Diseases in ROSES
published:
Sunday | August 3, 2008
Photos by Rita Elliott
Many roses are fragile beauties prone to an array of diseases. Here are some pointers on how to recognise 'what's wrong'.
You decide upon the cure, but whatever method (chemical spray or home-made remedy) you choose, it is always a good idea to first discuss the matter with your nursery man. Bring along some diseased leaves for better identification of problem.
Black spots on leaves
Black spots appear as dark circles with fringed edges on the leaves, and they cause them to yellow. The solution is to remove the infected foliage and pick up any fallen leaves around the rose.
Stunted or malformed young canes
Known as powdery mildew, this is a fungal disease that covers leaves, stems and buds. Mostly, it is spread by the wind. It makes the leaves curl and turn purple. Take action at once, as this particular disease could totally ruin your rose garden.
Blistered underside of leaves
A disease known as rust, it is characterised with orange-red blisters that turn black in fall. In spring it will attack the new sprouts.
Malformed or stunted leaves and flowers
The most likely cause of this is the presence of spider mites. These are tiny yellow red or green spiders which cling to the underside of the leaves. They will suck the juices from the leaves, but the application of relevant pesticide may help in treating this infestation.
Weak and mottled leaves showing tiny white webs underneath
This might be caused by aphids, which are small soft-bodied insects which are usually brown green or red.
Often found clustered under leaves and flower buds, they suck plant juices from tender buds.
Flowers that do not open or are deformed when they do open
Thrips could be the reason behind this deformation, which is caused by slender brown-yellow bugs with fringed wings, thriving inside the flower buds. The simplest method is to cut and discard all infested flowers. Don't throw the cuttings on the compost pit and spread the disease!
Fertilising container plants
Container plants need regular fertilising.
Q: We have planted a variety of vegetables and flowers in large clay pots on our patio. The plants were very healthy before being planted, but now the leaves look pale. What is wrong? Do they need fertiliser and, if so, what should we use?
Linda Brown - Miami
A: Container plants need regular fertilising since their roots can't travel through the garden soil in search of nutrients. Try fertilising with fish emulsion- and seaweed-based fertiliser. These contain small quantities of highly available nitrogen, which will help plants green up without stressing them.
It's also possible the plants have been stressed by drying out. Clay pots are porous and you need to be diligent with your watering to maintain consistent soil moisture. Check the soil with a finger; if the soil is dry down to your knuckle, then water. Also, mulch the soil with bark chips or hay to conserve moisture.
Tilling
Never work wet soil, especially clay. You may ruin the soil structure for the entire season and end up with solid, sun-baked clods. How can you tell if your soil is dry enough to till? If you pick up a handful of soil and can squeeze water from it, it's obviously too wet. If the soil compresses into a ball and stays that way, it needs more drying time. If it is dry enough to crumble in your hand, it is 'riable' and is ready to be worked.
