‘Intercropping-plus’ can help growers get to grips with pests

Originally published by Farming Future Food.

Intercropping, wildflower strips and even flowering weeds have a combined effect in reducing crop pest numbers and increasing populations of their natural enemies, according to two pieces of research.

In a two-year field study in Germany, scientists explored whether intercropping programs plus wildflower strips strengthened control of aphids and weeds. They grew faba bean and wheat, followed by bread seed poppy and barley, and additionally explored the effects of cover of the flowering weed German camomile (Matricaria recutita).

They found that both aphids and their predators were reduced on bean and poppy by intercropping, and wildflower strips increased the success of aphid predators in the bean-wheat system and reduced numbers of aphids in the poppy-barley system, although this reduction was only apparent when the strip was 10 metres from the crop, rather than 20.

Intercropping also reduced the presence of weeds by 60%, they discovered, although M. recutita turned out to be potentially a weed which brings benefits for growers, associated with lower aphid numbers and higher predator success.

Results to spur greater adoption?

“The study demonstrates the benefits of associating wildflower strips to intercropping to strengthen biological control and cropping system productivity,” the researchers wrote in Journal of Pest Science.

“Flowering weeds, maintained at an acceptable level through intercropping, turn out to be relevant functional biodiversity in interacting with wildflower strips for conservation biological control.”

While intercropping appears to have practical benefits both in the form of amplifying a valuable ecosystem system and increase land-use efficiency, they noted that its current adoption is low, particularly in Europe.

Deep dive supports varied measures

The findings of the experimental work are supported by a metanalysis of published studies to date looking at the impact of intercropping and measures implemented through agri-environmental schemes, such as flower strips, hedgerows and field margins.

The team of scientists found that across the studies analysed, intercropping tended to decrease numbers of crop-feeding herbivores and increase the abundance of their natural enemies, validating the effectiveness of sustainable pest control interventions both within fields and around them.

However, intercropping had stronger effects on both the agri-environmental schemes, and some effects were dependent on the distance of land features to crops. Variability the scientists observed in their analysis prompted them to temper the findings with a dose of caution for those looking to implement high performance biological control measures.

“Stakeholders must consider the appropriate spatial scale to foster suitable farm biodiversity strategies,” they said. “Different combinations of plant species diversity and design have very variable outcomes for arthropod abundance and pest control, and this needs to be considered in the context of the impact on crop production.”