Hi all. Just wondering if anyone can tell me what this caterpillar is? It has ravaged my leek crop. They seemed fine a couple of weeks ago, then I noticed the foliage was wilting. The caterpillars had started at the top of the plant and burrowed down through. Every leek in the patch was affected, and I lost 90% of the crop.
The picture shows one of the 'better' ones. You can see how the little beast poking his head out of the hole in the middle. They're cream/light green colour and about 1-2cm long, and 1-2mm wide. They have a red or grey head. They did most of the damage in early september.
One of my books (Hessayon) has similar-looking caterpillars affecting the roots, but these definitely started at the top and worked down. Any ideas?