BALFOUR  GREENHOUSES

• Insects and Mites
• Diseases
• Virus
• Physiological Problems

This page was created with the intent to offer some help in identification of common problems and diseases in Kalanchoe production. The text is largely based on our own experiences and on those of other Kalanchoe producers. We cannot guarantee the accuracy of the information contained in this page, and we would appreciate comments, critiques and additional data, which could be included in future updates.
We cannot give any advise with regard to the use of pesticides, because regulations and conditions vary greatly between the locations of various producers. We would encourage you to contact your local advisor or extension-specialist for answers to pest control questions.

Insects and Mites

Aphids

can be a serious problem in Kalanchoe, particularly in Winter and early Spring. Aphid populations may grow at an explosive rate if they stay unchecked. Aphid parasites, Aphidius colemanii, have worked far better for us than chemical control. Early detection of even small aphid populations is important for this biological control to work effectively.

Western Flower Thrips

appears in comparatively small populations. Nevertheless it is a serious pest. In  Kalanchoe, Thrips do not likely feed on flowers but rather on the tender tissue of the growing tips of actively growing plants. The damage shows as scars and deformations on the new leaves as they unfold some days after the feeding. Western Flower Thrips also acts as a vector for Impatiens Necrotic Spot Virus.

Biological control seems  possible in very controlled environments. We recommend to monitor your thrips population weekly with the help of sticky cards. Even small counts of adult thrips on the cards should be cause for concern in Kalanchoe crops.

   © 1.) Thrips damage on Kalanchoe leaves.

(click on thumbnail to see full size image)

Mealybugs

cause damage through feeding on axillary buds and growing tips. Mealybugs are hard to eliminate from the greenhouse, and early detection is again the key to good control. Fairly small populations can cause significant damage, because usually plants that have been infested cannot be marketed anymore. We recommend to make immediate spot-treatments wherever mealybugs are found in the greenhouse. All employees should be trained to identify and report even small numbers of these insects. Within the greenhouse, Mealybugs can be transmitted on hands or clothing of anyone that handles infested plants. We recommend to stop all work in the immediate area of the infestation until all affected plants are removed and plants, benches, and walkways have been treated appropriately.

Cyclamen Mites

can be a problem in Winter. First symptoms include stunted growth, deformed growing tips, and deformed and discolored flower buds. To identify cyclamen mites you should have a microscope with a magnification of 20X or more. Sometimes the mites are not easy to find. They often hide inside the flower buds or between the young leaves around the growing tip. Be sure to open some buds and to look at several locations when you check for these mites. Cyclamen mites do not seem to like warm temperatures. They are seldom a problem during summer months.

  © 1.) Damage from Cyclamen Mites

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Leaf Rollers

are the larvae of a moth species. The leaves roll up around the feeding larvae in a very typical pattern. Damage can be quite severe if an outbreak stays unchecked.

  © 1.) Leaf Roller

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Fungus Gnats Larvae

tunnel up in the stems of cuttings and young plants. The larvae are 2-4 mm long and worm like, with translucent to whitish appearance and a distinctive black head.  The damage is usually connected with an infection by a stem-rot fungus (see below). Damage control should include application of an appropriate soil fungicide.

 

Diseases caused by fungi

Powdery Mildew

is probably the most serious fungal disease in Kalanchoe. Identification is not easy, because an infection has to be very serious before you can see the well known white fluffy mold. In most cases the visible symptoms are limited to locally stunted growth, deformed leaves and growing tips, deformed flowers, and dark-grey scar tissue on leaf-nodes and along stems. Often the fungus itself is only visible under a microscope. Chemical control is difficult as many Powdery Mildew fungicides are phytotoxic on Kalanchoe.

  © 3.) © 2.) Powdery Mildew damage on Kalanchoe

(click on the thumbnails to see full size image)

Botrytis

can cause leaf and stem rot  in Kalanchoe during dark winter months. To avoid problems keep the foliage dry and allow for good air circulation within the crop. Drastic changes in the greenhouse air temperature can cause condensation, -and Botrytis infection-, on Kalanchoe leaves. Keep in mind that many Botrytis fungicides leave very visible residue spots on the leaves.

  © 1.) Botrytis infection

(click on thumbnail to see full size image)

Rhizopus

can develop in warm, humid conditions. The fungus is an opportunistic pathogen that infects weak, soft tissue. This disease can also occur during shipping if the environment is kept too warm and humid.

  © 1.) Rhizopus infection on stem

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Myrothecium

can be a problem during propagation in connection with Fungus Gnat infestation (see above). Problems are also possible in dense crops with little lateral air movement and warm-humid micro climates between the plants.

© 1.) Myrothecium infected stems

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Phytophtora, Thielaviopsis, Rhizoctonia, Cylindrocarpon and others

A variety of stem rots can affect Kalanchoe. Usually one of these fungi can be found on affected plants, but the damage is most often caused in combination with Fungus Gnats tunneling in the stem. Treatment should target the insects as well as the fungus. Poor watering practices can trigger severe outbreaks of stem rot.

  © 3.) Stem rot

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Pythium

The root system of Kalanchoe is very sensitive to inadequate watering. Too wet or too dry will cause problems. In our experience Pythium appears mostly as a secondary disease under poor conditions. Kalanchoe can survive on very few roots. If the conditions for the roots are not perfect, the plant will simply abandon part of its root-system. This may allow Pythium infections to get established

© 3.) Damage to the root system

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Virus in Kalanchoe

Kalanchoe Mosaic Potyvirus (Green Island Virus)

This is probably the most common virus in Kalanchoe. The virus appears to be very widespread in many modern Kalanchoe Hybrids. In most cases there are no visible symptoms. The virus will only show under poor growing conditions, and only in heavily infected plants. Symptoms are dark green mosaic-like spots on the foliage. In very severe cases there can be some growth inhibition. To our knowledge there are no immuno-assay tests available. Aphids seem to be vectors for this virus.

  © 1.) © 1.) Symptoms of Green Island Virus

(click on thumbnails to see full size image)

Impatiens Necrotic Spot Virus

This variation of Tomato Spotted Wilt Virus can cause a range of symptoms in Kalanchoe. Symptoms sometimes resemble damage from mistakes in cultivation. The virus is transmitted by Western Flower Thrips. Testing is available but can be unreliable..

    © 2.)© 2.)© 1.)INS Virus

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Yellow Spotted Virus

This virus causes symptoms of chlorotic and necrotic spots. We are not aware of any immuno-assay test for it. Kalanchoe cultures that are infected with this virus should be destroyed.

Kalanchoe Latent Virus

is sometimes referred to as KaV-1 and KaV-2. It is very rare that this virus shows any symptoms at all. ELISA tests are available.

Carla Virus

Symptoms are light green to yellow  mosaic-like spotting of the leaves. Tests for this virus are available.

Physiological problems

Spray Damage

Some pesticides can cause severe phytotoxicity damage on Kalanchoe flowers and leaves. Many EC formulations cauterize the cuticula on the leaves and petals. The result are discolored flowers and scars on the leaves.

   © 3.) © 2.) Damage from pesticide sprays

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Flower Damage

Many factors can cause flower damage in Kalanchoe. Constantly high relative humidities play a role in most cases. A good supply of calcium starting early in the crop, and efforts to keep the plants active should help to avoid this problem. Certain sensitive cultivars seem to develop specific types of flower damage under unfavourable conditions .

© 2.) Flower damage caused by water or high humidity

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Damage from too short nights

Kalanchoe need a minimum of 6 hours of darkness every night, even during longday treatment. Too long duration of night interruption can lead to chlorosis in the active leaves.

© 2.) Too much artificial light

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Ethylene damage

Ripening fruit in storage buildings or in retail stores produces ethylene-gas. Exposure to even small concentrations of ethylene may cause Kalanchoe to drop open flowers and abort all flower-buds within just days. This is an important consideration when shipping, storing, or displaying flowering Kalanchoe.

Malfunctioning CO2 generators can also cause ethylene damage in production greenhouses.

Stress

Stress to Kalanchoe can be caused by a number of factors. (water, light, temperature) In mild cases the plant might react merely with discoloration of the adult leaves. If the stress is severe, growing tips can start to produce ethylene internally. This leads to symptoms which are typical for ethylene-gas poisoning: Growth comes to a complete halt, growing tip turns intensive red, and flower buds may be aborted.

© 3.) Stress damage (internal ethylene poisoning)

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Chimera

Chimera are caused by genetic defects.

© 2.) Chimera

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photos © 1.)  copyright Nederlandse Algemene Keuringsdienst voor Bloemisterij en Boomkwekerijgewassen
photos © 2.)  reproduced with kind permission of Mr Ike Vlielander at Fides, De Lier
photos © 3.)  Balfour Greenhouses Ltd.
Last updated on February 2, 1998; Page designed by Albert Grimm