UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

SEP 10 2015 

MEMORANDUM 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: Response to Benefits and Usage Comments from Stakeholders, Received for the 

Dicrotophos Registration Review Docket 

FROM: Nikhil 

Biological 

Mallampalli, 

Analysis Branch 

Entomologist tit i c/ /k 

-

~ 

Biological and Economic Analysis Division 7503P) 

THRU: Arnet Jones, Chief 

Biological Analysis Branch 

Biological and Economic Analysis Division (7503P) 

TO: Khue Nguyen, Chemical Review Manager 

Neil Anderson, Branch Chief 

Ris~ Management and Implementatidn Branch 1 

Pesticide Reevaluation Division (7508P) 

BEAD Product Review Panel date: August 6, 2015 

INTRODUCTION 

In 2014, EPA released preliminary human health and ecological risk assessments in support of 

the registration review of dicrotophos for public comment. In this memorandum, BEAD 

responds to substantive comments that addressed the usage or pest management benefits of 

dicrotophos in cotton (which is the only currently registered agricultural use in the United 

States). 

For these comments, an itemized summary of each is shown below, with the BEAD response 

following immediately below each comment. In general, BEAD agrees with commenters that 

dicrotophos is an important pest control option where certain stink bug pests are persistent or 

high in populations. However, for other cotton insect pests BEAD has not changed its conclusion 

that growers are using several alternatives to a greater extent than dicrotophos. Most of the usage 

information in the comments supported the BEAD usage memorandum that is also part of the 

dicrotophos registration review docket (EPA-HQ-OPP-2008-0440). 

Details of the comments and BEAD's response follow below. 

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Comments from the Arizona (AZ) Pest Management Center. 

• Dicrotophos is used only on cotton, and exclusively for control of brown stink bug in AZ 

• Dicrotophos is used sparingly--only 12% AZ cotton acreage treated in 2013 

• Without stink bug control, the industry is vulnerable to aflatoxin contamination that 

affects injured plant parts 

• The current re-entry interval (REI) of 6 days is too restrictive; stakeholders wish to 

change it to 72 hrs. The 6 day REI prevents timely scouting and decision making in the 

field 

• Stink bugs are responsible for about 23% of total losses associated with insect damage -

an economic impact equivalent to $5.9 million 

• In replicated field efficacy trials, d1crotophos killed the largest fraction of brown stink 

bugs 

• The Arizona Pest management center submitted information on use distribution in AZ, 

median and 9Qth percentile use rates, and application timing 

BEAD Response 

BEAD appreciates the additional information on area treated in Arizona cotton and on the 

issue with aflatoxin. The importance of dicrotophos in recent years in Arizona cotton production 

has already been emphasized in BEAD's memorandum to EFED (Mallampalli et al. 2014). 

BEAD notes that several sources, including Arizona, also mention that acephate and bifenthrin 

still have good efficacy against the brown stink bug). That said, BEAD recognizes that stink bug 

management has become an increasing problem in recent years and that dicrotophos is one of a 

very limited set of effective options available to growers at the moment. 

Regarding a need for a shorter REI, BEAD notes that the Worker Protection Standard 

(WPS) guidance allows for exemptions to permit certified crop advisors wearing the appropriate 

personal protective equipment (PPE) to enter treated fields during an REI, in order to assess the 

need for any additional treatment. This should provide a way to continue to use IPM tactics to 

manage pests. Given this exception, and the lack of detail in this comment, it is not clear to 

BEAD why a shorter REI is so critically needed. 

Comments from the National Cotton Council (NCC) 

• Stink bugs are the most important target pest; NCC believes that there are no other 

effective alternatives for the management of stink bugs without killing beneficial insects. 

• Major insect pests for cotton (in general) are thrips, aphids, plant bugs, fleahoppers, stink 

bugs, leaf-footed bugs 

• Dicrotophos is critical as part of an effective IPM system, since effectiveness of seed 

treatments is limited to 30-40 days 

• To manage plant bugs, growers rteed to retain ability to apply dicrotophos at 0.33 lbs 

ai/acre three times per season, or 0.5 lbs ai/ A two times per season 

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• The comments from NCC included 9 letters from university experts in 8 cotton states. 

All oppose using untreated buffers in fields because it is counter to proper IPM practices, 

because it allows pests to migrate back into cotton from untreated areas and places undue 

burden on growers, since most infestations start from the edge of the field. 

• The current 14 day retreatment interval already too restrictive, a larger interval would be 

worse. The 14 day retreatment interval is acceptable most of the 'time, but problematic 

during periods of intense migration of adult brown stink bugs to cotton. 

BEAD Response 

BEAD appreciates the details provided in the NCC comments. The importance of 

dicrotophos as a control option for plant bugs and stinkbugs reflects the discussion in BEAD's 

own usage analysis (Mallampalli et al. 2014). However, proprietary data, summarized in 

Mallampalli et al. (2014) indicate that most growers in recent years have applied dicrotophos no 

more than two times per season, and the average rate is, at most, about 0.33 lb a.i./acre. BEAD 

also noted in 2014 that several alternatives including other organophosphates, pyrethroids, insect 

growth regulators, etc. are in use for plant bugs management. For stinkbugs, the list of · 

alternatives is shorter, and BEAD noted in its memorandum that for this set of pests effective 

alternatives appear to be much more limited. 

Regarding the assertion that the current 14 day retreatment interval is too restrictive, it is not 

clear to BEAD why growers cannot use one of the available alternatives if pest pressure is 

particularly high in cases where they cannot wait 14 days to control pests. Regarding the issue of 

"untreated" buffers that may be required for dicrotophos applications, BEAD capnot find a 

reason why such buffers could not be treated with alternatives to dicrotophos, assuming that their 

labels remain unchanged in this context. 

Therefore, it is not clear why such buffers would .create an insurmountable problem, at least 

in terms of stopping the inward spread of migrating stinkbugs and plant bugs. That said, BEAD 

agrees that such a combination strategy (i.e., treatment of buffers with alternatives plus 

dicrotophos treatment within fields) would increase overall pesticide usage on a given cotton 

field (and increase production costs to an unknown extent). 

Comments from AMV AC (registrant for dicrotophos) 

• Information on pest pressure and control strategies, with the following main points, was 

provided: 

For plant bug management, growers use 8-10 applications (of all insecticides, 

including but not limited to dicrotophos) in a growing season. Of these, key active 

ingredients used in resistance management rotation are thiamethoxam, imidacloprid, 

acephate, oxamyl, sulfoxaflor, and pyrethroids. Dicrotophos is applied after first bloom, 

in rotation after neonicotinoid insecticides are used. It is sometimes applied in the late 

season when there are mixed populations of plant and stink bugs. 

For stink bug management, growe s use 4-6 applications of insecticide in a 

growing season. Common active ingredients used are dicrotophos, acephate, pyrethroids, 

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and neonicotinoids. Three stink bugs occur in cotton - green, southern green, and brown. 

Dicrotophos works on all stink bugs, but is most effective against brown stink bugs. 

• Information on dicrotophos application parameters with the following main points, was 

also provided: 

For early season use (emergence to pre-bloom)-one application for thrips or 

leafhoppers is typical. For late season use (first bloom to 30 days prior to harvest -

Early season use cost is $4.50/A for dicrotophos compared to $12/A for acetamiprid. Use 

of acephate in lieu of dicrotophos triggers spider mites and cotton aphids. A broad 

assertion that dicrotophos is "essential" for late season use was made. 

• Information on aerial application and buffers with the following main points, was also 

provided: 

Aerial applicatio!l is critical for early and late season application. Wet field 

conditions prevent ground applications, particularly in the mid-South and Southeast. 

Growers rely on aerial application when weather is wet. AMV AC opposes buffers. 

Untreated areas ~ound fields is not acceptable IPM practice, and gives pests the 

opportunity to reinfect the field. 

• Information on retreatment interval was also provided: 

· Current 14 day retreatment interval allows growers flexibility while still limiting 

environmental impact. Further restrictions on the retreatment interval would increase use 

of other active ingredients and result in more harm to pollinators. 

BEAD Response 

BEAD appreciates the general information op. cotton pest management. BEAD has 

already pointed out the importance of dicrotophos as a control option where plant and stink bugs 

are involved (Mallampalli et al. 2014). Where thrips are a major pest, however, it is not clear to 

BEAD (from this comment) why growers could not use several other alternatives shown in use 

by proprietary data and recommended by several cotton production guides (e.g, MSU 2015, 

VGA 2014). These include acephate, aldicarb, imidacloprid, dimethoate, and spinetoram. 

In its 2014 memorandum, BEAD noted the value of dicrotophos as one plant and 

stinkbug control option, and discussed the recent usage and recominendations of some other 

insecticides for the same purposes, many of which were mentioned in the comment summarized 

above. However, BEAD did not see any discussion in the comment of the impact on yield or 

production costs if dicrotophos use was replaced with these alternatives. Without such 

information, BEAD must stand by its qualitative conclusion (Mallampalli et al. 2014) that 

dicrotophos is an occasionaUy important component of cotton pest management programs. 

Regarding the importance of aerial application, BEAD acknowledges that this treatment 

method appears to be more prevalent in mid-Southern cotton. This is supported by recent 

proprietary usage survey data. However, on a national scale, the vast majority of dicrotophos 

applications (over 80 % for the years 2008-2012) are made by ground-based equipment, 

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~ . ' . 

indicating that the majority of cotton growers in the country are usually able to apply dicrotophos 

this way. 

Regarding the tendency of acephate to cause outbreaks of mite and aphid pests, BEAD 

acknowledges that this insecticide has been described as increasing spider mite populations in 

hot, dry weather conditions (e.g., Reissig 2014). However, this effect can occur with other 

widely used cotton insecticides, such as neonicotinoids and some pyrethroids (MSU 2015, Smith 

et al. 2013). BEAD is unaware of research documenting a similar impact on cotton aphid 

populations and would consider any such information submitted by the commenter. BEAD is 

also unable to substantively evaluate the impact of such effects from acephate as a dicrotophos 

alternative, based on the content of the comment. 

The issue of "untreated" buffers has been addressed in BEAD' s response to the previous 

comment (above). 

REFERENCES 

Mallampalli, N, J. Becker, and D. Atwood. 2014. Information to support registration review of 

dicrotophos: cotton crop phenology in the southern U.S., recent dicrotophos use patterns; 

and potential alternative insecticides. Available at www.regulations.gov in docket EPAHQ-OPP-2008-0440. 

MSU. 2015. Insect Control Guide for Agronomic Crops. Available from Mississippi State 

University on the web at http://msucares.com/insects/cotton/index.html. [Accessed June 

2015]. 

Reissig, D. 2014. Alternatives to Acephate for Thrips and Dealing with Lackluster Management. 

Available on the web at http://cotton.ces.ncsu.edu/2014/05/alternatives-to-acephate-forthrips-and-dealing-with-lackluster-management/ [Accessed June 2015]. 

Smith, J.F., A.L. Catchot, F.R. Musser, and J. Gore. 2013. Effects of aldicarb and neonicotinoid 

seed treatments on twospotted spider mite on cotton. J. Econ. Entomol. 106(2): 807-815. 

UGA. 2014. Cotton Production Guide. Publication# CSS-14-01 of the University of Georgia 

College of Agricultural and Environmental Sciences Cooperative Extension. Available on 

the web at www.ugacotton.com. [Accessed June 2015]. 

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