Preventative action for feeding, fungicides and watering.
• Only feed if absolutely necessary – the soft growth of any plant that has been encouraged by the addition of high levels of nitrogen has been shown to be more susceptible to fungal diseases
Horticulturist Karel Goossens goes one step further and advises against feeding: “Pale, old plants in old gardens are more resistant. Don’t fertilise it.”
As you will have noticed by now, Box Blight is no different to any other controversial horticultural issue – advice will be contradictory. This is not particularly helpful, but taking the middle ground and avoiding extreme action will allow you to take considered action. One thing, though, is certain: over-feeding is potentially more dangerous than under-feeding
• Therefore, when planting, do NOT add fertilizer at the base of the hole
• If you do add a spring mulch, dig it in well – mushroom compost works well
• Trawl of the Internet and you’ll soon find a number of products (some completely natural) claiming to offer varying degrees of protection against Box Blight. They are unlikely to have been tested by an accredited body (such as the RHS) and while they are equally unlikely to cause any actual harm, caveat emptor. Some are not exactly cheap and, besides, if they really did work that well, news would have spread
• However, extensive work is being done to find an effective preventative fungicide – and they are much further ahead on the Continent. Professional gardeners in Germany and Belgium have access to formulations of difenoconazole and tebuconazole that are looking promising, though only tebuconazole is showing any effectiveness against both genetic types of Cylindrocladium. These fungicides are not (yet) available in the UK, though a licensed professional gardener may be able to acquire and apply them on your plants. But please remember, there is no guarantee it will be money well spent.
• The most commonly given advice is always to water the soil direct and NEVER from the top of the plant to avoid water settling on the leaves.
So what does one do after it has rained? Well, if the weather is warm and humid, you are around and not fast asleep, you could give your Box(es) a shake – robustly enough to shake off the rain drops, gently enough so as not to damage the plant(s). However, this will only make a marginal difference at best!
• Keep the soil moist and ensure there is good drainage – see PLANTING, above.