Pests
Symptoms Clusters of tiny soft green or gray insects on new growth and the undersides of leaves, sometimes with curled, sticky foliage.Colonies of green peach and other aphids gather on growing tips and leaf undersides; honeydew and the lodged insects contaminate a crop eaten fresh, and aphids can vector viruses. Cilantro's lacy foliage hides them, so scout closely. Cause Aphids are small sap-sucking insects that breed fast, especially on soft growth from too much fertilizer. They can spread plant viruses.Several aphid species feed on cilantro; they reproduce rapidly and favor the soft growth that excess nitrogen produces. Organic treatment Blast them off with a strong spray of water, or use insecticidal soap or neem oil on the leaf undersides, repeating every few days. Pick the leaves before a colony settles in.Dislodge colonies with a strong water jet or spray insecticidal soap or neem, covering leaf undersides; repeat every few days and conserve ladybugs, lacewings, and parasitoid wasps, which cilantro's own flowers attract. Prevention Welcome helpful insects like ladybugs and lacewings, go easy on nitrogen, check new growth often, and pick the quick crop young.Scout growing tips early, avoid overfeeding nitrogen, conserve natural enemies, and harvest the fast crop before colonies build; letting a few plants flower draws in aphid predators.
Symptoms Small wedge-shaped insects that hop or fly up when disturbed, plus yellowed, twisted, or stunted plants. The leafhoppers themselves do little chewing damage, but they can carry diseases that deform the plant.The beet leafhopper and aster leafhoppers feed on cilantro and, more importantly, transmit aster yellows and beet curly top virus, which yellow, distort, and stunt the plants. Infected plants do not recover and should be removed. Cause Tiny jumping insects that suck sap and, more seriously, spread diseases (aster yellows and curly top) that twist and yellow the plants.Leafhoppers (including the beet leafhopper, Circulifer tenellus) feed on the foliage and vector aster yellows and beet curly top virus; the disease damage far outweighs the feeding. Organic treatment Cover plants with a light row cover to keep leafhoppers off, pull and discard any yellowed, distorted plants right away, and clear nearby weeds that harbor the insects and the diseases.Exclude leafhoppers with floating row cover, rogue out symptomatic plants promptly since there is no cure for the viral diseases, and control weed reservoirs; insecticides give poor control of a mobile vector. Prevention Use row cover, clear weedy hosts around the garden, and remove infected plants early so they do not seed disease into the planting.Manage leafhoppers mainly by exclusion (row cover) and sanitation: remove weed reservoirs and rogue symptomatic plants, since spraying rarely stops a mobile virus vector.
Diseases
Symptoms Small dark, angular, water-soaked spots on the leaves that run along the veins and can merge into larger blotches, worst in cool, wet weather. Spotted leaves are not good to eat.Angular, vein-limited dark lesions on the foliage, sometimes with a yellow halo, spreading in cool, wet, splashy conditions; on a leaf crop even moderate spotting ruins the harvest. It is the most-reported cilantro disease. Cause A bacterial disease, the most common one reported on cilantro, that spreads through wet leaves and splashing water and often arrives on infected seed.Pseudomonas syringae pv. coriandricola, a seed-borne and splash-spread bacterium favored by cool, wet weather and overhead watering. Organic treatment Remove and destroy spotted leaves, avoid wetting the foliage, improve airflow, and start with clean seed. There is no spray cure in the home garden, so prevention matters most.Use clean, disease-free or hot-water-treated seed, avoid overhead irrigation, space for airflow, rotate away from cilantro and its relatives, and remove infected debris; copper has limited effect once it is established. Prevention Use clean seed, water at the soil line rather than over the leaves, space plants for airflow, and clear infected debris.Plant clean seed, switch to drip or soil-line watering, widen spacing, rotate, and remove crop debris that carries the bacterium over.
Symptoms Seeds that never come up, or seedlings that flop over at the soil line with a pinched, rotted stem and then die. It strikes in cold, wet soil.Poor stands from seed and pre- or post-emergence collapse of seedlings with water-soaked, pinched stems at the soil line, worst in cold, wet, poorly drained soil where cilantro's slow germination leaves seed sitting. Cause Soil fungi attack the seeds and tiny seedlings, especially when the soil is cold and soggy and the slow-sprouting cilantro seed sits a long time before emerging.Soilborne Pythium, Rhizoctonia, and Fusarium fungi attack germinating seed and seedlings; cold, saturated soil that slows cilantro's already slow germination favors them. Organic treatment There is no cure for an affected seedling, so focus on prevention: pull and discard collapsed seedlings.No rescue once seedlings collapse; manage by prevention and remove affected plants. Prevention Do not sow into cold, soggy soil, plant shallowly in well-drained ground, do not overwater, and use fresh seed so it comes up faster.Sow shallowly into well-drained soil under conditions that favor reasonably quick emergence, avoid overwatering, and use fresh, viable seed; some growers soak the dry seed to speed emergence past the vulnerable window.
Symptoms A white, powdery coating on the leaves and stems, usually later in the crop and in warm, dry-day weather. Heavily coated leaves yellow and are unpleasant to eat.A white, talc-like fungal growth on the foliage and stems, the most common fungal disease of cilantro, that builds in warm days with cool nights and crowded plantings; coated leaves lose quality. Cause A fungal disease (Erysiphe heraclei) that coats the leaves in white powder, favored by warm days, cool nights, and crowding.The fungus Erysiphe heraclei, favored by warm days and cool humid nights and by dense stands with poor airflow. Organic treatment Remove the worst leaves, open up the planting for airflow, and avoid crowding. Most home crops are harvested before it does much harm.Improve airflow with wider spacing, remove affected leaves, and avoid excess nitrogen; the fast leaf crop is usually cut before mildew matters, but a plant grown on for seed is more exposed. Prevention Space plants for airflow, avoid crowding and overfeeding, and pick the leaf crop young before mildew builds.Widen spacing for airflow, avoid heavy nitrogen, and harvest the leaf crop promptly; remove infected foliage on plants held for coriander seed.
Symptoms Mushy, slimy, foul-smelling collapse of the crown or stems, usually in warm, wet conditions or after the foliage has been damaged. Affected plants rot quickly.Wet, mushy breakdown of the crown and stems with a bad smell, caused by soft-rot bacteria entering through wounds in warm, wet, poorly drained conditions; the plant collapses fast. Cause Bacterial soft rot that enters through wounds and rots the tissue in warm, wet, poorly drained soil.Soft-rot bacteria (such as Pectobacterium species) invade through wounds and bruises and dissolve the tissue, favored by warm temperatures, wet soil, and poor drainage. Organic treatment Remove and discard rotted plants, improve drainage, avoid injuring the plants, and do not overwater. There is no cure once a plant is rotting.Remove and destroy affected plants, improve drainage and airflow, avoid wounding and overwatering, and do not work the bed when wet; no rescue once rot sets in. Prevention Plant in well-drained soil, avoid overwatering and injury, and keep the planting open so foliage dries.Site in well-drained soil, avoid waterlogging and mechanical injury, space for drying airflow, and clear infected debris.
