Ecological Effects of Transgenic Crops: Non-target Effects in Bt Cotton
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Transcript of Ecological Effects of Transgenic Crops: Non-target Effects in Bt Cotton
Ecological Effects of Ecological Effects of Transgenic Crops: Non-target Transgenic Crops: Non-target
Effects in Effects in BtBt Cotton Cotton
Steven E. NaranjoUSDA-ARS Phoenix, Arizona
&
Peter C. EllsworthUniversity of Arizona, Maricopa, Arizona
This presents the results of research only. Mention of a proprietaryproduct does not constitute endorsement or recommendation for its use by USDA.
Pest Complex - Western U.S. CottonPest Complex - Western U.S. Cotton
Lygus hesperus
Bemisia tabaci
Pectinophora gossypiella
Key Pests Sporadic and Minor Pests
Cotton bollwormTobacco budworm
ArmywormsLoopers
Cotton leafperforatorSaltmarsh caterpillar
Cutworms
FleahoppersPlant bugsStink bugs
Cotton aphidThrips
Spider mites
Insecticide Use PatternsInsecticide Use PatternsArizona CottonArizona Cotton
19901991
19921993
19941995
19961997
19981999
2000
Mea
n a
pp
lica
tio
ns
per
acr
e
0
2
4
6
8
10
12
14
0
2
4
6
8
10
12
14
Pink bollwormWhiteflyLygus Other
Bt cottonInsect growth regulators
Ellsworth and Jones 2000
Selective Insecticide UseSelective Insecticide UseArizona CottonArizona Cotton
1996 1997 1998 1999 2000
% A
crea
ge
trea
ted
0
10
20
30
40
50
60
70
80
Bt cotton Pyriproxyfen Buprofezin
Natural Enemy Complex -Western U.S.Natural Enemy Complex -Western U.S.Parasitoids Predators
30+ species
HyposterCopidosomaMicroplitis
LysiphlebusChelonusLespesia
EretmocerusEncarsiaAnaphes
Leiophron
50+ species
GeocorisOriusNabisZelus
CollopsHippodamia
DrapetisChrysoperla
LabiduraMisumenops
Natural Enemies – Pectinophora gossypiellaNatural Enemies – Pectinophora gossypiella
Predators
23 species described9 species (immunological ID)
Parasitoids
4 native species described (rare)16 exotic species introduced
(0 established)
General MethodsGeneral MethodsNon-target abundance/diversityNon-target abundance/diversity
Replicated experimental studies at MAC Treatments:
Bt cotton / conventional cotton Unsprayed for any pest Insecticides for all pests as needed
Sampling by sweep nets, beat buckets, whole plants, pitfall traps
ANOVA, EstimatorS V. 5 (Colwell) for diversity analyses
Natural Enemy AbundanceNatural Enemy AbundanceNo InsecticidesNo Insecticides
Misum Collops Geocoris Orius Nabis Zelus Chrysop Drapetis Hymen
Cu
m. a
rth
rop
od
-day
s (5
0 sw
eep
s)
0
400
800
1200
1600
2000
2400
Misum Collops Geocoris Orius Nabis Zelus Chrysop Drapetis Hymen0
400
800
1200
1600
4530 5611
0.98 0.37
0.40
0.340.03
0.08 0.24
0.28
0.57
0.700.23
0.89
0.18 0.66
0.160.16
0.39
0.51
1999
2000 Bt cotton Non-Bt
Natural Enemy AbundanceNatural Enemy AbundanceNo InsecticidesNo Insecticides
1999
9 Jun29 Jun
19 Jul8 Aug
28 Aug17 Sep
Cu
m. a
rth
rop
od
-day
s (5
0 sw
eep
s)
0
4000
8000
12000
160002000
9 Jun29 Jun
19 Jul8 Aug
28 Aug17 Sep
0
2000
4000
6000
8000
P = 0.18 P = 0.29Bt cottonNon-Bt
Natural Enemy AbundanceNatural Enemy AbundanceInsecticides as Needed (e.g. 1999)Insecticides as Needed (e.g. 1999)
Bt cottonNon-Bt
UnsprayedSprayed
Diversity(Fisher's alpha)
1999 20000
5
10
15
20
Evenness(Shannon)
1999 20000.0
0.2
0.4
0.6
0.8
*
Non-Bt Bt cotton
Community Structure – Pitfall TrapsCommunity Structure – Pitfall Traps(Bt vs. Non-Bt)(Bt vs. Non-Bt)
70
68
57 57
Community Structure – Pitfall TrapsCommunity Structure – Pitfall Traps(Sprayed vs. Unsprayed)(Sprayed vs. Unsprayed)
69
74
68
40
MethodsMethodsNatural Enemy FunctionNatural Enemy Function
Replicated experimental studies at MAC No insecticides Estimate rates of predation and parasitism
Sentinel pink bollworm egg masses (20 per plot)
Life tables for whitefly nymphs (50 per plot)
Natural Enemy FunctionNatural Enemy FunctionPredation on Pink Bollworm EggsPredation on Pink Bollworm Eggs
19 July 2001
Pro
po
rtio
n e
aten
0.0
0.2
0.4
0.6
0.8
1.0Bt cottonNon Bt
1 August 2001 30 August 2001
0.0
0.2
0.4
0.6
0.8
1.0
Natural Enemy FunctionNatural Enemy FunctionMortality of Whitefly NymphsMortality of Whitefly Nymphs
12 July 2001
Predation Parasitism
Mar
gin
al r
ate
of
mo
rtal
ity
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Bt cottonNon Bt
20 August 2001
Predation Parasitism0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Conservation Biological ControlConservation Biological ControlAn ExampleAn Example
Whitefly IPM in Cotton
Bt Cotton IGRs
Natural Enemies