Costs and Benefits of Controlling Diabrotica : The USA Experience . Paul D. Mitchell Agricultural and Applied Economics University of Wisconsin-Madison Presentation to EU DIABR-ACT Project Group Wageningen, Netherlands April 3, 2007. Outline of Presentation. - PowerPoint PPT Presentation
Costs and Benefits of Costs and Benefits of Controlling Controlling Diabrotica Diabrotica : : The USA Experience The USA Experience Paul D. Mitchell Paul D. Mitchell Agricultural and Applied Economics Agricultural and Applied Economics University of Wisconsin-Madison University of Wisconsin-Madison Presentation to EU DIABR-ACT Presentation to EU DIABR-ACT Project Group Project Group Wageningen, Netherlands April 3, Wageningen, Netherlands April 3, 2007 2007
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Costs and Benefits of Costs and Benefits of Controlling Controlling DiabroticaDiabrotica: : The USA Experience The USA Experience
Paul D. MitchellPaul D. MitchellAgricultural and Applied EconomicsAgricultural and Applied Economics
University of Wisconsin-MadisonUniversity of Wisconsin-MadisonPresentation to EU DIABR-ACT Project Presentation to EU DIABR-ACT Project
GroupGroupWageningen, Netherlands April 3, 2007Wageningen, Netherlands April 3, 2007
Outline of PresentationOutline of Presentation CRW species and distribution in USACRW species and distribution in USA Current problems in USACurrent problems in USA My work: Damage functions, IPM, IRMMy work: Damage functions, IPM, IRM Cost of CRW control and damage in Cost of CRW control and damage in
USAUSA
DiabroticaDiabrotica Pests of Corn in Pests of Corn in USAUSA
Western CRW Western CRW D. virgifera virgiferaD. virgifera virgifera Northern CRW Northern CRW D. barberiD. barberi Southern CRW Southern CRW D.D. undecimpunctata undecimpunctata
howardihowardi Mexican CRW Mexican CRW D. virgifera zeaD. virgifera zea
Major pests: Western and Northern CRW, Major pests: Western and Northern CRW, where I will focus except for this overviewwhere I will focus except for this overview
Northern Corn Rootworm
Western Corn Rootworm
Mexican Corn RootwormSouthern Corn Rootworm
Western Northern Southern
NortherNorthernn
WesternWestern
MexicanMexican
SoutherSouthernn
CRW Control Methods used in CRW Control Methods used in USAUSA
Crop Rotation (CRW mostly monophagous)Crop Rotation (CRW mostly monophagous) Most popular, but failing due to resistanceMost popular, but failing due to resistance
Soil Insecticides applied at plant for larvaeSoil Insecticides applied at plant for larvae Most popular alternative, but many not likeMost popular alternative, but many not like
Aerial Insecticide to stop adult egg layingAerial Insecticide to stop adult egg laying Popular where use aerial control for other pestsPopular where use aerial control for other pests
Bt Corn (transgenic insecticide)Bt Corn (transgenic insecticide) Convenient, effective, but needs refuge for IRMConvenient, effective, but needs refuge for IRM
Recent CRW Problems in Recent CRW Problems in USAUSA
Resistance ManagementResistance Management Development and spread of resistance Development and spread of resistance
to previously effective control methodsto previously effective control methods Implementation of IRM for Bt cornImplementation of IRM for Bt corn
Valuing new control technologiesValuing new control technologies Seed treatments and Bt corn relatively Seed treatments and Bt corn relatively
newnew Value of control in first-year cornValue of control in first-year corn
Rotation ResistanceRotation Resistance Rotation widely used to manage CRW, only Rotation widely used to manage CRW, only
corn following corn needed chemical controlcorn following corn needed chemical control Development and spread of WCR soybean Development and spread of WCR soybean
variant that lays eggs in non-corn crops (e.g., variant that lays eggs in non-corn crops (e.g., soybeans)soybeans)
NCR extended diapause increased so now NCR extended diapause increased so now many eggs hatch after 2 or more wintersmany eggs hatch after 2 or more winters
Both cause collapse of rotation for crw controlBoth cause collapse of rotation for crw control Both arose in mid 1990’s in different areasBoth arose in mid 1990’s in different areas WCR more rapid spread, NCR slower spreadWCR more rapid spread, NCR slower spread Rotated corn now needs rootworm control in Rotated corn now needs rootworm control in
many areas where it previously did notmany areas where it previously did not
Rotation Resistance in 2003Rotation Resistance in 2003
Effect of Rotation Effect of Rotation ResistanceResistance
Initially increased insecticide use, Initially increased insecticide use, especially in hard hit states of IL and INespecially in hard hit states of IL and IN
More recently, increasing adoption of Bt More recently, increasing adoption of Bt corn in IL and IN where had been corn in IL and IN where had been relatively low adoption of ECB Bt corn relatively low adoption of ECB Bt corn
Anecdotal data to support these claimsAnecdotal data to support these claims
0
10
20
30
40
50
60
1990 1995 2000 2005% A
cres
Tre
ated
with
Inse
ctic
ide IL
INIAMNMIOHWI
Note: We do not know that CRW was the Note: We do not know that CRW was the target pesttarget pest
0
10
20
30
40
50
60
1990 1995 2000 2005
% C
orn
Acr
es T
reat
ed
ILINIAIL BtIN BtIA Bt
Do not know target pest or % RW vs CB Bt Do not know target pest or % RW vs CB Bt corncorn
-202468
101214
2002 2003 2004 2005 2006
Add
itve
% In
crea
se B
t ILINIAMNWI
Demand for CRW EconomicsDemand for CRW Economics With rotation resistance spreading, many With rotation resistance spreading, many
farmers were suddenly interested in crw controlfarmers were suddenly interested in crw control What is the cost of crw damage in first-year corn?What is the cost of crw damage in first-year corn? When is crw control worth the cost in first-year corn?When is crw control worth the cost in first-year corn?
Seed treatments and RW Bt corn newly Seed treatments and RW Bt corn newly commercialized control methodscommercialized control methods What is the net benefit of a seed treatment? What is the net benefit of a seed treatment? What is the net benefit of RW Bt corn?What is the net benefit of RW Bt corn?
My work was a few papers, but mostly ExtensionMy work was a few papers, but mostly Extension
CRW IPM for Rotation CRW IPM for Rotation ResistanceResistance
CRW IPM in corn after corn rarely adoptedCRW IPM in corn after corn rarely adopted Lots of crw treatments were being applied Lots of crw treatments were being applied
that were not needed or were not economicalthat were not needed or were not economical Universities documented spread of rotation Universities documented spread of rotation
resistance so farmers know if in a risk arearesistance so farmers know if in a risk area Others worked to develop IPM for first year Others worked to develop IPM for first year
corncorn Pherocon AM traps in soybean fieldsPherocon AM traps in soybean fields Threshold: 5 beetles/trap/dayThreshold: 5 beetles/trap/day
I currently have grants to work on CRW IPM I currently have grants to work on CRW IPM for first-year cornfor first-year corn
RW Bt corn commercialized with refuge RW Bt corn commercialized with refuge requirement similar to that for CB Bt cornrequirement similar to that for CB Bt corn 20% refuge in field or in adjacent field20% refuge in field or in adjacent field
What is the cost of refuge? What is the cost of refuge? Does this cost justify the benefit of refuge?Does this cost justify the benefit of refuge? Can we manage resistance to rotation?Can we manage resistance to rotation? My Work on Economics of IRMMy Work on Economics of IRM
Simultaneous WCR resistance to Bt and rotationSimultaneous WCR resistance to Bt and rotation Effect of NCR extended diapause on Bt IRMEffect of NCR extended diapause on Bt IRM Economics of refuge compliance programsEconomics of refuge compliance programs Incorporating human behavior into IRM modelsIncorporating human behavior into IRM models
Damage FunctionsDamage Functions Addressing these economic questions led my Addressing these economic questions led my
research into estimation of pest damage research into estimation of pest damage functions with experimental datafunctions with experimental data
Standard methods use behavioral dataStandard methods use behavioral data Loss isLoss is = f(x), where f( = f(x), where f(∙∙) is damage function) is damage function x is an observable damage measure related to x is an observable damage measure related to
pest population density (root rating, NIS, etc.)pest population density (root rating, NIS, etc.) x = g(n), where n is pest population density x = g(n), where n is pest population density
and g(and g(∙∙) relates pest density to damage ) relates pest density to damage measuremeasure
lossloss NIS NIS CRW CRW $ $ x x n n (() ) f(x) f(x) g(n) g(n) Scientists conduct experiments to Scientists conduct experiments to
collect data on n and xcollect data on n and x Damage function f(x) connects Damage function f(x) connects
biology and economicsbiology and economics
ExampleExample Gray and Steffey (1998): 3 years of Gray and Steffey (1998): 3 years of
field experiments on root ratings and field experiments on root ratings and yield lossyield loss
Mitchell, Gray and Steffey (2004) used Mitchell, Gray and Steffey (2004) used these data to estimate these data to estimate = f(x), where = f(x), where is % loss and x is root rating (1-6 scale)is % loss and x is root rating (1-6 scale)
Application: Cost of WCR soybean Application: Cost of WCR soybean variant to example farmer in Illinoisvariant to example farmer in Illinois
Gray and Steffey (1998) Gray and Steffey (1998) DataData
Yield for soil insecticide treated and Yield for soil insecticide treated and untreated (control) plots: Yuntreated (control) plots: Ytt and Y and Ycc
Loss Loss = (Y = (Ytt – Y – Ycc)/Y)/Ytt YYtt = 200 bu/ac and Y = 200 bu/ac and Ytt = 150 bu/ac = 150 bu/ac = (200 – 150)/200 = 0.25: 25% loss= (200 – 150)/200 = 0.25: 25% loss Root Rating for both plots RRRoot Rating for both plots RRtt and RR and RRcc x = root rating difference RRx = root rating difference RRcc – RR – RRtt How much CRW increased damage indexHow much CRW increased damage index
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
0 1 2 3 4
root rating difference
prop
ortio
nal y
ield
loss
= RRc – RRt
=
Negative Loss ProblemNegative Loss Problem Experimental noise can dominate Experimental noise can dominate
treatment effect so treated yield < control treatment effect so treated yield < control yield, implying a “negative loss” (yield, implying a “negative loss” ( < 0) < 0)
Assuming pests can only cause positive Assuming pests can only cause positive damage, observed negative losses are due damage, observed negative losses are due to experimental noise/measurement errorsto experimental noise/measurement errors
Need econometric model that allows Need econometric model that allows observedobserved negative yield losses, but limits negative yield losses, but limits loss loss due to pestdue to pest to range 0 to 1 to range 0 to 1
Composed Error ModelComposed Error ModelMitchell et al. (2004)Mitchell et al. (2004)
Borrow two part error model from Borrow two part error model from technical efficiency estimation, assumetechnical efficiency estimation, assume
Experimental noise: Experimental noise: ~ N(0, ~ N(0,22)) Treatment effect: Treatment effect: ~ Exponential, where ~ Exponential, where
exponential pdf has parameter exponential pdf has parameter = q(x) = q(x) Estimate Estimate and parameters of q(x) and parameters of q(x)
captures experimental errorcaptures experimental error q(x) captures pest damageq(x) captures pest damage
For analysis, For analysis, = 0: no experimental = 0: no experimental noisenoise
Proportional Yield Loss from WCR Soybean Proportional Yield Loss from WCR Soybean Variant in IL for both Damage Models in Monte Variant in IL for both Damage Models in Monte
Carlo AnalysisCarlo Analysis
Lower st. dev. and losses range 0 – 1 with Lower st. dev. and losses range 0 – 1 with composed errorcomposed error
Cost ($/ac) of WCR Soybean Variant Damage in Cost ($/ac) of WCR Soybean Variant Damage in First-Year Corn in IL for 3 Levels of Farmer Risk First-Year Corn in IL for 3 Levels of Farmer Risk AversionAversion
Yang et al. (2007) Unbalanced Yang et al. (2007) Unbalanced Nested Component Error ModelNested Component Error Model Use from panel data methodsUse from panel data methods Conventional (OLS): Conventional (OLS): yytlrtlr = x = xtlrtlr + + uutlrtlr Nested Error: Nested Error: yytlrtlr = x = xtlrtlr + + tt + + tltl + + tlrtlr
tt ~ N(0, ~ N(0,) random year effect) random year effect tltl ~ N(0, ~ N(0,) nested location effect) nested location effect tlr tlr ~ N(0,~ N(0,) experimental noise) experimental noise
Estimate Estimate and and , , , and , and
Yang et al. (2007)Yang et al. (2007) Paper compares several estimatorsPaper compares several estimators Focus here on Conventional OLS and Focus here on Conventional OLS and
Net benefit ($/ac) of soil insecticide and Bt corn Net benefit ($/ac) of soil insecticide and Bt corn for WCR soybean variant control in 1for WCR soybean variant control in 1stst-year corn -year corn in ILin IL
Croff et al. (2007)Croff et al. (2007) Economics of CRW IPM in first year cornEconomics of CRW IPM in first year corn Need damage function for Node Injury Need damage function for Node Injury
Scale (NIS), not the old Root RatingScale (NIS), not the old Root Rating Use NIS and Yield data from standard Use NIS and Yield data from standard
side-by-side efficacy field trialsside-by-side efficacy field trials Have data from 17 different field trials, Have data from 17 different field trials,
giving a total of 795 observations of giving a total of 795 observations of NIS and associated % loss NIS and associated % loss
Example DataExample Data Make all possible Make all possible
pairings of obs. for pairings of obs. for NIS and yield loss NIS and yield loss from same site-from same site-yearyear
If have K obs., have If have K obs., have K!/(K-2)!2! total pairs K!/(K-2)!2! total pairs
Define Define so so NIS > 0NIS > 0 If NISIf NIS11 > NIS > NIS22, , λλ
= (Y= (Y22 – Y – Y11)/Y)/Y22 If NISIf NIS11 < NIS < NIS22, , λλ
= (Y= (Y11 – Y – Y22)/Y)/Y11
Estimation ResultsEstimation ResultsEstimated modelEstimated model = = x + exp(sx + exp(s00 + s + s11x)x)x is x is NIS, NIS, ~ N(0,1) ~ N(0,1), s, s00, and s, and s11 parameters parametersRR22 = 0.207 (noisy data) = 0.207 (noisy data)
Means 9.3% yield loss Means 9.3% yield loss per 1 unit of NISper 1 unit of NIS
EstimatEstimatee
t statt stat p valuep value
0.09310.0931 18.9218.92 < < 0.0010.001
ss00 – – 2.2732.273 – – 67.6167.61
< < 0.0010.001
ss11 0.11310.1131 3.0513.051 0.0020.002
-0.60
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
0 0.5 1 1.5 2 2.5 3
CRW Damage FunctionsCRW Damage Functions Form the basis of many types of economic Form the basis of many types of economic
analysis of CRW problemsanalysis of CRW problems Value of new control methodsValue of new control methods Benefit of eradication/suppressionBenefit of eradication/suppression Cost of invasive speciesCost of invasive species Impact of pesticide bans/regulationsImpact of pesticide bans/regulations Derive IPM action thresholdsDerive IPM action thresholds Derive Optimal IRM StrategiesDerive Optimal IRM Strategies
Some work done, more work in progress, Some work done, more work in progress, more work needs to be donemore work needs to be done
Impact of CRW in USA: Impact of CRW in USA: Updating Metcalf (1986)Updating Metcalf (1986)
Metcalf (1986): cost from treatment Metcalf (1986): cost from treatment expenditures and yield losses range expenditures and yield losses range $1 billion per year in U.S.$1 billion per year in U.S.
Based on a few sentences from Based on a few sentences from Metcalf’s “Forward” in Krysan and Metcalf’s “Forward” in Krysan and Miller’s (1986) Miller’s (1986) Methods for the Study Methods for the Study of Pest Diabroticaof Pest Diabrotica
Update analysis for to 2000 for USUpdate analysis for to 2000 for US
Soil insecticides are routinely applied to 50‑60% of Soil insecticides are routinely applied to 50‑60% of the corn (maize) acreage or as much as 30‑40 million the corn (maize) acreage or as much as 30‑40 million acres (12‑16 million ha) (Eichers et al., 1978). acres (12‑16 million ha) (Eichers et al., 1978). Present day costs of soil insecticide treatments range Present day costs of soil insecticide treatments range from $15‑20 per acre. During intensive outbreaks of from $15‑20 per acre. During intensive outbreaks of corn rootworms, aerial sprays are applied to as much corn rootworms, aerial sprays are applied to as much as 10 million acres (4 million ha) (Chio et al., 1978) at as 10 million acres (4 million ha) (Chio et al., 1978) at an additional cost of about $4‑5 per acre.an additional cost of about $4‑5 per acre.The root feeding of the beetles causes direct The root feeding of the beetles causes direct
damage to corn growth and corn yields. Corn damage to corn growth and corn yields. Corn rootworm infestations have been shown to decrease rootworm infestations have been shown to decrease yields of corn by 13‑16 bu per acre or 10‑13% (Apple, yields of corn by 13‑16 bu per acre or 10‑13% (Apple, 1971; Kuhlman and Petty, 1973). Thus the present 1971; Kuhlman and Petty, 1973). Thus the present day toll paid by U.S. farmers in treatment costs and day toll paid by U.S. farmers in treatment costs and crop losses is in the range of $1 billion per year.crop losses is in the range of $1 billion per year.
Overview of MethodOverview of Method Use Doane’s Market Research for 2000 Use Doane’s Market Research for 2000
(Alston et al. 2002) to obtain corn acres (Alston et al. 2002) to obtain corn acres by rotation, corn rootworm treated by rotation, corn rootworm treated acres, and treatment costs by regionacres, and treatment costs by region
Project (assume) root ratings for Project (assume) root ratings for treated and untreated corn acres by treated and untreated corn acres by region to estimate % yield lossregion to estimate % yield loss
Use regional average yields and Use regional average yields and average prices to develop cost of yield average prices to develop cost of yield loss with Mitchell et al. (2004) and loss with Mitchell et al. (2004) and Yang et al. (2007) damage functionYang et al. (2007) damage function
USDA RegionUSDA Region Corn AcresCorn Acres % trt% trt Cont. cornCont. corn % trt% trt 1st yr 1st yr corncorn
N G PlainsN G Plains 4,868 4,868 10.9%10.9% 1,442 1,442 33.8%33.8% 3,426 3,426 1.3%1.3%Prairie GwayPrairie Gway 9,931 9,931 31.6%31.6% 5,507 5,507 48.7%48.7% 4,424 4,424 10.3%10.3%Basin RangeBasin Range 212 212 33.7%33.7% 112 112 55.8%55.8% 99 99 8.6%8.6%Total USATotal USA 78,628 78,628 21,778 21,778 56,850 56,850
Table 1. Alston et al. (2002): Corn yield, Table 1. Alston et al. (2002): Corn yield, acres (1,000) by rotation, and % treated acres (1,000) by rotation, and % treated
for rootworm in each region in 2000for rootworm in each region in 2000
USDA RegionUSDA Region Ac TrtAc Trt costcost $/ac$/ac cont cont trt actrt ac
Basin RangeBasin Range 71 71 591 591 8.29 8.29 63 63 510 510 8.13 8.13 9 9 81 81 9.49 9.49 Total USATotal USA
14,197 14,197
171,510 171,510 8,271 8,271 98,811 98,811
5,926 5,926
72,699 72,699
Table 2. Alston et al.(2002): Corn Table 2. Alston et al.(2002): Corn rootworm treatment costs ($1,000) by rootworm treatment costs ($1,000) by
rotation and region in 2000rotation and region in 2000
Estimating % Yield LossEstimating % Yield Loss Counter-factual analysis: What would the root Counter-factual analysis: What would the root
rating (1-6 scale) be if no treatment were rating (1-6 scale) be if no treatment were applied: measures CRW “pressure”applied: measures CRW “pressure” Assume low, medium, and high pressureAssume low, medium, and high pressure For treated and untreated corn in each regionFor treated and untreated corn in each region For continuous and rotated corn in each regionFor continuous and rotated corn in each region
For treated acres, estimate RR after treatment For treated acres, estimate RR after treatment applied via Mitchell et al. (2004) RRapplied via Mitchell et al. (2004) RRtt = f(RR = f(RRcc))
Use Yang et al. (2007) to estimate % yield loss Use Yang et al. (2007) to estimate % yield loss from RR: from RR: = 0.0572 = 0.0572
Total LossTotal Loss 996996 500500Total CostTotal Cost 172172 172172
Total Loss and CostTotal Loss and Cost 1,1671,167 671671Continuous Loss Continuous Loss
PreventedPrevented441441 221221
Rotated Loss PreventedRotated Loss Prevented 342342 171171Total Loss PreventedTotal Loss Prevented 783783 393393
SummarySummary Corn Rootworm is a complex if four Corn Rootworm is a complex if four
insect species in USA spread insect species in USA spread throughout the Corn Belt and morethroughout the Corn Belt and more
Resistance management current hot Resistance management current hot issueissue Rotation resistance by WCR and NCRRotation resistance by WCR and NCR IRM for Bt corn and insecticidesIRM for Bt corn and insecticides Increased use of insecticides and Bt cornIncreased use of insecticides and Bt corn
Recent and on-going work on damage Recent and on-going work on damage functions to link entomology and functions to link entomology and economics, more to doeconomics, more to do
SummarySummary Using 2000 as base yearUsing 2000 as base year Loss from corn rootworm in U.S. ranged Loss from corn rootworm in U.S. ranged
$500 million to $1 billion per year$500 million to $1 billion per year Control costs around $170 million per Control costs around $170 million per
yearyear Control prevented $390 to $780 million Control prevented $390 to $780 million
in losses (2.3x to 4.6x return)in losses (2.3x to 4.6x return)
