Abstract
Abstract Field studies to assess effects of transgenic crops on nontarget organisms primarily have focused on nontarget abundance and diversity, whereas few have examined effects on nontarget community function. A 5-yr field study in Arizona assessed whether transgenic cotton producing the Cry1Ac toxin of Bacillus thuringiensis (Bt) had an effect on the natural enemy community’s impact on three key pests. Predator:prey ratios for Bemisia tabaci (Gennadius) and Lygus hesperus Knight were similar in unsprayed Bt and non-Bt cotton. Insecticide applications in positive control plots inconsistently altered ratios for B. tabaci. Predation indices based on the known feeding activity of selected predators showed that potential predator impact was unaltered by Bt cotton but was consistently depressed with insecticide applications. Sentinel eggs and pupae of Pectinophora gossypiella (Saunders) experienced the same rates of predation in both unsprayed Bt and non-Bt cotton. Cohort-based life tables for B. tabaci showed that rates of sucking predation, parasitism, and dislodgement (chewing predation in part) were unchanged by Bt cotton. Underlying experimental designs were sufficient to consistently detect changes of <20% in predator:prey ratios and predation indices and changes of <10% in rates of P. gossypiella and B. tabaci mortality with >80% power (α = 0.05). These long-term studies showed essentially no effects of Bt cotton on natural enemy function in Arizona cotton and further showed that minor reductions in density of several predator taxa in Bt cotton observed in a companion study may have little ecological meaning relative to natural enemy impact on key pests in the system.
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Claims 10
Claim · model-written summary
Predator to prey ratios for Bemisia tabaci were similar in unsprayed Bt and non-Bt cotton.
- Taxon
- cotton
Gossypium hirsutume0 - Treatment
- unsprayed Bte0
- Interactor
- Bemisia tabaci
Bemisia tabacie0pest - Outcome
- Predator:prey ratios for Bemisia tabacie0
- Direction
- similare0
- Comparator
- non-Bt cottone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Predator:prey ratios for Bemisia tabaci (Gennadius) and Lygus hesperus Knight were similar in unsprayed Bt and non-Bt cotton”
Claim · model-written summary
Predator to prey ratios for Lygus hesperus were similar in unsprayed Bt and non-Bt cotton.
- Taxon
- cottonGossypium hirsutume0
- Treatment
- unsprayed Bte0
- Interactor
- Lygus hesperus
Lygus hesperuse0pest - Outcome
- Predator:prey ratiose0
- Direction
- similare0
- Comparator
- non-Bt cottone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Predator:prey ratios for Bemisia tabaci (Gennadius) and Lygus hesperus Knight were similar in unsprayed Bt and non-Bt cotton”
Claim · model-written summary
Insecticide applications inconsistently altered Bemisia tabaci predator to prey ratios.
- Taxon
- CottonGossypium hirsutumt0
- Treatment
- Insecticide applicationse0
- Interactor
- B. tabaciBemisia tabacie0pest
- Outcome
- ratios for B. tabacie0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cotton”
e0“Insecticide applications in positive control plots inconsistently altered ratios for B. tabaci”
Claim · model-written summary
Bt cotton did not alter predation-index estimates of predator impact.
- Taxon
- cottonGossypium hirsutume0
- Treatment
- Bt cottone0
- Outcome
- potential predator impacte0
- Direction
- unalterede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“potential predator impact was unaltered by Bt cotton”
Claim · model-written summary
Insecticide applications consistently depressed predation-index estimates of predator impact.
- Taxon
- CottonGossypium hirsutumt0
- Treatment
- insecticide applicationse0
- Outcome
- potential predator impacte0
- Direction
- depressede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cotton”
e0“potential predator impact was unaltered by Bt cotton but was consistently depressed with insecticide applications”
Claim · model-written summary
Pectinophora gossypiella sentinel eggs and pupae had the same predation rates in unsprayed Bt and non-Bt cotton.
- Taxon
- cottonGossypium hirsutume0
- Treatment
- unsprayed Bte0
- Interactor
- Pectinophora gossypiella
Pectinophora gossypiellae0pest - Outcome
- rates of predatione0
- Direction
- samee0
- Comparator
- non-Bt cottone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sentinel eggs and pupae of Pectinophora gossypiella (Saunders) experienced the same rates of predation in both unsprayed Bt and non-Bt cotton”
Claim · model-written summary
Bemisia tabaci sucking predation, parasitism, and dislodgement rates were unchanged by Bt cotton.
- Taxon
- cottonGossypium hirsutume0
- Treatment
- Bt cottone0
- Interactor
- B. tabaciBemisia tabacie0pest
- Outcome
- rates of sucking predation, parasitism, and dislodgemente0
- Direction
- unchangede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cohort-based life tables for B. tabaci showed that rates of sucking predation, parasitism, and dislodgement (chewing predation in part) were unchanged by Bt cotton”
Claim · model-written summary
The study design could detect changes below 20% in predator to prey ratios and predation indices with over 80% power.
- Taxon
- CottonGossypium hirsutumt0
- Outcome
- predator:prey ratios and predation indicese0
- Value
- <20%e0
- Qualifier
- >80% power (α = 0.05)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cotton”
e0“sufficient to consistently detect changes of <20% in predator:prey ratios and predation indices and changes of <10% in rates of P. gossypiella and B. tabaci mortality with >80% power (α = 0.05)”
Claim · model-written summary
The study design could detect pest mortality changes below 10% with over 80% power.
- Taxon
- CottonGossypium hirsutumt0
- Outcome
- rates of P. gossypiella and B. tabaci mortalitye0
- Value
- <10%e0
- Qualifier
- >80% power (α = 0.05)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cotton”
e0“changes of <10% in rates of P. gossypiella and B. tabaci mortality with >80% power (α = 0.05)”
Claim · model-written summary
The authors interpret minor predator-density reductions in Bt cotton as having little ecological meaning for pest control.
- Taxon
- CottonGossypium hirsutumt0
- Outcome
- natural enemy impact on key pestse0
- Qualifier
- minor reductions in density of several predator taxa in Bt cottone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cotton”
e0“minor reductions in density of several predator taxa in Bt cotton observed in a companion study may have little ecological meaning relative to natural enemy impact on key pests in the system”
The same questions in other papers
transgenic · Bemisia tabaci · Gossypium hirsutum (cotton)Positive and negative results
3 papers in the same direction as this paper · 2 in the opposite direction
- positive
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See all 6 papers →insecticide · ecology: diversity · Gossypium hirsutum (cotton)Positive and negative results
12 papers in the same direction as this paper · 3 in the opposite direction
- positive
- positive
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See all 16 papers →transgenic · Pectinophora gossypiella · Gossypium hirsutum (cotton)Positive and negative results
2 papers in the same direction as this paper · 14 reporting no difference from an alternative
- positive
- positive
- positive
13 papers more in this group
See all 17 papers →transgenic · ecology: diversity · Gossypium hirsutum (cotton)Results agree
6 papers in the same direction as this paper
- negative
- negative
- no effect
3 papers more in this group
See all 7 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.