Bacterial black spot

small dark, water-soaked, greasy-looking spots on the young leaves that harden into raised BLACK spots with straight sides - angular, like little tiles - because the veins box them in. Each spot is often ringed by a yellow halo, and you may see black streaks running along the midrib.

raised black, star-shaped cracks that split the skin and weep a sticky gum. The skin around each crack goes dark and rough. These cracks let rot and fruit flies in, so the fruit can no longer be sold - this is the unmistakable, market-ruining sign.

black, sunken cracked cankers and dieback (dead tips) on the young twigs and branches. This wood is where the bacteria survive the dry season and re-start the attack each year, so it matters even though it is easy to miss.

(the commonest mix-up): anthracnose spots are round and sunken, NOT angular, they run down the fruit in dark tear-stain streaks, and they never ooze gum or form raised star cracks. Black spot is angular, raised, boxed in by the veins, and gummy on fruit. Sooty mould is different again - it wipes off with your finger, while black spot is embedded and won't rub away.

the danger window runs right through the wet season - from the new-leaf flush and flowering, through fruit set, to the maturing fruit before harvest. Check within 2-3 days after every windy rain, because that is exactly when the bacteria are splashed onto fresh, tender growth.

walk a big "W" through the orchard so you cover all four sides and the middle, not just the trees by the path. Stop at about 10 trees; at each one look at the new leaves, the flowers and young fruit, and the lower twigs - and check the shaded inside branches too, not only the sunny outside.

fresh angular black spots with a greasy edge or yellow halo on the new leaves, and any star-shaped cracks or beads of gum on the young fruit. Also find the old twig cankers and mark those trees so you can prune them in the dry season.

because copper can only protect healthy tissue and cannot cure a spot once it has formed, don't wait for a big count. The moment you find angular black spots on even 1 in 10 leaves, or a single spot on any young fruit, act. Better still, get protection on ahead of the rains and again at flowering and fruit set - before any spots appear at all.

avoid overhead or sprinkler watering (water sitting on the leaves spreads the bacteria), and never prune or handle the trees while they are wet - a fresh wet cut is an open door the bacteria walk straight through.

copper spray is a contact protectant - it coats the surface and stops NEW infections, but it cannot cure spots that are already there and it does not travel inside the plant (it is not systemic). Get the timing right: spray copper at the start of the rains, again at flowering and fruit set, and on through fruit development - always BEFORE wet, windy weather, so healthy tissue is already covered when the bacteria arrive. SAFETY: copper is poisonous - cover your skin, eyes, nose and mouth, spray in the cool, calm part of the day with the wind at your back, keep it off food, drinking water, children and bees, respect the pre-harvest interval (the least number of days the label tells you to wait between spraying and picking the fruit), and wash yourself and your clothes afterwards. RESISTANCE: do not lean on copper alone - over-using it breeds copper-tolerant bacteria (and over-spraying can mark or roughen the fruit skin), so always pair copper with the pruning, sanitation and windbreaks above.

if spots keep appearing despite protection, tighten the sanitation - in the next dry season prune out and burn more of the cankered wood and widen your windbreak, because the source is always in the twigs. On badly cracked, oozing fruit there is no cure: pick and remove them so rot and fruit flies do not spread, and count that fruit as lost. For a tree that is heavily cankered and dying back year after year, cut your losses - remove and burn it, and replant a less-susceptible variety on that spot.