Pests
Symptoms Lots of tiny round holes peppering the leaves, like buckshot, worst on young seedlings in spring. The beetles are very small, dark, and shiny, with big back legs, and they hop away like fleas the moment you get close. If you are growing turnips for the greens this really matters, since the chewed leaves are what you eat; for the root, fast-growing plants usually shrug it off, but tiny seedlings can be set back.Tiny, round shot-hole punctures riddling the leaves, the classic flea-beetle signature, heaviest on young spring seedlings and along bed edges. The beetles themselves are minute, shiny black or bronze, with enlarged hind legs, and they spring away like fleas when disturbed. On a turnip grown for greens the damage is more than cosmetic, since riddled leaves are the harvest; on a root crop a vigorous stand outgrows light feeding, but a seedling losing much of its leaf area slows down. Cause Small beetles that spend the winter in leaf litter and weeds and come out in early spring hungry for cabbage-family leaves. Turnips and their relatives (radish, mustard) are among their favorite foods. They do the most damage in spring and early summer and ease off as it gets hotter, so fall turnips usually face fewer of them.Adult flea beetles, chiefly the crucifer flea beetle (Phyllotreta cruciferae) and striped flea beetle (Phyllotreta striolata), which overwinter in leaf litter and field edges and emerge in early spring to feed on brassica foliage. Turnip, radish, mustard, and other crucifers are highly preferred hosts. Pressure is heaviest in spring and early summer and tapers as the season warms, which is one reason fall turnip crops face less of it. Organic treatment A healthy, well-watered turnip patch usually grows right through light damage. If the little seedlings are getting hammered, cover the row with a floating row cover (a light fabric) right after planting and tuck in the edges so the beetles cannot get under it. Dusting with kaolin clay helps, and sprays like spinosad or pyrethrin are options if seedlings are losing a lot of leaf. Check in the cool morning, when the beetles are slow.On a vigorous stand a well-watered turnip usually outgrows light feeding. Where pressure is heavy on seedlings, a floating row cover set at sowing and sealed at the edges excludes the beetles entirely, the most reliable home defense. Kaolin clay reduces feeding, and spinosad or pyrethrin products are labeled options if a seedling stand is losing more than roughly a quarter to a third of its leaf area; scout in the cool morning when the beetles are sluggish. Prevention Clear away old plants and weeds at the end of the season so fewer beetles survive the winter nearby. Covering the seedbed with a row cover is the surest fix for early spring turnips. Leaning on fall plantings, which get hit less, and keeping the turnips growing fast with steady water also help.Clean up crop debris and weeds at the end of the season to cut overwintering sites. A row cover over the seedbed is the most reliable defense for early spring sowings. Favoring fall plantings, which see lighter pressure, and keeping the stand growing fast with even moisture both reduce impact.
Symptoms The trouble is underground. Small white legless maggots tunnel into the turnip, leaving winding brown trails that spoil the root and let rot set in. Aboveground the plant may look pale, wilted, or stunted. It shows up most in cool, wet springs and in soil full of un-rotted material. A tunneled turnip is ruined, but pulling and tossing it right away gets the maggots out before they become the next generation of flies.The damage is underground: small, white, legless maggots tunnel and score the surface and interior of the root, leaving winding brown trails that ruin the turnip and open the door to rot. Aboveground, infested plants may look off-color, wilted, or stunted. It is most common in cool, wet springs and in soil rich in undecomposed organic matter. A scored root is unsalable but a useful sentinel, since pulling and destroying it removes maggots before they pupate. Cause The maggots (young) of the cabbage maggot fly, a small gray fly. It spends the winter as pupae in the soil, and in spring the females lay tiny white eggs at the base of cabbage-family plants. The eggs hatch in about a week and the maggots burrow into the roots for three to four weeks. It goes after the whole cabbage family, turnips, radishes, cabbage, broccoli, and is worst in cool, damp spring weather.Larvae of the cabbage maggot (Delia radicum), a small gray fly that overwinters as pupae in the soil. In spring the adults emerge and females lay white eggs at the base of crucifer stems and in nearby soil cracks; the eggs hatch within about a week and the maggots feed on roots for three to four weeks before pupating. It attacks the whole cabbage family, including turnip, radish, cabbage, and broccoli, with several generations a year and the worst damage in cool, moist spring weather. Organic treatment You cannot save a turnip that is already tunneled. Pull up and throw away (do not compost) the affected ones so the maggots cannot grow into more flies. There is no good home spray for this, and sprays do nothing once the maggots have already left the root, so prevention is the real fix.There is no rescue for a root already tunneled. Pull and destroy infested turnips (do not compost them) to keep maggots from completing their cycle. Insecticide drenches are difficult and rarely worthwhile in a home garden, and are pointless once the maggots have left the root to pupate, so the lever is prevention. Prevention The best home defense is a row cover laid over the bed right after sowing and tucked in at the edges, so the flies cannot reach the plants to lay eggs, just make sure the soil is not already carrying them from an earlier crop. Move turnips away from spots that grew cabbage-family crops recently, avoid fresh manure, and lean toward fall planting, which usually has fewer maggots than cool wet spring.A floating row cover sealed at the edges at sowing is the most effective home defense, since it blocks the egg-laying flies; be sure no flies are already in the soil from a previous crop. Rotate turnips and other crucifers away from beds that grew them recently, avoid fresh manure and freshly turned-under residue that attract the flies, and favor fall plantings, which see less pressure than cool wet spring.
Symptoms Little soft insects, often gray-green and sometimes dusty-looking, gather in clusters on the undersides of leaves and on new growth. Leaves curl and yellow and turn sticky from the sugary honeydew the aphids leave behind, which can grow a black sooty mold. On turnips these are usually the turnip aphid and cabbage aphid. They can also spread plant viruses, so knock them back early, especially if you are eating the greens.Clusters of small, soft-bodied insects, often grayish-green and sometimes coated with a waxy bloom, collect on the undersides of leaves and on new growth, leaving leaves curled, yellowed, and sticky with honeydew that can blacken with sooty mold. On turnips the culprits are typically the turnip aphid (Lipaphis erysimi) and the cabbage aphid (Brevicoryne brassicae). Beyond direct feeding they can transmit virus, so colonies on the greens are worth removing early. Cause Sap-sucking turnip and cabbage aphids that feed only on cabbage-family plants. They multiply fast in mild weather, especially on soft, over-fertilized growth, and fly in from weeds and other cabbage-family crops. They can be a real pest on fall turnip greens.The turnip aphid and cabbage aphid, sap-feeding insects specific to the cabbage family. Populations build fastest in mild weather and on lush, over-fertilized growth, and winged forms move them in from cruciferous weeds and other brassica crops. They can be a particular nuisance on fall greens crops. Organic treatment Spray the colonies off with a strong stream of water, which often does the trick. Ladybugs and other helpers usually take care of the rest; if not, insecticidal soap or horticultural oil on the undersides of the leaves works well. Do not over-feed with nitrogen, which just grows more aphids.A strong jet of water knocks colonies off the leaves and is often enough in a home garden. Natural enemies (ladybugs, lacewings, parasitic wasps) usually bring numbers down; where needed, insecticidal soap or horticultural oil sprayed on the undersides of leaves is effective, taking care to reach the protected cabbage-aphid colonies. Avoid over-fertilizing with nitrogen, which fuels buildup. Prevention Let helpful bugs like ladybugs live in your garden by not spraying broadly, go easy on nitrogen fertilizer, and pull cabbage-family weeds nearby. Check the undersides of leaves now and then so you catch aphids while there are only a few, and clean up old plants at the end of the season.Encourage beneficial insects by avoiding broad-spectrum sprays, keep plants from being pushed with excess nitrogen, and control nearby cruciferous weeds that host the aphids. Inspect new growth and the undersides of leaves so colonies are caught small, and clear crop debris at season end.
Symptoms Showy black-and-orange (or black-and-red) shield-shaped bugs on the leaves, leaving pale, blotchy, stippled spots where they have sucked the juices out. A lot of them can yellow and kill leaves and even kill small plants. It is mainly a warm-weather pest, worst on fall and winter turnips and greens in the South.Striking black-and-orange (or black-and-red) shield-shaped stink bugs feeding on the foliage, leaving pale, blotchy, stippled or wilted patches where they have sucked sap; heavy feeding can yellow and kill leaves and stunt or kill young plants. It is chiefly a warm-region pest, most damaging on fall and overwintering brassicas in the South, and it readily attacks turnip and its greens. Cause The harlequin bug, a stink bug that feeds almost only on cabbage-family plants. The adults spend winter in garden trash in warm areas and get active as it warms up, with several generations a year. Look for its odd barrel-shaped, striped eggs lined up in two neat rows under the leaves.The harlequin bug (Murgantia histrionica), a stink bug that feeds almost exclusively on cabbage-family plants. Adults overwinter in garden debris in warmer regions and become active as the weather warms, with several generations a year; the barrel-shaped, black-and-white striped eggs are laid in neat double rows on the undersides of leaves. Organic treatment Pick off the adults, the young, and the striped egg rows by hand and drop them in soapy water, which works well if you start early. Pull and destroy badly infested plants and clean up cabbage-family debris. Insecticidal soap helps on the young bugs, and a patch of mustard planted as bait can draw them together so they are easy to remove.Handpick adults, nymphs, and the distinctive egg rows into soapy water, which is effective in a home garden caught early. Remove and destroy heavily infested plants and brassica debris that harbor them. Insecticidal soap helps on nymphs; a trap crop of mustard or another preferred crucifer can concentrate the bugs for removal. Prevention Clean up old cabbage-family plants and weeds at the end of the season, which is the biggest help since that is where the bugs spend winter. Rotate where you plant brassicas, check under the leaves for the striped eggs, and plant a little mustard as bait if the bug keeps coming back.Clear cabbage-family crop debris and weeds at season end to remove overwintering sites, the single most useful step. Rotate brassicas, scout the undersides of leaves for the egg rows, and use a trap crop where the bug is a recurring problem.
Diseases
Symptoms Aboveground the plant looks stunted and yellow and wilts in the afternoon sun, then perks up at night. Underground is the giveaway: instead of a clean turnip, the roots swell into lumpy, club-shaped galls that eventually rot. It lives in the soil and builds up when you grow cabbage-family crops in the same spot over and over, especially in wet, acidic soil.Aboveground, plants are stunted and yellowish and wilt in the heat of the day even in moist soil, recovering overnight. The diagnostic sign is below ground: the roots are swollen, distorted, and clubbed into gnarled, spindle-shaped galls rather than forming a clean turnip, and they later rot. It is a soilborne disease that builds up where crucifers are grown repeatedly and is favored by wet, poorly drained, acidic soil. Cause A soil organism (Plasmodiophora brassicae) that attacks the roots of cabbage-family plants and survives in the soil for years. Wet, poorly drained, acidic soil makes it worse, and it spreads on dirty tools and on soil moved from an infected bed.Plasmodiophora brassicae, a soilborne pathogen that infects the roots of cabbage-family plants and persists in soil as resting spores for many years. Wet, poorly drained, acidic soils favor infection, and the disease spreads on contaminated soil, tools, and transplants. Organic treatment There is no way to cure a plant that has it, so pull and throw away (do not compost) the affected ones. The fix is for next time: improve drainage, add lime to raise the soil pH toward 7.2 to 7.5, which holds the disease back, and keep cabbage-family crops out of that spot for a few years.There is no cure once a plant is infected; remove and destroy affected plants and do not compost them. Management is preventive across seasons: improve drainage and lime the soil toward a neutral to slightly alkaline pH of about 7.2 to 7.5, which suppresses the pathogen, and rotate crucifers out of the bed for several years. Prevention Do not grow turnips or other cabbage-family crops in the same bed year after year; move them on a multi-year cycle. Keep the soil well drained and add lime to raise the pH toward neutral, and avoid carrying soil from an infected bed on your tools. A raised bed with clean soil avoids it where it is a known problem.Rotate turnips and other crucifers on a multi-year cycle (a long rotation of several years is advised where it is established), since the pathogen builds in soil grown to the family. Keep soil well drained and limed toward a neutral to slightly alkaline pH, start with clean soil and tools, and avoid moving soil from an infested bed. Raised beds with clean mix sidestep the problem where it is entrenched.
Symptoms Raised white or cream blister-like spots on the undersides of the leaves, with a faint yellow patch on the top of the leaf opposite each blister. A bad case can twist the leaves. It mostly affects the leaves, so it matters most when you are growing turnips for greens, and it likes cool, damp weather.Raised, white to cream, blister-like pustules form on the undersides of leaves, with a faint yellow spot on the upper surface opposite each lesion. Heavy infection can distort leaves and, less commonly, the growing point. It is chiefly a foliar disease, most damaging on turnips grown for greens, and is favored by cool, moist weather. Cause A fungus-like water mold (Albugo candida) that lives on cabbage-family plants, survives on old plant debris, and spreads in cool, wet weather by spores carried on wind and splashing water. There is no home spray for it, so the fix is in how you grow the crop.Albugo candida, a water mold (formerly classed as a fungus) specific to crucifers that survives as thick-walled resting spores on crop debris and in soil and spreads by airborne and splash-borne spores in cool, wet conditions. No fungicides are registered for it in the home garden, so control is cultural. Organic treatment There is no spray for the home garden, so pick off and throw away infected leaves and the worst plants, and help the plants dry out by giving them room. Water at the soil instead of overhead, and clear away cabbage-family weeds and old debris that carry it.There is no home chemical control; remove and destroy infected leaves and badly affected plants to reduce spread, and improve airflow and drying. Cultural control carries the load: water at the base, space for airflow, and clear cruciferous weeds and debris that carry it. Prevention Do not grow cabbage-family crops in the same spot repeatedly, clear away old plant debris and weeds, and water at the base instead of overhead. Give plants room so the leaves dry fast, and choose a tolerant variety if it keeps coming back.Rotate crucifers, clear and destroy crop debris and cruciferous weeds that harbor the spores, and avoid overhead watering. Space and thin for airflow so foliage dries quickly, and use tolerant varieties where the disease recurs.
Symptoms Pale green to yellow angular patches on top of the leaves, with a grayish or white fuzzy growth underneath in damp weather; the spots later turn tan and papery. It mainly hurts the leaves and is worst in cool, wet weather, like a rainy fall, which is also when turnip greens are growing.Small, angular, pale green to yellow lesions on the upper leaf surface, bounded by the veins, with a grayish to white downy growth of spores on the corresponding undersides in damp weather. Affected areas later turn tan and papery. It chiefly disfigures the foliage and is most damaging in cool, moist conditions such as a wet fall. Cause A fungus-like water mold (Peronospora parasitica) that infects cabbage-family plants in cool, wet weather, best around 50 to 60°F. It survives on old plant debris and spreads in damp air and splashing water.Peronospora parasitica (also called Hyaloperonospora parasitica), a water mold that infects crucifers in cool, moist conditions, with infection favored around 50 to 60°F. It survives on crop debris and related hosts and spreads in moist air and splashing water. Organic treatment You cannot cure infected leaves, so pick off and throw away the worst ones and help the plants dry out by giving them room. Keeping the leaves dry does most of the work; a copper fungicide is a last resort in a very wet stretch.There is no cure for infected tissue; remove and destroy affected leaves to reduce spread, and improve airflow and drying. Cultural control is the mainstay for a home crop, with copper fungicides a last resort in a persistently wet season. Prevention Water at the soil instead of overhead, give plants room so air moves through, and stay out of the bed when the leaves are wet. Move turnips away from where you grew cabbage-family crops, clean up old debris, and pick a tolerant variety if it keeps showing up.Water at the base rather than overhead, space and thin for airflow, and avoid working among wet plants. Rotate away from crucifers, clear crop debris, and where it recurs choose tolerant varieties.
Symptoms Small, round, dark spots on the leaves, each with a yellow ring around it and faint target-like circles inside, that grow and run together in wet weather and turn sooty in the center. It mostly affects the leaves, so it matters most for turnip greens, and a bad case can slow the plant down.Small, circular, dark spots on the leaves, each with a yellow halo and characteristic concentric rings, that darken to a sooty center as spores build up and enlarge and merge in wet weather. It is primarily a foliar disease, most important on turnips grown for greens, and severe infection can reduce vigor and quality. Cause Alternaria fungi that can travel on seed and survive on old plant debris, spreading in splashing water and needing wet leaves to take hold. Warm, humid weather with wet foliage brings it on.Alternaria fungi (chiefly Alternaria brassicae), which are seedborne and survive on crop debris, spreading in splashing water and needing leaf wetness to infect. Warm, wet weather and prolonged wet foliage drive it. Organic treatment Pick off the worst leaves, water at the soil in the morning so leaves dry quickly, and clean up debris. Using clean seed and giving plants room for airflow handle most of it; a copper fungicide can help in a very wet spell if you start early.Remove badly spotted leaves, water at the base in the morning so foliage dries, and clear debris. Clean seed and airflow are the main home levers; a copper fungicide can help in a persistently wet season if started early. Prevention Use clean seed, water at the base instead of overhead, give plants room so the leaves dry, and clear away old plant material between plantings.Use clean seed, avoid overhead watering, space for airflow, and rotate crucifers and clear debris that carry the fungi between seasons.
Symptoms Yellow, V-shaped patches creeping in from the edges of the leaves, with the point of the V aimed at the center vein, and the veins in those patches turning black. The leaves yellow and die, and a bad case can rot the plant. It is a bacterial disease that hits the whole cabbage family in warm, wet weather.Yellow, V-shaped lesions advancing inward from the leaf margins, with the V pointing toward the midrib and the veins in the affected area turning black. Infected leaves yellow and die, and severe infection can rot the plant and move into the root. It is a bacterial disease of the whole cabbage family, spread in warm, wet conditions. Cause A bacterium (Xanthomonas campestris) that can travel on seed and splashing water and gets into the leaves through their edges and any wounds. Warm, humid, wet weather brings it on, and it spreads on infected seed, water, tools, and old plant debris among cabbage-family plants.Xanthomonas campestris pv. campestris, a seedborne and splash-spread bacterium that enters through leaf margins (water pores) and wounds. It is favored by warm, humid, wet conditions and spreads on contaminated seed, water, tools, and crop debris across cabbage-family crops. Organic treatment You cannot cure leaves that are already infected. Pull and throw away affected plants, stay out of the bed when the leaves are wet, and clean up old plant material. Clean seed and rotating where you plant cabbage-family crops handle most of it.There is no cure for infected tissue. Remove and destroy affected plants, avoid working among plants when the foliage is wet, and clear crop debris. Starting with clean seed and rotating crucifers do most of the work in a home garden. Prevention Use clean, disease-free seed, do not grow cabbage-family crops in the same spot repeatedly, and clear away old plant debris. Water at the soil instead of overhead, do not handle wet plants, and give them room so the leaves dry fast.Start with clean, disease-free seed, rotate crucifers out of the bed for at least a year or more, and clear debris that harbors the bacterium. Water at the base rather than overhead, avoid handling wet plants, and space for airflow so foliage dries quickly.
