The effect of within-crop floral resources on pollination, aphid control and fruit quality in commercial strawberry

In the absence of pollinating insects commercial strawberry (Fragaria x ananassa) yields would fall by approximately 45%, while damage from aphids is estimated to cost growers at least 1% of annual yields in the UK alone. This combined effect could result in losses of over £100 million per year for the UK economy. We investigated whether incorporating floral resources within commercial polythene-clad tunnels could improve pollination services and aphid control and, hence, strawberry fruit quality. In a randomised block experiment (using 3 x 6 m plots), coriander (Coriandrum sativum) field forget-me-not (Myosotis arvensis) and corn mint (Mentha arvensis) plants were inserted in rows of commercially-grown strawberries. Their effect on numbers of naturally occurring flower visitors, aphids and aphid predators was compared. Counts of flower visitors, including visitors to sown flower species, were higher in coriander and mint plots. However strawberry flowers received more insect visits in control plots. Fruit from forget-me-not plots were lower in sugar than fruit from controls, while fruit from mint plots had fewer fertilised seeds than fruit from control plots. Strawberries from coriander plots did not differ from control fruit on any fruit quality measures. Crucially, proportions of marketable fruit did not differ across treatments. Aphid numbers did not differ between treatments even though coriander significantly increased the numbers of lacewing eggs laid on aphid-infested strawberry plants in coriander plots. Hence, although there were no negative effects on the proportions of marketable fruits with intercropping, the benefits received were limited. It might be that in a different growing season the effect would be more pronounced but this would need to be weighed up against the cost of implementing such interventions.