Pests
Symptoms You'll see pale, winding tunnels in the leaves that widen into large tan blisters or blotches. If you hold a leaf up to the light, you can sometimes see the tiny maggot inside. The damaged parts are not good to eat.Slender, winding mines in the foliage enlarge into translucent tan blotches; heavily mined leaves are unmarketable and the crop is the leaf, so even light feeding matters. The pale legless maggots are visible inside the leaf against the light. Cause A small fly lays eggs on the underside of the leaves, and the maggots that hatch tunnel inside the leaf between the top and bottom layers, eating as they go. Spinach, beets, and chard are its favorites.The spinach leafminer (Pegomya hyoscyami) overwinters as pupae in the soil and emerges around mid-May; females lay rows of white eggs on leaf undersides, and the maggots tunnel between the leaf surfaces. There are three to four overlapping generations a season on spinach, beets, chard, and goosefoot weeds. Organic treatment Once a maggot is inside a leaf, sprays do not reach it well, so pick off and destroy mined leaves as soon as you see them, before the maggots drop to the soil. Crushing the maggot inside the leaf works too.Insecticides poorly reach larvae inside the leaf, so rely on cultural control: pick and destroy mined leaves before larvae drop to pupate, and crush maggots in the leaf. Spinosad has some activity on young larvae; abamectin is a conventional option. Prevention Cover the plants with a light row cover right after sowing so the flies cannot lay eggs, and pull nearby weeds like lambsquarters that host the pest. Rotating where you grow spinach, beets, and chard each year also helps.Exclude the egg-laying flies with floating row cover or insect netting from sowing, control goosefoot weeds (lambsquarters, chickweed, nightshade) that host the pest, rotate away from where spinach, beets, or chard grew, and deep-cultivate in spring to bury overwintering pupae.
Symptoms Clusters of tiny soft green or gray insects on the undersides of leaves and on new growth, sometimes with curled, puckered leaves and a sticky coating. They are hard to wash out of crinkled savoy leaves.Colonies of green peach or other aphids on leaf undersides and growing tips distort and pucker the foliage; honeydew and sooty mold downgrade the crop, and curly savoy leaves are hard to clean. Aphids also transmit cucumber mosaic and other viruses. Cause Aphids are small insects that suck sap from the plant. They breed quickly, especially on soft growth from too much fertilizer, and they can spread plant viruses.Several aphid species feed on spinach; they reproduce rapidly, favor the soft growth that excess nitrogen produces, and are most damaging as virus vectors. Organic treatment Blast them off with a strong spray of water, or use insecticidal soap or neem oil, making sure to hit the undersides of the leaves. Repeat every few days until they are gone.Dislodge colonies with a strong water jet or spray insecticidal soap or neem, covering leaf undersides; repeat every few days. Conserve ladybugs, lacewings, and parasitoid wasps. Prevention Welcome helpful bugs like ladybugs and lacewings, go easy on nitrogen fertilizer, and check the new growth often so you catch them early.Scout growing tips early, avoid overfeeding nitrogen, conserve natural enemies, and use row cover, which doubles as leafminer exclusion.
Symptoms Lots of tiny round holes peppering the leaves of young plants, made by small dark beetles that jump like fleas when you come near. Heavy damage can stunt seedlings.Small round shot-holes pepper the leaves of young plants; the tiny dark beetles jump when disturbed. Damage is mostly cosmetic on a leaf crop but can stunt or kill seedlings at high pressure. Cause Flea beetles are small jumping beetles that chew little holes in young leaves. They hurt small seedlings the most, since a tiny plant cannot outgrow the damage.Flea beetles chew the foliage of young spinach and are most damaging at the seedling stage; the holes mar the harvested leaves. Organic treatment Cover young plants with a row cover, and if there are many beetles use a spinosad spray or a kaolin clay coating. The main goal is to get the seedlings big enough to shrug it off.Protect seedlings with row cover and spray spinosad or apply kaolin clay if pressure is high; the aim is getting plants past the vulnerable seedling stage. Prevention Use row cover from sowing, keep seedlings strong with steady water and food so they grow past the damage, and clear weeds nearby.Row cover from sowing, vigorous seedlings kept evenly watered and fed, and clean cultivation of nearby weeds.
Symptoms Ragged chewed holes in the leaves, green or striped caterpillars on the plants, and dark droppings. They are mostly a warm-season and southern problem.Ragged feeding holes with green or striped larvae and frass; cabbage loopers, beet armyworms, and corn earworms feed on spinach, mostly in warm-season and southern plantings. Cause Several moths lay eggs on the leaves, and the caterpillars that hatch chew the foliage. Because you eat the leaves, even a little chewing is a problem.The larvae of several moths feed on spinach foliage; on a leaf crop even modest defoliation reduces the harvest. Organic treatment Spray Bt, which is safe and targets only caterpillars, or pick them off by hand. Spray again after rain since it washes off.Apply Bt (Bacillus thuringiensis) or spinosad targeting young larvae, and hand-pick where practical; repeat after rain. Prevention Use a row cover, clean up old plants and weeds where moths shelter, and check the undersides of leaves for eggs and small caterpillars.Use row cover, clean up crop debris and weed hosts, and scout leaf undersides for eggs and early instars.
Diseases
Symptoms Pale yellow patches on the tops of the leaves with a fuzzy gray-purple mold on the undersides, mostly in cool, damp, crowded conditions. Bad cases yellow and collapse the leaves.Irregular pale-yellow lesions on the upper leaf surface with grayish-purple sporulation beneath (the blue mold), spreading in cool, wet, humid weather; lesions brown and the leaves collapse. It is the most important spinach disease. Cause A mold-like disease that loves the same cool, wet weather spinach grows in, and spreads through wet leaves and splashing water. Crowded plants and long leaf wetness make it worse.Peronospora effusa, an oomycete favored by cool temperatures, long leaf wetness, and high humidity; it spreads by wind- and splash-borne spores and survives on debris and as oospores, with many physiological races that overcome resistance. Organic treatment Remove the worst leaves, open up the airflow so leaves dry faster, and water at the soil instead of over the plants. It is hard to stop once it gets going, so prevention matters most.Cultural control dominates: improve airflow, avoid overhead irrigation, remove infected leaves and debris; copper has limited efficacy. There is no rescue once it is established in humid weather. Prevention Grow resistant varieties (this is the main defense), space plants for good airflow, water at the base, and rotate where you plant spinach each year.Plant resistant cultivars (the primary tool, choosing the broadest race resistance available), widen spacing for airflow, use drip rather than overhead water, and rotate away from spinach for several years.
Symptoms White, blister-like bumps on the undersides of leaves, with yellow spots on top. Badly spotted leaves are not good to eat.White, blister-like pustules on leaf undersides with chlorotic spotting above; severe infection distorts and downgrades the foliage. A serious disease in the southern and south-central states. Cause A different mold-like disease, not a true rust, that makes white pustules on the leaves and spreads in cool, moist weather. It can ruin a crop quickly.The oomycete Albugo occidentalis, favored by cool nights, warm days, and leaf wetness; it spreads by splash- and wind-dispersed spores and survives on debris. Organic treatment Remove and destroy infected leaves, improve airflow, and water at the soil line. As with downy mildew, prevention works better than trying to cure it.Remove infected leaves and debris, improve airflow, and avoid overhead irrigation; chemical options are limited for the home garden. Prevention Choose resistant varieties where it is common, space plants out, avoid wetting the leaves, and rotate your planting spot.Grow resistant cultivars where white rust is endemic, space for airflow, use drip irrigation, and rotate away from spinach.
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 germination is slow. Cause Soil fungi attack the seeds and tiny seedlings, especially when the soil is cold and soggy and the seeds are slow to come up. Spinach sown in cold wet ground is at risk.Soilborne Pythium, Rhizoctonia, and Fusarium species attack germinating seed and seedlings; cold, saturated soil that slows emergence favors them. Organic treatment There is no cure for an affected seedling, so focus on prevention. Pull and discard collapsed seedlings.No cure once seedlings collapse; manage by prevention and remove affected plants. Prevention Do not sow into cold, soggy soil, plant at the right depth in well-drained ground, do not overwater, and use fresh seed so it comes up fast.Sow into well-drained soil when temperatures favor quick emergence, avoid overwatering, use fresh viable seed, and consider treated seed where damping-off is chronic.
Symptoms Older leaves yellow and wilt even though the soil is moist, and the wilting spreads up the plant, which is stunted and may die. It is worse in warm soil.Progressive yellowing and wilting from the lower leaves upward despite adequate soil moisture, with stunting and plant death; symptoms intensify as soil warms through the season. Cause A soil fungus infects the roots and clogs the plant's water pipes, so it wilts and yellows. It lives in the soil for years and is worse when the soil warms up.Fusarium oxysporum f. sp. spinaciae, a soilborne vascular pathogen that persists for years and is favored by warm soil and acidic conditions; once established it limits where spinach can be grown. Organic treatment There is no cure once a plant is infected, so pull and destroy wilted plants. Put your effort into rotation and timing for next time.No effective cure; remove and destroy infected plants and manage the soilborne population by rotation and timing. Prevention Plant spinach in the cooler parts of the season, keep the soil near neutral (not acidic), and do not grow spinach in the same spot year after year. Resistant varieties help where it is a problem.Schedule the crop for the cool side of the season when soils are cooler, maintain a near-neutral pH, use long rotations away from spinach, and choose resistant cultivars where the wilt is established.
