Industrial agriculture is killing bees and other pollinators, thus paradoxically threatening future crop production because 35% of world crops need pollination. In the USA honeybees have declined by 59 % in 61 years, and weed diversity by 50 % in 70 years. Bretagnolle and Gaba report the unexpected benefits of weeds for bees and crop production.
Industrial agriculture is a major cause of global warming due to greenhouse emissions of CO2 and N2O. Reducing the tillage is a potential solution because emissions are lower. However, in organic farming, the lack of herbicide should favour weed infestation. But are weeds really a problem for productivity? Armengot et al. compared the effect of reduced and conventional tillage on crop yields and weeds in a 2002-2011 field experiment under organic farming. They found that despite higher weed infestation by perennial species under reduced tillage, yields of wheat, sunflower and spelt were similar for both tillage systems. Therefore findings show that reduced tillage is a viable cropping system for organic farming.
Crop weeds are a major cause of economic loss. Recent changes such as global warming and pesticide-free cropping are changing weed patterns in agriculture. For example, thermophile weeds – weeds that like warm – such as tumbleweeb (Amaranthus retroflexus) have become more abundant in some cropping systems due temperature and precipitation changes. The review article by Peters et al. analyses the ecological mechanisms ruling weed migration.
Fostered by climate change the parasitic weed Phelipanche ramosa infests host crops such as tomato, hemp, tobacco and oilseed rape at an increasing rate. This weed can cause more than 80% yield loss of oilseed rape. To solve this issue knowledge on the way parasitic weeds infect oilseed rape is needed in order to design agroecological solutions. A report by Gibot-Leclerc et al. shows unexpectedly that the P. ramosa weed grows faster on slow-growing Brassicaceae – the oilseed rape family – than on fast-growing mouse-ear cress A. thaliana. This finding demonstrates for the first time that the growth of parasitic plants does not depend only of the growth speed of the host plant.