vlog#28 - The harvesting of onions begins

I’ve started to harvest the onions that I planted from sets in seed trays, back at the beginning of April, and then into the garden raised beds in May. They’ve had almost five months of growing and the foliage had begun to fall over, so it was time to harvest.

I discovered some had white rot which, according to the RHS website, is “a disease of plants of the allium family, especially bulb onions, garlic and leeks, caused by the soil-borne fungus Stromatinia cepivora, which can persist in the soil for many years. Symptoms are:

Above ground, the first symptom is yellowing and wilting of the foliage, especially in dry weather.
Under wetter conditions the plants may not wilt, but will become loose in the soil.
Below ground, the pathogen rots the roots and then invades the bulb.
White, fluffy fungal growth appears on the base of the bulb, and later this growth becomes covered in small, round, black, seed-like structures called sclerotia.

Stromatinia cepivora is an unusual fungus in that it does not produce any spores of importance to the normal life cycle. It exists in the soil as round black resting structures (sclerotia) about 0.5mm (1/32in) diameter, which remain dormant so long as no members of the onion family are grown.

Sclerotia can detect certain volatile chemicals unique to alliums and when these are sensed the sclerotia germinate, producing fungal growth which invades the roots directly. Fresh sclerotia are then formed on the rotting bulbs and re-contaminate the soil.

Sclerotia can remain in the soil for at least 15 years, though they will not always live this long. They can only germinate once and the fungus will then die out if it can not infect. Both sclerotial germination and fungal growth are inhibited above 20°C (68°F), so in the UK the problem is more severe in cool, wet summers; in warmer climates the disease is only a problem over the winter months.”. Given the weather we’ve had this season I’m not surprised I’ve seen white rot on the onions.

There is some evidence that using garlic infused water on the ground of an empty vegetable bed may induce the sclerotia to germinate, but with nothing to feed on the soil-borne fungus will die out.

I also spotted some caterpillars, of which I’m unsure as to the genus or species.

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TTFN,
Tone