Garlic - Guidelines for Cultivation

Pests and Diseases

The crop is subjected to most of the usual Allium pests and diseases. In normal practice there are three situations that require special attention:

Stem Eelworm: This pest can devastate crops and reduce yields considerably if not prevented. Hot water treatment of cloves should control it.
Virus: Onion Yellow Dwarf is the main one involved but stocks may harbour up to three or four other virus. At worst plants are killed, at best some stocks are capable of carrying certain virus without showing the symptoms. Stocks of a number of varieties from Efford EHS were ‘cleaned up’ by David Walkey of IHR Wellesbourne. A trial demonstrated that virus free stocks gave better yields than infected stocks of most varieties. The viruses are spread by aphids. It is hoped that a limited supply of cleaned up stocks will be available through R & D services eventually.
Penicillium attacks bulbs (and cloves) in store readily. The slightest bruising or mechanical damage allows disease entry

Varieties and Stocks

In the early 1980’s, many stocks of varieties of garlic were acquired and tried. There are two main types – the broad leafed varieties are early, e.g. Blanc de la Drome - and secondly, the narrow leafed types, e.g. Fructidor. Fructidor has always proved the most reliable and consistent giving good yield of good quality. Latterly better French stocks of this and other varieties have become more widely available. Most of the stock from France has been partially ‘cleaned up’. When selecting bulbs for replanting it is important to only plant back the best by selecting the most vigorous plants. Other useful varieties providing good stocks can be obtained are Rose du Var, Printanor, Messidrome and Thermidrome. Stocks from warmer climates should be avoided because they are unlikely to be acclimatised to our conditions.

Harvesting and Storage

Harvesting begins in late July. Bulbs required for market should be harvested as soon as the top leaves turn yellow. If lifting is delayed, quality will quickly deteriorate especially if the weather becomes wet.. The skins are subject to staining once the bulbs are mature. High temperatures are required for ripening. Growers either lay the bulbs out in glasshouses or open rain-proof sheds. At Efford excellent quality has been obtained by following the same procedure as for drying bulb onions after harvest. Providing they are left very dry, bulbs of late varieties will store for up to 6 months at ambient, beyond this it is suggested bulbs are kept for a further 2 months at 0.5 C. However this is one topic where some investigation is justified.

Yields

Many commercial marketable yields are as low as 5 t/ha; good growers can achieve 10 t/ha and up to 15 t/ha should be possible according to trial results.

Some Other General points

At Efford observations and feasibility studies have been carried out on the following:

• Planting cloves into 43 mm peat blocks in December if soil conditions in autumn have been too wet for planting. This worked well and produced good quality bulbs – but expensive.
• Growing the crop in ‘bulb nets’ (Rosewarne EHS). The idea was to aid lifting. The crop grew well, but as lifting is required before the tops die down a great tangle resulted when trying to extract the bulbs from the nets.

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