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Root-Knot Nematodes

Root-Knot Nematodes

Meloidogyne spp.

Nematodealso: Nematodes, Root knot nematode

Microscopic soil-dwelling roundworms that invade plant roots and force them to form knotty galls. Hidden underground, they show up as plants that wilt, yellow, and languish for no clear reason, and the swollen, galled roots found when you dig give them away.

🔎 How to spot it

The nematodes themselves are too small to see, so you diagnose them by the roots: dig up a struggling plant, wash the soil off, and look for the characteristic round swellings or galls along the roots, from pinhead-sized up to about an inch and often beaded in a row. Above ground, plants are stunted, pale or yellowed, and wilt in the heat despite adequate water, often in patches across the bed.

🥀 Damage it causes

By feeding in the roots and forming galls, the nematodes block the flow of water and nutrients, so plants are stunted, yellowed, wilt easily in warm weather, respond poorly to fertilizer and water, and yield little; severe infestations kill plants. Tomato, carrot, pepper, cucumber, melon, and many other vegetables are susceptible, and the galls also open the door to root-rot fungi.

🛡️ Prevent it

Plant resistant varieties where you can, such as tomatoes marked with the N (for nematode) in the VFN code on the label. Rotate with resistant or non-host crops like grains and certain cover crops, though the wide host range of the nematode limits rotation. Build soil with organic matter to support beneficial organisms, keep tools and transplants clean, and solarize badly infested beds under clear plastic in the hot months.

🧯 If it is already here

There is no home cure once roots are galled, so management is about lowering the population for next season: pull and destroy heavily infested plants with their roots, fallow or solarize the worst beds, and add organic matter. Then come back to that ground with resistant varieties and a rotation away from favored hosts. A dense marigold cover crop turned into the soil can suppress some nematode populations.

💡 Good to know

Because the damage is underground and looks like a nutrient or water problem, root-knot nematode is often missed until you dig and find the telltale galls, so checking the roots of a stunted plant is the key diagnostic step. They spread on soil, water, tools, and infested transplants, so good sanitation and resistant varieties are the backbone of living with them.

🌱 Plants it attacks

714 plants in the library can be attacked by this pest

Acorn SquashAdirondack Blue PotatoAdzuki BeanAfrican Blue BasilAfrican MarigoldAgapanthusAgeratumAgrimonyAji Amarillo Pepper🍓Albion StrawberryAlice du Pont Mandevilla🥔All Blue PotatoAlmondAloe VeraAmbrosia CornAmerican BasswoodAmerican Beauty Dragon FruitAmerican BeechAmerican PersimmonAmethyst Falls WisteriaAmish Paste TomatoAnaheim PepperAnemoneAngelique TulipAngeloniaAniseAnise HyssopAnjou PearAnnabelle Smooth HydrangeaAnnual VincaApeldoorn TulipApple MintApril Tryst CamelliaArbequina OliveArizona Sun Blanket FlowerArkin CarambolaArmenian CucumberAroniaArp RosemaryArugulaAshwagandhaAsian PearAsian PersimmonAtemoyaAtlantic Giant Pumpkin🥕Atomic Red CarrotAucubaAugust Beauty GardeniaAunt Molly's Ground CherryAutumn Joy SedumAvocadoBachelor's ButtonBalsam FirBalsam PoplarBanana PepperBarbara Karst BougainvilleaBartlett PearBay LaurelBayberryBeach PlumBeauregard Sweet PotatoBecky Shasta DaisyBee Balm🍅Beefmaster TomatoBenarys Giant ZinniaBengal Tiger CannaBetter Boy Tomato🥬Bibb Lettuce🍅Big Beef TomatoBig Boy TomatoBilberryBing CherryBitter MelonBlack BeanBlack Beauty EggplantBlack Beauty ZucchiniBlack Beluga LentilBlack Cherry TomatoBlack CrowberryBlack Currant🍉Black Diamond WatermelonBlack Kabouli ChickpeaBlack Krim TomatoBlack RaspberryBlack Sapote🥬Black Seeded Simpson Lettuce🥕Black Spanish RadishBlack Tartarian CherryBlack WalnutBlack-Eyed PeaBlack-eyed Susan VineBlood OrangeBloomsdale SpinachBlue Bird DelphiniumBlue Bird Rose of SharonBlue FescueBlue Lake Green BeanBluecrop BlueberryBocking 14 ComfreyBok Choy

For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.