Questions related to diseases in plants:

How do I identify and control bulb rot?

How do I identify and control honey fungus?

How do I identify and control potato blight?

How do i identify and control tulip fire?

Why do my plants have spotted and brown leaves?

How do I identify and control damping off? coming soon

How do I tackle powdery mildew? coming soon

How do I identify and deal with tuber rot? coming soon

Your questions answered:

Q: How do I identify and control bulb rot?


What does it look like?

There are several types of bulb rot all with similar effects. The main symptom is non-appearance of your daffs in spring. Narcissus smoulder shows its hand by producing a white fungus on the outside of the bulb (once you've dug it up to see what’s happening). If the bulb is suffering from basal rot the bulb will be rotting from its base upwards and will be brown. Either way, if the bulb is cut in half it will look soft and brown. They aren’t going to recover.

What causes it?

Fungus spores in the soil.

What damage does it do?

Bulbs will either not shoot at all or, if erupted, they will have yellow foliage, no or very few flowers which could be distorted.

How to sort it:

The spores live in the soil, so avoid growing where bulbs have previously been affected. If bulbs are lifted after flowering, check and dispose of any infected bulbs and store them in a cardboard box in a dry shed. Bulbs dislike wet soil so when planting always plant in sandy, free draining soil – if you have soil that’s on the damp side, place 2-3cm of horticulture grit in the bottom of the planting hole and place bulbs - root down - on this, then backfill with a free draining compost or grow in containers with plenty of gravel in the base.

Enjoy your daffs and narcissus this spring!

Q: How do I identify and control honey fungus?


What does it look like?

This is bad news. Honey fungus, or Armillaria to be technical, is a species of fungi that attack and kill the roots of many woody and perennial plants. Plus, it’s all going on underground unseen by the naked eye. When walking around the garden, look out for a small tree, shrub or perennial that was doing so well last year but is now looking rather sick or may have died completely. Get your magnifying glass out as closer inspection will be necessary to examine the plant. See if you can spot a white fungal growth, a bit like the skin of a mushroom, between the bark and wood usually at ground level. Or if it’s autumn you may see clumps of honey coloured toadstools, but they’re not around for long and often only on infected wood in autumn. 


Above ground you’ll see the upper parts of a plant die - hopefully only one -  and this can be a ‘sudden death’ especially during periods of hot dry weather. If it’s a slow lingering death then branches may die back over several years or produce leaves that are small and pale looking. A flowering plant may fail to flower or produce loads of flowers and fruit or berries; it’s a last-ditch attempt at survival before it dies.

You may also see leaves turning to autumn colour far too early or cracking and bleeding of the bark at the base of the stem.

If you could see below ground you would find dead and decaying roots and more of the white fungal growth spreading through the soil

How to sort it:

There are no chemicals available for control of honey fungus. If honey fungus is confirmed, the only effective way to get rid of it is to dig out and burn all of the infected root and stump material. This will destroy the food base on which the fungus feed and they can’t grow if there’s no food source.

At GLG, we believe that prevention is better than cure and this is certainly the case with Honey Fungus. The first line of defence is regular deep cultivation which will break up the white fungus and limit spread. Some pretty drastic action is needed to prevent it spreading to other areas. A physical barrier such as a 45cm deep vertical strip of butyl rubber (pond lining) or heavy-duty plastic sheet buried in the soil will block the progress of the fungus through the soil. It should protrude 2-3cm above soil level.

Or, if you’ve inherited it and it’s quite widespread then avoid the most susceptible plants and instead use plants that are rarely affected by honey fungus such as Acer negundo, Arundinaria (and other bamboos), Buxus sempervirens, Carpinus betulus, Chaenomeles, Erica, Fremontodendron, Garrya, Ginkgo, Hypericum, Jasminum, Juglans nigra, Larix, Nyssa, Pittosporum, Quercus ilex (holm oak), Tamarix, and Vaccinium.

Hopefully you’ve caught it early and it’s only one plant that’s been affected so taking the preventative steps above will do the trick.

Q: How do I identify and control Potato Blight?


What is it?

Potato blight is devastatingly destructive and can wipe out your potato and tomato plants overnight. It was responsible for the Irish potato famine in 1845. It's also a tricky individual as, like many bugs such as our own common cold, it is mutating and adapting all the time. I have to say it's also hard to control.

What does it look like?

Don’t be surprised if you suddenly find your plants infected. It can happen overnight following a spell of warm and wet weather. Watery spots on leaves soon develop and start to rot. Brown lesions on stems can develop, eventually resulting in rotten tubers or fruits.

How to sort it:

First up, you can try growing blight resistant varieties of potato and tomato. Work is ongoing at breeding stations around the world and various strains of potato and tomato are now available which are resistant to blight. Remember they’re resistant and not immune - you may still get a slight attack but nothing on the scale of other susceptible varieties.

Another good tip for reducing the severity of an attack is to keep the leaves of your potatoes and tomatoes dry. Obviously, this is impossible in rainy weather but if you ever have to water by hand only wet the soil. Never stand there idly spraying water over the canopy of leaves because the spores of potato blight need water on leaves to move.

Covering plants in times of blight attack can reduce infection but will not stop it. You can always avoid potato blight by only growing early varieties – ones that crop before late summer when blight is more prevalent.

Blight is a bit of a headache for gardeners who love growing their own spuds and toms. But good gardening practice and an eye on the weather will reduce infections. 

Q: How do I identify and control Tulip Fire?


What does it look like?

If new tulip foliage looks twisted and covered in brown spots, you know there’s a problem. If this is followed by the emergence of tan-spotted flowers, immediate action needs to be taken. If left, the weakened plant will suffer a second wave of attack from grey mould making the whole sorry lot look a mess.

To make things more complicated the infected plants develop black patches called ‘sclerotia’ on the roots and bulb itself. These can reside in the soil and continue to affect the plant for its entire life. It’s curtains for your tulips.

How to sort it:

Once your tulips are affected by Botrytis tulipae, there is little hope of recovery. The fungus thrives in cool, damp spring weather. So, the two major culprits at play are weather and fungus spores which like to overwinter in the soil and, given the right conditions, will come to life and attack.

There are several approaches to treatment. Firstly, all affected foliage and flowers should be removed and destroyed by burning. Then, get the spade out to dig up and inspect the bulbs. Any bulbs or roots with black spots should be discarded but not on the compost heap Any remaining healthy bulbs should be re-planted in a place well away from the affected area. There are no chemical controls available, so I would remove and discard the soil from the area and replace with new compost and sharp grit to improve the drainage – this fungus loves damp.

At Great Little Garden, we believe that prevention is better than cure so always plant tulip bulbs in a sunny, dry position in free draining soil; lift and store overwinter in a dry shed; and buy healthy, solid bulbs.

Plant tulip bulbs late in autumn - November is still OK. It all helps keep this dreadful disease at bay.

Q: How do I control and identify Leaf Spots?


The question ‘Why do my plants have spotted and brown leaves?’ is one of the most asked questions by gardeners and houseplant lovers. Broadly speaking ‘leaf spot’ is caused by either a fungal or bacterial infection and, without running lab tests, it’s difficult to identify the problem. But there are differences, so get your magnifying glass out and do a bit of inspection work or you may even be able to see the differences with the naked eye.

What do they look like?

If a fungal infection is present, the spots will have a white centre -  that’s the fungus growing. If it’s bacterial ‘leaf spot’, the spots will be dark brown or black and more patchy - sometimes with a yellow halo edge. In both cases if not treated, leaves will yellow, wither and die.

How to prevent them:

Prevention is always better than cure so always keep plants growing healthily. The spores and bacteria are most active when there is plenty of moisture and warm temperatures, i.e. a typical UK summer. But with warmer and wetter winters on the rise, conditions are ideal for leaf spot spores to not just survive but also thrive. Reducing the areas where they snooze over winter is a great way to reduce future infections. 

  • Remove all dead leaves, weeds and debris from around the base of the plants. Do this in autumn and again in spring to tidy up any straggly fallen leaves.
  • Follow this with a mulch to prevent any splash back re-infecting the plant.
  • Clean and disinfect secateurs, gardening knives and pruning saws if you are tidying up diseased material. A simple antibacterial wipe will do the job well.
  • When planting up a garden, allow plenty of air to circulate around plants. Moving air prevents spores getting a hold, particularly in the case of vegetables and fruit.

How to treat:

It is relatively easy to sort out fungal problems. Fungicidal sprays will prevent your plant’s fungus from spreading. It will have a limited effect on damaged leaves but things won’t get worse. Sulphur sprays or copper-based fungicides can be applied weekly at first sign of disease to prevent its spread - these organic fungicides will not kill leaf spot, but will again prevent the spores from germinating so are good for controlling the spread. Remember to choose a spray that is not harmful to bees and other pollinating insects and never spray open flowers.

 Keep things healthy and you shouldn’t have problems. But if you do, treat quickly and all will be good again.