This is a member review of one leaf-wash product, rewritten for clarity. The product is Dr. Schimmel S.M.T – Plant & Leaf Wash. Growers in Europe and Australia often recommend it to each other. They use it against spider mites and russet mites, and to clean leaves from the vegetative stage into early flowering.
The review is based on the original poster’s own use. It does not say how many plants were treated, in what room or for how long. Read the results below as one grower’s impressions, not as a measured trial.
What Dr. Schimmel S.M.T is and how it works
S.M.T is not a chemical pesticide. It is a leaf wash that works by physical contact. According to the original post, it acts in four ways:
- It breaks the protective outer layer of spider mites.
- It blocks their spiracles (the tiny breathing holes on a mite’s body), so the mites dry out and die.
- It washes eggs and young mites (larvae) off the leaves.
- It cleans dust, honeydew (the sticky sugar that sap-sucking insects leave on leaves) and light mould from the leaf surface.
Because it kills by contact, it only works on mites and eggs that the spray actually reaches. Mites hiding on the underside of leaves or inside webbing survive if you miss them.
The manufacturer’s claim: no residue, and safe to use during flowering. The original poster found no published residue data to back this up. Before you spray flowering plants, ask the supplier for a certificate of analysis (COA, a lab report showing what is in the product) or send a flower sample for a residue test. The purpose is simple: a buyer or auditor will test your dried flower, and you want to know the result before they do.
What you can do: spray the underside of every leaf, not only the top, and check with a magnifier the next day to see whether live mites remain.
What the original poster liked
- Fast at light to moderate levels: mites were visibly fewer after 2 sprays.
- Gentle on the plant: no leaf burn, no flower burn and no chemical smell were seen.
- Easy to use: mix with water, spray, wait, then wipe the leaves.
- Cleans thoroughly: dust and honeydew came off completely.
- Ingredients: made from plant-based ingredients and organic surfactants (wetting agents that help the spray spread over the waxy leaf surface).
“No flower burn” and “no residue” are two different questions. The first means the plant was not visibly damaged. The second is about what stays on the flower, and only a lab test answers it.
The post does not give a mixing rate or say how long to wait before wiping. UK retailers list the rate as 25 ml in 3 litres of warm water, sprayed just before the dark period. They give no contact time. Use the rate on the label of the pack you buy. Wiping removes the dead mites, eggs and loosened dirt, so the next spray reaches clean leaf.
What you can do: test the wash on 2–3 plants first and look at them after 24 hours. You learn whether your cultivar tolerates it before you treat the whole room.
Where it falls short
S.M.T does not solve every mite problem.
Heavy outbreaks. When there is a lot of webbing and the leaves are curling, S.M.T cannot clear the mites on its own. The original poster combined it with a bio-acaricide (a mite-killer made from natural or microbial ingredients), abamectin, or Beauveria bassiana (a fungus that infects and kills insects and mites).
It does not replace an IPM programme. Integrated pest management (IPM) means combining prevention, regular checks, beneficial insects and treatments, instead of relying on one spray. S.M.T is only a leaf wash. It is not a systemic pesticide (a product the plant absorbs and carries inside its tissue), so it gives no protection once it has dried.
It needs repeat sprays. Spray every 3 days for 7–10 days. The repeats catch mites that hatch from eggs the first spray missed.
Translator’s note: in Thailand, spider mites multiply fastest in hot, dry weather, so the months before the rainy season and air-conditioned rooms with low humidity are the high-risk times. A 3-day spray interval suits this, because at 30–35 °C a new generation of mites develops quickly. Spraying in the cool of the morning or evening also reduces stress on the leaves.
Translator’s note: Thai law allows only pesticides registered with the Department of Agriculture (กรมวิชาการเกษตร), used as the label says. This applies to abamectin, to any bio-acaricide and to Beauveria bassiana products. Check the registration number on the label before you buy. Check also whether the label allows use on cannabis and how many days must pass between the last spray and harvest. We could not confirm that Dr. Schimmel S.M.T is registered with the Department of Agriculture or officially sold in Thailand. Before you buy it, ask the seller for the Thai registration number. See also what you may legally spray under Thai GACP.
What you can do: before an outbreak, decide in writing which product you will use at which level of infestation. Record the date, product and dose of every spray, because a GACP auditor will ask for this record.
Quick comparison with SV Biotech MiteTech
The table shows the original poster’s impressions. No numbers or trial data support these ratings. A separate member review of MiteTech is on the forum.
| Point | Dr. Schimmel S.M.T | SV Biotech MiteTech |
|---|---|---|
| How it works | Leaf wash, blocks breathing holes (physical action) | Biological extract, destroys mite cell membranes |
| Effect seen | Moderate | Moderate to good |
| Organic level | Very high | High |
| Kills eggs | Yes | Yes |
| Heavy outbreaks | Moderate | Fairly good |
| Cost | High | Lower |
| Technical documents | Limited | Clear (Thai brand) |
Conclusion
- S.M.T: most suitable for gentle leaf washing and light infestations.
- MiteTech: more suitable for moderate to heavy infestations on a farm.
What you can do: check 10 leaves per bed with a magnifier twice a week. Count mites per leaf and note the result. If numbers are low, a leaf wash like S.M.T may be enough. If you see webbing or curling leaves, move straight to a registered acaricide inside your IPM plan.
Have you used Dr. Schimmel S.M.T or MiteTech in a Thai grow? Post your results below: the product, your dose, the temperature in your room and how many sprays it took.