The problems with insect pests in agricultural landscapes and home gardens could be reduced if the natural enemies had better living conditions. Ulf Nilsson describes the idea behind the so-called "conservation biological control" in his doctoral thesis at SLU. Modern agricultural landscapes often lack nectar-producing plants, which provide food for parasitic wasps, and undisturbed wintering areas for predatory beetles and spiders.
In his doctoral work at SLU, the horticulturist Ulf Nilsson studied the conditions for enhancing the biological control of the Lily Beetle (Lilioceris lilii) and Cabbage Root Fly (Delia radicum).
He inventoried the enemies of the Lily Beetle in three regions of southern Sweden and in the Stockholm area. Totally, four species of parasitic wasps that attacks the Lily Beetle was found. The presence of the different species varied between regions. Between 21 to 57 per cent of the Lily Beetle larvae were parasitized depending on region and year.
- The effect of parasitic wasps on the Lily Beetle can be strengthened if the soil around the lilies is left untouched in the fall, says Ulf Nilsson. Cultivation of soil in the autumn involves a risk to damage the overwintering stage of the parasitic wasps.