Curry Leaf

This is the single most important thing to know about growing curry leaf in the United States. Research has found it MORE attractive to the psyllid than citrus itself, and it is used deliberately as a trap plant for that reason - while being immune to the greening bacterium, so the tree stays healthy while breeding the insect that infects your lemon tree. Keep it well away from citrus in quarantined areas, scout every flush, and never move plants or leaves across state lines.

Tiny brown-mottled insects about an eighth of an inch long perched nose-down at a sharp angle on the tips of new shoots - the posture is the giveaway, and no other pest of these plants holds it. Yellow-orange nymphs packed into the unopened flush, along with white waxy curls and tubules of honeydew that look like tiny springs. New leaves that emerge twisted, notched, curled or stunted, with a sticky shine and later black sooty mold on the growth below. A cloud of small insects that jump and fly when you disturb a flush. Ants working the shoot tips. Check every new flush from the moment it pushes, since that is the only growth the insect breeds on, and use a hand lens - the adults are easy to mistake for aphids at a glance.

Act on the flush, not the calendar. Knock light populations off with a hard jet of water, and rub out colonies on a small plant by hand. Horticultural oil and insecticidal soap kill nymphs and adults on contact and are the right choice on anything you eat, but they must coat the shoot tips thoroughly and be repeated every seven to ten days while the flush is soft. Prune off heavily infested flushes and bin them rather than composting them. Where the disease is present, area-wide programs may call for a soil-applied systemic or a coordinated spray schedule - follow your state's guidance rather than improvising, and use only products labeled for the plant, observing the pre-harvest interval on anything you harvest for the kitchen. Removing a badly infested plant that sits beside healthy citrus is sometimes the responsible answer. Report finds so local programs can track spread.

Buy plants only from a licensed local nursery, and never accept or move these plants, cuttings or leaves out of a quarantined area - that is how the insect and the disease travel between regions, and in most quarantined states it is against the law. Inspect every new flush through the growing season, since the insect breeds only on tender new growth, and water and feed steadily rather than in bursts so the plant pushes fewer and less concentrated flushes to defend. Do not plant a preferred host right beside your citrus. Leave the lady beetles, lacewings, syrphid larvae and the parasitic wasp Tamarixia radiata alone, because they do most of this work where broad-spectrum sprays are not used. Report a suspected find to your state agriculture department or extension office; regional programs depend on early detection and will often survey and advise for free.

The Asian citrus psyllid is a tiny mottled brown sap-sucking insect, roughly the size of an aphid, that feeds only on citrus and its relatives in the Rutaceae family. Adults sit at a distinctive nose-down angle on new shoots, and the yellow-orange nymphs cluster on the unopened flush producing curled waxy tubules of honeydew. The feeding itself twists and distorts new growth but rarely kills a plant. Its real significance is that it is the vector of citrus greening (huanglongbing), the incurable bacterial disease that has devastated citrus across Florida, Texas and parts of California. A psyllid population on any Rutaceae host inside a quarantined area is a reservoir that carries the disease to nearby citrus, which is why the movement of these plants and their leaves is federally regulated. It breeds only on tender new growth, so populations track the flush cycle rather than the calendar.

The commonest way this plant dies, and almost always self-inflicted. A semi-dormant winter plant in short days uses hardly any water, and a well-meaning owner watering a leafless tree back to health drowns it. Water perhaps once every three or four weeks indoors, use a gritty free-draining mix in a pot that actually drains, and never leave it standing in a saucer of water.

Wilting in the middle of the day on a plant whose soil is damp - the classic tell, and the reason people water a rotting plant and finish it off. Leaves yellowing from the bottom up, dull off-color foliage, and growth that stalls for no visible reason. Whole shoots, or one side of the plant, collapsing while the rest still looks fine. Soft, dark, or mushy tissue at the base of the stem or at the crown, sometimes with a sour smell. Lift a failing plant and look at the roots: healthy ones are firm and pale, rotted ones are brown or black and slimy, and the outer layer slips off between your fingers leaving a thread of core behind. Seedlings that topple over at soil level are the same problem, called damping-off.

There is no cure for tissue that has already rotted, so act on the conditions rather than looking for a spray. Stop watering at once and fix the drainage - open up compacted soil, or move the plant to a raised, sharply drained position or a container. Lift a badly affected plant, cut away every soft dark root and rotted section with a clean blade back to firm pale tissue, and replant only the healthy parts into fresh free-draining soil or mix. Often the better move is to give up on the plant and save its offspring instead: cuttings, offsets, or divisions taken from firm healthy growth root readily and give you a clean start. Bin the rotted material rather than composting it, and correct the drainage before you replant, because the rot comes straight back in the same wet spot.

Drainage is the whole defense. Match the plant to the site first - something that wants sharp drainage will not survive heavy clay or a low, water-collecting spot however well you tend it. Where the ground is heavy, plant on a raised bed, berm, or slope, or grow in a container. Set plants at the depth they were already growing, since burying the crown or the root flare is a common cause of rot, and keep mulch pulled back a few inches from the stem base instead of piled against it. Water the soil rather than the calendar: check that the top inch or two is dry before watering again, cut back hard in cool weather and winter dormancy, and never leave a pot standing in a full saucer. Do not plant or dig in soggy ground, and go easy on rich amendments for plants that want it lean. Rotate annual crops, and start with clean healthy plants and fresh mix.

Root rot is not one organism but a group of soil fungi and water molds - Pythium, Phytophthora, Fusarium, Rhizoctonia and others - that sit harmlessly in most soils and only turn destructive when the ground stays saturated. Waterlogged soil drives the air out, the roots suffocate, and the weakened tissue is invaded and goes soft, brown, and stringy. Because the damage is underground you usually see it first as something that looks like drought: wilting, yellowing, stunting, a plant that does not respond to being watered. Overwatering, heavy compacted ground, a low spot that collects runoff, a pot with no drainage or a saucer left standing full, and cold wet soil in winter are the usual causes. Once roots have actually rotted there is no cure - this is a problem you prevent rather than treat.

The main pest of an overwintered curry leaf, and close to inevitable on a plant standing in dry heated air all winter. Fine pale stippling on the leaflets and webbing in the leaf joints are the signs; a plant already shedding leaves for dormancy hides the damage until it is bad. Rinse the whole plant in the shower every few weeks, keep it off the radiator, and inspect weekly from November.

Fine pale stippling or speckling across the upper leaf surface, as though the color had been sandblasted out of it, and later a dull bronze or rusty cast over the whole leaf. Delicate webbing across leaf joints, shoot tips, and undersides - that comes with a heavy infestation and means you caught it late. Leaves that dry, curl, and drop early while the plant looks thirsty no matter how much you water it. Hold a leaf over a sheet of white paper and tap it: the specks that fall and then start walking are mites. With a hand lens, look on the undersides for the mites themselves, pale or reddish, and their round translucent eggs. Damage that shows up first on the hottest, dustiest, most sheltered side of a plant, or on a pot sitting near a radiator indoors.

Start with water. A strong jet aimed at the leaf undersides, repeated every few days for a couple of weeks, knocks populations down and breaks the cycle - on many plants that alone ends it. On anything that regrows quickly, shearing back badly infested growth resets the plant to clean foliage. If it keeps building, spray insecticidal soap or horticultural oil directly onto the undersides where the mites actually live, and repeat every five to seven days for three rounds: contact sprays do not kill the eggs, so a single application always fails. Anything you spray must be labeled for the plant you are treating - follow the label and observe its pre-harvest interval on anything you eat. Predatory mites are an effective release in a greenhouse or on an indoor plant. Above all, correct the heat, dust, and drought stress that caused it, or the mites simply come back.

Do not let plants get drought-stressed - that is the single strongest trigger, and a plant watered steadily through heat is far less likely to have a mite problem at all. Hose the foliage down, undersides included, during hot dry spells: it knocks mites off, washes away the dust they thrive in, and raises the humidity around the plant for a while. Indoors and under cover, keep the air from going hot, dry, and stagnant, wipe or rinse the leaves occasionally, and keep pots away from radiators and heating vents. Inspect any plant carefully before you bring it indoors for winter or set it among others, since mites almost always arrive on something else. Avoid broad-spectrum insecticides: they wipe out the predatory mites, lacewings, and lady beetles that do most of this work for you, and reliably leave you with a worse outbreak than you started with.

Spider mites are not insects but tiny sap-feeding arachnids, smaller than a grain of salt, and you almost always notice the damage before you notice them. They live on the undersides of leaves and drain the cells one at a time, which is why the leaf goes finely stippled with pale dots before it bronzes and dries. They breed explosively in hot, dry, dusty, still air - a generation can pass in a week at high temperature - so a barely visible population becomes a webbed, bronzed plant within a fortnight. Drought-stressed plants and plants wintered indoors in dry heated air are the classic hosts. Broad-spectrum insecticides make matters worse rather than better, because they kill the predatory mites and lady beetles that normally hold mites in check.