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Organic farming promotes diversification strategies to enhance ecological
functions. However, early field studies suggested that not all cereal polycultures
confer benefits in terms of pest control. Our research involved a trait-based field
study to evaluate the advantages of different wheat polycultures on aphid
control and yield. We also explored the bottom-up and top-down effects underlying
aphid control. We established 10 treatments replicated in five organic
fields: three wheat monocultures (Florence-Aurora [FA], Montcada [MO], and
Forment [FO]), a mixture with similar-traits cultivars (FAMO), and a mixture
with different-traits cultivars (FAFO), each duplicated with and without a
burclover undersowing. We analyzed aphid abundance, number of aphids per
tiller, parasitism rate, predatory arthropods’ abundance, and crop yield. FAFO
and burclover undersowing significantly lowered aphid abundance and the
number of aphids per tiller on FA. However, the treatments did not affect the
abundance of predators or parasitism rates. Finally, wheat yield was similar
across treatments, except in 2021 season when FA yielded significantly less. Our
findings suggest that polycultures’ benefits on aphid control are cultivar specific.
Mixing wheat cultivars with complementary functional traits (height and odor
profile) and the association of wheat monoculture with a burclover undersowing
enhances aphid control by bottom-up effects without compromising crop yield.
Nevertheless, stacking the cultivar mixtures with burclover undersowing did not
outperform the results of a single diversity practices, probably because of functional
redundancy of resistant cultivars and burclover cover.
Citació
Ecosphere, vol.16, núm. 2 (2025), e70076