Quince

While the tree is leafless, train it to an open vase and thin crossing wood - a mature quince needs little beyond the removal of suckers and watersprouts. Cut out all blackened, cankered wood now: find the lower edge of the canker, trace it back to where that branch attaches, and cut at the next branch juncture down without damaging the branch collar. Quince is one of the most fire-blight-susceptible plants grown, and Erwinia amylovora overwinters in those cankers. Winter is when the bacteria are not moving through the tree, so it is the safe time to cut; and the cankers you leave are the exact source of the ooze that infects next spring's blossoms.

Give quince only a light nitrogen application in spring, and skip it altogether on a tree that is already growing vigorously or that showed blight strikes last season. Resist the urge to push a slow young tree with fertilizer. Fire blight bacteria colonize succulent, fast-growing shoot tips, and anything that favors rapid shoot growth increases the severity of the damage. On a host this susceptible, a heavy feeding buys you blight rather than fruit - which is why extension guidance for quince specifically calls for light nitrogen.

Coat the fruit with kaolin clay (Surround WP) once the petals drop, and re-coat every 7 days through egg-laying - the white film only works while it is intact, so renew it after heavy rain. Expect white residue on the fruit. Curculio cuts crescent-shaped scars into young fruit to lay eggs; the clay film makes the surface unrecognisable to her rather than killing her, so it must be there before she arrives.

Once the leaves are out and cool wet weather sets in, spray copper octanoate (Cueva) and repeat while the rains continue. Do not wait for spots to appear - this is a protectant and it must be on the leaf before the rain that carries the spores. Water at the ground rather than overhead so foliage is not left wet for hours. Diplocarpon mespili overwinters in diseased leaves and shoots, and its spores are splashed onto foliage by rain, needing only 8 to 12 hours of leaf wetness to infect. Susceptibility does not drop as leaves mature, so a wet spring can strip a quince bare and cost it the season's growth.

If you are not bagging, spray spinosad about ten days after the petals have dropped, which is when the first eggs are hatching, and repeat on the label interval while the generation runs. Scout from late spring through harvest and pick off any fruit with a frass-filled hole, sealing it in a bag in the sun for a week rather than composting it. The larva is exposed only in the short window between hatching and boring into the fruit, so the material has to already be on the skin at egg hatch. A spray aimed at the adult moth, or at fruit already tunneled, does nothing.

When the fruitlets are half an inch to an inch across, roughly four to six weeks after petal fall, slip a paper bag or nylon footie over each fruit you intend to keep and close it at the stem. Bag only clean, uninfested fruit. It is tedious on a tall tree, but it is the most effective home control there is. Codling moth larvae hatch and bore into the fruit quickly, and once inside they are beyond the reach of any spray - which is why the frass-plugged entry hole is usually the first thing a grower notices. A physical barrier placed before egg hatch is the one control that does not depend on timing a spray to an insect you cannot see.

Through the growing season, look for shoot tips that have wilted and bent backward into a shepherd's crook, with leaves turned orange to brown and the wood beneath blackened. Look too for small shriveled fruitlets with blotchy necrosis that ooze in warm humid weather. On quince, cut these strikes out as soon as you find them rather than waiting for winter, removing and destroying the wood. Fire blight is devastating on European quince - dieback can kill a young tree in a single season and persist in an older one for years. Infections that begin in the blossoms run down into the wood, and a strike left in place is what becomes the overwintering canker, so on a host this susceptible the usual advice to wait for dormancy is outrun by the disease.

Let the fruit colour on the tree from green through pale green to a deep even gold, and pick then - just ahead of the first frost. Handle each fruit gently and set it down rather than dropping it into the basket. Colour, not feel, is the maturity signal: quince is tough and hard even when fully ripe, so firmness tells you nothing and waiting for softness only walks the crop into a freeze. The gold stage in late fall, right before first frost, is the best time to pick.

After harvest and leaf drop, rake up the fallen leaves and destroy them - burn, bin, or bury, but do not compost them and do not leave them as mulch under the tree. Take out dead shoots and blighted twig tips in the same pass. Quince leaf blight overwinters in diseased leaves and shoots, and those leaves are the entire source of the spores that are splashed up onto next spring's new foliage. Clearing them is the one control that acts before the season starts, and it is the reason a raked tree needs less copper in spring than an unraked one.