HEEELP!!!

Here's hoping that some avid reader has lived in Europe and can charge to my rescue.

While June here in Central Belgium was very dry and warm (but not by US standards, that's for sure); we have had three weeks of cool, rainy weather.

This morning, I went out to my vegetable patch and noticed that (overnight, it seems) two of my twelve tomato plants are exhibiting signs of either a bacterial or viral infection. And they're going down fast.

The leaves and stems are turning black, and some fruit has begun to rot. (Nothing's ripe yet, but they were certainly looking gorgeous until all of this nonsense started.)

Some background: In none of the garden centers I visited, nor the markets, were the tomato plants labelled like I'm used to seeing in both the US and the UK (where we were stationed for two years). Other than indicating if the plant is Roma, Patio, Grape, etc, etc, there's nothing to indicate the plant's level of disease resistance. So, even though I have three varieties, I may have bought a bunch of weak plants - and they all did come from the same garden center.

In the States or the UK, I'd know where to turn and what to buy to try to combat the spread of what seems to be a disease.

Here, I'm a little lost - and my French is abysmal. So, if anyone can direct me to a product that's readily available on the Continent, I'd greatly appreciate it.

P.S. My beans have powdery mildew, if you can believe that.

Thanks in advance for any and all advice.