The environmental impact of controlling weeds using broad spectrum herbicides in genetically modified herbicide tolerant crops: the Farm Scale

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1 The environmental impact of controlling weeds using broad spectrum herbicides in genetically modified herbicide tolerant crops: the Farm Scale Evaluations explained by Dr. Alan M. Dewar Broom s Barn Research Station representing the consortium

2 GMHT costs & benefits Possible benefits reduced use of herbicides less persistent herbicides later sprays less need for insurance sprays Possible harm greater efficiency of weed control cleaning up weedier fields effect on invertebrates & birds

3 The null hypothesis: H 0 There is no difference between the management of GMHT varieties and that of comparable conventional varieties, in their effect on the abundance and diversity of arable plants and invertebrates. Wildlife not food safety or gene flow This research will not only address GM crops. This is an extremely important opportunity to gain a more detailed understanding of the effects of agricultural management on farmland wildlife generally Michael Meacher, 1999

4 Number of trial sites Crop Beet Maize Spring rape No. of sites beet maize SOSR

5 Treatments Non GM variety + Conventional herbicide programme GMHT variety + broad spectrum herbicide to which it was tolerant For beet glyphosate (Roundup Biactive) For maize and spring rape - glufosinate ammonium (Liberty)

6 Design considerations Halved-fields Conventional herbicides applied according to normal practice GMHT management = cost-effective weed control Effects on populations are multiplicative Power aim for 80% chance to detect x1.5-fold effect Sites representative of where crop grown in GB Farms aim to include relatively large proportion of less-intensively managed

7 Sampling within half-fields Margins Transects into crop five quadrats per transect

8 What we did We counted: 700,000 plants 17,000 bees 13,000 butterflies We trapped: 500,000 seeds 1.5 million invertebrates We made >4000 visits to fields analysed >7000 datasets

9 Time of application of first herbicide Beet Conventional % of sites treated GMHT Weeks after sowing

10 Time of application of first herbicide Maize Spring oilseed rape % of sites treated Conventional GMHT % of sites treated Conventional GMHT Weeks from sowing Weeks from sowing

11 Number of herbicide sprays 4 *** *** Number of sprays ** Conv GMHT 0 S. beet F. beet Maize SOSR Crop Significance *** p<0.001, ** p<0.01; = not significant

12 Number of seeds /m 2 Seedbanks and seed production Initial seedbank Beet Conventional *** Seed rain during year GMHT Seedbank after year 1 Seedbank after year 2 No. of sites (64) (65) (48) (24) Significance *** p<0.001, ** p<0.01, * p<0.05; = no significant difference *

13 Number of seeds /m 2 Seedbanks and seed production Initial seedbank Conventional Seed rain during year Maize = no significant difference GMHT Seedbank after year 1 Seedbank after year 2 No. of sites (57) (54) (25) (9)

14 Number of seeds /m 2 Seedbanks and seed production Initial seedbank Spring oilseed rape Conventional *** Seed rain during year GMHT Seedbank after year 1 Seedbank after year 2 No. of sites (65) (65) (40) (12) Significance *** p<0.001, ** p<0.01, * p<0.05; = no significant difference

15 Density of broad-leaved weeds: Beet Number of weeds /m *** *** ** Conventional GMHT Post emergence Pre-Glyphosate After all herbicides Final harvest Follow up year 1 Follow up year 2 No. of sites (64) (54) (62) (63) ( 48) (22) Significance *** p<0.001, ** p<0.01, * p<0.05 = no significant difference

16 Density of broad-leaved weeds: Maize Number of weeds /m Post emergence After all herbicides Final harvest Conventional *** *** *** Follow up year 1 GMHT Follow up year 2 No. of sites (58) (52) (45) (15) (6) Significance *** p<0.001, ** p<0.01, * p<0.05; = no significant difference

17 Density of broad-leaved weeds: Spring Number of weeds /m ** Post emergence *** After all herbicides rape Final harvest Significance ** p<0.01, * p<0.05 = no significant difference Conventional Follow up year 1 GMHT Follow up year 2 No. of sites (65) (62) (63) (38) (9) **

18 Biomass of weeds pre-harvest Biomass (g/m2) *** *** ** Beet Maize S. Rape Biomass lower on GMHT beet and s. rape Biomass higher on GMHT maize Significance *** p<0.001, ** p<0.01 = no significant difference

19 Invertebrate survey methods Pitfall traps Vortis suction sampling Gastropod refuge traps Bee / butterfly transects

20 Groups studied Rove beetles Ground beetles Bees Springtails Spiders True bugs butterflies Slugs and snails

21 Invertebrates on soil surface Invertebrate group Beet Maize Spring rape Carabids No effect* No effect No effect Staphylinids No effect No effect No effect Spiders No effect* No effect* No effect* Springtails No effect* No effect* No effect* Slugs No effect No effect No effect* * Some significant effects on some occasions with some species or families

22 Pests and natural enemies on crop plants Pest Beet Maize Spring rape * Some significant effects on some occasions

23 Invertebrates in Vortis samples Group Beet Maize Spring oilseed rape

24 Bees in crops Number per year * Conv GMHT Beet Maize Spring rape Crop * significantly less at P<0.05

25 Butterflies in crops Number per year ** ** Conv GMHT 2 0 Beet Maize Spring rape Crop ** significantly less at P<0.01

26 Conclusions Fewer herbicides were used in the GMHT halves of all three crops Herbicide treatments produced fewer weeds, weed biomass and seeds in GMHT beet and spring rape, but more in maize These differences were due to the efficiency of control of the various herbicide regimes, NOT GMHT PER SE

27 Conclusions: consequences No effect on ground beetles, rove beetles, spiders, springtails, slugs, pests, but some effects on individual species consistent with diet Fewer butterflies in GMHT beet and rape, but differences larger between crops Fewer bees in GMHT beet

28 Source of data Special issue of : Philosophical Transactions of the Royal Society Volume 358 Number 1439 Pages

29 Acknowledgements This study was funded by DEFRA Thanks are due to the large number of staff who collected all the samples, and especially to the farmers who participated, often in the face of hostility from neighbours, and anti-gm extremists