Crop association to improve biological control: case study on pea and wheat aphids

Nowadays, strategies used to control aphids in fields of pea, Pisum sativum L., and wheat, Triticum aestivum L., still rely on synthetic insecticides which have negative effects on the environment and human health. This research focused on the development of sustainable alternative methods, with special emphasis on cultural practices and plant management systems. Increasing the diversity within crops may have several beneficial effects on pest control, creating attractive habitats for indigenous beneficial fauna and simultaneously deterring pests – the ‘push-pull’approach. In this field study, two wheat/pea associations (mixed cropping and strip cropping) where compared to monocultures of pea and wheat. The abundance and diversity of adult aphidophagous insects (predators and parasitoids) were accessed weekly using yellow traps, while aphids were observed directly on plants. In both crops, the percentage of plants infested with aphids and density of aphid colonies were significantly higher in monocultures during periods of aphid abundance. Mixed cropping was particularly beneficial for the pea, whereas strip-cropping was more efficient for the wheat. The abundance of beneficials was significantly higher in monocultures comparing to the other treatments. Quantitative aphid-natural enemy food webs showed that the abundance of the two main ladybird species, Coccinella septempunctata L. and Propylea quatuordecimpunctata (L.), increased with the occurrence of Acyrthosiphon pisum (Harris) on pea plants. Abundance of the two main species of Syrphidae, Sphaerophoria scripta (L.) and Eupeodes corollae (F.), increased with the occurrence of Sitobion avenae (F.) and Metopolophium dirhodum (Walker) on wheat plants. This study shows that increasing diversity within crops can help lower aphid infestations. However, additional methods are needed to more efficiently attract aphidophagous beneficials and promote the natural control of aphids.