads aged for seven days appeared to be hardened and contain minimal moisture in contrast to the improved beads which were flexible, suggesting more water retention.

[0033] Referring to FIGS. ID and IE, no longlegged ants were attracted to the standard hydrogel beads aged for 14 days, 28 days, and 98 days whereas ant counts were significantly greater (P < 0.05) on all hydrogel beads containing 10%, 20%, and 30% glycerol at all time intervals (14 d: 5 min, F = 88.980, df = 3, 12, P = 0.000; 10 min, F = 49.598, df = 3, 12, P = 0.000; 20 min, F = 49.915, df = 3, 12, P = 0.000; 30 min, F = 99.906, df = 3, 12, P = 0.000; 28 d: 5 min, F = 139.302, df = 3, 12, P = 0.000; 10 min, F = 61.180, df = 3, 12, P = 0.000; 20 min, F = 52.744, df = 3, 12, P = 0.000; 30 min, F = 18.421, df = 3, 12, P = 0.001). This further suggested that 10% to 20% glycerol composition did not influence bait attractiveness. Improved hydrogel beads that were aged remained flexible and transparent in appearance, unlike the standard hydrogel beads which hardened and became opaque as they aged, as shown in FIG. 2.

[0034] Identical trials with ghost ants yielded similar results to those with longlegged ants. Ghost ants became more attracted to improved hydrogel beads compared to standard beads as both were progressively aged. FIG. 3 is an example with beads aged 28 days, in which differences in attractiveness are shown.Example 3 : Peak foraging time of longlegged ants

[0035] Example 3 was conducted to investigate the peak foraging time of longlegged ants in the field. The experiment was carried out at three replicate locations on the island of Oahu, Hawaii. Each replicate was conducted at one location per day. At each location, numbers of ants feeding on hydrogel beads were recorded every two hours from 0700h to 2100h using digital pictures. 20 minutes prior to each recording interval, three fresh alginate hydrogel beads formulated with 25% sucrose and no glycerol were placed next to each other on each of 10 laminated index cards (Scotch’s self-laminating cover, Scotch Brand, MN, USA) placed on the ground near longlegged ant foraging trails. At each time point, the ants feeding on the old hydrogel beads were swept away and the old hydrogel beads were replaced with three new hydrogel beads. Temperature and humidity were recorded at each time interval throughout the experimental period. This assessment was not conducted with ghost ants at least in part because they did not have an apparent diurnal foraging pattern in the indoor environments, where they commonly occur.

[0036] Environmental conditions on the trial days were typical, with temperature ranges between 23 °C and 32 °C, relative humidity between 45% and 72%, wind speeds between 5miles per hour (mph) and 15 mph, and no significant rainfall. Higher numbers of ants were recorded on index cards in early morning and late evening with the peak foraging activity between 0700h and 0900h and between 1900h and 2100h, as shown in FIG. 4. Air temperature was lower and relative humidity was higher during these periods (e.g., 64% to 70% between 0700h and 0900h, 63% to 69% between 1900h and 2100h). These results to select the morning bait application time for Example 4.Example 4: Field efficacy test

[0037] Using the optimal foraging time identified from Example 3 and the optimal concentration of glycerol identified from Examples 1 and 2, Example 4 was conducted to determine the efficacy of standard and improved hydrogel baits laced with 2% analytical grade boric acid (Sigma Aldrich, St. Louis, MO, USA) on field populations of longlegged ants on Oahu. Field assessments were conducted at six sites with high foraging activity of longlegged ants. The six sites were randomly assigned to one of two treatments: the improved hydrogel baits (2% boric acid with 20% of glycerol in 25% sucrose solution) or the standard hydrogel baits (2% boric acid in 25% sucrose solution). Two additional sites served as control sites.

[0038] Hydrogel baits were produced following the methods in Example 1 to obtain finished alginate beads containing 25% sucrose, 2% boric acid, and either 0% glycerol or 20% glycerol. Each site was treated once with approximately 500 g of the improved or standard hydrogel baits at an application rate of 10 g / m2. The hydrogel baits were hand-distributed with approximately 10 piles of 50 g each, separated from each other by at least several meters and placed along multiple active ant trails on the soil. Hydrogel baits were applied once between 0700h and 0900h during their peak foraging times. Field sites were monitored on day 0 (pre-treatment), and weeks 1, 2, 3, 4, 6 and 8 post-treatment using monitoring traps, which included of 50-ml centrifuge tubes (Celltreat Scientific Products, MA, USA) containing a cotton ball soaked with 25% sucrose solution.

[0039] At each site, 10 monitoring traps were placed along the foraging trails between 0700h and 0900h. After 30 minutes, the traps were collected, capped, and the number of ants in each trap was recorded. Numbers of ants were summed across the 10 monitoring traps at each site on each monitoring date. The difference in total ant counts among monitoring time points within the standard and improved bait treatments were assessed by the Friedman test, a nonparametricalternative to a one-way repeated-measures analysis of variance. At least in part because the Friedman test indicated a significant difference among different monitoring time points, the Conover all-pairwise comparisons test was used to compare ant counts between all pairs of monitoring time points within the standard and improved bait treatments (Statistix). Data from the two untreated control sites were used to track the natural seasonal variation of ant activity but were not used for the statistical analyses.

[0040] The longlegged ant trials described herein were repeated with domestic populations of ghost ants. All methods and analyses were the same, except baits were applied to the inside corners of homes, along ant trails around the homes, or both.

[0041] After a single field application using the standard hydrogel baits (no glycerol), longlegged ant numbers in the monitoring traps were significantly reduced compared to the pretreatment data by 2 weeks post-treatment. However, ant numbers gradually rebounded and by 4 weeks post-treatment were not significantly different from pre-treatment levels (Friedman test: F = 14.3; P = 0.03; Figure 5A). In contrast, for a single treatment using the improved hydrogel baits (containing 20% glycerol), ant numbers in the monitoring traps remained low and were significantly different from pre-treatment levels from week 2 through week 8 post-treatment (Friedman test: F = 15.4; P = 0.02; Figure 5B), indicating residual activity of the improved hydrogel bait. At 3 weeks post-treatment, ant numbers in the monitoring traps were reduced by 66%, the highest percent reduction observed during the assessment period, as shown in FIG. 5B. Concurrently, numbers of ants in monitoring traps at the two untreated control sites did not show any decline during the assessment period, and instead exhibited a 3.2% to 22.8% increase during weeks 1 to 8 relative to pre-treatment levels.

[0042] After a single application of standard hydrogel baits in urban homes, numbers of ghost ants in monitoring traps were significantly reduced compared to pre-treatment levels by 2 weeks post-treatment. However, ant numbers gradually rebounded and by 6 weeks posttreatment were not significantly different from pre-treatment levels, as shown in FIG. 6A (Friedman test: F = 13.4; P = 0.04). In contrast, after a single treatment using the improved hydrogel baits (containing 20% glycerol), ant numbers in the monitoring traps remained low and were significantly different from pre-treatment levels from week 2 through week 8 posttreatment, as shown in FIG. 6B (Friedman test: F= 16.9; P = 0.01). At 4 weeks post-treatment, ant numbers in the monitoring traps were reduced by 64%, the highest percent reductionobserved during the assessment period. Concurrently, numbers of ants in monitoring traps at the 2 untreated control sites did not show any decline during the assessment period, and instead exhibited a 0.0% to 14.1% increase during weeks 1 to 8 relative to pre-treatment levels.

[0043] Although this disclosure contains many specific embodiment details, these should not be construed as limitations on the scope of the subject matter or on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this disclosure in the context of separate embodiments can also be implemented, in combination, in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments, separately, or in any suitable sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0044] Particular embodiments of the subject matter have been described. Other embodiments, alterations, and permutations of the described embodiments are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results.

[0045] Accordingly, the previously described example embodiments do not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure.

Claims

WHAT IS CLAIMED IS:

1. An insect bait comprising: a hydrogel substrate; and a formulation on the hydrogel substrate comprising: glycerol; and boric acid.

2. The insect bait of claim 1, wherein the hydrogel substrate comprises alginate.

3. The insect bait of claim 1, wherein the hydrogel substrate comprises polyacrylamide.

4. The insect bait of claim 1, wherein the formulation comprises 10% to 30% vol / vol glycerol.

5. The insect bait of claim 1, wherein the formulation comprises 20% to 30% vol / vol glycerol.

6. The insect bait of claim 1, wherein the formulation comprises 1 wt% to 5 wt% of the boric acid.

7. The insect bait of claim 1, wherein the formulation further comprises a sugar.

8. The insect bait of claim 7, wherein the sugar comprises sucrose.

9. The insect bait of claim 1, wherein the formulation comprises 20% to 30% w / vol sucrose.

10. The insect bait of claim 1, wherein the formulation further comprises a surfactant.

11. The insect bait of claim 10, wherein the formulation further comprises an oil-based substance.

12. The insect bait of claim 1 1, wherein the oil-based substance comprises an essential oil.

13. An insect bait station comprising the insect bait of claim 1.

14. A method of preparing an insect bait, the method comprising: preparing a conditioning solution with an active ingredient; and hydrating a hydrogel substrate with the conditioning solution.

15. The method of claim 14, wherein the conditioning solution comprises sucrose and glycerol.

16. The method of claim 14, wherein the conditioning solution comprises 20% to 30% w / vol sucrose.

17. The method of claim 14, wherein the conditioning solution comprises 10% to 30% vol / vol glycerol .

18. The method of claim 14, wherein the conditioning solution comprises 20% to 30% vol / vol glycerol.

19. The method of claim 14, wherein the active ingredient comprises boric acid.

20. The method of claim 14, wherein the hydrogel substrate comprises alginate, polyacrylamide, or both.

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