Our Purple Loosestrife is growing vigorously, with no blemishes, not a trace of insect damage to the leaves. Our customers will be delighted. But is the absence of resident insects on wildflowers a good thing or bad? Surely biodiversity is more than just wildflowers, it includes the insects that normally feed on them.
The protective chemicals produced by Purple Loosestrife are enough to deter almost all insects, but three species have managed to break through the defences, the Black-margined Loosestrife Beetle (Gallerucella calmariensis) and Golden Loosestrife Beetle (Gallerucella pusella), and a weevil, Hylobus transversovittalus. They are common throughout the UK, are found wherever Purple Loosestrife grows and feed on virtually nothing else. As a result they keep this vigorously growing plant in check so that it rarely becomes particularly invasive.
But if these insects are not present we are faced with a very different situation as wetland enthusiasts in North America are well aware. Imported by accident and as a garden plant, on escaping into a wetland area it rapidly chokes out native species of plants and the diverse habitats associated with them. Native insects suffer, as does birdlife and the mammals that live there. The absence of two leaf beetles and a weevil alters the balance of nature in Wetlands over large areas of the United States. Without them Purple Loosestrife has proven virtually impossible to get rid of.
The only solution has been to introduce the missing insects from Europe into at least 27 States Fortunately they are so specific in their food plants that native American species remain untouched.
If it is not only the wildflowers that have been eliminated from large tracts of the UK countryside by over-intensive agriculture, house building etc, but also the insects and other invertebrates that depend upon them, and on which not only they but the ecology of the area depends, rewilding becomes a lot more complex than simply putting back the wildflowers. If the associated invertebrates have been pushed too far away to be able to move back in themselves, to try and restore some sort of balance, we would then need to reintroduce them. Far easier to prevent the destruction of wildflower populations in the first place.