Nematodes on orchids

Orchids are among the most exquisite and beautiful plants, capable of gifting you with their beauty and fragrance for many years. However, like all plants, orchids are susceptible to various diseases and pests. One of the most dangerous enemies of orchids is nematodes — microscopic worms that can cause significant harm to the plants if not addressed in time. In this article, we will discuss how to identify nematodes on orchids, the symptoms of their presence, and how to properly treat your orchid to restore it to its former glory.

What are nematodes?

Nematodes are microscopic worms belonging to the roundworm phylum (nematoda) that can parasitize plants, damaging their roots, tissues, and vascular system. On orchids, they most often affect the roots but can also penetrate stems and leaves. Nematodes can cause stunted growth, yellowing leaves, and even the death of the plant if timely measures are not taken.

Stages of the nematode life cycle

1. Egg

Female nematodes lay eggs in plant tissues, soil, or substrate. The eggs are protected by a dense shell, making them resistant to adverse conditions.

• Duration: 5–10 days (depending on temperature and humidity).

2. Larva (juvenile stages i-iv)

Larvae go through several molting stages:

• First molting: occurs inside the egg before hatching.
• Subsequent stages: larvae penetrate the roots or tissues of the orchid, feeding on cell sap.
• Duration: 1–3 weeks, depending on environmental conditions.

3. Adult (imago)

Adult nematodes reach 0.5–2 mm in length. They reproduce rapidly through sexual or parthenogenetic reproduction, laying hundreds of eggs.

• Lifespan: 2 to 3 months.

Favorable conditions for nematode development

1. Temperature: +20…+30°c — optimal range for most species.
2. Humidity: high humidity (60–80%) promotes their reproduction.
3. Substrate: old, poorly drained, or contaminated substrate.

How to recognize nematodes on orchids?

Nematodes on orchids are difficult to spot as they are microscopic organisms. However, there are characteristic signs of their presence that can help you detect an infestation early.

1. Yellowing and wilting leaves: the first signs of nematode infestation are yellowing and wilting of the leaves, especially at the bottom of the plant. The leaves lose their firmness and become soft to the touch.
2. Stunted growth: an orchid affected by nematodes will show slow growth, and blooming may be sparse or nonexistent. This is because nematodes damage the roots, disrupting the plant's nourishment.
3. Root damage: nematodes damage the orchid's roots, which can lead to rot. If you remove the orchid from its pot, you'll notice that the roots become soft, dark, and can easily break off.
4. Vascular damage: nematodes can also penetrate the plant's vascular system, leading to disrupted transpiration and nutrient processes. Light or yellow stripes may appear on the leaves as a result of vascular damage.
5. Nodules or swellings on the roots: sometimes, you may notice small nodules or swellings on the roots — this could also be a result of nematode damage.

To confirm the presence of nematodes on your orchid, laboratory analysis is required, as they can only be identified under a microscope. However, by closely examining the plant, you may notice several signs that suggest a potential infestation.

For a better understanding of how nematodes appear on orchids, see the nematode on orchid photo below.

Nematodes on orchids: treatment and control

Once you detect nematodes on your orchid, it is crucial to act immediately to treat the plant. Here are several methods to effectively control these pests:

• 1. Remove infected soil

Nematodes often reside in the soil and on the roots, so the first step is to remove the infected soil. Gently remove the orchid from the pot, clean the roots of the old substrate, and carefully inspect them for damage.

• 2. Root treatment with hot water

To kill nematodes, you can treat the orchid’s roots with hot water. Submerge the roots in water at 45-50°c (113-122°f) for 5-10 minutes. This method helps kill nematodes without harming the orchid itself. After the treatment, rinse the roots with cold water.

• 3. Use of chemical pesticides

For more severe infestations, chemical treatments can be used to control nematodes. Effective products include fumigants or soil treatment systems containing substances that kill nematodes. Examples of such products are vermisan or metam-sodium. Be sure to follow the instructions on the label when using chemical treatments.

• 4. Repot the orchid in fresh substrate

After treating the roots, the orchid should be repotted in fresh, sterile substrate. This will help prevent re-infestation by nematodes. Ensure that the new substrate has not been previously contaminated.

• 5. Use of biological pesticides

If you prefer more eco-friendly and safe methods, biological pesticides can be used, such as nematocide or trichoderma. These products contain beneficial microorganisms that fight nematodes without harming the orchid.

• 6. Regular prevention

Once you have rid your orchid of nematodes, it is essential to carry out regular preventive treatments. Regularly inspect the plant for signs of damage, maintain optimal growing conditions, and avoid overwatering.

Conclusion

Nematodes on orchids are a serious threat to the health of your plants. However, with timely diagnosis and the use of proper treatment methods, you can eliminate these pests and restore your orchid to health. By using methods such as root treatment, chemical pesticides, biological remedies, and regular prevention, you can keep your orchids healthy and beautiful.

If you've noticed nematodes on your orchids, don't delay in addressing the problem. The sooner you take action, the quicker your plant will recover!