Pests
Symptoms Tiny, slender pale-yellow to brown insects hiding down in the leaf folds, leaving silvery or whitish streaks and flecks on the green blades. Bad infestations make the foliage look bleached and papery.Onion thrips (Thrips tabaci) feeding in the leaf axils and folds, producing silvery-white stippling, streaking, and a bleached, papery look on heavy pressure; they favor hot, dry weather. On chives the damage is usually cosmetic, but a severe year degrades a leaf crop. Cause Thrips are minute sap-sucking insects, common on onion-family plants, that rasp the leaves and are worst in hot, dry weather. Chives usually shrug them off, but a heavy year can mark the leaves.Thrips tabaci, the principal allium thrips, rasps leaf surfaces and feeds on the sap; populations build fast in hot, dry conditions and on stressed plants. Organic treatment Hose the plants down to knock thrips off, shear a badly streaked clump to the base so it regrows clean, and use insecticidal soap on the leaves if needed. Rinse cut leaves before use.Dislodge with a strong water jet, shear a heavily infested clump to the base to remove the population and force clean regrowth, and spray insecticidal soap or spinosad if warranted; conserve natural enemies (minute pirate bugs, lacewings). Keeping plants unstressed and watered blunts outbreaks. Prevention Keep plants watered in hot spells, welcome helpful insects like lacewings and pirate bugs, and cut a marked-up clump back to force fresh leaves.Avoid drought stress, conserve natural enemies, cut back streaked foliage to reset the clump, and avoid siting chives beside heavily thrips-pressured onion or garlic plantings.
Symptoms Rows of white dots punched down a leaf where the adult fly fed, then wavy pale mines inside the leaves, with small maggots or brown seed-like pupae tucked into the leaf bases. It shows up in spring and again in fall.Allium leafminer (Phytomyza gymnostoma): lines of white oviposition punctures down the distal leaf, followed by larval mines and brown puparia lodged in leaf sheaths and bulbs. The University of Maryland lists chive (A. schoenoprasum) among its hosts; wounds open the door to secondary bacterial and fungal rots. Cause The allium leafminer is a small fly whose larvae tunnel inside onion-family leaves, including chives, and burrow toward the base. It is a newer pest in parts of the eastern United States.Phytomyza gymnostoma, an invasive allium-specific fly with a spring flight (roughly March into May) and a fall flight (September into October); larvae mine toward the leaf base and bulb, with up to dozens of pupae per plant in severe cases. Organic treatment Cover plants with floating row cover in early spring and again in fall to keep the flies off, cut off and destroy mined leaves, and clean up plant debris.Exclude the adults with floating row cover timed to the spring and fall flights, remove and destroy mined foliage, and sanitize crop debris; spinosad or azadirachtin can help where pressure is high. Rotation away from recently infested allium ground reduces carryover. Prevention Use row cover during the spring and fall flights, remove mined leaves, and keep the bed clean.Row-cover through both flight periods, remove infested leaves, sanitize residue, and separate new plantings from pressured allium beds.
Symptoms Yellowing, wilting, and stunted growth as small white maggots tunnel into the base of the plant and the bulbs below the soil, sometimes rotting the crown. Worst in cool, wet springs.Onion maggot (Delia antiqua) larvae mining into the basal plate, roots, and bulbs, causing wilting, yellowing, stunting, and crown rot; damage is worst in cool, moist springs and where allium debris accumulates. Established chive clumps are seldom destroyed but can be set back. Cause Onion maggots are the larvae of a fly that lays eggs at the base of onion-family plants; the maggots eat into the roots and bulbs. Chives are rarely hit hard, but a clump can be damaged.Delia antiqua overwinters as pupae in the soil; spring flies lay eggs at plant bases and successive generations attack roots and bulbs, favored by cool wet weather and by cull and debris that lure egg-laying. Organic treatment There is no rescue for a maggot-riddled crown, so remove badly affected plants. Use row cover to keep the flies off, and clean up debris and culls that attract them.Remove and destroy infested plants, exclude flies with floating row cover, and sanitize debris and culls; rotation and avoiding dense allium plantings limit buildup. No effective organic rescue exists once larvae are in the crown. Prevention Cover plants with row cover in spring, avoid leaving old bulbs and debris around, and do not crowd alliums together.Row-cover early, sanitize allium residue, rotate, and avoid clustering chives with other alliums that concentrate the fly.
Symptoms Clusters of tiny soft green or gray insects on the leaves and flower stalks, sometimes with sticky residue. Chives rarely get them badly, and their scent even helps keep aphids off nearby plants.Occasional aphid colonies on foliage and scapes; chives are among the most aphid-free herbs (their odor is credited with repelling aphids from neighbors), so infestations are minor and sporadic rather than a standing threat. Cause Aphids are small sap-sucking insects that breed fast on soft growth. They are an occasional, minor visitor on chives.Several aphid species may alight on chives in flushes of soft growth, but the plant's sulfur compounds make it an inhospitable host, so colonies rarely persist. Organic treatment Blast them off with a strong spray of water or use insecticidal soap, and rinse cut leaves before use. It is seldom needed.A water jet or insecticidal soap handles the rare colony; conserve ladybugs, lacewings, and hoverflies, which the chive umbels also feed when in bloom. Prevention Welcome ladybugs and lacewings, go easy on nitrogen, and check flower stalks now and then.Avoid excess nitrogen, conserve natural enemies, and monitor scapes; control is seldom warranted on chives.
Diseases
Symptoms Pale, fuzzy gray-violet patches on the leaves in cool, damp weather, with the blades yellowing and collapsing. It spreads fastest in wet, crowded, poorly drained plantings.Downy mildew (Peronospora destructor) producing pale oval patches that turn violet-gray with sporulation under moisture, with leaves paling, yellowing, and collapsing; it is favored by cool (below about 75°F), humid, wet conditions and affects chives among many alliums. Cause A fungus-like disease of the onion family, favored by cool, humid, wet conditions, that can affect chives along with onions, garlic, and leeks.Peronospora destructor, an oomycete spread by wind and splashing water and favored by cool, moist weather and long leaf-wetness periods; crowded, poorly drained plantings hold it. Organic treatment Remove affected leaves, improve airflow by dividing crowded clumps, water at the base rather than over the leaves, and cut a badly hit clump back so it regrows in drier weather.Manage culturally: divide crowded clumps and space for airflow, irrigate at the soil line, remove infected foliage, and shear a heavily affected clump to regrow under drier conditions. The home garden has no reliable cure once it is established. Prevention Space and divide plants for airflow, water at the soil line, and avoid soggy, shaded, crowded spots.Open the canopy by dividing, water at the base, site in well-drained sun, and avoid the cool, wet, crowded conditions the pathogen needs.
Symptoms Bright orange raised spots or streaks (pustules) scattered on the leaves. Heavily rusted blades yellow and dry up. It is more common in wet seasons and on crowded, over-fed plants.Allium rust (Puccinia species) forming bright orange to rusty raised pustules on leaves and scapes, with chlorosis and dieback of heavily infected foliage; it is favored by moist conditions, crowding, and lush high-nitrogen growth, and affects chives along with garlic, leeks, and onions. Cause Rust is a fungal disease of the onion family, including chives, that shows as orange pustules on the leaves and spreads by airborne spores in damp weather.Puccinia rust fungi spread by airborne urediniospores in humid weather; dense stands and excess nitrogen worsen it. Organic treatment Cut off and destroy rusty leaves or shear the clump to the base to regrow clean, thin crowded plantings for airflow, and avoid overhead watering and heavy nitrogen.Shear infected foliage (a hard cut to the base removes the pustules and regrows clean), divide to open crowded clumps, avoid overhead irrigation and heavy nitrogen, and remove debris. Fungicides are rarely warranted in a home planting. Prevention Give plants room and airflow, water at the base, go easy on nitrogen, and remove rusty foliage promptly.Divide for airflow, moderate nitrogen, irrigate at the soil line, and cut out rust early before it spreads.
Symptoms Yellowing, wilting plants whose roots and crown rot, with a fluffy white mold and tiny black specks (like poppy seeds) at the base. Affected plants do not recover, and the disease stays in the soil for many years.White rot (Sclerotium cepivorum) causing yellowing, wilting, and a soft rot of roots and crown, with a fluffy white mycelium and abundant tiny black sclerotia at the base; the sclerotia persist in soil for many years, and the disease affects chives with onions, garlic, and leeks. Cause White rot is a serious soil fungus of the onion family that rots the roots and crown. Once it is in the soil it lasts a very long time, so keeping it out is the whole game.Sclerotium cepivorum, a soilborne fungus favored by cool, moist soil; its long-lived sclerotia make an infested site unusable for alliums for a decade or more, so exclusion and sanitation are the only real controls. Organic treatment There is no cure. Remove and destroy affected plants along with the soil around the roots, and do not plant chives, onions, or garlic in that spot again. Never move infected soil or plants to a clean bed.No rescue: rogue out affected plants with surrounding soil, avoid spreading infested soil on tools or transplants, and do not replant alliums in the site. Long rotation is the standing management. Prevention Start with clean plants, do not bring in soil from an infected garden, and rotate onion-family plants to fresh ground.Plant clean, sclerotia-free stock, quarantine infested ground from alliums, sanitize tools, and never import garden soil of unknown history.
Symptoms Small whitish sunken spots on the leaves in cool, wet weather that can run together and brown out the tops, sometimes with a gray fuzzy mold. It is worst in humid, crowded plantings.Botrytis leaf blight and neck rot (Botrytis species) producing small white sunken leaf spots that coalesce into blast and tip dieback under cool, moist conditions, sometimes with gray sporulation; humid, crowded stands favor it, and it affects chives among the alliums. Cause Botrytis is a gray-mold fungus of the onion family that spots and blights the leaves in cool, damp, crowded conditions.Botrytis fungi favored by cool, wet, humid weather and dense canopies; splashing water and leaf wetness spread the spores. Organic treatment Remove spotted leaves or shear the clump to regrow, open up crowded plantings for airflow, and water at the base instead of over the leaves.Cull spotted foliage or shear the clump to regrow, divide to open the stand, irrigate at the soil line, and remove senescing debris. Fungicides are seldom needed on a home chive planting. Prevention Space and divide for airflow, water at the soil line, and clean up dead foliage.Divide for airflow, water low and early, and sanitize dead foliage to cut inoculum.
