How to Deal with Pest and Disease in Herb Garden


Fortunately herbs are not generally troubled by many pests and diseases. The point to remember is that strong, well grown plants are more resistant to pest and disease attack (though they are not necessarily less likely to be attacked in the first place). Because herbs are used in small quantities, a few insect pests can fairly quickly be washed or brushed off after picking.

Aphids (greenfly and blackfly) are likely to appear on any plant making soft lush growth, generally clustering near the growing tips. Because of their remarkably efficient method of reproduction, huge numbers can build up very rapidly. Watch out for them particularly on herbs which are growing in the house or greenhouse. Often the easiest method of control is to pinch out and crush the infested tips of plants. Another remedy is to spray with water to which you have added a small amount of detergent.

Pest Disease  Herb Garden

Lovage can be disfigured by celery leaf miner, a grub which tunnels within the leaves, leaving a thin ribbon of dead tissue. Pick off and crush affected leaflets. Parsley is often attacked by carrot fly. This small fly lays eggs in the soil near the roots of carrots, parsnips and parsley: the grubs which hatch out live in the roots, eating tunnels out of them. Because this reduces the efficiency of the plants’ system for obtaining food and water from the soil, they soon begin to show symptoms of distress, though a minor attack will not produce very serious results. The older leaves begin to yellow and flag, and become tinged with red; plant growth slows or stops. Carrot fly attack is much worse in some years than others. It can be halted by using a soil insecticide (see precautions below). Raising two batches of parsley seedlings a year ensures you will have some replacement plants coming along. To some extent carrot fly can be carried over from one season to the next in the soil, so choose a fresh site or grow in containers of sterilized potting compost after an outbreak.

The most troublesome disease that’s likely to attack your herbs is mint rust. This can attack all varieties of mint and is characterized by rusty orange, powdery spots on the undersides of the leaves. It has a very severe effect on plants and there is no cure. One way round the trouble is to lift some of the creeping underground stems in autumn, wash off the soil and immerse them in hot water, 44°C (110°F), for about ten minutes. This should kill the disease, but take care not to damage the rhizomes by allowing the temperature to go any higher. Rinse in cold water before replanting in a fresh bed of clean soil.

A different type of rust sometimes affects chives, especially in mild areas. If plants are badly affected it is best to destroy them and raise new stock from seed.

When using any chemical on edible plants, whether it is a fungicide or insecticide, you must take certain precautions. First read the instructions on the bottle or pack fully, making sure the particular chemical is suitable for use on edible crops, and if so, how long you must wait between application and harvesting. Wherever possible, choose a chemical that has a short interval between spraying and picking—some require only a day, while others could be up to a fortnight. Also, read the small print, where you could well find a list of specific plants that could be damaged by the chemical concerned.

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About the Author: Greenery always attracts Arthur Kunkle. He has a big garden where he plants many fruits and vegetables. His passion for gardening motivates him to write and share different tips on gardening.

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