Pests
Symptoms Plump green caterpillars banded with black and dotted yellow-orange, chewing the leaves and stems, sometimes stripping a stalk. They are the larvae of the black swallowtail butterfly, and many gardeners leave them be.Larvae of the black swallowtail (Papilio polyxenes) feeding on the foliage, banded green and black with yellow spots; on parsley they are seldom numerous enough to do real damage, and parsley is one of their host plants, so most growers tolerate or relocate them rather than spray. Cause Big green-and-black striped caterpillars that eat the leaves. They turn into beautiful black swallowtail butterflies, so they are usually welcome guests rather than a real problem.The caterpillar stage of the black swallowtail butterfly, which lays eggs on parsley and other carrot-family plants; populations on a home planting are normally small. Organic treatment If you want every leaf, just pick the caterpillars off by hand and move them to a spare plant. They are easy to see and there are rarely many. Planting a little extra parsley lets you share with the butterflies.Hand-pick where leaf loss matters and relocate the larvae to a sacrificial plant; Bacillus thuringiensis (Bt) controls them if needed, but on parsley they rarely warrant it. Many gardeners deliberately grow extra parsley as a swallowtail host. Prevention Pick them off by hand, grow a few extra plants to share, and enjoy the butterflies they become.Scout occasionally and hand-pick if leaf loss matters; tolerate the small numbers a home planting usually sees, and plant extra parsley as a host plant for the butterflies.
Symptoms Clusters of tiny soft green or gray insects on new growth and the undersides of leaves, sometimes with curled, sticky foliage.Colonies of aphids on growing tips and leaf undersides, the most common parsley pest; honeydew and the lodged insects contaminate a crop eaten fresh, and aphids can vector viruses. Parsley'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 parsley; 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. Rinse picked leaves well before use.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 the parsley umbels attract when allowed to flower. Prevention Welcome helpful insects like ladybugs and lacewings, go easy on nitrogen, and check new growth often.Scout growing tips early, avoid overfeeding nitrogen, and conserve natural enemies; letting a second-year plant flower draws in aphid predators.
Symptoms Tunnels and rusty-brown trails in the roots and lower stems, stunted or off-color plants, and grubs at the crown. These carrot-family root pests hit parsley too.Larvae of the carrot rust fly (Psila rosae) and the carrot weevil mining the taproot and crown of parsley, a carrot-family host; damage shows as rust-colored tunneling, stunting, and secondary rot, worst where Apiaceae are grown in the same ground year after year. Cause Small root maggots from carrot-family pests that tunnel into the parsley root and crown, leaving rusty trails and weak plants.The carrot rust fly and carrot weevil lay eggs near carrot-family plants; their larvae bore into the roots and crowns. They build up where carrots, parsley, and their relatives repeat in the same bed. Organic treatment Cover the bed with floating row cover to keep the flies off, rotate parsley away from where carrots or parsley grew, and clean up crop debris in fall.Exclude the adults with floating row cover from emergence, rotate out of Apiaceae ground on a multi-year cycle, delay sowing past the first fly generation where it is severe, and remove crop residue that harbors overwintering stages. Prevention Use a row cover, move parsley to a fresh spot each year, and clear away old plants in fall.Manage by exclusion (row cover) and rotation: keep parsley out of recent carrot-family ground, time sowings around the fly's generations, and sanitize residue.
Diseases
Symptoms Small tan to brown spots with darker edges scattered across the leaves, sometimes with tiny dark specks in the centers, worst in wet weather. Heavily spotted leaves are not good to eat.Numerous small circular tan-to-brown leaf lesions, often with dark pycnidia in the centers, the most commonly reported parsley disease; it spreads in cool, wet, splashy conditions and can arrive on infected seed, and on a leaf crop even moderate spotting ruins the cutting. Cause A fungal leaf-spot disease, the most common one on parsley, that spreads through wet leaves and splashing water and can come in on the seed.Septoria petroselini, a seed-borne and splash-spread fungus 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. Pick and use the clean leaves promptly.Use clean or treated seed, water at the soil line, space for airflow, rotate away from parsley and its relatives, and remove infected debris; the home garden has no reliable spray cure 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 fungus over.
Symptoms Wilting, yellowing plants whose crown or roots have turned brown, soft, and mushy, usually in wet, poorly drained soil. Affected plants collapse and do not recover.Soilborne crown and root rots (Pythium, Phytophthora, Rhizoctonia, and related fungi) attacking parsley's taproot and crown in saturated, poorly drained ground; symptoms are wilting, stunting, and a browned, decayed crown, often on plants held over a wet winter. Cause Soil fungi rot the parsley root and crown when the soil stays too wet, especially over a soggy winter.Soilborne water-mold and fungal rots (Pythium, Phytophthora, Rhizoctonia) favored by waterlogged, poorly drained soil and overwatering. Organic treatment There is no cure for a rotting plant, so remove it. Improve drainage, plant in raised or loosened beds, and do not overwater, especially in winter.Remove affected plants; manage by prevention: well-drained or raised beds, loosened soil for the taproot, moderate winter watering, and rotation out of ground where Apiaceae rotted before. Prevention Plant in well-drained soil, do not overwater, and pull any plant whose crown has gone soft and brown.Site in well-drained, loosened soil, avoid waterlogging (especially overwinter), and rotate away from beds with a rot history.
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 parsley's slow germination leaves seed sitting for weeks. Cause Soil fungi attack the seeds and tiny seedlings, especially when the soil is cold and soggy and the slow-sprouting parsley seed sits a long time before emerging.Soilborne Pythium, Rhizoctonia, and Fusarium fungi attack germinating seed and seedlings; cold, saturated soil that prolongs parsley'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 soak the seed first so it comes up faster.Sow shallowly into well-drained soil under conditions that favor reasonably quick emergence, avoid overwatering, and soak the dry seed to shorten the vulnerable slow-germination window.
