helping HAND
Tips for tackling this month’s problems
WHAT’S CAUSING BROWN SPOTS ON MY PLANTS?
Clean green leaves are a simple indication that your fruit and vegie plants are doing okay. When brown spots appear, it’s only natural to feel concerned. There are a number of possible causes, some due to pathogens and weather conditions, others as a result of our own actions.
FUNGAL DISEASE
This is the most common cause of brown spots. Every garden has a range of fungal spores floating around just waiting for a chance to land on some nice moist plant tissue, where they can anchor and reproduce. Beginning as small spots, they then grow into bigger spots that start to join up. Eventually, the brown, diseased leaves drop to the ground, where they provide a source of fungal spores for further infection.
Poor air circulation and humidity is like icing on the cake for these troublesome organisms because the leaves and stems stay wet for longer, making conditions even better for them. Your first line of defence is to thin fruit-tree branches and avoid overcrowding in the vegie patch. Also, avoid wetting plants when watering and try not to overwater, particularly when conditions are cool or you’ve had
a lot of rain. Consider, too, that plants that are troubled by leaf spots may just need a more sunny or airy position, or the drainage may need improving.
Hygiene is important, to minimise unwanted spread, so trim or pick off damaged growth on a regular basis and collect any fallen material. Place this material in the rubbish bin, not the compost, where there is a risk of later spreading spores around the garden. Always disinfect your pruning tools with a 1:10 bleach solution after use.
When disease is persistent, identify it so you can treat with an appropriate organic fungicide, such as wettable sulfur, copper hydroxide or a potassium bicarbonate product. These are most effective when applied as a preventative soon after the symptoms are noticed. In some cases, it’s best to remove diseased plants altogether. Look for varieties that are known to be disease resistant, and avoid planting crops susceptible to the same disease in that spot.
OTHER CAUSES
Pelletised synthetic fertilisers that land on foliage can burn and cause spots. Always spread these types of fertilisers carefully to avoid contact with plants, and apply according to recommended rates. Cold damage can also cause marks on the leaves, so cover the plants to protect foliage on chilly nights.