Appendix 1 Agronomic characteristics of the organic and conventional winter wheat fields included in the study.

Farming system / Organic / Conventional
Crop rotation / Legume/ winter wheat/ polyculture / Winter wheat/ winter barley
Tillage / 2-3 times
20 cm of depth / 3 times,
15 cm of depth
Cereal / Winter wheat cv. Bonpain / Winter wheatcv. Etecho
(2 fields), Soissons (2 fields)
Sowing density (kg ha-1) / 180-200 / 170-200
Nitrogen inputs (kg N ha-1) / Green manure and occasionally
hen droppings (<160) / ~ 180 of pig slurry/year
< 100 of mineral N at times
Weed control / Mechanical * / Chemical **
Pests and diseases control / None / None

* Once after seedling growth stage of wheat.

** All conventional farmers applied Glyphosate (N-(phosphonomethyl) glycine at 2.5 L ha-1) and 2-4-D (2,4-dichlorophenoxyacetic at 1.3 L ha-1) as pre-emergence non-specific herbicides, Splendor 25 SC (Tralkoxidin at 1.6 L ha-1) as a post-emergence grass herbicide and Oxytril (ioxinil, bromoxinil, plus mecoprop at 2 L ha-1) as a broad-leaved herbicide.

Vegetal groups / Organic / Conventional
Grasses (C3)
Avena sativa L. / 4 / 0
Avena sterilis L. / 7 / 12
Bromus diandrus Roth / 0 / 5
Bromus sterilis L. / 0 / 4
Hordeum distichon L. / 0 / 1
Lolium rigidum Gaudin / 17 / 18
Forbs
Anagallis arvensis L. / 5 / 0
Anacyclus clavatus (Desf.)Pers. / 1 / 0
Anchusa italica Retz. / 4 / 0
Atriplex patula L. / 1 / 0
Centaurea scabiosa L. / 13 / 1
Cirsium arvense (L.) Scop. / 23 / 0
Convolvulus arvensis L. / 30 / 5
Euphorbia sp. / 1 / 0
Euphorbia falcata L. / 1 / 0
Filago pyramidata L. / 0 / 1
Fumaria officinalis L. / 6 / 1
Galium tricornutum Dandy / 30 / 6
Kickxia spuria (L.) Dumort / 1 / 1
Lepidium draba L. / 11 / 3
Muscari sp. / 1 / 0
Papaver hybridum L. / 5 / 0
Papaver rhoeas L. / 21 / 16
Polygonum aviculare L. / 7 / 8
Polygonum convolvulus L. / 1 / 0
Potentilla reptans L. / 1 / 0
Rapistrum rugosum (L.) All. / 15 / 0
Roemeria hybrida (L.) DC. / 1 / 0
Scandix pecten-veneris L. / 3 / 0
Silene vulgaris (Moench.) Garcke / 2 / 0
Sonchus asper (L.) Hill / 0 / 1
Sonchus oleraceus L. / 2 / 0
Legumes
Coronilla scorpioides (L.) Koch / 14 / 0
Medicago lupulina L. / 17 / 0
Medicago sativa L. / 14 / 0
Vicia ervilia (L.) Willd. / 3 / 0
Vicia hirsuta (L.) Gray / 1 / 0
Vicia hybrida L. / 5 / 0
Vicia peregrina L. / 8 / 0
Vicia sativa L. / 9 / 0

Appendix 2 Absolute frequencies of weed species surveyed in organic and conventional fields. Number indicates the number of plots/samples where the species has been found during the two sampling periods (see text for more details).

Appendix 3 Mean total abundance (± SEM)of aphids and their specialist natural enemies captured by suction sampling in organic and conventional fields. The total number of specimens is also indicated (T). Aphids are categorized as forb-specialist and grass-specialist.

Flowering-wheat stage Milk-ripening stage

Organic ConventionalOrganicConventional

X±SE TX±SE TX±SE TX±SE T

Forb aphids10.5±0.320.3±0.3128.8±7.31154.0±1.016

Grass aphids215.3±2.36132.5±28.2130142.0±63.2568208.8±51.1835

Primary parasitoids3.3±1.31215.0±4.3635.5±1.32215.0±4.356

Aphidius sp.3117313

Aphidius avenae Haliday0020

Aphidius ervi Haliday820918

Aphidius rhopalosiphi Stefani-Pérez319110

Aphidius uzbekistanicus Luzhetzki06415

Diaeretiella rapae (M’Intosh)0110

Praon volucre (Haliday)0020

Predators0.0±0.000.0±0.005.9±0.61105.9±1.8108

Coleoptera:Coccinellidae

Coccinella septempunctata (L.)002519

Hippodamia variegata (Goeze) (D)0021

Propylea quatuordecimpunctata (L.)0011

Hemiptera:Nabidae

Nabis (Nabis) punctatus A. Costa00111

Neuroptera:Chrysopidae

Chrysopasp. larvae3007186

1Forb aphids include: Aphis craccivora Koch, Aphis fabae Scopoli,Acyrthosiphon pisum (Harris), Dysaphis sp. & Brachycaudus sp., Hyadaphis foeniculi (Passerini), Phorodon humuli (Schrank), Therioaphis riehmi (Börner),Therioaphis trifolii (Monell), Uroleucon sp.

2 Grass aphids contain: Forda sp., Melanaphis donacis (Passerini), Metopolophium dirhodum (Walker), Rhopalosiphum padi (L.), Schizaphis graminum (Rondani), Sipha maydis Passerini, Sitobion avenae (Fabricius), Tetraneura nigriabdominalis (Sasaki).

3Although it is feasible that more than one species were included in Aphidius sp. and Chrysopa sp., as we couldn’t certify it we count it as one species

Appendix 4- Relationships between aphids and Aphidiinae wasps (Braconidae) marked with signals (x) based on literature review and expert advice.

Acyrthosiphon / Aphis / Brachycaudus / Dysaphis / Macrosiphum / Melanaphis / Metopolophium / Phorodon / Rhopalosiphum / Schizaphis / Sitobion / Uroleucon
Aphidius avenae Haliday, 1834 / x / x / x / x / x / x
Aphidius ervi Haliday, 1834 / x / x / x / x / x / x
Aphidius rhopalosiphi De Stefani-Pérez, 1902 / x / x / x / x
Aphidius uzbekistanicus Luzhetzki, 1960 / x / x / x / x
Diaeretiella rapae (M’Intosh, 1855) / x / x / x / x / x / x
Praon volucre (Haliday, 1833) / x / x / x / x / x / x / x / x / x / x / x / x