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Using weeds to reduce pest insect numbers in organic vegetable crops - a desk study

Defra Project OF 0329

Project Completion: March 2006

Project Leader: Dr Andrea Grundy

Key Contributor: Dr Rosemary Collier

Project summary

Weeds and pest insects are two of the major constraints to the production of high quality organic vegetable crops, primarily because control measures available to UK growers are extremely limited. Several studies have shown that the numbers of pest insects found on crop plants are reduced considerably when the crops are allowed to become weedy. However, if weeds are not removed by a certain stage of crop growth, the weeds start to compete with the main crop and yield begins to decline. At present, Warwick HRI has robust models that are used independently to predict the onset of weed competition and the timing of pest insect attacks. However, in practice, growers have to manage weeds and pest insects at the same time and so the decisions they make often involve compromises. The aim of this project is to demonstrate how the existing crop protection models could be used to optimise weed and pest insect control in organically-grown vegetable crops.