olive Verticillium wilt

Symptoms

Half a tree wilting in summer while the other half stays green, blackish discoloration in cross-section of affected wood, partial recovery in winter then relapse, dieback over 2–4 seasons.

Plants affected

• dahlia
• florist's chrysanthemum
• cotton (upland cotton)
• okra (lady's finger)
• Japanese maple
• olive tree
• eggplant
• Japanese barberry
• globe artichoke
• peony
• Red maple
• Sugar maple

Easily confused with

• olive quick decline syndrome

  How to tell them apart: On olive, both cause branch dieback but the management is completely different. Verticillium dahliae: a SOIL fungus giving sudden one-sided wilt of individual branches with brown vascular streaking in the wood, often partial recovery, NOT notifiable. Xylella fastidiosa subsp. pauca (EU quarantine, NOTIFIABLE): leaf scorch with a yellow halo spreading to whole-canopy desiccation, spittlebug-vectored, no cure - if you see spreading scorch, treat it as SUSPECTED Xylella and contact the plant-health authority BEFORE pruning.

• tomato spotted wilt virus

  How to tell them apart: Verticillium dahliae is a soilborne vascular wilt fungus: leaves yellow and brown from the lower/older foliage upward, often on just one side of the plant or one side of a leaf (V-shaped marginal/interveinal scorch), and wilting is permanent. The diagnostic sign is internal: slice a stem near the base and you see brown to grey-brown vascular streaking in the woody ring. Symptoms intensify in cool, moist conditions and the plant slowly collapses over weeks. Tomato spotted wilt virus is thrips-transmitted and shows surface markings, not vascular browning: concentric chlorotic/necrotic ring spots, line and oak-leaf patterns, bronzing, and irregular dark blotches on leaves, often with one-sided distorted growth and stunting; cut stems show NO internal vascular discoloration.

• grey mould (Botrytis)

  How to tell them apart: Verticillium dahliae is a soilborne vascular wilt: lower leaves yellow then brown and die, often on one side of the plant or one branch first, while the stem stays firm and dry. The giveaway is internal — slice a stem near the base and you see brown streaks in the water-conducting tissue just under the surface, with no mould outside. Botrytis cinerea (grey mould) is a surface rot: stems and crown develop soft, water-soaked tan-to-brown lesions that often start at wounds, dead flowers or dense damp foliage, and in humid conditions a fuzzy grey mat of spores grows over the rotted area. If you see grey fuzz or soft mushy collapse it is Botrytis; if the wilt is dry with clean internal brown vascular streaking it is Verticillium.

• vine weevil

  How to tell them apart: Verticillium dahliae (verticillium wilt): an above-ground fungal vascular disease. Wilting and yellowing often start on one side of the plant or on lower/older leaves first, frequently in a V-shaped wedge from the leaf margin. Leaves may show pale-yellow to brown necrosis between the veins while staying attached, and the plant collapses gradually over days even when the soil is moist. The diagnostic sign is internal: cut a lower stem lengthways and look for brown to dark streaks staining the conducting tissue (vascular discolouration) — the roots themselves stay firm and intact. Otiorhynchus sulcatus (black vine weevil): an insect, and the damage is mechanical, not vascular. The sudden wilt is caused by white, legless, C-shaped grubs (up to about 1 cm, with a tan-brown head) that have eaten the fine roots and chewed the bark off the crown and main roots below soil level. Lift a wilting plant and the rootball will be loose, gnawed and often falls apart, with grubs visible in the compost; the stem interior is clean with no vascular streaking. Adult weevils (dull black, ~9 mm, pear-shaped) leave tell-tale crescent notches bitten out of leaf edges at night.

• sclerotinia stem rot

  How to tell them apart: Sclerotinia sclerotiorum produces a soft, watery rot at the crown and stem base of the artichoke, covered with dense white cottony (fluffy) mycelium; inside the hollowed stem and on the rotting crown you find hard black sclerotia the size of small seeds or peas. Affected plants wilt suddenly and the lower stem becomes bleached and shredded. It favours cool, wet, humid conditions and dense canopies. Verticillium dahliae causes a slower, progressive vascular wilt: lower and outer leaves show wedge-shaped interveinal and marginal yellowing turning brown, often on one side of the plant, with no surface mould. Cutting the stem or crown lengthwise reveals brown streaking in the internal vascular ring; there is no white fluff and only microscopic microsclerotia in dead tissue.

• Ramularia leaf spot of artichoke

  How to tell them apart: Look for discrete, well-delimited leaf spots on the artichoke foliage: small angular-to-rounded lesions, pale tan to greyish-brown centres often surrounded by a darker or yellow halo. In humid conditions a fine whitish-grey fuzz (sporulation) may appear on the underside of the spots. Damage stays clearly spotty and leaf-localised, the spots enlarge and coalesce but the vascular tissue of cut stems and petioles remains clean and white. The plant does not wilt as a whole; older outer leaves show the spots first. Verticillium wilt is diffuse, not spotty: whole leaf sectors turn pale with interveinal chlorosis (yellowing between the veins) and dry to a marginal scorch, frequently on one side of the plant or one half of a leaf. Affected outer leaves wilt and collapse during the heat of the day. The decisive sign is internal: slice a stem or large petiole lengthwise and look for brown to greyish vascular streaking. No discrete spots and no fuzzy sporulation on the leaf surface.

• drought stress

  How to tell them apart: Drought stress on Acer palmatum scorches leaves uniformly: crispy brown margins and tips spread inward across the WHOLE canopy at once, symptoms worsen on the hottest, most exposed side, and a deep watering brings partial recovery. Verticillium dahliae (Verticillium wilt) instead strikes ASYMMETRICALLY — one branch or one side of the tree suddenly wilts and dies back while the rest looks healthy, often mid-summer with no recent dry spell. The decisive sign is internal: peel back the bark or cut a wilting branch and look for olive-green to brownish streaking in the sapwood (vascular discoloration); drought leaves the wood clean and pale.

• sunburn / leaf scorch

  How to tell them apart: On Acer palmatum, abiotic sunburn produces uniform marginal and interveinal browning with crispy, papery tan-to-brown leaf edges, distributed evenly on the most sun- and wind-exposed outer canopy, with no wilting of green tissue and no discolouration in the wood. Verticillium dahliae instead causes sudden one-sided wilting and leaf scorch confined to a single branch or sector of the crown, where leaves curl and collapse while still partly green, and peeling the bark of an affected limb reveals tell-tale olive-green to grey-brown streaking in the sapwood. The clinching sign is this internal vascular staining and the branch-by-branch (sectorial) dieback of Verticillium versus the even, surface-only, exposure-driven scorch of sunburn.

• fig branch dieback / Botryosphaeria canker

  How to tell them apart: On Japanese maple both wilt a limb at a time, but Verticillium dahliae attacks from inside the wood: peel the bark or cut a dying branch and you find olive-green to brown streaks running lengthwise in the sapwood, while leaves scorch at the margins and curl on whole limbs without bark cankers. Botryosphaeria dothidea works on the surface: look for sunken, darkened, often cracked cankers on the bark, sometimes oozing, studded with tiny black pimple-like fruiting bodies (pycnidia), and the wood under a canker browns only locally around that lesion rather than as continuous internal streaking. Verticillium dieback often follows wet soil or replant sites; Botryosphaeria dieback typically follows drought, sunburn or pruning wounds on stressed trees.

• mint rust

  How to tell them apart: Puccinia menthae (mint rust) and Verticillium dahliae (Verticillium wilt) both yellow mint foliage, but the diagnostic signs are clear once you look closely. Turn leaves over: mint rust shows raised, powdery orange-to-rust-brown pustules (and earlier, pale yellow swollen spots with distorted, thickened young shoots) scattered on the LOWER leaf surface, all on healthy soil. Verticillium wilt shows NO pustules — instead yellowing and brown marginal scorch appear one-sided or on a single shoot/branch, the plant wilts in heat, is stunted, and a cut through a lower stem reveals brown streaking of the internal vascular tissue. In short: orange dust under the leaf = rust; one-sided wilt plus brown stem-vessel streaks = Verticillium.

• pistachio rust

  How to tell them apart: On Pistacia terebinthus both Pileolaria terebinthi (pistachio rust) and Verticillium dahliae (Verticillium wilt) start as diffuse interveinal yellowing, scorch and premature leaf drop, but the decisive signs differ. Pileolaria terebinthi forms small round-to-irregular reddish-brown or purplish pustules ringed by a yellow halo on the leaf, petiole and fruit; turn the leaf over and you find raised powdery rust spore masses on the underside, while the wood stays clean when cut. Verticillium dahliae shows NO pustules: instead one or a few branches wilt and die back (often one-sided), and slicing a wilting twig reveals brown to greyish streaks or rings in the vascular wood, with symptoms worst in hot, dry spells.

• Okra powdery mildew (endophytic, Mediterranean)

  How to tell them apart: Both Leveillula taurica (powdery mildew) and Verticillium dahliae (Verticillium wilt) start as yellow blotches on okra leaves, so they are easy to confuse early. The deciding test is the leaf UNDERSIDE: with Leveillula taurica you find a white-to-grey powdery spore layer directly under the yellow patches, and the plant does not wilt at the stem. Verticillium dahliae leaves the underside CLEAN (no powder) — instead the yellowing is often one-sided or wedge-shaped between the veins, the plant wilts in the heat of the day, and if you slit a lower stem lengthwise you see brown streaks in the wood. Powder under the leaf = Leveillula; brown streaks inside the stem + wilting = Verticillium.

Common questions

How do I recognise olive Verticillium wilt on dahlia?

Half a tree wilting in summer while the other half stays green, blackish discoloration in cross-section of affected wood, partial recovery in winter then relapse, dieback over 2–4 seasons.

Do I have to report olive Verticillium wilt?

No. olive Verticillium wilt is not a notifiable organism, so there is nothing to report to an authority. Treat it as a normal garden problem.

How is olive Verticillium wilt treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.