The term ‘Clivia Pests’ include bacteria, viruses, fungi and insects.
- Clivia plants are evergreen plants, hardy, drought tolerant and enjoy partial shade.
Pests become a problem when the growing/cultivation conditions are not ideal. The poor management that contributes to problems is overcrowding of plants, monoculture – only Clivia plants in the area – possible cross contamination with viral infection when using the same utensils for cutting or pruning different Clivia plant leaves, some of which may be infected. The viral disease to be wary of is the Tobacco Mosaic virus that causes a mottled, mosaic pattern on the leaves. Practice hygienic gardening methods and prevent problems occuring. This includes removing dead and damaged leaves, leaves infected with mealie bug or fungal infection.
The main problem pests infecting Clivia plants are:
a) Amaryllis caterpillar (Lily borer, Brithys crinii) This caterpillar is the most destructive of the pests affecting Clivia. Take more interest in your Clivia plants and be on the lookout for these larvae that are mainly active during the warmer months of the year. The moths that lays the eggs of these larvae, fly at night and lay their eggs on the underside of the Clivia leaves. (Other plants are also targeted. The Crinum lily is both an indicator plant and one of the favourite plants to infect. The first sign of the hatching larvae being present, are markings on the upper side of the leaf that show where the hatched larvae are feeding. The larvae grow quickly and the larvae like to move and feed towards the base of the leaves, the growth point. The adult worms when they reach the growth point of plant cause the destruction of the main stem of the Clivia. Once the worms are controlled, you may be fortunate enough to have offsets grow from the base of the original plant.
To control these worms – larvae, requires the gardener to be alert and pick off the worms from the leaves as they are destroying the Clivia leaves. The other more convenient method is to use a pesticide. Inorganic pesticides are not popular and we learn of the contamination of streams and waterways! There are organic pesticides available, involving friendly bacteria (Bacillus thuringiensis), which are ingested by the larvae and destroy their digestive system and subsequently die. You must adhere to the instructions and repeat spraying required for the organic pesticide is to be effective. For those of us who wish to use inorganic insecticides, there are several available. The insecticides available are mainly contact or systemic. The contact pesticide is sprayed on to the leaves. The effect in on pests on the leaves. The systemic insecticide may be sprayed on to the leaves or used as a drench. The systemic insecticide is absorbed into the plant and the effect of the poison protects the whole plant. Caution is required when working with the inorganic pesticides. Avoid windy conditions and cover your skin surfaces and face. Use the correct dosage of the insecticide to avoid poisoning. The contact pesticide sprays, will wash off with water and need to be reapplied after rain and watering in the garden. Using a wetter or sticker solution with the contact spray allows a uniform coverage of the leaves and does not wash off as easily.
b) Mealy bugs.
This is a major problem for Clivia growers. More disfiguring of plants than lethal. Poor cultivation conditions like overcrowding – poor air movement between plants, weather conditions – hot conditions. The bugs are found on the underside of the leaves, often older leaves, but anywhere if the infestation is severe. To control these pests a systemic pesticide or contact pesticide or mineral oil may be used. As with all pests the earlier they are detected and managed the easier they are to control.
c) Scale.
There are several types of scale and they spread at an alarming rate. Early detection is important. The hard bodies of the scale often remain on the leaves after they die and need to be scraped off. The scale often discolours the leaf and leaves a light green colour around the scale insect. Management here is with pyrethroids or an oils like oleum or neem oil.
d) Snout beetles.
More prevalent in the Cape province of South Africa. They feed and leave a nothched patterns on the edges of the leaves. Control with a pyrethroid. A sticker or wetter may allow a longer effectiveness of the pesticide.
e) Thrips.
These pests are minute – small and cause damage to the edges of the leaves. They often spend the winter in the soil of the plants. New growth promotes their multiplicaton. Pyrethroids are effective in controlling these pests – follow the instructions.
f) Snails and slugs.
These pests flourish in damp conditions. They rasp the leaves to eat them. The shiny trail is an indication of their presence. Any snail bait may be used, but water destroys the effectiveness of the bait.
g) Fungal diseases.
The brown marks on your Clivia leaves are usually caused by a fungus called Colletotrichum (anthracnose). The spores causing the damage may spread to adjacent leaves and plants by watering, rain or by wind. Damaged leaves need to be removed to stop the spread. If the damage is extensive use a systemic fungicide and follow the instructions. A contact fungicide may be used when the damage is not extensive. Systemic fungicides may affect blooming so avoid using them when there is flower formation in Spring, rather physically remove the damaged leaves.
h) Bacterial infections
The common bacteria involved here is Erwinia carotovora. Most garden centres don’t sell bacteriacides. The mass of damaged leaves has a strong smell. Physically scrape the rotten tiussue away and apply sodium hypochlorite – bleach or potassium permanganate to affected site. New growth may occur from the base of the plant.
i) Viruses
It is not always easy to know if you have a viral infection present in your Clivia leaves. A mosaic pattern is what is used to identify the presence of a viral infection. Some leaves display patterns that mimic the mosaic patterns when the feeding programme is deficient. If in doubt isolate the plant and try feeding high nitrogen fertilizers. There is no cure for a viral infection in a plant and they should be removed and not used for compost making.