Clivia assassins – pests and diseases

Clivia is really quite a resistant little genus, with only a few serious pests and diseases that can be life threatening . Others, though not lethal, can seriously affect a plant’s appearance and growth . General hygienic culture conditions like good drainage, removal of infected plants and material and a spray programme can successfully prevent these pests and diseases from becoming a serious problem .

Just a note of caution when working with toxic chemicals: Read the instructions of all chemicals before use! Make sure that chemicals can be mixed without detrimental effects to treated plants – if not stated as mixable, test it first on a few plants before you treat your whole collection .

Plant pests

Lily borer ( crini, Brithys pancratii) Brithys species, also known as , are serious pests amongst members of the . They target , Cyrthanthus, , Nerine, Amaryllis and Clivia, to name a few. This destructive pest has three to four generations in nature annually and if a severe infestation occurs it can destroy plants within a few days. The Breakfast! The yellow and brown-black banding is easily distinguishable with its yellow and black or brown pattern of the Brithys caterpillar makes it easy to recognise . Only a mushy pseudo stem remains banding pattern. Young larvae emerge from a cluster of after Mr Caterpillar’s visit .

Growing eggs, usually on the underside (abaxial side) of leaves, and then start to tunnel into the leaf. Once inside, the larvae eat the soft tissue between the outer two epidermal cell layers, tunnelling their way towards the base of the leaf. Older caterpillars can even attack the bulbs, rhizomes or pseudo stems. They reach maturity when they’re approximately 40 mm in length. The larvae develop into pupae, which eventually mature into . Moths have two sets of wings: a darker, outer pair covering a lighter second pair. This pest is usually active in spring through to autumn (i.e. southern hemisphere from September through to April). r

Brithys with her eggs neatly arranged on the abaxial side of the leaf Brithys larvae in action . Various caterpillars can be seen in their Visible eggs and larvae can be squashed. Smaller larvae, inside leaves, are “home-made halos” towards the bottom of the leaf . Note that there protected from contact and stomach insecticides by the epidermal cell are two egg batches, one at the tip layers. A systemic insecticide is the best solution, probably with one of of the leaf, now brown-black due to tissue damage and fungal or the following active control agents: bifenthrin, deltamethrin, trichlorfon bacterial infection, and a second or cypermethrin. The same treatment can also be used for the lily batch on the bottom left, not caterpillar, Spodoptera pieta, a greenish caterpillar with pale lengthwise hatched yet . stripes. These larvae usually eat the softer tissue between the leaf veins to produce a skeleton-appearance on the adaxial side of the leaf.

Mealy bug Mealy bugs, members of the family Pseudococcidae, are usually not life threatening but can severely damage plants, thereby causing entrance points for viral and bacterial diseases. These small (3–6 mm) are covered with a white, waxy powder over their flat, oval-shaped bodies. Young, tender new growth is usually targeted and under severe infestations young leaves can be destroyed. Some species can also attack plant roots. Mealy bugs are

Growing clivias

shade-loving and prefer the undersides (abaxial side) of leaves, leaf sheaths and the tightly packed leaf bases of the pseudo stem. There are numerous products available for this pest and both systemic and contact insecticides can be used. In small infestations, methylated spirits can be used to wipe the leaves clean; otherwise products with the following active control agents can be used: chlorpyrifos, bifenthrin, mercaptothion, to name a few.

Mealy bugs prefer shade and can Other less common pests usually be found within leaf folds and on other shady, cool spots . Grasshoppers sometimes attack leaf edges but are usually not a serious pest. Catch them by hand or spray with carbaryl.

Leaf miners include various larvae of small moths and flies that can tunnel between the epidermal layers of the leaf. This allows entry points to other pathogens that will result in leaf death and unattractive appearance. Use bifenthrin or dichlorvos.

Scale insects are small, circular, flat insects (1–2 mm) with un-segmented bodies. Mature females are stationary, feeding on the same place for their Locusts do mechanical damage, usually to leaf margins . whole life. Colonisation takes place early via young adults. Chlorpyrifos, mineral oils or mercaptothion can be used to treat infested plants.

Snails and slugs attack the leaves, young buds and soft new growth. Catch them by hand or use carbaryl and/or metaldehyde.

Snout beetles, of the family Curculionidae, are dark brown to grey-black in colour and can be 5–25 mm in length. They target leaf edges resulting in large, round lesions, but only attack bulbous plants sporadically. A good contact or stomach insecticide usually works well (chlorpyrifos, mercaptothion). Good for gourmets (with garlic) – bad for clivias! Rodents attack plant roots or carry berries off to a hidden den. Various methods are available to treat infestations.

Fungal and bacterial pathogens

Bacterial and fungal pathogens prefer warm and moist conditions. Make sure that your medium drains well, that you don’t over-water and that there is good air movement. Rats do their own seed collecting Once you have noticed fungal or bacterial infection, remove the infected with no regards for your hybridising programme . plant or seedling immediately. Cut the infected plant tissue away with

Growing clivias a knife (sterilised after each cut) until there is no apparent infection left and allow the plant tissue to air dry after a good sulphur dusting. Beware of too much water. Sometimes the only treatment is to destroy the whole plant, including the soil, to prevent further spreading.

Damp-off (rot) is probably the most devastating disease amongst Clivia and can be caused by various fungi including Fusarium, Phytophthora, Pythium and Rhizoctonia. Occurring in growth media or spreading via contaminated water and unsanitary practices, these destructive fungi cause rot and Root rot – the silent and invisible enemy, until it’s too late! Drainage dieback at an alarming rate. Phytophthora prefers warm wet conditions and is usually the problem . occurs in waterlogged or poorly drained mediums, with plants showing drought symptoms. Pythium is devastating in seedling trays but can be easily prevented by cleaning and sterilising seeds before planting. A good systemic fungicide will take care of both these fungi. Rhizoctonia infection looks very similar to Erwinia (bacterial) rot, with plant tissues having a watery appearance. Beware of this fungus when transplanting plants and make sure not to over-pot. Use benomyl or thiophanate to treat infected plants. Fusarium infection is usually recognised by a wilting appearance and is almost always lethal. Benomyl might help.

Leaf dieback can be a major problem in Clivia and is believed to be the result of Macrophoma agapanthii. Leaves start dying from the tips, giving them the appearance of dried parchment, until the whole leaf dies. Cut the infected leaves back with sterilised scissors and seal the wound with flowers of sulphur or fungicide (i.e. mancozeb, dithiocarbamate).

Collar rot, caused by Sclerotium rolfsii, is almost always lethal and Leaf dieback has many causes, occurs in very high temperatures and humidity. Infected medium and/ from root rot to mineral deficiencies . or unsanitary culture conditions cause spreading of this fungus. Try dichlorophen, fludioxonil or pencycuron.

Rusts are yellow to red-brown pustules on the epidermis of leaves and can be caused by numerous fungi. They’re not lethal, but can weaken plants and make them prone for more severe fungal attacks. Use triazole, mancozeb, triforine or chlorothalonil to treat infected plants.

Erwinia carotovora is responsible for crown and soft bacterial rots.

This bacterium enters via wounds or stomata and cause a putrefaction Leaf damage by the sun should not smell. Use copper hydroxide or an antibiotic like tetracycline. be mistaken for disease .