Rust and smut diseases on veg are caused by a range of fungi that each tend to specialise in specific plants so bean rust, for example, won't spread to other types of vegetable.

They are generally more of a nuisance than a serious threat to your plants, but a few can become troublesome and sweetcorn smut can make a spectacular mess of the plants it affects.

Broad bean rust is very common, and appears as dark brown spots on the undersides of the leaves. It can lead to defoliation, but tends to only appear late in the season so rarely has much effect on the crop.

French and runner beans are affected earlier, by a related rust, but it has little effect on plant growth.

Leek rust appears to be on the increase, and affects garlic and chives also, appearing as bright orange streaks on the leaves. Leeks generally recover once the cold weather arrives, but rust can reduce growth and make plants unappetising. Control it on chives by cutting affected plants to ground level.

Sweetcorn smut affects the developing ears creating swollen galls which then burst to release clouds of black spores. Luckily it usually only affects a small part of the crop. Onion smut produces dark powder streaks on seedlings of the onion family. The spores can live in the soil for 20 years so your best defence is to raise seedlings in pots of compost before planting out. There are no fungicides approved for use on any rusts or smuts.

To reduce attacks, avoid too much nitrogen fertiliser that encourages soft growth. If disease strikes, remove badly affected parts and consign them to the dustbin.

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