It’s hard to overstate how horrifying Panama disease is. It is literally wiping out the banana industry across the globe. But even if you aren’t a commercial grower, your banana plant is at risk.
Panama disease is quick-acting, spreads easily, and is highly destructive. Once it reaches your property, the chances are extremely high that your banana will be infected.
If you are growing bananas, you absolutely must read on and get acquainted with this devastating fungal disease.
What We’ll Discuss:
What is Panama Disease?
Panama disease is also known as fusarium wilt and is caused by a fungus called Fusarium oxysporum f. sp. cubense tropical race 4, syn. F. odoratissimum. Fusarium is a soil-borne fungus that can live in the soil without a host for years.
The fungus infects the plant’s vascular system and can infiltrate all parts, from roots to stems to leaves. It clogs the xylem of the plant, preventing water movement, causing wilting and tissue death. Using the plant’s central system means it can travel fast and annihilate the host plant in no time at all.
Panama disease is the most destructive banana disease worldwide. A different race wiped out the ‘Gros Michel’ cultivar decades ago, and this new race is expected to wipe out the ‘Cavendish’ cultivar eventually.
‘Cavendish’ makes up the vast majority of commercial banana crops and is the one you find in grocery stores. Because this is a monoculture industry, it’s susceptible to the widespread devastation of this nature.
Different races of this fungus target different banana cultivars, making it a significant threat to banana cultivation.
Experts are working on breeding a resistant cultivar, but until then, we are left dealing with this significant issue.
How it Spreads
Panama disease primarily infects its new host through young root development, whether that’s new roots or young plants.
It attaches itself to the fine hairs on the plant roots and enters via any damaged areas. Such damage can be due to insect impact, tools, transplanting, propagating, or even pet digging. Microscopic worms called nematodes can even create entry holes.
This horrible disease will also infect root-cutting propagations and penetrate any soil near the host plant.
It is easily spread through water droplets that move through the soil or the air. It can also be carried on gardening tools, shoes, skin, and pretty much anything else it comes in contact with.
Waterlogged soil and humid environments are highly likely to accommodate this disease and other similar fungal pathogens. High temperatures, along with moisture and humidity, are favored conditions for the development of the Fusarium fungus.
The disease can live in the soil for up to 40 years, and if detected, replanting susceptible cultivars must be avoided.
Races of Panama Disease
Four known races of this disease can impact banana plants, and the severity of the disease depends on the cultivar of the banana you’re growing.
The different races are referred to as Foc (for Fusarium oxysporum f. sp. cubense) and given an R number (with R meaning race). You’ll also see them referred to as TR1, TR2, TR3, and TR4.
Foc R1
This race of Panama disease infects the banana cultivars ‘Lady Finger,’ Gros Michel, ‘Sugar,’ and ‘Ducasse.’ It all but destroyed ‘Gros Michel’ plants worldwide in the 1950s to 1960s, particularly in Latin America, where they were grown commercially.
‘Gros Michel’ was the commercial favorite, and the emergence of the disease destroyed entire banana empires. So much so that ‘Cavendish’ was grown to supersede ‘Gros Michel,’ as it proved to be more resistant to Foc R1.
This race exhibits prominent symptoms, with yellow leaves leading rapidly to necrosis, and a skirt of dead and decaying leaves. The dead, brown leaves aren’t aborted by the banana plant but remain in place until the plant dies.
Foc R1 has been a significant issue in subtropical areas and moisture-prone regions.
Foc R2
This race primarily infects cooking bananas and plantains such as ‘Blue Java’ and ‘Bluggoe.’
As this race develops, as with other races, it causes a blockage of the host plant’s vascular tissue. This prevents the plant from taking up and transporting water in order to supply essential nutrients.
It was discovered and confirmed as a race of Fusarium soon after Foc R1 was identified in the mid-20th Century.
Foc R3
This race target was thought to target bananas, but we have since found that it infects Heliconia species. Foc R3 was thought to infect ‘Gros Michel’ and plantains, but we now know that’s not the case.
This race has been reclassified as F. oxysporum f.sp. heliconiae and is not of concern to bananas.
Foc R4
This race is the one destroying the banana industry today, just as R1 destroyed it in the 1950s and 60s. Discovered after the devastation of R1, it doesn’t just harm ‘Cavendish.’
Even though this race poses a huge threat to the global ‘Cavendish’ banana market, it can also be found in other cultivated and wild banana plants.
Its spread has been slower than R1s’, mainly due to biosecurity controls implemented after we learned from the first race. For example, R4 only reached Australia in 1997 and the Americas in 2019, but was first identified in Taiwan around 1967. That’s a long stretch of keeping it contained.
Signs and Symptoms
Once a plant is infected, it’s toast. However, early detection and action could save your other plants and prevent the disease from spreading.
Older parts of the plant, such as leaves, are often the first to show signs of Panama disease. Here are the signs:
- Yellowing of lower leaves progressing up to top leaves
- Purple or black coloring following the yellowing of leaves
- Signs of water or nutrient stress, like wilting
- Splitting of the plant stem
- Brown streaks on the stem
- Vascular discoloration on foliage and stem
- Rotting branches, fruit, and foliage
- Plant growth is stunted
- Premature ripening of fruit
- Severely reduced fruit yield
- The plant lacks vitality, quickly deteriorating
If you cut the plant open, you’ll see brown streaks and necrotic areas.
These symptoms can vary depending on the cultivar of banana and the specific race of the Fusarium fungus causing the infection.
Panama Disease Treatment
There is no treatment that will stop or reverse Panama disease. Eventually, it will kill the host plant and move on to destroy others.
As a soil-borne disease, it’s not contained within the host plant and can spread easily in the ground. Therefore, early detection and removal or quarantining of the infected plant is vital.
Unfortunately, this disease is highly resistant to fungicides, including topical, injected, and soil treatments. Eradication of this disease from the garden can be a lengthy and difficult task, particularly for the home gardener who has more limited resources.
Take care when working around the plants so as not to damage root systems through digging or planting.
Always remove and destroy infected plants and plant debris properly to prevent the spread of the disease to other areas of the garden. Keep weeds out of the garden, as well.
There are studies showing the beneficial bacterial strain CSR-D4 Bacillus licheniformis can help kill Fusarium spores in the soil. Beneficial fungi in the Trichoderma genus also show promise.
Solarizing the soil is one of the best ways to kill Fusarium spores. Read our guide on how to solarize your soil. If you want to be extra certain to kill off the pathogen, solarize well once, turn the soil over, and solarize again.
Even then, you might want to plant a Fusarium-immune species for a few years to help the soil become re-established without risking the disease. Solarized soil is depleted and needs a few years to develop a healthy colony of beneficial fungi and nutrients.
Prevention
Above all, practice good hygiene when working in the garden. The disease can be easily transferred on the bottom of shoes, tools, splashing water, pets, gloves, and anything else that can carry a soil particle.
You can’t see the spores that cause Panama disease with the naked eye, so take hygiene precautions at all times.
Biological controls can reduce the hospitable environment in which the fungus grows. Adding certified clean, good-quality organic matter or compost will assist with proper drainage and improve soil health. Both are key prevention steps.
Use permaculture principled practices as much as possible in the garden to encourage a healthy balance of microorganisms and nutrients. That means avoiding harsh chemicals, rotating plants, and working to nourish the soil.
Always observe and quarantine new plants for a week or so to ensure their health before adding them to your garden. If in doubt, throw them out.
Keep plants well-spaced to avoid disease transmission.
You might be able to choose resistant cultivars from a local grower. They’ll know what works in your area and what has shown some resistance. Since Foc R4 is the major problem right now, it’s probably smart to avoid ‘Cavendish’ altogether.
Cover Crops and Plant Rotation
Plant cover crops to suppress weeds and support the natural biome of the soil. This will make the soil stronger and less inhabitable to this disease in the first place.
When it comes time to replenish your stock, consider planting rotating crops and avoiding replanting bananas in the same soil. Banana plants don’t live long and are usually only productive for a few years.
When you need to replace them, plant something else in its place for at least five years. Then, you can rotate the bananas back in.
Rotate with crops that aren’t hosts to the Panama disease and Fusarium to break the disease cycle. Remember, this disease only infects Musa and Heliconia species, so literally anything else is fine.
Another tactic to deter this disease is to interplant alongside your bananas. A large group of bananas is more susceptible to the disease than one single plant surrounded by something different. Maybe try pineapples, agave, mangoes, or papayas in between.
Care should be taken when intercropping, as harvesting crops can damage the root systems, and competition for nutrients needs to be avoided. Don’t plant any root veggies nearby.
Panama disease reminds us that it’s not just plant health that is important. The soil rhythm and balance must also be nurtured.
