Your apple tree looked healthy in spring. Now it is July and the leaves are yellowing, spotting, or already on the lawn. (You were not planning a second career in plant diagnostics. Nobody is.)
Most apple tree leaf problems in Surrey and the Fraser Valley come down to one of five causes. And a lot of them — honestly more than most people expect — you can handle yourself.
The five causes of apple tree leaf problems
Quick answer: Apple tree leaves change because of fungal disease, nutrient deficiency, water stress, pests, or natural seasonal timing. In BC, the most common cause by far is apple scab — a fungal disease that thrives in our wet spring weather. The good news is most mild cases do not require a professional. The bad news is that misdiagnosing it and applying the wrong fix can set the tree back a full season.
The tricky part is that several of these conditions look similar from a distance. Yellow leaves mean a dozen different things. You need to look at the pattern, the location in the canopy, and the time of year before you can tell what is going on.
Fungal diseases: the most common reason in BC
Apple scab is the one most Surrey homeowners are actually dealing with. It is caused by the fungus Venturia inaequalis. Wet, cool springs — which describes most of our April and May in the Fraser Valley — are exactly what it needs to spread.
Look for olive-green or brown spots on the leaf surface, usually appearing by June. The tissue around the spots turns yellow. By midsummer, a heavily infected tree may drop a large portion of its canopy early. You will often see matching spots on the fruit.
Mild cases do not kill the tree. But three or four heavy infection seasons in a row will weaken it significantly. Rule of thumb: if less than 25% of the canopy is affected, you can manage it yourself. Clean up fallen leaves immediately — rake and bag them, not compost. The spores overwinter in the leaf litter. That single step makes a real difference the following spring.
Fire blight is different. It is bacterial, caused by Erwinia amylovora. Leaves and shoots look scorched — brown or black, wilted, with the tips of branches curling into what arborists call a shepherd's crook. The giveaway is the ooze. If you see sticky amber-coloured liquid on the bark near the affected wood, that is fire blight.
Unlike apple scab, fire blight cannot be managed effectively by a homeowner once it spreads beyond a single shoot. Removing infected wood requires cutting at least 30 centimetres below the visible symptoms and disinfecting your tools between every cut with a 10% bleach solution. Get the cut point wrong and you spread it further. If fire blight has reached the main trunk or the graft union near the base, the tree is likely beyond saving. This is where you call someone.
Powdery mildew shows as white, powdery patches on new growth and young leaves. It looks alarming. It is actually one of the less damaging fungal issues — improving air circulation through the canopy (which is a pruning job) usually clears it up without further intervention.
Cedar apple rust is worth knowing about in BC. It requires two hosts to complete its life cycle: junipers or cedars on one side, and apple or crabapple trees on the other. Bright orange or yellow spots on the upper surface of the apple leaves in spring and early summer, sometimes with spiky orange growths on the underside — that is cedar apple rust. It does not kill the tree but weakens it year over year. The Canadian Food Inspection Agency has a useful identification guide if you want to confirm the diagnosis.
Nutrient deficiencies and soil problems
Iron deficiency chlorosis is the most common nutrient issue for apple trees in BC. The pattern is specific: yellowing between the leaf veins while the veins themselves stay green. It looks striking — a mottled yellow-green — and people often panic when they see it.
The cause is usually pH. In alkaline soil (pH above 7), iron becomes unavailable to the tree even when it is physically present in the soil. Adding chelated iron is a short-term fix. Correcting the pH is the longer-term solution. A soil test from a local garden centre costs about $30 and tells you exactly what you are dealing with.
Nitrogen deficiency produces a more general yellowing — whole leaves, starting with older growth in the lower canopy, turning pale yellow-green. A nitrogen-rich fertiliser applied in early spring usually resolves this within a season. In Surrey, April is the right time.
Magnesium deficiency causes yellowing between the veins on older leaves, similar to iron deficiency but usually less severe. A tablespoon of Epsom salt (magnesium sulphate) dissolved in a litre of water applied to the soil is a simple first step worth trying. If it does not improve in three to four weeks, the issue is probably something else.
I reckon a third of the homeowners who call about yellowing apple tree leaves are looking at a nutrient issue rather than a disease. The soil in Surrey — particularly in yards that have been lawned over for years — is often depleted. A basic soil test before you spray anything saves a lot of money and effort.
Water stress — too much or too little
Too much water and not enough water look surprisingly similar on an apple tree: yellowing leaves, premature drop, wilting. The difference is in the context and the timing.
Too much wateris more likely in BC's spring — particularly if your yard has heavy clay soil and poor drainage. Apple trees do not tolerate waterlogged roots. If leaves are yellowing in late April through June after heavy rain, check whether water pools at the base of the tree after a storm. If it does, the roots are being deprived of oxygen. The tree is stressed before fungal disease even enters the picture, and stressed trees are far more susceptible to infection.
Too little water becomes the problem in July and August. The Fraser Valley gets dry summers. An established apple tree can survive without supplemental watering, but a tree that is already fighting disease or pests has less reserve. During a dry stretch, one deep watering per week is more useful than light watering daily. You want the water to reach the root zone, not just sit on the surface.
The BC government's drought monitoring page is worth bookmarking if you have fruit trees — it shows current drought levels by region, which helps you decide when to supplement watering.
Pests on apple tree leaves
Pests are the cause people jump to first. Nine times out of ten, by the time I look at the tree on-site, the actual problem is disease or nutrients. That said — pests are real and they are worth knowing.
Aphids cluster on new growth and the underside of leaves. The leaves curl and pucker. Look closely and you will see the insects themselves — small, usually green or black, clustered on the stems. Ladybirds and lacewings eat them naturally, so the first response is patience and a hard spray of water to knock them off. If they persist, diluted dish soap and water is effective and does not harm the tree.
Spider mites cause fine stippling on leaves and a bronze discolouration in hot, dry weather. They thrive in July and August in the Fraser Valley. They become much more aggressive if you have killed off their natural predators with broad-spectrum pesticides. This is worth knowing before you spray.
Codling moth larvae tunnel into the fruit rather than the leaves directly, but a heavy infestation weakens the tree enough that you will see leaf drop later in the season. Pheromone traps are effective for monitoring. The BC tree fruit industry management guidelines cover codling moth control in plain language.
How to diagnose the problem yourself
The pattern on the leaf tells you a lot before you touch anything.
| What you see | Likely cause |
|---|---|
| Spots with yellow halos, leaves yellowing and dropping by July | Apple scab |
| Brown, scorched shoots with curl at tips + amber ooze on bark | Fire blight — stop, do not touch |
| Yellow between veins, veins stay green | Iron or magnesium deficiency |
| Whole leaves pale yellow-green, lower canopy first | Nitrogen deficiency or water stress |
| Holes or curled leaves with insects visible | Aphids or other pests |
| Orange or yellow spots on upper leaf surface in spring | Cedar apple rust |
| White powdery coating on new growth | Powdery mildew |
Where on the tree matters. Lower canopy yellowing starting in early summer usually points to nutrients or water. Upper canopy spotting after a wet spring points to fungal disease. Whole-tree decline mid-season usually means the problem started earlier and was not caught.
Take a photo before you treat anything. If you end up needing us, a before-photo is far more useful than a description.
When to treat it yourself vs. when to call
I'll tell you when you do not need to call us. More arborists should do that.
Handle it yourself:
- Mild apple scab (under 25% canopy affected) — rake and bag fallen leaves promptly. Apply a copper-based fungicide before buds break next spring if it was a bad year.
- Aphid infestation — spray with water or diluted dish soap. Encourage natural predators before reaching for anything stronger.
- Nitrogen or magnesium deficiency — soil amendment in early spring.
- Powdery mildew on new growth — the crown thinning approach to pruning for air circulation is usually sufficient.
- Yellowing in late August — if the rest of the tree looks healthy, this is just autumn starting early. Apple trees drop older leaves before the season ends.
Call an arborist when:
- You see fire blight spreading beyond a single shoot — incorrect pruning spreads it and is worse than no intervention
- More than 30–40% of the canopy is affected by disease across two or more consecutive seasons
- Branch dieback with ooze or discolouration near the base of dying wood
- You have tried treating for two seasons and the tree is still declining
- You are considering removing the tree — get a second opinion first
I have seen homeowners remove perfectly salvageable apple trees because they misdiagnosed a treatable fungal infection. I have also seen people spend three summers treating a tree that had fire blight established in the rootstock. Both outcomes are expensive in different ways. A $150 assessment saves the guesswork.
For a broader look at what tree disease can look like and when it matters, our guide to tree fungus covers identification across a wider range of species.
What an arborist visit costs
Honest numbers, because nobody publishes them and they should.
| Service | Typical rate (CAD) |
|---|---|
| Tree assessment / consultation | $150 (credited toward work if you proceed) |
| Crown thinning to improve air circulation | $300–$800 depending on size and access |
| Deadwood and diseased branch removal | $250–$600 |
| Full tree removal (if necessary) | $400–$1,400 depending on size |
We will tell you at the assessment whether the tree is worth treating and what it will cost. If the honest answer is that removal is the better call, we will say that too — and give you the removal quote while we are there. No second visit required.
For a full breakdown of what affects tree health assessment and what we look for, that post covers the process in more detail.