UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

DATE: June 30, 2014 

SUBJECT: Addendum to the risk assessment for the proposed new use of spirotetramat on 

lawns and turf in a formulated product (12ESP703 SC Insecticide) with 

imidacloprid (PC 392201; DP Barcode 413577) /J . 

FROM: 

Environmental 

Joseph DeCant,

Risk 

. Ecologist 

Branch 5 _4 

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Environmental Fate and Effects Division (7501P) jl p. · ,po 7 

THROUGH: Mah T. Shamim, Ph.D, Branch Chief 

Environmental Risk Branch 5 

Environmental Fate and Effects Division 

TO: Rita Kumar, Risk Manager Reviewer 

Reuben Baris, Risk'Manager #07 

Insecticide and Rodenticide Branch 

Registration Division (7505P) 

The Environmental Fate and Effects Division (EFED) completed a risk assessment for . the 

proposed new use of spirotetramat on turf and lawns in a formulated product with imidacloprid in 

February of 2014 (D413577). In the risk assessment, EFED highlighted the risk associated with 

the use of spirotetramat alone on turf and lawns as well as these risk concerns in light of the overall 

risk picture associated with the proposed formulated product. This addendum provides further 

detail in terms of the differentiation between the risk picture associated with the proposed use of 

spirotetramat on turf and lawns within the context ofthe proposed formulated product, as well as 

corrections to the risk profile of the formulated product. 

The risk assessment (D413577) contains a table that illustrates the risks associated with 

spirotetramat alone compared to the overall risk picture of the formulated product based on 

previous assessments of both spirotetramat and imidacloprid that evaluated use rates similar to the 

rates in the proposed formulated product. This addendum provides a revised Table 1 that 

illustrates this comparison in the risk profiles and updates some of the risk conclusions associated 

with the formulated product based on previous risk assessments. When comparing the risk 

profiles, it is evident that the formulated product has a much broader risk profile than spirotetramat 

alone. The risk profile for the formulated product is primarily driven by the inclusion of 

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imidacloprid in the formulated product. Imidacloprid is already registered on turf, and the first 

EFED risk assessment for turf and lawn uses related to imidacloprid was conducted in 1993 

(D179364) at a maximum rate of 0.5 lb a.i./A, which is the currently proposed rate. However, 

EFED methods have evolved considerably since the first assessment, and so the contribution of 

imidacloprid to the risk profile of the formulated product is a function of a more recent assessment 

as the original assessment on turf and lawns did not capture the entire risk picture of imidacloprid.

Table 1. Summary of environmental risk conclusions for various taxa exposed to 

spirotetramat alone and the formulated product for the proposed use on turf and 

lawns.

Assessment Endpoint

Identified Risk of 

Concern with 

Spirotetramat Alone

Identified Risk of Concern with the 

Formulation

Acute and Chronic Risk to 

Freshwater and Estuarine/marine 

Fish

None None

Acute and Chronic Risk to 

Freshwater and Estuarine/Marine 

Invertebrates

None Acute and Chronic risk to freshwater and 

estuarine/marine invertebrates

Aquatic Benthic Invertebrates None Acute and Chronic risk to freshwater and 

estuarine/marine benthic invertebrates

Aquatic Non-Vascular and 

Vascular Plants None None

Acute and Chronic Risk to Birds Chronic risk to birds

Chronic risk to birds (see description

below for more information regarding the 

uncertainty in this conclusion)*

Acute and Chronic Risks to 

Mammals None Acute risk to mammals**

Risks to Upland and Wetland 

Plants None None

Risk to Pollinating Bees Risk to pollinating bees Risk to pollinating bees

*In the risk assessment (D413577), the risk summary stated that risk of concern related to acute and chronic 

risk to birds. However, the risk of concern for spirotetramat and imidacloprid based on previous assessments at 

the proposed maximum application rates is only for chronic risk.

**In the risk assessment (D413577), the risk summary stated that the risk of concern related to chronic risk to 

mammals. However, the risk of concern relates to acute risk to mammals based on a previous assessment of 

imidacloprid at the maximum use rate of 0.5 lb a.i./A.

This first risk assessment for imidacloprid on turf (D179364) found risk of concern to aquatic 

invertebrates, birds, and fish. It is important to note that the risk for fish was derived from the 

uncertainty associated with a lack of data on chronic toxicity of imidacloprid to fish. Since this 

assessment, the registrant has submitted additional data on the chronic toxicity of imidacloprid to 

fish that shows low toxicity on a chronic basis. Consequently, there is no chronic risk of concern 

to fish from the formulated product. 

In contrast, the risks of concern to avian and aquatic invertebrate species remain for the proposed 

formulated product. The risk of concern to aquatic invertebrates associated with the formulated 
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product is also driven solely by imidacloprid at the proposed use rates. Spirotetramat contributes 

to the risk to birds as its chronic toxicity presents a risk of concern based on a previous assessment 

(D398764, banana/plantain use) that assessed an application rate similar to the currently proposed 

use rate. A more recent evaluation of imidacloprid on caneberry (D334030+) at 0.5 lb a.i./A 

corroborates the concern for birds from the original assessment of imidacloprid use on turf and 

employed updated terrestrial modeling methods. The presence of imidacloprid as it relates to food 

avoidance may attenuate this risk from spirotetramat, though there is some uncertainty in this 

conclusion. The uncertainty in the conclusion on avoidance derives from the high acute toxicity 

of imidacloprid, yet avoidance behavior is evident in the dietary toxicity studies with imidacloprid. 

As noted in the imidacloprid assessment (D334030+), the avoidance of birds to imidacloprid 

treated food items is a learned response mediated by post-ingestional distress. In other words, 

birds will initially feed on imidacloprid contaminated food items that lead to a toxic response. If 

the birds survive, they stop feeding on the contaminated food. In addition, incidents related to 

imidacloprid have been recorded of secondary toxicity to birds whereby surfaced dead grubs 

appeared to have been eaten by birds, resulting in the death of several young and adult robins.

Consequently, it appears that dose and tolerance of the bird to an initial consumption of 

imidacloprid may determine the potential for mortality to birds that consume food items 

contaminated by the formulated product where both spirotetramat and imidacloprid are toxic to 

birds. It seems then that imidacloprid likely drives the risk of concern for birds as well with this 

formulated product, either leading to avoidance or mortality depending on the dose of imidacloprid 

and the initial tolerance of the bird.

The updated risk assessment for imidacloprid on caneberry (D334030+) also differed from the 

original assessment of imidacloprid on turf for mammals. This assessment on caneberry, using 

updated terrestrial modeling methods, found acute risk to mammals at the maximum application 

rate of 0.5 lb a.i./A, which is the same application rate in the proposed formulated product. 

Consequently, imidacloprid also drives the risk to mammals for the proposed formulated product 

with both spirotetramat and imidacloprid. In terms of synergy between spirotetramat and 

imidacloprid, EFED evaluated the acute oral toxicity data related to mammals for the formulated 

product (MRID 48977303) relative to the data for spirotetramat alone. The acute oral LD50 for 

spirotetramat technical is >2000 mg a.i./kg, whereas for imidacloprid technical the LD50 is 424 mg 

a.i./kg and more closely matches the toxicity of the formulated product (500 mg/kg). The data on 

the formulated product combining both spirotetramat and imidacloprid therefore does not show 

synergy related to acute mammalian toxicity but rather confirms that the risk to mammals is likely 

driven by imidacloprid in the formulated product.

In summary, the risks of concern contributed by spirotetramat alone in the formulated product, as 

noted in D413577, relate to chronic risk to birds and risk to pollinating bees and potentially other 

beneficial arthropods. The risks of concern for other taxa, and likely the concern for birds as well,

associated with the formulated product highlighted in Table 1, however, are driven by 

imidacloprid.