DISEASES

This disease causes the most fast sudden spectacular death of Pinguicula threatening most often our “Mexican” Pinguicula collections.

This is during spring or hot summer days (or in hot terrarium) that this epidemic diseases occurs. Warning signs of this disease are a loss of vigor and no new leaf growth, plants have non-mucilaginous and dull green leaves. If you dig up your plant, you will note that no yound white roots are produced, and if previously they had some healthy, the roots turn brown, shrivel and die.

The rootless base of the plant becomes a black stump that looks like a tap root. The base of the leaf petiole then turn rusty-brown before the centre of the rosette blackens and the whole plant dies in few days.

It is amazing to see that the tips of the leaves are still green while their bases are brown.

Microscopic observations Dr. Laurent Legendre did, have shown each time a fungus identified as Fusarium. He noted also the presence of numerous nematodes. He suggested, following his microscopic observations, that the browning heart death in Mexican Pinguicula is associated with a combinaison of Fusarium and nematodes attack.

It is known that Fusarium spore and hyphae naturally present in the soil are normally unable to penetrate intact tissue meaning that they are unable to penetrate the healthy roots of our Pinguicula. But female nematodes enter the roots to feed. This leads to a weakening of the plants and Fusarium is able to enter the wounds made by the nematodes. This is the reason of the expansion of the disease from the center to the edge of the rosette.

- one is acting prevently against Fusarium with good growing bases and using a specific fungicide.

Not using the tray method : this is also an important source of spreading Fusarium spore in non infected area.

Some fungicides are available to amateurs collections and acting more or less on Fusarium :

(50 % de benomyl) but it is no longer available world wide as the company DuPont stoped to produce it in 2001.

140 g/l. of Oxyquinoline Potassium Sulfate (Sulfate double d’oxyquinoline and potassium).

Laurent Legendre wrote that most fungicides only stop momentarily the development of the fungus and should be told fungistats as its growth will resume about two weeks later.

You have to know that nematicides only reduce colonies, grandly, but never eradicate them.

Laurent had good success in Australia contaminated amateurs collections using this method : quarantine of the infected plants, improving ventilation, keeping the plants totally dry. Several weeks after, new growing points could be seen at the base of the petiole and at the center of the sick rosette.

This is also a sudden spectacular death for Pinguicula from the southeastern USA Pinguicula. The symptom appears in late winter/early spring when the temperature is raised too rapidly. It is characterized by a browning of the tip of the leaves that spread towards the center of the rosette.

On contrary of the previous disease, biological studies have shown that no pathogen were present.

This symptom occurs on winter-resting plants during rapid elevations of temperature, most likely stems from an internal metabolic imbalance resulting from a differential acceleration of the various metabolic pathways during temperatures rises. Enzymatic systems work as a chain factory so that the greater excitation of some elements by increased temperature over others will lead to the accumulation in the tissues of the plant of intermediate toxic metabolites that can lead to self poisoning. This explanation is compatible with the observation that, once induced, the dying back never stop even if the necrotic area is cut off).

Slower elevations of temperature are the only way of preventing this disease. Wild plants are prevented from this. In its natural environments, slower temperature elevations are more common than in greenhouses and allow survival since they provide more time for the plants to re-equilibrate their enzymatic activities and adapt to higher temperatures.

This is a filamentous fungus (first time mentioned by Casper in 1966) that esmaculates Pinguicula by infecting their pollen. The pollen appearing purple instead of yellow. It seems to touch only some temperate Pinguicula populations. For example, a population of Pinguicula longifolia subsp. dertosensis near Tortosa in Spain is totally infected by Ustillago Pinguiculae (J. Steiger in ……).

Close of the flower of Pinguicula dertosensis from Tortosa.

Photo : Eric Partrat

- May 2003 -

This does not allow infected Pinguicula to produce seeds. The fungus is spread through the flowers and pollinators: the anthers of infected Pinguicula plants are transformed into sporangia. Thus, the risk of becoming infected is related to flowering. Only a fraction of all mature individuals in a Pinguicula populations flowers a given year in wild. One reason for this could be to decrease the risk of becoming infected in wild. On the other hand, the infected plants are bigger that non infected Pinguicula. The fungus should then try to increased the flowering frequency in infected Pinguicula in a way of probably enhancing its fitness since this would increase the opportunities to spread and infect new plants. One could thus hypothesise that the fungus stimulates infected Pinguicula individuals to flower more frequently than non-infected individuals. Studies are under processing to confirm this hypothesis.

If you find a plant in your collection that is infected by this fungus, you must remove the plant as soon as possible as no treatment is available up to now.

The symptom is the formation of a round hole developped in the middle of the leaf lamina that expands to the rest of the leaf in a few days. This start at the spot where the leaves touch the growing mix and involves the total disappearance of leaf tissue.

The appearance of such holes can lead to the death of a whole leaf but rarely in the death of the whole plant.

Hole formation process on a leaf of a Mexican Pinguicula

Photo : Eric Partrat

This is again indirectly caused by fungus : Botrytis cinerea or Trichoderma sp.. These two types of fungus are necrotrophic pathogens that normally live upon dead plant parts. Trichoderma species are rarely pathogenic to plants and even act as biological control agents by preventing Pythium. Laurent Legendre observed that the Botrytis extracted seems to be incapable of infecting healthy Pinguicula leaf.

The holes are in fact the result of a potassium/calcium deficit in the plant due to a poorness of the soil.

A change of soil will lead to a disappearance of the hole formation process in few weeks.

This is a strange symptom : an healthy hibernaculum in winter revealing in early spring an empty hibernaculum. The heart of the plant seems to have been eaten totally inside the hibernaculum.

This is caused by a fungus, Pythium. Most of the time, the plant is able to produce new plantlets few weeks later but sometimes, the plant rot completely.

It is important to note that it is better to prevently treat the hibernaculum with a chemical product against Pythium. Unfortunately this product is very rare.

The following products have also propamocarbe Hcl in their composition and are authorized for garden use (in 2003).

The following fungicide also work against Pythium and used to be available in France :

It is amazing to compare the plants in habitat and the plants we grow. The latter are paler and even whiter. This is not really dangerous and result in a deficiency in various microelements such as zinc, boron or iron. Again, a better soil will lead to a re-greening of the leaves in few months.