Discover how apple fungicides like tebuconazole, propineb, mancozeb, difenoconazole, and hexaconazole affect soil health, beneficial fungi, and orchard resilience. Learn which are most harmful, why soil biodiversity restoration matters, and why chemical use should be a last resort for sustainable, regenerative apple farming.

Tebuconazole

What it is & why farmers use it
Tebuconazole is a systemic triazole fungicide widely relied on to control apple scab and powdery mildew. It interferes with sterol biosynthesis in the fungus, damaging its cell membranes and stopping disease spread.

Impact on soil health
Research shows tebuconazole can damage beneficial soil fungi, especially arbuscular mycorrhizae, which are critical partners for apple roots to acquire nutrients and maintain disease resistance. It reduces key soil enzymes and disrupts soil carbon cycling, which weakens the natural resilience of the orchard. Moderate-to-high persistence means residues can stay in soil for months, affecting earthworms and other soil fauna. This pattern undermines regenerative principles by making the orchard more dependent on synthetic inputs instead of a healthy soil food web.

Impact on human health
Tebuconazole is moderately hazardous (WHO Class III). It is generally safe under label PPE, but animal studies report potential liver effects and — very importantly — reproductive toxicity (including impacts on fertility, sperm quality, and fetal development) at high exposures. There is no conclusive evidence of carcinogenicity, but the reproductive risk is well-documented.

Regenerative perspective
Tebuconazole is not compatible with regenerative farming because of its repeated harm to mycorrhizae and soil biodiversity. It should only be a rescue tool in extreme disease conditions and must be balanced with intensive soil rebuilding practices, such as compost applications, green manures, and strong crop rotations to maintain soil health.

Propineb (Antracol)

What it is & why farmers use it
Propineb is a contact dithiocarbamate fungicide, forming a protective film on leaves to stop fungal spores from germinating. It is used against leaf spots and apple scab, especially in early sprays.

Impact on soil health
Propineb breaks down relatively faster than triazoles but can still temporarily harm beneficial soil microbes. Of greater concern is its breakdown product, propylene thiourea (PTU), which may disrupt thyroid function in animals and persists for weeks to months in moist soils. However, propineb does not severely harm mycorrhiza compared to triazoles and has only moderate toxicity for earthworms, making it somewhat less disruptive in a regenerative system if used carefully.

Impact on human health
Propineb itself is moderately hazardous (WHO Class III), but PTU, its metabolite, is a proven thyroid toxicant, which is why repeated, careless exposure should be strictly avoided. There is no strong evidence of cancer effects at label rates, but long-term PTU accumulation is still a concern.

Regenerative perspective
Propineb is not truly regenerative, but it is less damaging to soil biodiversity than tebuconazole or hexaconazole. If needed, it should be rotated carefully, supported with cover crops and compost to detoxify residues, and never repeated blindly.

Mancozeb (Zeneb, Polyram, Dithane)

What it is & why farmers use it
Mancozeb is a widely used dithiocarbamate fungicide, providing contact protection against scab, Alternaria, and other foliar pathogens. It is cheap, broad-spectrum, and still common worldwide.

Impact on soil health
Mancozeb has significant negative effects on earthworms and soil microbiology, disrupting populations of beneficial soil microbes and harming enzyme activity critical for nutrient cycling. Its breakdown product, ethylene thiourea (ETU), is an endocrine-disrupting compound and a suspected carcinogen, with evidence of thyroid toxicity in mammals. ETU is relatively persistent and may remain in orchard soils long after spraying, especially in low-OM or compacted soils.

Impact on human health
Mancozeb itself has low acute toxicity (WHO Class U), but its ETU metabolite is a major concern. Repeated or careless handling of spray residues can increase risks of endocrine disruption and possibly cancer in the long term, although data is mostly from chronic exposures, not single field uses. Always use PPE and do not spray near open water sources.

Regenerative perspective
Mancozeb is fundamentally incompatible with regenerative farming because it severely disrupts earthworms, microbial populations, and long-term soil biological diversity. It might be used only as a last-resort, emergency product, and even then, aggressive soil-restoring practices (cover crops, organic mulches, bioinoculants) are essential afterward to rebuild the soil ecosystem.

Difenoconazole

What it is & why farmers use it
Difenoconazole is a systemic triazole fungicide, working against apple scab and powdery mildew, and is prized for its longer residual effect, reducing the need for frequent reapplication.

Impact on soil health
Like other triazoles, difenoconazole disrupts sterol biosynthesis in soil fungi as well as in pathogens, harming beneficial mycorrhizal fungi, reducing soil microbial diversity, and lowering soil enzyme activities. Persistence can be moderate to high, lasting for a couple of months. This repeated stress on soil biology reduces regenerative potential and makes the orchard more chemically dependent.

Impact on human health
Difenoconazole is classified as slightly to moderately hazardous (WHO Class II–III). Studies show it may affect liver enzymes and has raised concerns about endocrine effects in high-dose animal tests, though no strong human cancer evidence exists.

Regenerative perspective
Difenoconazole is not regenerative, for the same reasons as other triazoles: it damages soil mycorrhiza and suppresses key soil organisms. If absolutely needed, rotate it carefully and recover soil biology with organic matter, biofertilizers, and reduced tillage to build resilience.

Hexaconazole

What it is & why farmers use it
Hexaconazole is a systemic triazole fungicide often used in high-value orchards for its long protective window against scab, powdery mildew, and some rusts.

Impact on soil health
Hexaconazole strongly disrupts mycorrhizal fungi and other beneficial soil microbes, similar to tebuconazole, which leads to reduced phosphorus uptake, weaker tree resilience, and greater reliance on chemical fertilizers. Its moderate persistence means residues can accumulate with repeated use, weakening the soil food web season after season.

Impact on human health
Hexaconazole is moderately hazardous (WHO Class III). While no conclusive human carcinogenic evidence is reported, animal studies show liver effects and some potential endocrine disturbances at higher doses, underlining the need for strict PPE.

Regenerative perspective
Hexaconazole cannot be considered regenerative. Its repeated use is fundamentally opposed to regenerative soil principles because it harms the mycorrhizal network and reduces soil biodiversity. If used, it must be rotated and followed by aggressive soil restoration through composts, mulches, and living cover crops to regain soil balance.

Which is worst for regenerative soil health?

Mancozeb (Zeneb, Polyram) is the most destructive, harming earthworms, breaking soil enzyme chains, and introducing ETU, a suspected carcinogen and endocrine disruptor.
Hexaconazole and tebuconazole are next worst, because they strongly disrupt mycorrhiza and lead to a chemically dependent orchard in the long term.
Propineb is less damaging but still harms the soil’s microbial balance if overused. Difenoconazole is in the same category as other triazoles, moderately harmful to soil biology.