Fire blight of pear and quince in Azerbaijan, Isfahan, Khorasan and Zanjan enters through the blossom and through wounds. Cut a bent shoot twenty to thirty centimetres below the symptom, and disinfect the secateurs.
Fire blight is a bacterial disease that, in Iran's pear and quince orchards — particularly in East and West Azerbaijan, Zanjan, parts of Khorasan and the cooler orchards of Isfahan — builds severe outbreaks every few years. The grower sees a black, bent shoot and sometimes takes it for frost damage or a superficial scorch. The classic sign is a shoot bent like a shepherd's crook: the tip of a young shoot dies, turns brown to black and stays bent downwards. On the blossom, a sudden scorching of petals and pedicel appears in warm, humid spring weather. Bacterial ooze may appear on the infected tissue as sap-like droplets. Quince is more susceptible than pear in some years, and one infected quince at the edge of the orchard becomes the inoculum source for next year's blossom. The disease also moves through pruning wounds, hail and pollinating insects, but in spring the main entry point is the open flower.
Blossom infection: where next year is built
The bacterium survives in overwintering cankers on the trunk and thick branches. As the weather warms and humidity rises it oozes and reaches the flower. If several days of mild weather with high relative humidity coincide with full bloom — a situation that recurs in the spring of Azerbaijan and Zanjan and in some years in Mashhad and Neyshabur — blossom infection advances quickly and moves from the pedicel into the one-year-old shoot. Spraying after petal fall has missed that window. Blossom management means reducing overwintering inoculum before bud swell, avoiding sprinkler irrigation onto the flowers, and, if necessary, using copper compounds at defined times before bloom or at its start, at a rate that does not burn the flowers. Copper is not a miracle, and repeating it on soft tissue causes phytotoxicity. Timing and even coverage matter more than the brand on the can. In Isfahan, where spring is sometimes drier, the disease may stay milder, but one week of rain during flowering is enough to build an outbreak.
Pruning out the disease: twenty to thirty centimetres lower, with clean secateurs
Cut a symptomatic branch back into healthy tissue, not at the edge of the blackening. The practical rule in Iranian pear and quince orchards is to cut at least twenty to thirty centimetres below the last visible sign. If a canker has reached a thick branch or the trunk, a surface cut into the bark is not enough; you must remove the dead tissue back to sound wood and decide whether the tree still has a bearing structure or is a permanent source of inoculum. Disinfect the blade between every cut. Alcohol, or a dilute bleach solution with a sufficient contact time, is better than wiping it on a dusty rag. Pruning on a dry, cool day, with less sap flow, reduces spread. Pruning in rain or immediately after hail offers the open wound to the bacterium. Take the cut branches out of the orchard the same day; leaving them under the tree keeps the inoculum. Clean the secateurs and saw again at the end of the job so they do not go onto a healthy quince tomorrow.
- Mark the crook-shaped shoots and cut them the same week, in dry weather.
- Make the cut twenty to thirty centimetres below the darkened tissue.
- Disinfect the blade between trees, not only at the end of the row.
- Do not chip infected branches in the orchard or spread them as mulch.
- Treat a quince at the edge of the orchard as seriously as the main pear; a forgotten quince builds an outbreak.
Nitrogen at flowering, soft tissue, and the disease's open door
Heavy nitrogen fertiliser in late winter and at flowering builds soft, sappy growth. That very tissue is both more suitable for the bacterium to enter and quicker for it to move through inside the shoot. A quince orchard where urea is tipped at the foot of the tree to green it up usually sees more scorched shoots in June of the same year. Base the nutrition on soil and leaf tests, and split the nitrogen so it arrives after fruit set and during balanced growth, not at the peak of bloom. Excessive irrigation during flowering raises the humidity of the canopy. In Zanjan and Azerbaijan, where spring is cooler and wetter, that combination is more dangerous than in a dry orchard in Isfahan. Balanced potassium and calcium help the strength of the tissue, but they do not replace sanitary pruning. Leave out the top-dressing over a flowering canopy.
- Winter: find the cankers and remove them before bud swell.
- Before bloom: if needed, one copper application with even coverage and without phytotoxicity.
- Bloom: avoid overhead irrigation on the canopy and top-dressed nitrogen.
- After seeing the shepherd's crook: prune with a twenty to thirty centimetre margin and disinfect the blade.
- Summer: weekly monitoring of the shoots, especially after hail or a warm humid wind.
- Autumn: look again at the trunk and thick branches for overwintering cankers.
Do not try to finish fire blight with a single all-season spray. The blossom window, clean secateurs and less nitrogen are three things every pear orchard can do.
Treat quince and pear as one file
In many orchards of Khorasan and Isfahan, a few quince trees have been planted on the edge or within the pear rows. Quince has a long flowering period and susceptible tissue, and it can hold the inoculum even when the pear shows fewer symptoms that year. Pear cultivars are not uniform either; some local cultivars are more susceptible. That is not a reason to convert the whole orchard to an advertised cultivar without looking at the fire blight history of that same valley. Resistance is relative and breaks in a spring that suits the disease. Planting distance and canopy ventilation dry the blossom faster. In a dense orchard with tall weeds under the row, morning moisture lingers. Bees are needed for fruit set; time the copper programme so it overlaps as little as possible with the peak of pollinator flight. The aim is not to remove the bees; the aim is to reduce the bacterial inoculum on the flower.
Fire blight of pear and quince in Azerbaijan, Isfahan, Khorasan and Zanjan survives on late pruning, nitrogen at flowering and dirty secateurs. Treat copper as a tool of timing, not as a brand of salvation. Take the crook-shaped shoot off the same week and below the symptom. Put monitoring in the orchard calendar from before bud swell until after summer hail. In the pome fruit orchards of these provinces, Farin Kesht Taban writes the spring programme around canker monitoring, the blossom window and nutrition, so that repeated spraying does not take the place of pruning.
