Aphid performance and population development on their host plants is affected by weed–crop interactions

• Some farming practices, like organic farming, lead to greater numbers of weed plants incrop fields. These fields may give us some insights into any benefits that may be gained frombiodiversity (e.g. improved pest control services) and allow us to understand the mechanismsbehind crop–weed interactions.2. The influence of two common weeds, lamb’s-quarters Chenopodium album and charlockSinapis arvensis, on performance of the bird cherry-oat aphid Rhopalosiphum padi in springsownbarley Hordeum vulgare is evaluated in three field experiments. Observations in fieldexperiments indicated that the presence of S. arvensis reduced aphid population developmentin the barley crop significantly, but this effect was not observed in barley grown withC. album.3. Observed effects in the field were further studied in laboratory experiments with regard toaphid growth and reproductive performance. Above- and below-ground interactions ofS. arvensis and C. album with barley were tested using twin-exposure cages. Aphid performancewas negatively affected when barley plants had root contact with S. arvensis. Theresults of these laboratory experiments showed a difference in mode of action of the twoweeds.4. Synthesis and applications. The results support the potential of associated resistance, mediatedby neighbouring plants, in minimizing herbivore damage of focal plants and highlightedthe mechanism by which herbivores might be affected. Since chemical exchange between plantneighbours can potentially occur in any plant community, increased understanding could bevaluable for existing and new agroecosystems, invasion biology and sustainable crop production.To get a balance between herbicide and insecticide control, agricultural production systemsneed to focus on the thresholds of weed and insect tolerance, taking the associatedresistance of biodiversity (here weeds) into account. Agricultural biodiversity may providemany long-term benefits over monoculture, from reducing pesticide pollution to preventinginsecticide resistance. Our study is an important step forward in general understanding of theeffects of vegetational diversity on herbivore population dynamics.

Ämnesord

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Jordbruksvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Agricultural Science (hsv//eng)

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