Onion Pests And Diseases

Onions can be fairly hardy but there are a number of problems that can be found. Onions can be a major boon in the garden as their scent chases away some flies like carrot root fly but it can attract other pests.

Onion root fly only usually occurs in directly sown onions as the flies are attracted by the smell when the young onions are thinned out. The onion root fly lays its eggs at the base of the onion and when the larvae hatch from the eggs they bore into the leaves and the top of the bulb and it will rot. The leaves die away. There is no cure once the crop has been affected other than removing the infected bulbs and destroying them. The bulbs can be protected by fleece or mesh laid around them to stop the flies getting to the base of the plant.

The allium leaf miner is a pest that is very common in Europe and whilst not common in the UK there are concerns that it will become a problem. There are no known cures. The flies lay their eggs and the larvae eat their way into the bulb and it is then vulnerable to other fungal and bacterial diseases, the bulbs should be removed and destroyed. Protecting the plant from the flies by covering with fleece or mesh will help.

Onion white rot is a bad fungal disease for which there is no cure and changing the variety does not help. It is seen as a white fungal deposit around the roots and base of the bulb. Lift the infected plants and destroy them and do not plant in this area for 8 to 10 years to remove the problem.

Onion thrips can attack the leaves giving a white damaged appearance and can reduce the size of the crop. They are usually related to hot dry weather.

Onion neck rot usually damages the onion bulb as they rot from the neck particularly in storage and this can be caused by thick necked onions but if the bulb is dried well a quickly this can be stopped.

Why not also see How To Grow Onions

By Richard Allen -