Diagnose a Sick Tree

Symptoms

• Yellow-orange powdery pustules on leaf undersides
• Corresponding pale yellow spots on the upper leaf surface
• Premature, heavy leaf drop (often mid-summer)
• Severely affected trees may defoliate entirely

Cause

Fungal pathogen Physopella fici. Spreads via airborne spores and thrives in warm, humid conditions with poor air circulation.

Treatment

• Remove and bin (do not compost) all fallen leaves
• Improve air circulation by thinning dense inner growth
• Apply a copper-based or sulphur fungicide at first sign of infection
• Avoid wetting foliage when watering; water at the base
• Repeat fungicide applications every 10–14 days during humid weather

Symptoms

• Wilting or drooping even when soil is moist
• Yellowing or browning leaves from the bottom up
• Stunted new growth or sudden dieback of branches
• Roots appear brown, soft, and mushy when checked

Cause

Overwatering combined with poorly drained soil creates anaerobic conditions that allow fungal pathogens (Phytophthora, Pythium, or Fusarium spp.) to attack and kill root tissue.

Treatment

• Allow the soil to dry out significantly between waterings
• For container trees: repot into fresh, well-draining mix; trim all brown or mushy roots before repotting
• Improve in-ground drainage by amending soil with grit or perlite
• Apply a phosphonate-based drench (e.g., Aliette) for Phytophthora
• Severely affected trees may not recover; propagate healthy cuttings as insurance

Symptoms

• Mosaic or mottled yellow-green patterning on leaves
• Distorted, puckered, or unusually shaped leaves
• Stunted, deformed figs; reduced crop yield
• Symptoms may be mild or severe depending on strain and tree vigour

Cause

Fig mosaic virus (FMV) — a complex of related viruses transmitted primarily by the fig leaf mite (Aceria fici). Also spread by grafting or propagating from infected wood. There is no cure once a tree is infected.

Treatment

• No chemical cure exists; management focuses on reducing spread
• Control fig mite populations with horticultural oil or sulphur spray in early season
• Never propagate cuttings from an infected tree
• Remove and destroy severely affected trees to protect others nearby
• Source new plants from certified virus-tested stock where possible

Symptoms

• Bleached, tan, or papery patches on fruit skin or bark
• Fruit cracks, shrivels, or fails to ripen on the affected side
• Bark on the south- or west-facing side cracks and peels
• More common on recently moved plants or after heat waves

Cause

Intense, direct sunlight — especially on fruit, bark, or foliage that has not been gradually acclimated. Sudden moves from shade to full sun, or extreme heat events, are the most common triggers.

Treatment

• Provide 30–50% shade cloth during the hottest part of the day (typically afternoon)
• When moving a potted tree to a sunnier spot, acclimatise over 1–2 weeks
• Whitewash the trunk with diluted white latex paint to reflect heat
• Ensure the tree is adequately watered — drought stress worsens sunscald damage
• Damaged fruit will not recover; remove it to reduce disease entry points

Symptoms

• Figs look normal on the outside but smell fermented or sour when cut open
• Interior flesh is watery, off-coloured, or full of liquid
• Small fruit flies (Drosophila) hovering around ripening figs
• Oozing or weeping from the ostiole (the small opening at the fig's base)

Cause

Yeasts, bacteria, and sometimes the short-cycle wasp (Blastophaga psenes) enter through the ostiole, triggering internal fermentation. Warm, wet conditions accelerate the process. Damaged or cracked fruit is especially vulnerable.

Treatment

• Harvest figs promptly as they ripen — don't leave them on the tree past peak
• Remove and bin (never compost) any dropped or rotting figs immediately
• Reduce overhead irrigation; avoid wetting the fruit
• Hang yellow sticky traps near the tree to monitor and reduce fruit fly pressure
• For persistent problems, fine netting over individual fruit clusters can help

Symptoms

• Tiny rust-brown or silvery stippling across the upper leaf surface
• Leaves curl, pucker, or develop abnormal bud distortion ("bud mite" damage)
• Fine webbing on leaf undersides (spider mite species)
• Stunted shoot tips and misshapen new leaves in spring
• Fig mosaic virus symptoms often accompany infestation — the fig leaf mite is its primary vector

Cause

Two main culprits: the fig leaf / bud mite (Aceria fici), an eriophyid mite too small to see with the naked eye that feeds inside buds and transmits Fig Mosaic Virus; and spider mites (Panonychus or Tetranychus spp.) that colonise leaf surfaces during hot, dry spells. Both thrive when natural predator populations are depleted by broad-spectrum insecticide use.

Treatment

• Apply a dormant-season horticultural oil spray (2%) before bud break to smother overwintering mites
• During the growing season use a sulphur-based miticide or insecticidal soap; apply to leaf undersides
• Avoid broad-spectrum insecticides that kill predatory mites and wasps
• Increase humidity around the tree — spider mites hate moist conditions; mist foliage on hot days
• Introduce or encourage predatory mites (Phytoseiidae) as a biological control
• For bud mites: prune out and destroy heavily distorted shoot tips in early spring

Symptoms

• Trails of ants running up and down the trunk and branches
• Small brown, grey, or white dome-shaped bumps fixed to bark and stems (armoured scale) or soft, waxy white clusters (soft scale / mealybug)
• Sticky honeydew residue coating leaves and surfaces below
• Black sooty mould growing on the honeydew deposits
• Leaves turning yellow and dropping; overall vigour decline

Cause

Scale insects (Ceroplastes, Parthenolecanium, and related species) pierce bark and phloem to extract sap. They excrete excess sugars as honeydew, which ants actively farm — the ants protect scale colonies from predatory insects in exchange for the honeydew. Breaking the ant–scale mutualism is often the key to control.

Treatment

• Apply a physical ant barrier: wrap the trunk with a 10 cm band of horticultural glue (e.g., Tanglefoot) on a collar of tape — never apply glue directly to bark
• Prune out heavily infested branches and bin the material
• Scrub armoured scale off bark with a soft brush dipped in soapy water
• Apply horticultural oil or systemic neonicotinoid (last resort) to kill scale crawlers in early summer
• Once ants are excluded, natural predators (ladybirds, parasitic wasps) usually suppress the scale colony within a season

Symptoms

• Dense black colonies massing on soft new shoot tips and the undersides of young leaves
• Shoot tips curl, pucker, and fail to extend normally
• Sticky honeydew on leaves and surfaces below; sooty mould follows
• Ants tending the colonies (same mutualism as with scale)
• General wilting of new growth in heavy infestations

Cause

Aphis fabae overwinters as eggs on spindle trees (Euonymus) and migrates to a wide range of summer hosts including figs. Winged females arrive in late spring and quickly establish large colonies. Outbreaks are worst in warm, dry weather and when natural enemies are absent.

Treatment

• Pinch out or prune the most heavily colonised shoot tips immediately
• Blast colonies off with a strong jet of water; repeat every few days
• Apply insecticidal soap or neem oil directly onto colonies, ensuring good coverage of leaf undersides
• Encourage or introduce natural predators: ladybirds, lacewing larvae, parasitic wasps, and hoverfly larvae
• Apply ant barriers on the trunk to prevent ants from protecting the colony (see Ants & Scale above)
• Avoid high-nitrogen feeds that produce the soft, sappy growth aphids prefer

Symptoms

• Tiny perfectly round entry holes (1–2 mm) in the bark of trunks and larger branches
• "Toothpick" or matchstick-like protrusions of white frass extruding from entry holes — the most diagnostic sign
• Sudden wilting and dieback of an entire branch (a branch may die within days of attack)
• Gummy or dark staining around entry holes on some species
• Multiple attack points often occur on stressed, weakened, or recently transplanted trees

Cause

Ambrosia beetles are tiny (<3 mm) wood-boring weevils. The female bores into the sapwood and inoculates the gallery with ambrosia fungus (Fusarium or Raffaelea spp.), which the larvae then feed on. The fungus itself blocks the tree's vascular system, causing rapid wilt. Beetles are strongly attracted to ethanol volatiles given off by stressed or wounded trees; healthy, vigorously growing trees are rarely attacked.

Treatment

• Prevention is far more effective than cure — keep trees well-watered and fertilised to maintain vigour
• Avoid wounding bark during pruning; make clean cuts and seal large wounds with pruning paint
• Remove and destroy (burn or bin, never compost) any infested wood immediately to prevent emergence of a new generation
• Preventive bark sprays with permethrin-based insecticide on the trunk and scaffold branches during beetle flight season (warm spring days) can deter egg-laying
• Ethanol-baited traps placed nearby can monitor and reduce local beetle populations
• A tree with extensive gallery damage through the main trunk is unlikely to recover; focus on salvaging cuttings

Symptoms

• Fig Blight / Twig Dieback: Branches wilt suddenly and die back from the tip; leaves turn brown but remain hanging ("flagging"); dark, sunken cankers appear on the bark at the base of the dead section
• Pink Blight: A pale salmon-pink to white powdery fungal crust growing on the surface of shaded or interior bark and branches
• Affected bark beneath the crust is killed; branches girdle and die
• Both diseases are most active and visible in warm, humid conditions
• Fruiting bodies (tiny black pycnidia) may be visible on blighted bark with a hand lens

Cause

Fig blight is caused by Botryosphaeria (and related) fungi — opportunistic pathogens that infect through wounds, sunscald, or frost-damaged bark. Pink blight is caused by Erythricium salmonicolor (formerly Corticium salmonicolor), a basidiomycete fungus that colonises bark in dense, humid, poorly ventilated conditions — especially on shaded interior branches. Both are secondary invaders that preferentially attack already-stressed trees.

Treatment

• Prune out all blighted wood at least 15–20 cm below the visible infection margin; sterilise tools between cuts with 70% alcohol or a 10% bleach solution
• For pink blight: scrape off the fungal crust, then paint the exposed area with a copper-based fungicide paste
• Improve air circulation by thinning the canopy interior — pink blight thrives in stagnant, humid air
• Apply copper oxychloride or mancozeb sprays preventively during wet seasons, targeting the bark and branch unions
• Minimise wounding; protect cuts and any frost-damaged bark from further infection
• Dispose of all pruned material by burning or binning — do not compost

Symptoms

• Branches fail to break bud in spring — no leaves by late May
• Pith is brown, hollow, or discoloured when a branch is cut open
• New spring growth emerges then suddenly blackens and collapses (late frost strike)
• Bark splits, cracks, or weeps sap in late winter or early spring
• Entire top of tree dead back to the ground; roots may still be alive

Cause

Temperatures below the tree's cold-hardiness threshold kill water-conducting tissue in the wood. Bark tissue is more vulnerable than roots. Sudden temperature swings — a warm spell followed by a hard freeze — cause the most damage. Even cold-hardy varieties like Chicago Hardy can lose top growth in a severe Chicago winter without adequate mulching or protection.

Treatment

• Do not prune dead wood until late spring — wait to see where new growth emerges before cutting
• Scratch a bud or make a small cut on the branch: green or white pith = alive; brown, dry, or hollow = dead
• Cut dead wood back to a live bud; make clean angled cuts and seal large wounds
• Mulch the root zone heavily (6–10 inches) each autumn to protect the root system from hard freezes
• For in-ground trees: wrap trunks with burlap or foam pipe insulation before temperatures drop below 20°F
• Container trees: store in an unheated garage or shed — above 15°F is sufficient; the tree does not need light while dormant

Symptoms

• Small unripe figs dropping off before they develop — often pea- to marble-sized
• Tree appears otherwise healthy with good foliage and no visible pest damage
• Drop occurs mid-summer during main-crop development, or after the breba crop finishes
• No mold, rot, or insect damage visible on dropped figs
• Drop is worse in hot, dry spells or shortly after heavy nitrogen feeding

Cause

Fig drop has several triggers: moisture stress during the critical fig-swelling period is the most common. Excess nitrogen pushes leafy growth at the expense of fruit development. Root disturbance (repotting mid-season), insufficient sunlight, or a sudden temperature extreme can also cause the tree to abort developing figs. Some varietal drop — especially breba drop — is entirely normal and not a cause for concern.

Treatment

• Water consistently during fig development — never let the soil dry out completely when figs are swelling
• Switch from high-nitrogen feed to a low-N, high-K fertiliser (e.g., tomato feed) once figs begin to form
• Avoid repotting or disturbing roots from mid-spring through harvest
• Ensure maximum sun exposure — figs need at least 8 hours of direct sun to hold a full crop
• Some self-thinning is normal; only investigate if the tree drops nearly all of its figs consistently

Symptoms

• Gray, fuzzy powdery mold growing on fruit, stems, or dormant wood
• Soft, water-soaked patches on ripening or stored figs that turn brown then gray
• Mold appearing on cut ends of dormant wood during winter storage
• Rapidly expanding rot in cool, humid or poorly ventilated conditions
• Affected tissue collapses and shrivels once the mold dries

Cause

Botrytis cinerea is an opportunistic fungus that thrives in cool (60–75°F), humid conditions with poor air circulation. It is particularly common during overwintering — when bare-root or container trees are stored in garages or basements — and on late-season fruit that does not get enough warmth to ripen before autumn rains arrive. Wounds, dead leaves, and damp soil are common entry points.

Treatment

• Improve air circulation immediately — space out stored trees, open vents, run a fan periodically
• Remove and bin all infected material; Botrytis spreads rapidly via airborne spores
• For dormant stored trees: inspect monthly, remove any moldy stem sections, reduce ambient humidity
• Apply a sulphur-based or copper fungicide at the first sign on actively growing trees
• Avoid overhead irrigation; always water at the base
• Store dormant trees at 25–45°F with minimal soil moisture — don't let the medium stay wet

Symptoms

• Nitrogen deficiency: uniform yellowing of older, lower leaves while new growth stays green; overall pale, washed-out appearance
• Iron / manganese chlorosis: yellow tissue between green veins on young upper leaves; the veins themselves stay distinctly green
• Overall stunted growth or smaller-than-normal new leaves
• Leaf edges turning brown or looking scorched (potassium deficiency or salt build-up in containers)
• Symptoms often appear after a long dormant period, after heavy rain, or in the same soil/container for several years

Cause

Container figs are especially prone — nutrients leach quickly with frequent watering. Nitrogen deficiency causes generalised yellowing from the bottom up. Iron and manganese chlorosis typically appears on young growth in alkaline or waterlogged soil where micro-nutrients are locked out even when physically present. Chicago's tap water is moderately alkaline (pH 7.5–8.0), which can push soil pH high enough to cause chlorosis in container trees over time.

Treatment

• For nitrogen deficiency: apply a balanced liquid fertiliser (e.g., 10-10-10 or fish emulsion) every 2–3 weeks during the growing season
• For iron chlorosis: apply chelated iron (Fe-EDTA) as a soil drench or foliar spray; check and lower soil pH if it is above 7.0
• Use rainwater or filtered water where possible — Chicago tap water is alkaline and can raise soil pH over time
• For containers: repot into fresh mix every 2–3 years; nutrients deplete faster than in-ground
• Do not over-correct nitrogen — excess N causes lush leafy growth at the expense of fruit set and increases fig drop