I am growing Chinese/Japanses pumpkins in Western Australia.
They are growing ok and flowerbuds have started to come but I have noticed that the leaves near the root-base of the vine are turning yellow at the edges, going brown and dying.
Also, along the veins of the leaves the leaf tissue is turning clear, as if the fluid-equivalent of blood coming into the leaf and killing the chlorophyll. Some of the leaves have whitish blobs on them, not unlike mould.
This 'pox' seems to be travelling along the vine from the root end. Leaves are dying off steadily along the vine although new leaf-stalks are budding.
I can send photos. No sure how to get them into this post though.
They get a lot of water directly on their roots.
The soil is mostly sand with some humus (land was previously a market garden)
There is a shade cloth to baffle the vicious WA sun