Ant Control and Insecticide Runoff around Urban Houses - American

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Chapter 23

Ant Control and Insecticide Runoff around Urban Houses Les Greenberg* and Michael K. Rust Department of Entomology, University of California, Riverside,California 92521, United States *E-mail: [email protected].

Most requests for pest control during the spring and summer months in southern California concern Argentine ant (Linepithema humile) infestations, the number one reason homeowners call pest management professionals (PMPs). Two of the most common insecticides used to control these ants are bifenthrin and fipronil. However, they have been found in urban waterways in quantities that are lethal to a variety of aquatic invertebrates. Our studies measured the efficacy of these products in controlling the ants and how much drained into the street. In addition to these trials around urban households, we constructed a concrete wall and pad where both insecticides could be sprayed and irrigated to determine how much drained off. Around houses, we concentrated our efforts on the driveways since they are the most direct route to the street for water runoff due to rain or irrigation. We compared different bandwidths and concentrations. This chapter mostly focuses on fipronil, and draws major conclusions that (1) fipronil compounds can persist in the environment for over a year, (2) lower concentrations of the fipronil pin stream applications can reduce its runoff, (3) treatments of the ants can be effective without treating the driveway, (4) if fipronil is not applied to the driveway, the subsequent runoff is barely higher than background levels, and (5) fipronil should not be applied within 30 days of the rainy season.

© 2019 American Chemical Society Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

Introduction The outdoor application of insecticides to control ants, cockroaches, fleas, and spiders has been one of the mainstays of pest management professionals (PMPs) for nearly 70 years, especially during the spring and summer months (1, 2). The chemical use patterns of PMPs and homeowners changed from organochlorine to organophosphate insecticides in 1988 with the ban on chlordane and lindane (3) and later to pyrethoids in 2003 with the ban on organophosphates (OPs) to comply with regulatory changes. The OPs diazinon and chlorpyrifos were banned by the US EPA for most urban uses in 2000 and 2001 (4, 5). Pyrethroids replaced chlorpyrifos and diazinon, as shown by their steady increase in structural use (6). Concomitant with their increase in use, pyrethroids have been more frequently detected in urban creeks and rivers at concentrations shown to be toxic in laboratory toxicity studies (7–9). To mitigate pyrethroid runoff, the US EPA has mandated label changes (10) and the California Department of Pesticide Regulation (CDPR) has enacted surface water regulations to mitigate pyrethroid runoff (11). Nonetheless, pyrethroids (especially bifenthrin) are still being detected at concentrations potentially detrimental to aquatic life. Fipronil, a phenylpyrazole insecticide, became one of the most important insecticides utilized by PMPs to control Argentine ants (Linepithema humile). It has come under scrutiny in urban runoff (12), with label changes restricting its use. The importance of certain seasonal pests in California has changed over time. In the 1980s and early 1990s, the cat flea (Ctenocephalides felis felis) was a significant pest, and outdoor broadcast sprays were regularly applied by PMPs. After the registration of on-animal treatments to control cat fleas in 1995, the emphasis in residential pest control in California shifted almost exclusively to Argentine ants. In a survey of a large San Diego pest control company, more than 85% of the requests for pest control were concerned with Argentine ant infestations, and they remain the number one reason homeowners call PMPs in southern California (13). In addition, spiders were an important pest for homeowners, especially cellar marble spiders (Holocnemus pluchei) because of the unsightly webbing on structures (14). The goal of studies done at the University of California (UC), Riverside, has been to find treatments that are effective against Argentine ants around houses while minimizing the runoff of these treatments into the street and stormwater systems. Some of the variables tested included different active ingredients (AIs), different insecticide formulations, and different application techniques. Most of the AIs were formulations of pyrethroids, fipronil, or botanicals. Formulations of pesticides that we have tested include sprays, granules, and baits. One of the major problems in testing insecticide treatments outdoors around structures is the amount of variability between houses. Differences in the square footage treated, the landscape around the foundation’s structure, and irrigation patterns used by the homeowner make direct comparisons between houses complicated. The houses we used typically had three or more bedrooms, with front lawns, an adjacent driveway that connects with the street, and lawn irrigation. They are typical of houses in a Mediterranean climate with dry summers and wet winters from November to March. These neighborhoods would be considered of 452 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

moderate density. Recommendations about when to use insecticides are specific to these areas that have a rainy season. To complement our studies around houses, during 2012, a wall on a concrete slab was constructed at the Agricultural Operations at UC Riverside (15) to simulate a house’s wall–driveway interface. Using the concrete wall and pad, we replicated and compared insecticide runoff when different bandwidths, concentrations, or formulations of insecticides were applied using a fixed volume of irrigation. The effect of different bandwidths on runoff is not well-understood, even with previously published material on this topic (16–18). PMPs have limited abilities to alter the amounts of pesticides being applied around structures and still provide satisfactory pest management. They can vary the concentration of the insecticide or the width of the band, depending upon the label recommendations. It is very difficult for PMPs to accurately alter their spray rate since a majority of companies lack pressure regulators on their equipment. With this in mind, studies were conducted observing factors PMPs could easily do themselves or incorporate into their business models. Every summer, the urban entomology research group at UC Riverside collaborates with homeowners who let us use their houses for testing different products and methods for controlling ant infestations. For a period of 10 years, we also have collected water samples from their driveways to measure the quantity of insecticides running down the driveway and onto the street. This chapter deals only with bifenthrin and fipronil studies between 2014 and 2016.

Figure 1. Left, wall with placards showing different treatments and bottles in place. Metal gutters direct water runoff from each segment to a bottle that is placed at base of pad. Right, sample bottle collecting runoff from wall and pad.

The Office of Pesticide Programs of the US EPA has published invertebrate aquatic life benchmarks for pesticides (19). For fipronil, the acute benchmark is 0.11 µg/L, or 0.11 ppb = 110 ng/L, and the chronic benchmark is 0.011 µg/L, or 11 ng/L. The fipronil-sulfone and fipronil-desulfinyl degradates are approximately 3–100 times less toxic than fipronil itself. For bifenthrin, the respective benchmark 453 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

values are 0.8 and 0.0013 ng/L. Ideally, our runoff values from houses should be lower than both the acute and chronic benchmarks.

General Methods at the Constructed Wall and Pad The wall that was constructed on campus is 0.91 m high and 11 m wide. The concrete pad on each side of the wall is 3.05 m wide by 11 m long (Figure 1). There are twelve 0.91 m wide segments on each side of the wall (east and west sides) for a total of 24 segments that can be used for treatments. Two coats of latex paint were applied to the wall. Strips of metal flashing separate each of the segments so that runoff can be collected for each individual segment. The flashing narrows down at 3.05 m from the wall to a spout where water samples are collected. Irrigation sprinklers on both sides of the wall were adjusted to give an equal distribution of simulated rain on both the wall and pad. In this manner, the treated segments could be exposed to specific amounts of simulated rainfall.

Figure 2. Preparation for spraying one wall segment. This treatment will go 0.6 m up and 0.9 m out from the base of wall. Plywood separates adjacent segments for spraying. 454 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

Two large pieces of plywood placed at each end of the segment during spraying ensured that sprays did not contaminate the other segments (Figure 2). To apply different bandwidths of insecticides to the wall and concrete pad, sheets of paper were taped to the wall and concrete pad. The different applications to the wall and the treatments are described below.

General Methods around Houses Water Runoff from Houses Water samples were collected from each of the treated houses to determine the amount of insecticide runoff. Before treating the houses, the driveways and the driveway–garage door interface were thoroughly washed with a hose. The samples were collected on the driveway 6.1 m from the garage by setting up a water dam across the driveway (Figure 3). The dam consisted of two wooden segments with foam bottoms connected with a hinge that allowed the dam to open and cover most of a typical driveway. The dam was wrapped with thin plastic sheets before collecting a sample (the plastic was replaced at each house). A garden hose was used to flush water down the driveway from the garage toward the dam where a 1 L sample was collected. The volume of water used was recorded with a rainwave gauge attached to the hose.

Figure 3. Water dam and sample collection from house trials with water flushed from garage door–driveway interface to the dam. 455 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

Efficacy of Treatments in Controlling Argentine Ants Houses were selected based on the number of ants present and the slope of the driveway to the street. A gentle slope (3–5%) facilitated the collection of water samples. The homeowners permitted us to monitor and treat the ant infestations around their houses. In addition, they allowed us to wash the driveway when water samples were collected. The efficacy of treatments was calculated from a reduction in ant foraging based on adjusted weight loss from monitoring vials of sugar water before and after treatment, rather than being based on numbers of ants counted or trapped. Details of these methods have been described elsewhere (16–18). Unless otherwise stated, we used five houses per treatment. These same houses were used for water runoff analysis. Spray treatments around houses were done with a 1 gal B&G sprayer using a Multeejet C&C 4-way Tip (B&G model #5800-CC) that also allowed for fine or coarse spray patterns and pin stream (2.54 × 2.54 cm) applications. We attached a pressure gauge (1535 Gauge 0-60 B&G Red) to keep the tank pressure at 20 psi so that we could maintain a constant delivery of spray. The houses were monitored 1 week before and up to 1, 2, 4, and 8 weeks after the treatment.

Bifenthrin Studies 2014 The main objectives in the house studies were to determine how the bandwidth of insecticides applied around structures affected both the control of ant populations and the quantity of pesticide runoff. Bifenthrin is one of the most widely used pyrethroids showing up in runoff studies and is the one we used in these studies (Talstar P, 7.9% bifenthrin, FMC Corp., Philadelphia, PA).

Table 1. Wall Treatments Using Various Concentrations of Bifenthrin AI (g/ m2)

Total AI (g)

36.30

0.063

0.0352

1.4 m2

56.78

0.025

0.0352

0.093 m2

22.00

0.380

0.0352

Bifenthrin AI concn. (%)

Area sprayed

Vol. of spray (ml)

0.3 m up by 0.3 m out A

0.097

0.56 m2

0.6 m up by 0.9 m out B

0.062

5.1 cm up by 5.1 cm out C

0.160

Treatment

456 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

PMPs typically apply bands of insecticide around house foundations to prevent ants from entering the structures. Historically, these bands have been as wide as 1.8 m from the foundation. In recent years, bifenthrin at the house foundation has been applied 0.61 m up and 0.91 m out from the foundation. Questions concerning application techniques remain. Does a narrow band of insecticide provide more or less runoff than a wide one? And which bandwidths are most effective in controlling ants?

Wall and Pad Applications In 2014, we tested whether different bandwidths of bifenthrin affected its runoff.

Methods Before the 2014 applications, the wall and pads were scrubbed with detergent and thoroughly washed. The day after cleaning the wall, we turned on the water sprinklers and collected water samples for a pretreatment analysis. We chose three different bandwidths to apply to the wall and contiguous pad (Table 1). We used a wide band application of bifenthrin (0.61 m up and 0.91 m out), a narrower band (0.3 m up and 0.3 m out), and a very narrow band (5.1 cm up and 5.1 cm out). Each of the 3 treatments had 4 replicates, for a total of 12 treated segments. A bandwidth treatment was randomly assigned to each segment. Bifenthrin was applied to keep constant the total mass of AIs applied per wall segment. To accomplish this task, we varied both the time of the spray application and the concentration of the bifenthrin suspension. The wide band was sprayed with the lowest concentration of bifenthrin with the longest spray time. The narrowest band was sprayed with the highest concentration and the shortest spray time. Using spray concentrations ranging from 0.062–0.16% bifenthrin, each band received a total mass of 0.0352 g of bifenthrin.

Results The mean pretreatment bifenthrin concentration was 17.6 ± 2.6 ng/L (mean ± SE). Figure 4 shows runoff one day posttreatment. The 5.1 × 5.1 cm band (C) had the lowest runoff at 82,000 ng/L and the widest band (B) was the highest at 323,000 ng/L. The 5.1 × 5.1 cm band runoff was significantly lower than the other two treatments (p < 0.05, Tukey’s HSD test).


Figure 4. Runoff of bifenthrin from concrete wall and pad during 2014. See Table 1 for treatment details. Treatments: A = 0.3 m × 0.3 m; B = 0.61 × 0.91 m; C = 5.1 × 5.1 cm. N = 4. Graph shows mean runoff with standard errors. Bars with the same letter are not significantly different. Total amount of bifenthrin applied was constant (0.0352 g) for the different bandwidths.

Discussion The narrowest band (5.1 cm × 5.1 cm) had the highest amount of bifenthrin applied per unit area (0.380 g/m2), the same total AI as the other bands, and statistically lower runoff than the 0.61 m × 0.91 m or 0.3 m × 0.3 m bands. One possible explanation for this finding is that in the initial runoff, surface area of a treatment was more important than the total amount of AI applied, but additional studies are needed to be certain.

House Applications The two objectives of the 2014 bifenthrin field trials were to determine the impact of the different bandwidths and buffer zones of bifenthrin on ant treatment efficacy and the mass of pesticide runoff. 458 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

Methods Bifenthrin was applied at the label rate of 29.6 ml per 3.79 L finished spray preparation (0.062% bifenthrin AI), applied per 92.9m2. The bifenthrin treatments consisted of (A) a 5.1 cm × 5.1 cm band around the house foundation, (B) a 0.61 m × 0.91 m band at the building foundation, and (C) the standard 0.61 m × 0.91 m band at the building foundation plus a treatment along the lawn–driveway edge. Bifenthrin was not applied along the garage door–driveway interface. Each of the three treatments was replicated five times. Bifenthrin Runoff Figure 5 shows runoff of bifenthrin at days 1 and 28 posttreatment. At days 1 and 28, the narrow band A (5.1 × 5.1 cm) had the least runoff numerically, although the variability in the amounts of bifenthrin detected was too high to show significant differences. On day 1, the treatment including the driveway (C) had the highest runoff. In general, the narrow band treatments were trending lower than the others.

Figure 5. Runoff of bifenthrin from Riverside homes during 2014. Treatments: A = 5.1 × 5.1 cm; B = 0.61 × 0.91 m; C = 0.61 × 0.91 m plus a treatment applied along the lawn–driveway edge. Bifenthrin was not applied at the garage door in any of the treatments. N = 5. 459 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

Bifenthrin Efficacy Figure 6 shows the efficacy of the three bifenthrin treatments in reducing ant numbers. The standard treatment (C) of the 0.61 m × 0.91 m band and a treatment along the edge of the driveway had the greatest percentage of ant reductions on weeks 1 and 2; the 5.1 cm × 5.1 cm application (A) had the best outcome at week 4. The latter outcome is surprising because PMPs and researchers have always assumed that wide bands of bifenthrin are necessary for control. It is possible that since a narrow band concentrates the insecticide at the wall–ground interface where ants tend to walk, it may be effective for a longer period of time.

Figure 6. Efficacy of bifenthrin house treatments during 2014. Treatments: A = 5.1 × 5.1 cm; B = 0.61 × 0.91 m; C = 0.61 × 0.91 m plus a treatment applied along the lawn–driveway edge. N = 5. Bifenthrin was not applied at the garage door in any of the treatments.


Fipronil Wall and Pad Study 2015 Methods Table 2 shows the fipronil wall treatments done in 2015 and 2016 using Termidor SC 9.1% fipronil. The standard treatment (labeled rate, A) for houses for both 2015 and 2016 was a 30.5 × 30.5 cm band that used 1.9 L of 0.06% fipronil per 48.8 linear m (29.7 m2). The other 2015 treatments used 0.95 L, one-half the fipronil mass of the standard treatment, either as a pin stream (C2, 2.5 cm up the wall × 2.5 cm out from the wall) or a 15.2 × 15.2 cm band (D). The standard and the reduced swath treatments were done with a coarse fan spray setting, whereas the pin stream setting provided a very narrow but concentrated spray.

Table 2. Fipronil (0.06% Finished Solution) Treatments on the Constructed Wall during 2015 and 2016 Treatment

Treatment swath at base of wall

Labeled rate (2017 label, standard treatment) A

30.5 × 30.5 cm band

C1 C2

2.5 × 2.5 cm pin stream band

C3 Reduced swath D

Actual amount of fipronil used/area

Year

1.9 L

3.8 μg/cm2

2015, 2016

157 ml

3.8 μg/cm2

2016

0.95 L

μg/cm2

2015

1.9 L

45.8 μg/cm2

2016

0.95 L

3.8 μg/cm2

2015

Projected treatment volume per 48.8 linear meters

15.2 cm up, 15.2 cm out band

22.9

Each side of the wall with its 12 segments was considered a block in a randomized block design. There were 3 treatments, with 8 replicates of each treatment, for a total of 24 treated segments on the wall. On each side of the wall, treatments were randomly assigned to the wall segments. The two sides were treated 1 week apart. Prior to application, the wall was washed with Liquinox detergent and water. Due to constraints on resources, no pretreatment samples were collected (the wall had last received treatments 1 year earlier). It was assumed that after cleaning the constructed wall, there would be very little fipronil remaining (although 2016 data shows some residues exist after 1 year). Samples were collected 1 and 30 days posttreatment.


Table 3. Day 1 Percentage Fipronil Runoff Reduction from the Wall and Pad between Treatments A and C2 during 2015a Compound

Mean % reduction with pin stream treatment

Median % reduction with pin stream treatment

Fipronil

80.2**

92.9**

Fipronil desulfinyl

84.2**

94.2**

Fipronil sulfide

71.6*

87.8**

Fipronil sulfone

71.6*

87.3**

a

The table shows fipronil and its three most common degradates. N = 8. * p < 0.05. ** p < 0.01. See Table 2 for treatment details. A = 30.5 × 30.5 cm band with 1.9 L; C2 = 2.5 × 2.5 cm pin stream with 0.95 L.

Table 4. Fipronil Day 30 Posttreatment Wall and Pad Runoffa Treatment 0.3 × 0.3 m (A) Chemical

15.2 × 15.2 cm (D)

2.54 × 2.54 cm (C2)

Median concentrations (ng/L)

Fipronil

0.01

0.01

0.01

Fipronil desulfinyl

12.96

13.13

6.28

Fipronil sulfide

5.01

6.02

2.09

Fipronil sulfone

6.75

5.87

4.76

Mean concentrations (ng/L) Fipronil

5.15

7.33

3.69

Fipronil desulfinyl

23.97

13.75

8.58

Fipronil sulfide

5.53

6.63

2.57

Fipronil sulfone

10.46

9.28

4.88

a

The table shows fipronil and its three most common degradates. N = 8. See Table 2 for treatment list. A = 1.9 L solution; D = 0.95 L solution; C2 = 0.95 L solution.

Results At 1 day after treatment, the 0.95 L pin stream wall application (C2) had significantly less runoff than either the 1.9 L standard treatment (A) or the 0.95 L, 15.2 × 15.2 cm band treatment (D) (for fipronil and each degradate; p < 0.05). The pin stream application had greater than 80% reduction of fipronil and fipronil desulfinyl and greater than 70% reduction of the sulfide and sulfone degradates (Table 3). On the other hand, there were no significant differences between treatments A and D for fipronil or its degradates. At 30 days posttreatment, 462 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

there were no statistically significant differences in runoff among the treatments. However, runoff amounts from the pin stream applications were numerically lower. Table 4 shows 30-day posttreatment runoff means and medians. Most values are below the fipronil chronic aquatic benchmark value of 11 ng/L, and all are below the acute benchmark of 110 ng/L. Within each treatment, the reduction in runoff between day 1 and day 30 for all compounds was more than 99%.

Discussion The large reduction in the runoff of fipronil and its degradates at 30 days posttreatment (greater than 99%) shows that applying fipronil at least 30 days before a rain would significantly reduce its runoff. Although we did not look at other intervals, 30 days posttreatment gives sufficient time for breakdown of fipronil and its degradates to concentrations below US EPA benchmarks. Furthermore, a 2.54 × 2.54 cm (0.95 L) pin stream application gave reduced runoff compared with a 0.3 m × 0.3 m (1.9 L) and a 15.2 × 15.5 cm (0.95 L) application. Reducing the bandwidth from 0.3 m to 15.2 cm does not reduce runoff. However, reducing the amount of finished solution to 0.95 L with a pin stream application reduces initial fipronil runoff. Bandwidth appears to be a more important factor in initial runoff than the volume of fipronil applied. Additional research is needed to determine how bandwidth influences runoff (investigated in 2016 trials). More details about the above fipronil wall study and two additional fipronil house studies from 2014 and 2015 can be found in a 2016 CDPR final report (20).

Fipronil Wall and Pad Study 2016 Objective The study aimed to determine the effect of bandwidth and amount of fipronil applied on runoff of fipronil and its degradates.

Methods Table 2 describes the wall treatments applied in 2015 and 2016 using 0.06% fipronil finished solution. During 2016, three treatments were applied, each replicated six times. Samples were collected 1 and 30 days posttreatment. Treatment A is the standard label application of 30.5 cm up and 30.5 cm out from the foundation using 1.9 L of 0.06% fipronil. Treatment C1 was applied as a pin stream application (2.54 × 2.54 cm band) at 1/12 the mass of the standard label rate per linear foot. Treatment C3 was applied as a pin stream application using 1.9 L of 0.06% solution per linear foot, identical (except for spray swath) to the label treatment A. Prior to application, the walls were washed with Liquinox detergent and water, and pretreatment values were obtained from the three wall segments that had the highest fipronil runoff the previous year. 463 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

Results In the pretreatment samples, fipronil sulfide was the major component with median runoff of 62 ng/L, followed by fipronil sulfone, fipronil, and fipronil desulfinyl, with median concentrations of 10, 5, and 1 ng/L, respectively. At one day posttreatment (Figure 7), the standard treatment (A) had numerically higher median runoff than other treatments for all fiproles (fipronil and each of its degradates).

Figure 7. 2016 concentration of fipronil and degradates in runoff from 1 L water samples collected 1 day posttreatment from the constructed wall trials. A = 30.5 × 30.5 cm band standard treatment with 1.9 L applied; C1 = 2.5 × 2.5 cm pin stream with 157 ml applied; C3 = 2.5 × 2.5 cm pin stream with 1.9 L applied. N = 6. See Table 2 for further details. The horizontal line in each treatment box shows the median value and the whiskers show the ranges of values. Asterisks are near outliers; circles are far outliers.


At 30 days posttreatment (Figure 8), the pin stream application with 157 ml of 0.06% fipronil (treatment C1) had the lowest median runoff for fipronil and each of its degradates. Although the sample size is low (n = 6 replicates), for fipronil, the C1 runoff compared with the standard treatment A runoff is close to statistical significance (analysis of variance using log-transformed data, p = 0.07). The C1 runoffs of the sulfide and desulfinyl degradates were statistically lower than that of the A treatment runoff (p = 0.046 and 0.018, respectively). Furthermore, the C1 runoff for the combined data for all fiproles was significantly reduced (p = 0.047) when compared with treatment A runoff.

Figure 8. 2016 concentration of fipronil and degradates in runoff from 1 L water samples collected 30 days posttreatment from the constructed wall trials. A = 30.5 × 30.5 cm band standard treatment with 1.9 L applied; C1 = 2.5 × 2.5 cm pin stream with 157 ml applied; C3 = 2.5 × 2.5 cm pin stream with 1.9 L applied. N = 6. See Table 2 for further details. The horizontal line in each treatment box shows the median value and the whiskers show the ranges of values. Asterisks are near outliers; circles are far outliers.


Discussion The wall had a fipronil application one year previous, and the pretreatment residues show that fipronil and its degradates can persist at least that long at concentrations above US EPA chronic benchmarks. For example, one of the pretreatment samples contained 74 ng/L of fipronil. These residues had persisted through the hot summers in Riverside and from rainy season washoff, as well as through the pretreatment wash. The constructed wall is on UC Riverside’s Agricultural Operations on campus and is not near any urban structures that could have received fipronil treatments other than what we applied. It is not surprising that treatment C1 had significantly less runoff than the others because this treatment had 1/12 of the AI applied of the standard treatment A or the pin stream applied at 1.9 L (C3). It is possible that the pin stream application with 157 ml of 0.06% fipronil (C1) had mostly washed off at 1 day posttreatment and that less remained to wash off at 30 days. This finding is significant for justification of the use of pin stream application as a mitigation method to reduce fipronil runoff if the actual mass of fipronil is reduced. However, if fipronil mass is not reduced, using a pin stream application will not reduce fipronil runoff (21). More details about the aforementioned wall study can be found in a 2017 CDPR final report (22).

Fipronil House Study 2016 Objectives There were two main objectives. First, we wanted to know how different bandwidths of fipronil sprayed around house perimeters affected the efficacy of ant control and fipronil runoff. Second, we wanted to know the effect of not spraying fipronil on the driveway–garage door interface on ant control and fipronil runoff. Methods After the washed driveways had dried, pretreatment water samples were collected at 3 of the 5 houses for each of the 4 treatments, for a total of 12 samples, whereas posttreatment samples consisted of 20 samples (5 houses for each of 4 treatments). The fipronil trials consisted of four treatments (Table 5): the labeled rate applied around the entire house perimeter with a 30.5 × 30.5 cm band (A1); the labeled rate applied as a pin stream at the garage door and a 30.5 × 30.5 cm band around the rest of the house (A3); the labeled rate as a pin stream application around the entire house perimeter (C2); or the labeled rate with no application at the garage door and a 30.5 × 30.5 cm band around the rest of the house (G). Fipronil treatments were applied within a few days of collecting the pretreatment samples. After application, water samples were collected at 1 and 30 days posttreatment. The houses used for water sampling were also used simultaneously to measure Argentine ant numbers. For this project, we measured ant numbers before application (pretreatment) and at 1, 2, 4, 6, and 8 weeks posttreatment. 466 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

Table 5. Fipronil House Treatments 2016a ID A1

A3

C2

G

a

Application spray swath

Spray volume

Garage door

band spray, labeled rate (30.5 cm up/30.5 cm out)

1.9 L of a 0.06% Termidor SC finished dilution per 92.9 m2

Using hose

House perimeter

band spray, labeled rate (30.5 cm up/30.5 cm out


None

Garage door

pin stream (2.5 cm up/2.5 cm out)


Using hose

House perimeter



None

Garage door



Using hose

House perimeter



None

Garage door

No application of any pesticide or insect control method

None at the driveway–garage door interface

Using hose

House House perimeter



None

Area

Runoff method

A1 is the standard label treatment with which the others are compared. N = 5.

Results Efficacy of Treatments There were no significant diffences in ant numbers among the four treatments for any of the posttreatment dates (Kruskal-Wallis test, p > 0.05). Pin stream application or no application to the driveway–garage door interface controlled ants as well as did the standard treatment (Figure 9).

Runoff Concentration Figure 10 summarizes the data for runoff of the parent fipronil molecule (degradates not shown). Pretreatment runoff of fipronil and its degradates ranged from 2.8 to 323 ng/L. These houses had a fipronil treatment the previous year and experienced rain during the winter months, in addition to the pretreatment 467 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

washdown of the driveway. In spite of these conditions, many of the results were above the chronic and acute US EPA benchmarks.

Figure 9. Ant reductions from house runoff trials during 2016. See Table 5 for the treatment list; A1 is the standard treatment. N = 5. The horizontal line in each treatment box shows the median value and the whiskers show the ranges of values. Asterisks are near outliers; circles are far outliers. At 1 day posttreatment, there were high concentrations of fipronil and degradates in the runoff. For the parent compound (Figure 10), concentrations were above US EPA acute benchmarks for all treatments. Treatment G (no application to the driveway–garage door area) had the lowest median value of all the fiproles at 1 day posttreatment. For example, compared with the standard treatment (A1), G had an 88% reduction in fipronil runoff and a 92% reduction in runoff of the sum of all three degradates. At 30 days posttreatment, Treatment G had a 35% reduction in runoff of the parent compound fipronil and a 71% reduction in the sum of all degradate runoff compared with the labeled treatment A1. The fipronil runoff profile at 30 days posttreatment appears similar to the pretreatment profile (Figure 10). Discussion The pretreatment samples show that traces of fipronil and its degradates are still present one year after application, suggesting that it is hard to completely remove these residues. Treatment G, which had no driveway treatment, showed the lowest runoff of all treatments on day 1 posttreatment. Thirty days 468 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

posttreatment, G had reductions in ant numbers similar to the standard treatment (A1). During 2016, there was no loss of ant control when fipronil was not applied to the driveway–garage door interface. More details about the above house study can be found in a 2017 CDPR final report (22). Two additional fipronil house studies from 2014 and 2015 can be found in a 2016 CDPR final report (20).

Figure 10. Runoff of parent fipronil compound around houses in 2016. See Table 5 for treatment list. N = 5 houses. Note that day 30 runoff profile is similar to the pretreatment profile. The horizontal line in each treatment box shows the median value and the whiskers show the ranges of values. Asterisks are near outliers, circles are far outliers.

Conclusions Our goal was to identify best management practices for controlling ants around houses while mitigating potential runoff of fipronil. Around urban houses, driveways are the most direct route of pesticide movement to the streets and stormwater drains that feed into urban waterways. For that reason, we considered 469 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

applications at the driveway of prime importance. The constructed wall helped test various hypotheses relating to applications of different bandwidths and concentrations of these two insecticides. Those studies were combined with similar trials around houses to get a real-world perspective on how to reduce runoff. To summarize some significant findings about fipronil from our studies: • • • •

•

Fipronil and degradates can persist in the environment for more than 1 year at concentrations above US EPA chronic benchmarks; Pin stream applications that reduce the fipronil mass have lower fipronil runoff than the labeled fipronil rate; Ant efficacy can be maintained around the house perimeter if fipronil is not applied to the driveway–garage door interface; When fipronil is applied to the house perimeter but not to the driveway–garage door interface, fipronil runoff concentrations are similar to background levels; and Fipronil should not be applied 30 days prior to the rainy season or during California’s rainy season.

The continued finding of fipronil in urban waterways has led to a new product label for Termidor SC in California (23). The new standard label (effective 2018) allows the use of only 0.95 L per 92.9 m2 of Termidor SC 0.3% finished dilution applied up to four times per calendar year and no reapplication intervals of less than 60 days. Furthermore, it may not be applied on driveways. PMPs may be concerned that ant control cannot be maintained with these reduced rates of fipronil application. However, our experience with a CDPR Pest Management Alliance grant (24) is encouraging. Before the studies described here, various applications of fipronil sprays to control Argentine ants had been tested. Applications of 11.3–15.1 L of 0.06% fipronil along the foundation (30.5 cm up and 30.5 cm out) and along structural guidelines, trails along the edge of sidewalks, driveways, and nests provided more than 90% reduction in ants for at least 8 weeks (25). In conjunction with bifenthrin granules, similar spray applications provided more than 93% reduction for at least 8 weeks (26). When 4 L of 0.06% fipronil were applied as a 5 cm band along the foundation and around doors, windows, and points of entry, there was an 80% reduction in the number of ants at week 8 (27). Similarly, a pin stream application of 4 L of fipronil provided 85% reductions for 6 weeks compared with a 46% reduction when applied as a fan spray (28). When 2 L were applied as a pin stream, there was only a 26% reduction at week 6. As the amounts of fipronil applied around the structure were reduced, the levels of ant reductions also decreased. The level of customer satisfaction for PMPs is measured by the number of complaints and retreatments and successful treatment strategies that result in less than 3% retreatments (24). For example, PMPs were able to successfully reduce the amount of pyrethroids applied to control ants by at least 50% and maintain excellent customer satisfaction. The reductions were achieved by a number of different means depending upon the company and its standard 470 Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

operating procedures. Eliminating every-month applications and beginning every-other-month or quarterly applications helped reduce applications by 50–60%. Another strategy was to replace the pyrethroid applications with alternative sprays and baits. Both of these approaches, however, were dependent upon the use of fipronil sprays early in the ant season and late summer applications when necessary. During the Pest Management Alliance trials, the reductions in the applications of pyrethroids and the alternative strategies employed were well-received by the customers. The technicians on the Integrated Pest Management (IPM) routes did not spend more time servicing accounts. In some cases, the IPM routes had slightly higher insecticide costs than the conventional routes. However, these were not significant. In fact, several of the PMPs have adopted these IPM routes throughout the company. Based on our experience with the Pest Management Alliance, it is likely that the reduced levels of fipronil use mandated by new labels, when supplemented with botanicals, granular products, and ant baits, will satisfy residential customers.

Acknowledgments We acknowledge the valuable assistance during these studies by the California Department of Pesticide Regulation and especially Mike Ensminger, Robert Budd, and Kean Goh. Fred Ernst was invaluable in construction of equipment and in methodology for doing water runoff studies. The laboratory of Jay Gan did the chemical analysis of the water samples. Contract 13-C0031 was funded from the US EPA Cooperative Agreement Performance Partnership Grant # 00T11414 and contract 14-C0102 was funded from the Department of Pesticide Regulation Fund (an internal strategic investment project).

References 1. 2.

3.

4.

5.

Ebeling, W. Urban Entomology; Division of Agricultural Sciences, University of California: Berkeley, CA, 1978. Mallis, A. In Handbook of Pest Control: The Behavior, Life History, and Control of Household Pests, Edition 10; Hedges, S. A., Moreland, D., Eds.; Mallis Handbook and Technical Training Company: Cleveland, OH, 2011. Suspended, Cancelled, and Restricted Pesticides; United States Environmental Protection Agency: Washington, DC, 1990. https:// nepis.epa.gov/Exe/ZyPDF.cgi/20011E0G.PDF?Dockey=20011E0G.PDF (accessed Aug 24, 2018). Interim Reregistration Eligibility Decision Facts; United States Environmental Protection Agency: Washington, DC, 2004. https://archive.epa.gov/pesticides/reregistration/web/pdf/diazinon_ired.pdf (accessed Aug 27, 2018). Interim Reregistration Eligibility Decision for Chlorpyrifos; United States Environmental Protection Agency: Washington, DC, 2001. 471

Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

https://www3.epa.gov/pesticides/chem_search/reg_actions/reregistration/ ired_PC-059101_28-Sep-01.pdf (accessed Aug 26, 2018). California Pesticide Information Portal (CALPIP); California Department of Pesticide Regulation: Sacramento, CA, 2013. http://calpip.cdpr.ca.gov/ main.cfm (accessed Aug 24, 2018). Amweg, E. L.; Weston, D. P.; You, J.; Lydy, M. J. Pyrethroid Insecticides and Sediment Toxicity in Urban Creeks from California and Tennessee. Environ. Sci. Technol. 2006, 40, 1700–1706. Holmes, R. W.; Anderson, B. S.; Phillips, B. M.; Hunt, J. W.; Crane, D. B.; Mekebri, A.; Connor, V. Statewide Investigation of the Role of Pyrethroid Pesticides in Sediment Toxicity in California’s Urban Waterways. Environ. Sci. Technol. 2008, 42, 7003–7009. Weston, D. P.; Lydy, M. J. Urban and Agricultural Sources of Pyrethroid Insecticides to the Sacramento-San Joaquin Delta of California. Environ. Sci. Technol. 2010, 44, 1833–1840. Environmental Hazard and General Labeling for Pyrethroid and Synergized Pyrethrins Non-Agricultural Outdoor Products; United States Environmental Protection Agency: Washington, DC, 2017. https://www.epa.gov/ingredients-used-pesticide-products/environmentalhazard-and-general-labeling-pyrethroid-and (accessed Aug 24, 2018). Surface Water Protection in Outdoor Nonagricultural Settings; California Department of Pesticide Regulation: Sacramento, CA, 2013. http:// www.cdpr.ca.gov/docs/legbills/calcode/040501.htm#a6970 (accessed Aug 24, 2018). Budd, R.; Ensminger, M. P.; Wang, D.; Goh, K. S. Monitoring Fipronil and Degradates in California Surface Waters, 2008–2013. J. Environ. Qual. 2015, 44, 1233–1240. Field, H. C.; Evans, W. E.; Hartley, R.; Hansen, L. D.; Klotz, J. H. A Survey of Structural Ant Pests in the Southwestern U.S.A. (Hymenoptera: Formicidae). Sociobiology 2007, 49, 151–164. Vetter, R. S.; Reierson, D. A.; Rust, M. K. Cobweb Management and Control of the Spider Holocnemus pluchei (Araneae: Pholcidae) on Buildings. J. Econ. Entomol. 2011, 104, 601–606. Greenberg, L.; Rust, M. K. Final Report: Runoff from Concrete Wall; California Department of Pesticide Regulation: Sacramento, CA, 2013. https://www.cdpr.ca.gov/docs/emon/surfwtr/contracts/ucriverside_11C0086_final.pdf (accessed Aug 29, 2018). Greenberg, L.; Rust, M. K.; Klotz, J. H.; Haver, D.; Kabashima, J. N.; Bondarenko, S.; Gan, J. Impact of Ant Control Technologies on Insecticide Runoff and Efficacy. Pest Manage. Sci. 2010, 66, 980–987. Greenberg, L.; Rust, M. K.; Richards, J.; Wu, X.; Kabashima, J. N.; Wilen, C.; Gan, J.; Choe, D.-H. Practical Pest Management Strategies to Reduce Pesticide Runoff for Argentine Ants (Hymenoptera: Formicidae) control. J. Econ. Entomol. 2014, 107, 2147–2153. Greenberg, L.; Rust, M. K.; Wright, S.; Choe, D.-H. Argentine Ant Control Around Homes: Efficacy of Treatments and Urban Runoff. Int. J. Pest Manage. 2017, 63, 242–250. 472

Goh et al.; Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management ACS Symposium Series; American Chemical Society: Washington, DC, 2019.

19. Aquatic Life Benchmarks for Pesticide Registration; United States Environmental Protection Agency: Washington, DC, 2017. https:// www.epa.gov/pesticide-science-and-assessing-pesticide-risks/aquatic-lifebenchmarks-pesticide-registration (accessed Aug 24, 2018). 20. Greenberg, L.; Rust, M. K.; Ensminger, M. P. Final Report for CDPR June 2016, Contract 13-C0031; California Department of Pesticide Regulation: Sacramento, CA, 2016. http://cdpr.ca.gov/docs/emon/surfwtr/contracts/ ucriverside_13-C0031_final_rpt.pdf (accessed July 28, 2018). 21. Budd, R.; Luo, Y.; Singhasemanon, N. Addendum: Evaluation of Alternative Fipronil Use Scenarios: Modeling Results, Runoff Trials, and Product Efficacy; California Department of Pesticide Regulation: Sacramento, CA, 2017. http://cdpr.ca.gov/docs/emon/pubs/ehapreps/analysis_memos/ fipronil_addendum_6-26-17_update.pdf (accessed July 28, 2018). 22. Greenberg, L.; Rust, M. K.; Ensminger, M. P. Final Report for CDPR Contract #14-C0102; California Department of Pesticide Regulation: Sacramento, CA, 2017. https://www.cdpr.ca.gov/docs/emon/surfwtr/ contracts/ucriverside_14-C0102_final_report.pdf (accessed July 28, 2018). 23. Singhasemanon, N.; Gutierrez, C. Surface Water Mitigation Measures for Certain Fipronil Products; California Department of Pesticide Regulation: Sacramento, CA, 2017. https://www.cdpr.ca.gov/docs/dept/prec/2017/ 081817_fipronil.pdf (accessed Aug 28, 2018). 24. Rust, M. K. Integrated Pest Management Alliance Grant Urban Pest Ant Management (DPR Grant No. 07-PML-G001); California Department of Pesticide Regulation: Sacramento, CA, 2010. https://www.cdpr.ca.gov/ docs/pestmgt/grants/final-reports/urban_pest_ant_mngmt.pdf (accessed July 28, 2018). 25. Klotz, J. H.; Rust, M. K.; Greenberg, L.; Field, H. C.; Kupfer, K. An Evaluation of Several Urban Pest Management Strategies to Control Argentine Ants (Hymenoptera: Formicidae). Sociobiology 2007, 50, 391–398. 26. Klotz, J. H; Rust, M. K.; Field, H. C.; Greenberg, L.; Kupfer, K. Controlling Argentine Ants in Residential Settings (Hymenoptera: Formicidae). Sociobiology 2008, 51, 579–588. 27. Klotz, J. H; Rust, M. K.; Field, H. C.; Greenberg, L.; Kupfer, K. Low Impact Directed Sprays and Liquid Baits to Control Argentine Ants (Hymenoptera: Formicidae). Sociobiology 2009, 54, 101–108. 28. Klotz, J. H.; Rust, M. K.; Greenberg, L.; Robertson, M. Developing Low Risk Management Strategies for Argentine Ants (Hymenoptera: Formicidae). Sociobiology 2010, 55, 779–785.


Ant Control and Insecticide Runoff around Urban Houses - American

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