1. Good Organic Gardening - January-February 2016

Remove any infected fruit and foliage.
Remove any dead wood and twigs, and
burn if possible.
Practise crop rotation with annuals.
Avoid overhead irrigation and improve
air circulation.
Choose disease-resistant varieties.
Black spot (roses &
pawpaws)
Black spot is a broadly used common name for
a variety of fungal issues that — you guessed
it — exhibit black spots on foliage, flowers and
fruit. Roses are renowned for black spot fungal
issues and, even though not often eaten (well,
the flowers and hips can be), they are such an
important and widely grown flowering plant
in gardens across the world that people are
always looking for organic options when it
comes to controlling pests and diseases.
Black spot can be more prevalent on roses
in warm, humid subtropical areas. The signs,
of course, are the tell-tale black spots and
yellowing of foliage, which can then drop off.
It can even attack the stems of the rose and
cause dieback. With all this going on, the
plant can become weakened, prone to other
diseases and insect attack, and produce
fewer and smaller blooms.
As for pawpaws, it’s the onset of cooler
winter weather that can bring on a nasty case
of black spot.
Control
Choose varieties that are diseaseresistant
if possible; in warmer climates
some of the old-fashioned teas and China
roses do remarkably well.
Spray with an organic fungicide such as
Eco-fungicide to not only kill existing
spores but also change the pH on the
surface of the leaves and plant stems,
making them more alkaline and less
habitable for fungal diseases. Use a small
of amount of Eco-oil mixed into the spray
to help it stick to the plant.
Copper and sulphur-based sprays can
also be used.
Remove any disease-affected leaves and
throw them into the bin.
Make sure you are giving your plants the
right growing conditions with the required
hours of sun a day and good airflow. This
will help prevent fungal problems.
Avoid watering the foliage, especially in
the late afternoon.
Keep plants healthy and less vulnerable
to disease attack by feeding with
recommended organic fertilisers
throughout the growing seasons and
when recommended.
Applications of seaweed will also be
of benefit and act as a preventive,
strengthening the cell walls of the
plant and encouraging stronger,
healthier growth.
Consider spraying the ground around the
plant with fungicide as well, to catch any
spores lingering there.
Pawpaws lacking in potassium,
magnesium or phosphorus can be more
susceptible. Add potassium (sulphate of
potash), phosphorus (rock dust minerals
and/or magnesium (Epsom salts) to the
feeding regime to ensure no deficiencies.
Disease distress | PLANT HEALTH
Peach leaf curl
This fungal disease affects peaches
and nectarines in cooler climates.
Symptoms include puckering of foliage
and sometimes even quite severe
distortion with a pinkish blotching or
discolouration. The leaves will usually
drop prematurely. This, in turn, affects
fruit production.
Leaf curl remains secretly dormant
on these deciduous fruit trees, appearing
and infecting foliage as soon as the first
shoots appear.
Control
There is no effective treatment for it once
this disease has a foothold, so prevention
is the key.
Spray trees with a copper-based spray
just as the growth buds start to swell.
Be sure to spray the branches and
trunk as well, to catch any spores
that have been resting dormant
over winter.
Trees that are infected need all
the help they can get, so keep up
the applications of liquid seaweed
as a foliar spray. Regular watering
and the application of organic fertilisers
will help the tree to survive through
the growing season.
After leaf drop in winter, gather up all
the old foliage and follow the above
directions in late winter and again
early spring.
Applications of gypsum for added
calcium will also strengthen the plant
cell walls against disease attack.
Black spot on roses
Peach leaf curl needs
preventive treatment
Good Organic Gardening | 55