Plant traits and cultivar mixtures

Pest organisms almost always face greater top-down control from predatory enemies in wild plant populations as compared to domesticated crops in cultivations. Two reasons for this are:

1. that our domesticated crops have lost the ability to recruit predatory organisms, and
2. that plantations are genetically homogeneous (monocultures).

Plant traits that favor predators

Predatory organisms are often affected by the plants on which their herbivorous prey live. Such effects on predators are partly dependent on the chemical properties of the plants (e.g. defense compounds) and partly about so-called rewarding plant traits (e.g. pollen and nectar). CBC investigates how these plant traits can be optimized from the perspective of the predatory organisms, in order to promote biological control mediated by predators.

Increased genetic diversity through cultivar mixtures

High botanical diversity is disadvantageous for pests (which are often specialized), while predators (which are often generalists) are favored by diversity. For this reason, biological control usually works better in intercropped systems than in monocultures. The disadvantage of intercropping is that such cultivation systems are often more labor-intensive than monocultures.

At CBC, we are examining an interesting compromise between intercropping and monocultures, namely cultivar mixtures where several varieties of the same crop are mixed in the same field. If the genetic and phenotypic variation between different cultivars is large enough to improve biological control, then cultivar mixtures could be a better solution than intercropping for many growers.