Reader's question

Mrs Hennessy from Darlington has a climbing rose which she describes as very healthy but which has developed black spots on some of the leaves.

She wants to know what she can do about it.

YOUR plant has almost undoubtedly developed a case of black spot, which is a very common disease on roses. Black spot can be identified by black or brown patches on the leaves that are irregular in shape and often join together. The leaves turn yellow and fall off. If left untreated, it will strip the plant of all leaves, and after several seasons will slowly weaken and eventually, kill the rose.

Treating black spot can be much more effective when you understand the life cycle of the disease. It starts in late spring when black spot spores, which over-winter in the soil, are blown or splashed by rain onto the rose bush. When the weather warms up, and especially if it is also damp, the disease spreads throughout the plant.

The diseased leaves die and fall off onto the soil below allowing the spores to over-winter in readiness to infect the plants again next spring.

The key to controlling black spot is to attack it at two points in its life cycle, first, when the infected leaves fall to the ground, and second, in late spring when spores already within the plant begin to rear their ugly heads.

The first line of attack is to pick up and destroy all the leaves on the ground. Try to do this as often as possible. This will prevent re-infection during the season and reduce the number of spores that over-winter in the soil. In addition, frequent turning over of the top few inches of soil will help expose the spores to frost and will kill some.

Secondly, if you are not opposed to using chemicals in the garden, spray with a systemic fungicide, such as Rose Clear, in late spring and again two weeks later. This will attack the disease well before it has gained a stronghold and is at its weakest.

Further spraying should only be necessary when signs of the disease are apparent later in the year.

Another weapon against black spot is to grow varieties that are resistant to the disease. Most plant nurseries and catalogues can recommend them, but they will tend to be the more modern varieties.

Jobs this week

■ BEGIN harvesting French beans as they form on the plant. Try to resist the temptation to let them grow huge, but pick them when they are nice and tender.

■ MAKE sure that tomatoes in the greenhouse are getting a regular watering. Keep an eye out for any signs of blight (browning of the leaves or fruit).

■ GRASS cutting should be a regular undertaking now, as and when the showers allow. Little and often reduces the risk of scalping the lawn and letting weeds and moss take hold.

Brigid presents the BBC Tees Gardening show on Sundays from 1pm to 2.pm.

Questions can be answered on the day by emailing brigidpress@bbc.co.uk anytime during the week, or texting 07786-200995 and phoning 01642- 225511 during the show.