Rust (pictured) is a fungal disease that affects garlic, leeks and onions. It can impact bulb development and also kill your whole crop. But unless, you had a really bad case of rust or it happened early on in the bulb development stage, you should be able to harvest your garlic as normal and eat it. Chop off the infected leaves as soon as you spot rust and discard of them in the rubbish – not your compost bin as this will spread the infection. Also, give your hands, clothes and gardening tools that might have come into contact with the fungus a good wash to stop the spread. Harvest the garlic when you normally would – don’t pull it up early.