Sweetcorn Pests And Diseases

Sweet Corn grows well in the right conditions but often it is grown in unsuitable climates and it will struggle in those conditions. There are not too many problems in the UK but elsewhere there are a range of problems. It does need a good warm growing period and the soil should be well above 50 degrees C when planted.

The major problems are: -

Stewarts Bacterial Wilt, which causes the plants not to grow fully and wilt, it can occur at any time in the life of a plant but more often in small plants. The tassels may well die before pollination and the leaves have yellow streaks. It is caused by bacteria from the corn flea beetle, it is more prevalent after mild winters when the beetles survive better over the winter. Destroy the infected plants, it can be controlled by crop rotation, use of insecticides and there are also wilt resistant varieties of sweet corn that can be used. It is a fairly common problem throughout the world.

Corn Blight (Southern or Northern) is a fungal disease that comes from rotting stock and plants from the winter. There will be brown marking on the leaves and lesions. It can be controlled by crop rotation, destroying the old plants after harvest and ploughing the ground if there is still a problem, fungal control can be used but this is often government controlled.

Corn Smut is caused by a soil fungus and while it looks dreadful it is not disastrous. Grey or white growths appear on the ears or tassels and they later grow black and burst. These growths should be removed early and destroyed, if this can be done successfully it can get rid of the problem. Crop rotation will stop the programme in future years

European Corn Borer is an inch long caterpillar, which has come from the larvae of a moth, which lays its eggs on the undersides of the leaves. Broken stalks and sawdust around the base show the presence of the borer and the stalks can be cut out and destroyed or the whole plant destroyed. Spray the plant with an insecticide every 5 days and it should control the problem.

Corn Earworm is a small caterpillar, to get better results pick a better variety that reduces the problem. The earworms eat the silk ends of the kernel but if a dropper of mineral oil is put on each kernel it will deter them and the kernel can still be used.

Birds like to feed on the kernels so the plants may need bird scarer’s. the noisy type not scarecrows.

Racoons in the USA, where the bulk of corn is grown, are a major problem, as they can smell the ripe corn. If they can be scared off prior to ripening it will save a lot of trouble. Once the racoons have tasted the corn the get hooked and life becomes intolerable. Erect a 3 foot fence around the patch or play music overnight.

This is a great crop but it is also interesting to a range of predators from bugs to raccoons. Resistant seed and good housekeeping will help profus

By Richard Allen -