Caught out again!

Every year about this time I notice the defoliation of my Solomans Seal (polygonatum hybridum). And every year it's too late by the time I see the damage. The underside of the leaves are covered with gray caterpillar-like grubs intent on their annual destruction.

Does it matter? Probably not, except from an aesetic point of view . It doesn't seem to affect the vigour of the plants which experience shows come back the following year as strongly as ever.

But it does rankle just a bit! 

So as with most challenges in the garden it helps to do a bit of research. I already know the culprit is the Solomon`s Seal sawfly ( Phymatocera aterrima). It's related to the sawfly that is responsible for defoliating gooseberries, willows and several other plants. But each sawfly is specific to their own food source in this case Solomon's Seal.

The larvae look like caterpillars but differ by having at least 6 pairs of prolegs where as true caterpillars have a maximum of 5 pairs. If you look at them in a certain light they look almost luminous. They tend to eat out the leaf between the longitudinal rib veins leaving it in tattered ribbons.The common name comes from the saw-like appearance of the ovipositor which the adult uses to cut into plant stems to lay eggs.

The sawfly overwinter in cocoons in the soil and the adult female flies emerge in May and June to lay their eggs . These hatch out within days and the larvae feed for the following month, usually on the undersides of the leaves so that the damage is done by the time you notice it. They return to the soil for the winter and the cycle begins again.

There is however only one generation of sawfly per season. 

As an organic gardener the only acceptable method of control is to pick them off laboriously by hand. So excuse me I'm off to rescue what's left of my Solomon's Seal.