EFFECTS OF BT TRANSGENIC AND CONVENTIONAL INSECTICIDE CONTROL ON THE NON-TARGET NATURAL ENEMY COMMUNITY IN SWEET CORN - PowerPoint PPT Presentation

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EFFECTS OF BT TRANSGENIC AND CONVENTIONAL INSECTICIDE CONTROL ON THE NON-TARGET NATURAL ENEMY COMMUNITY IN SWEET CORN

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Title: EFFECTS OF BT TRANSGENIC AND CONVENTIONAL INSECTICIDE CONTROL ON THE NON-TARGET NATURAL ENEMY COMMUNITY IN SWEET CORN


1
EFFECTS OF BT TRANSGENIC AND CONVENTIONAL
INSECTICIDE CONTROL ON THE NON-TARGET NATURAL
ENEMY COMMUNITY IN SWEET CORN
  • CHRISTELA AMALI
  • KODITUWAKKUARACHCHI
  • PGIA/2014/110

2
CONTENT
  • Introduction
  • Materials and Methods
  • Data collection
  • Statistical Analyses
  • Results and Discussion
  • Conclusion
  • References

3
INTRODUCTION
  • Sweet corn containing a gene from the bacterium
    Bacillus thuringiensis
  • The pesticide-incorporated plants
  • Cry1Ab marker transgenes
  • Control efficacy is remarkably high, preventing
  • 100 European corn borer
  • 95 corn earworm
  • Use of Bt sweet corn hybrids can reduce the
    number of insecticide applications by 75 to 100.

4
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5
  • Factors that can cause effects to natural enemies
  • Reduction in host or prey popultions
  • Indirect contact with Cry protein by feeding on
    intoxicated orgaisms
  • feeding directly on plant parts (e.g., pollen)
  • changes in plant chemical

6
  • Sweet corn represents an ideal crop system for
    comparing potential non-target effects of
    transgenic Bt and conventional insecticide
    control.

7
MATERIALS AND METHODS
  • Plots were arranged in a split-plot design with
    four replicate blocks.
  • Whole plot treatments included two hybrid types
  • (1) Bt hybrid Attribute
  • (2) its nontransgenic isoline, Prime Plus
  • Subplots consisted of 16 rows that were 30 m
    long.
  • Bt-treated subplots received one application
  • nontransgenic corn received five applications

8
Data Collection
  • Diversity of invertebrates representing
    foliage-dwelling and soil surface communities
  • whole plant inspections - examining 8 randomly
    chosen plants per plot, starting at mid-whorl
    and then continued weekly until harvest
  • pitfall traps - four pitfall traps per plot over
    7- day intervals.
  • sticky cards - supported on cane poles at canopy
    level during the whorl- tassel stages and
    at ear level from anthesis until harvest.

9
Statistical Analyses
  • Treatment and time effects on the mean abundance
    of each taxonomic group were tested by ANOVA.
  • To test for treatment by time effects at the
    community level, principal response curve (PRC)
    analysis was used to distill the time-dependent,
    community-level effects of the treatments into a
    graphical form

10
RESULTS AND DISCUSSION
  • Foliage-Dwelling Community
  • Bt plots fluctuates around the zero line of the
    control indicating that no significant changes in
    community structure.
  • Changes in community structure coincided with
  • non-Bt plots sprayed five times compared with Bt
    plots sprayed once.

11
  • no significant differences in the population
    trends over time for the Bt and non-Bt natural
    enemy communities.
  • Natural enemies in insecticide-treated plots were
    reduced by
  • BT(1X) - 21
  • Non BT (5X) - 33
  • The predator groups significantly reduced were
    Orius flower bugs, coccinellids, lacewing eggs,
    spiders, and soldier beetles.

12
Aerial Community
  • No differences between aerial communities in the
    Bt and non-Bt plots
  • Significant departures from the control
    community when insecticides are applied.
  • Non-Bt plots that received five applications of
    insecticides showed greatest reduction.

13
  • Natural enemies which were adversely affected by
    the insecticides were
  • Predaceous bugs
  • Coccinellids
  • Scelionid parasitoids

14
Aerial Population densities
  • No significant differences in the population
    trends over time for the Bt and non-Bt natural
    enemy communities
  • Natural enemies in insecticide-treated plots were
    reduced by
  • BT (1X) - 21
  • Non BT (5X) - 33

15
Surface-Dwelling Community
  • The community of natural enemies measured by
    pitfall traps consisted with predator groups
    comprised 24 of the total captures.
  • Ground surface communities indicated a
    significant difference between treated Bt and
    non-Bt communities changed after insecticides
    were applied.

16
  • Natural enemies which were adversely affected by
    the insecticides were
  • rove beetles, spiders, and coccinellids
  • Ants and ground beetles were the least affected.

17
Population densities
  • No significant differences in the population
    trends over time for the Bt and non-Bt natural
    enemy communities
  • Natural enemies in insecticide-treated plots were
    reduced by
  • BT (1X) - 48
  • Non BT (5X) - 70
  • Rove beetles and spiders were the most disrupted
  • Ants and carabids were the least affected.

18
Soil-litter Community four weeks after harvest
  • Most diverse, consisting of more than 60
    taxonomic groups
  • Litter populations of all predators were
    consistently higher in the Bt plots and generally
    lower in the insecticide-treated plots

19
CONCLUSIONS
  • Bt hybrid significantly reduced the densities
    and damage caused by European corn borer and corn
    earworm.
  • Densities of predators in the Bt litter were
    significantly higher
  • Broad negative impacts on pest species and many
    natural enemies
  • Bt plots ( 1 X ) ------------ 21 to 48.
  • non-Bt plots ( 5 X) ------ 33 to 70.
  • No unexpected negative effect of BT corn on
    nontarget organisms and insecticide control cause
    far greater than any effect of BT transgenic
    control

20
References
  • Betz, F.S., B.G. Hammond, and R.L. Fuchs. 2000.
    Safety and advantages of Bacillus
    thuringiensisprotected plants to control insect
    pests. Reg. Tox. Pharmacol. 32 156-173.
  • Candolfi, M., F. Bigler, P. Campbell, U.
    Heimbach, R. Schmuck, G. Angeli, F. Bakker, K.
    Brown,
  • G. Carli, A. Dinter, D. Forti, R. Forster, A.
    Gathmann, S. Hassan, M. Mead-Briggs, M. Melandri,
  • P. Neumann, E. Pasqualini, W. Powell, J. N.
    Reboulet, K. Romijn, B. Sechser, T. Thieme, A.
  • Ufer, C. Vergnet, and H. Vogt. 2000. Principles
    for regulatory testing and interpretation of
    semifieldand field studies with non-target
    arthropods. Journal of Pesticide Science 73
    141-147.
  • Jepson, P. C., B. A. Croft, and G. E. Pratt.
    1994. Test systems to determine the ecological
    risks posed by toxin release from Bacillus
    thuringiensis genes in crop plants. Molecular
    Ecology 3 81-89.

21
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