PESTS AND DISEASES
By David Marks
Sweetcorn are one of the least troublesome vegetables to grow in the UK especially once the seedlings have established themselves and started to grow away strongly.
Young seedlings are often attacked by pigeons but we have a fire-proof and almost free solution to that problem. After that stage, sweetcorn in the UK are virtually pest and disease free aside from the dreaded slugs – yes slugs, read more below about the leaf damage they can cause.
See our previous page here for a cheap and very effective method of controlling bird damage.
In years when slugs are thriving they can often cause immense damage to young and not so young sweetcorn plants. They eat the leaves and the damage they cause is often mistaken for other pests because it is unlike the damage caused normally by slugs. The the pictures below show just what happens.
The slug which causes the damage is typically a small whitish one you can see in the picture above, click the picture to enlarge it and see more clearly. Towards the top of the picture you can see the damage done to the leaves.
The above picture (again, click to enlarge it) shows more clearly the odd damage done to the sweetcorn leaves. It's reduced the leaves to an almost lace like consistency and shredded it entirely. The reason for this peculiar form of damage is simple, the leaves of sweetcorn plants have strong ribs to them which the slugs find difficult to eat so they attack the softer parts in between the ribs.
Slugs are one of the gardeners worst enemies and they can decimate a crop of young sweetcorn in less than a week if left to their own devices. That plant pictured above was fine five days ago! And the slugs didn't only eat one plant they ate all sixteen of my plants in the same time frame. Our page dedicated to identifying and dealing with slugs can be found byclicking here.
The lower leaves of sweetcorn frequently turn yellow and then die down. If the majority of the leaves look green and healthy then you don't have a problem. If the top of the leaves are turning yellow then this is probably a nitrogen deficiency. A dose of a nitrogen rich fertiliser should cure the problem.
One of our reader’s asked why their sweetcorn has produced no tassels or cobs. Without tassels being produced then no cobs will be produced so the real question is simply why are no tassels produced. The key reason for this is that some form of stress has occurred to the plant at the time tassels would normally begin to be produced.
The first possible cause of this is unusually high temperatures. However in the UK the temperatures are very unlikely to reach those levels. By far the most likely cause is a lack of water at the key time when tassels would normally be produced. The solution is to ensure the plants are watered in dry periods throughout their life. Mulching around the plants with organic matter (grass clippings are fine) will help ensure an even supply of water to the roots.