What Do You Do When Verticillium Wilt Hits Your Plants?

Verticillium Wilt Cannabis
December 18, 2020

As a marijuana grower, you know there are countless enemies – all out to get the plants. Most of them, though, do not stand a chance as long as you stick to the fundamentals of gardening. Providing the ideal environmental conditions, for example, already eliminates many of the threats. Even so, some diseases such as verticillium wilt can strike when you least expect, causing catastrophic damages. Your defense against the treacherous causative organism is to arm yourself with knowledge – the first steps towards prevention and treatment.

Verticillium Wilt on Flowering Cannabis

The key to neutralizing any predicament is knowing precisely what is happening. You cannot rectify or fix a problem unless you have identified the cause. Verticillium wilt by itself is a potentially deadly disease. As if that is not enough, its symptoms are similar to numerous other common maladies. Because of that, misdiagnosis is likely to occur, thus making proper treatment too late.

You can reduce this disease’s risk by choosing a naturally hardy strain and starting with high-quality marijuana seeds. Furthermore, amending the soil with compost and ensuring adequate drainage helps keep causative pathogens at bay.

Being careful and diligent in providing the best conditions, though, is not enough to guarantee trouble-free cultivation. Not even when you make the environment hostile to causative organisms. Knowing verticillium wilt can still occur is precisely the reason why you want to keep on reading. You want to know how to identify and get rid of this disease.

What is Verticillium Wilt?

Early Stages of Verticillum Wilt

Verticillium wilt is a fungal disease of the roots that affects hundreds of plant species, including marijuana. The threat of this disease alone is enough for many commercial farming operations to turn to fumigation. Although it is chemical-based and harms the environment, the fear of ruined crops justifies the means.

Verticillium fungi thrive in moist, nutrient-rich soils. It is most troublesome in locations with a humid climate and an average temperature of 68-82°F. They cause widespread damage to the plants by attacking the roots and through xylem – the vascular tissue that transports water and dissolved nutrients, to reach other parts. The fungi cause a blockage in the xylem to slow down water transport while releasing toxins. This results in leaves turning yellow and wilting.

How Do You Recognize Marijuana Verticillium Wilt?

The signs of verticillium wilt are evident in the leaves and spread to other parts of affected plants. You should inspect the plants daily and watch out for these:

  • Leaves, especially those near the base, turning yellow, drooping, and dying.
  • Plant wilting severely without warning during the hottest time of the day.
  • Plant stems, especially near the bottom, turns brown. Other parts may turn grayish-brown.
  • Verticillium wilt affects isolated parts of plants, and you may see branches dying.

How Do You Prevent or Get Rid of Verticillium Plants?

Perhaps the right question is if it could be treated. First of all, not many people can diagnose verticillium wilt correctly. Even if you did, there is nothing much you can do – except rip the plant off the ground. Once the verticillium fungi infect a plant, it is as good as dead.

You also do not want to reuse the soil. For sure, more causative fungi are waiting to pounce on the next plant(s). If you have other plants that do not appear to be infected, you can do one thing. Prepare a new potting or soil mix in a sterile container. Transplant the remaining plants and observe for signs of infection. Hopefully, they have not yet been attacked. Do note that it is highly possible that trying to save these plants may turn out to be an exercise in futility. You could be wasting time, effort, and resources (new soil mix).

As for preventing verticillium wilt, here are the best practices:

1. Choose Strains with Strong Genetics

Choosing the source – whom to buy from – is of utmost importance. Only the most reputable and trusted seed bank can provide you with high-quality seeds. You can rest assured that the products are authentic, fresh, and come from the best mother plants.

Dubious sources may pass off one strain as another. They might be old or produced from frankly mediocre plants. These are concerns you do not have to deal with when buying marijuana seeds from a proven supplier. More importantly, high-quality seeds grow into healthy plants with almost no weaknesses in growth patterns. Their strong genetics allow them to have better resistance to pests and diseases.

2. Use High-Quality Soils

Avoid using cheap, ordinary soils. You want to harvest the best versions of buds – both in terms of potency and terpene profile. That is possible only with the use of high-quality potting mix or soils.

The reputable brands provide products that are sterile, free of harmful pathogens. At no time did you envision growing marijuana halfway and then having to ditch them all. Although you have to pay a little more, that is the price to pay for peace of mind.

Keep in mind that if you did encounter verticillium wilt on the off chance, ditch the soil used. These nasty fungi can live on for many years. It would be best to discard them and buy new ones.

3. Have Adequate Drainage

Verticillium fungi, as well as many other pathogens, thrive in a warm and high moisture environment. That is why you do not want the substrate to accumulate excessive water. If need be, amend the soil, such as with perlite, to ensure proper drainage.

For growing outdoors in the ground, do note that the water needs to drain downhill. If the surface is flat, build a small trench (French drain) with a 1-3% rock-filled downhill grade to prevent water pooling.

4. Best Practices in Growing Outdoors

Suppose you intend to grow marijuana directly in the ground. In that case, there are things you can do to reduce verticillium wilt and other fungal diseases.

Solarize the Soil

One of the best ways and the least practiced among marijuana outdoor growers is soil solarization. It is an environment friendly, free, and reliable method of preparing the soil to reduce or eliminate threats.

Essentially, you till the soil, add in compost, water, and cover with a transparent polyethylene tarp to trap the solar energy. The sun’s heat raises soil temperature to kill:

  • Bacteria
  • Fungi
  • Insects
  • Nematodes
  • Mites
  • Weed and Weed Seeds

Generally, you’d let the sun cook the nasty organisms for three weeks. Do make sure to time it when it is mostly sunny and hot.

Crop Rotation

You might also consider rotating crops, more so when you have harvested plenty of buds. It is a time-tested practice that allows you to diversify the crops (and produce) and prevent diseases. If you ever experienced any fungal infection, including verticillium wilt, grow cover crops – such as mustard, broccoli, or sudangrass – resistant to fungi. In the future, you can try soil solarization to eliminate the fungi, making it possible to grow marijuana again.

5. Grow Marijuana Using Hydro

Hydroponic Cannabis in DWC Bucket

Some geographical locations have an increased risk of verticillium wilt. For example, the Pacific Northwest’s warm and humid climate in the United States had higher infection rates than others. If that is the case, then try growing marijuana in a hydroponic system. This way, you do not have to deal with soil preparation and maintenance.

Hydro provides numerous advantages. However, it also comes with some challenges – none of which includes soil-borne diseases.

Avoid Verticillium Wilt at All Costs

Verticillium fungi are among the worst organisms that should never be introduced to the soil and allowed to thrive. Once they infect the roots, it does not take long for them to reach the host plant’s different parts through the xylem. Not only do they choke off water transport, but they also release toxins.

Infected plants have no chance at all. Even the soil is rendered practically useless. Of course, there are ways to neutralize the fungi first before growing marijuana again. Outdoors, for example, you could employ crop rotation and soil solarization. If you cultivate in containers – outdoors or indoors – you might as well replace the soil. Remember to sanitize everything, such as pots and tools, before starting again.