Q&A - Diseases

There are all sorts of diseases that affect plants but on the whole most do not have too detrimental effect on your garden plants and can be easily treated. See also our Q & A's on garden pests such as aphids, blackfly, worms, moles, squirells and garden pets.

Q. I have black splotches on my apples particularly on the leaves, as you can see from the attached photo. What is the cause and
remedy?

A. It is always difficult to give a diagnosis from a photograph but it looks like a combination of things. The curling leaves are likely to be caused by aphids (most probably greenfly), which can be controlled by a general insecticide. The leaf spots look like apple scab and you should pick off and destroy infected fruit and leaves and prune out any weak branches. Spray with a fungicide that contains carbendazim, mancozeb or triforine with bupirimate. You should also feed with a general fertiliser and water regularly to encourage healthy growth.

Q. I gather new roses will not thrive in an old rose bed. How can I escape
the problem of Rose sick soil, or how long would I have to wait for the soil to recover?

A. The best thing you can do is replace the soil to a depth of about 60cm (2ft) or wait about 7 years. You can also plant other non-related plants which is by far the easiest option.

Q. We are growing tomatoes for the first time in the back garden. They are growing well and tall and are in terracotta pots in the sun. The fruit are growing and beginning to turn red now but some fruit are turning black at their base from a very young stage while the rest remains green. Can you tell us what we can do about this and what may be the cause please?

A. It sounds as if the problem is blossom end rot which can affect plants grown in containers. It is caused by dry conditions which prevent the plant from taking in sufficient calcium. It can also be caused by very acidic compost. You should remove the affected fruit and water well.