What's it look like?
As the name suggests, leaf spot produces small brown sunken spots on the leaves of cucurbits, lettuce and pelargoniums. The spots grow bigger and form holes which can join up causing large dead areas.

What it attacks
Leaves and stems of pumpkins, cucumbers, zucchini, lettuces and ivy pelargoniums. Sometimes fruit can also be affected and develop large brown spots up to 10mm on the skin and flesh under the spot.

What to do before it arrives
Install a drip system irrigation. Bacteria spread by irrigation water falling on unaffected leaves. Water in the morning only.
Choose disease free seed and do not collect seed from infected plants.
Make sure there's good air circulation around plants. That means not planting them too close together. Letting plants trail over an embankment or retaining wall can help since bacterial is soil borne.
Spray a preventative spray of diluted chamomile tea every week. Use a seaweed solution to build resistence and practise crop rotation.
A protective layer of clean straw mulch can help. Make sure tools are clean.

What to do if you already have problems
Remove any infected leaves as soon as you see it occurs. Do not compost. Remove any fallen leaves from the ground near the plants. Apply fresh mulch.
Use drip irrigation instead of hose watering or sprinklers. Apply a seaweed solution to the plant regulary, this will toughen the new growth and give protection against the fungus.
Poor air circulation can increase the problem. Remove plants if they're overcrowded.
A bordeaux mix may be necessary in severe cases.