Pests and Diseases
- which pest or disease do my plants have?
Pests - beasties
Diseases - fungal
natural is your garden? | ants
| aphids | blackspot
| botrytis -
grey mould | caterpillars
beetle larvae | fairy
rings | leatherjackets
beetle | mealybugs
| powdery mildew
| red spider mite
| rust | slugs
and snails | vine
weevils | whitefly
Unwelcome visitors: cats | foxes | frogs | moles Weeds: clearing a neglected area, general weeding
Every species of plant or animal that has yet been discovered has at least one unique parasite or disease that affects it uniquely. So there are more parasites and disease causing organisms than any other kinds. Fortunately (I use the word in a relative manner) there are not so many pests and diseases that the average gardener will come across and in most cases it will be one of the following.
At the end of each description, there is a link to a page of more detail on that particular pest and how to deal with it.
Grey Mould - Botrytis
Signs - Stems and flowers become covered with a velvety greyish, fungal growth (that looks particularly unpleasant.)
Damage - A very common fungus which produces spores that are always around in the air. They attack plants through areas of damage. At first, small pale brown or white patches appear as the flowers start to rot.
Signs - Very descriptive these fungal diseases - looks like the pant is going rusty. Orange-brown pustules develop initially on the undersides of leaves. These may be unnoticed for some time, so by the time the pustules appear on the upper leaf surface and are noticed, the disease has taken hold.
Damage - Badly affected plants can be so weakened they are unable to withstand winter frosts.
Signs - Purplish-black usually rounded blotches appear on leaves, which then start to yellow and fall early. Stems may be affected in severe cases.
Damage - Badly affected plants may die as they are so seriously weakened they cannot withstand the winter frosts. It is very unsightly.
Signs - White powdery mould appears on the leaves, stems and buds. Young growth in particular is affected. The disease is encouraged by the plant being dry at the roots with damp stagnant air around the top.
Damage - Looks unsightly and causes leaves to drop early. If the plant is well established this is a relatively harmless disease. However, care should be taken with younger plants since these may be drastically weakened.
From the newsletter
This year seems to have become the year of the fungus. I've noticed it on all kinds of plants that have contracted some vague illness that can't quite be pinpointed. Discoloured leaves that are brown at the edges, maybe tending to black, but still alive rather than dry and crispy. A common question has been regarding a "sooty" deposit on plants, this is almost certainly "sooty mould" that is not growing on the plant as such, but on the sticky honeydew exuded by aphids higher up in the leaves. The sooty mould is a fungus that feeds on the sugary excretions, in itself it will not directly harm the plant, but it will cause discolouration and block light. The honeydew itself will also make it easier for other infections to take a foothold.
There have also been a whole host of emails about dying hedges and conifers. Brown patches that have been growing slowly for some time, that have suddenly become much larger and killed more of the hedge or tree. There are a number of possible causes of this - all fungal. What is probably happening is that the hedge or tree has been poorly for a while, but this warm damp summer came along and it became party time for the fungus. What can be done about it? Not a lot really once it's started to happen. It's more a case of removing dead or dying growth that may spread within the plants and then in the future carrying out basic hygiene. Dead leaves for instance from diseased plants should leave the garden in the wheelie-bin, down the tip or up in smoke, they shouldn't go on the compost heap or the infection will continue.
Spraying your plants with a general fungicide will help to reduce the effect or extent of the infection, but not completely eliminate it. Remember a garden is simply a collection of novel exotic food for all the local pests and diseases to have a go at!
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