Caterpillar infestation of Agapanthus
Agapanthus plants in Royal Ascot are suffering from an infestation by a caterpillar that burrows down into the core of the plant. The pictures below show what this infestation looks like.
Healthy Agapanthus plants Infested Agapanthus Burrowing marks on leaves
Caterpillar bores down into core of plant The culprit! Mystery caterpillar.
We consulted Richard Jamieson at Kirstenbosch, and he responded as follows:
A caterpillar which attacks Agapanthus plants first appeared in the South-Western Cape two or three years ago and reports of its presence are mainly from the Constantia/Newlands and Kenilworth areas.
Dr. Mike Picker, an entomologist at the University of Cape Town is in the process of identifying the caterpillar, which he believes has been brought down to the Cape with Agapanthus plants from upcountry, i.e Gauteng.
We must differentiate between two species of caterpillar. One of which eats the Agapanthus leaves and I do not consider it much of a problem. The new one in our area bores into the centre of the Agapanthus plants and also attacks the flower buds. This caterpillar has very distinctive black dots spaced all over its body.
A customer last year had a bad infestation and she followed my advice which was to clear away as many of the dead leaves and rotten bits as possible and then to spray with the insecticide ‘Ripcord’®. This year her plants have re-sprouted strongly and she has control over the caterpillar. Agapanthus plants have several adventitious buds on the stem/rhizome below the main growing point and easily re-sprout if the main shoot dies.
At Kirstenbosch Garden Centre we had a small outbreak in spring but one spray with ‘Ripcord’® had them crawling out of the centre of the plants and dying. My partner who is happier using an eco-friendly method used Margaret Roberts ‘Caterpillar spray’ (it contains Bacillus thuringensis, a natural bacteria) and has had excellent results.
Gardeners are always challenged by new pests and we will have to be vigilant and spray at the first sign of an attack. So it is not doom and gloom and I believe the pest will find its equilibrium and the panic will subside.
Everybody who has Agapanthus in their gardens or precincts are advised to spray for the caterpillar
The active ingredient of Ripcord® is a pyrethroid. Pyrethroids are synthetic insecticides based on natural pyrethrum. Natural pyrethrum is an insecticide made from the dried flower heads of chrysanthemum plants. It has been used as in insecticide for centuries, and as a lice remedy in the Milddle East called Persian powder. Early history showed the Chinese used pyrethrum as a cure for tapeworms and other worms in human stomachs and intestines... no deaths reported.
One of the advantages of pyrethrum and pyrethroids is that it is specific to insects and does not affect mammals or birds. But they are toxic to aquatic organisms.
Mammals and birds are able to quickly metabolise and eliminate pyrethrum; even very high doses are gone within 24 hours and there is no observed after effects. Some people may be allergic and the concentrate should be handled with the respect every insecticide deserves because it can irritate the soft skin of nasal, eye and reproductive areas. Many dogs are regularly bathed in pyrethrum washes; poultry and prized caged birds, which have a faster metabolism than mammals, have been completely dunked in it to kill mites and lice.
More about Agapanthus
Agapanthus is commonly known as "Lily of the Nile", but it is not a lily and all of the species are native to South Africa from the Cape to the Limpopo River.
	Agapanthus is a genus of herbaceous perennials that mostly bloom in summer. The leaves are basal and curved, linear, and up to 60 cm long. They are arranged in two rows.
	Agapanthus africanus is found only in the Western Cape Province, which is a winter rainfall area. The plants grow from the Cape Peninsula to Swellendam, from sea level up to 1000 metres, mainly in mountainous terrain in acidic sandy soil. They often grow between rocks and even in depressions on sheets of sandstone rock. The plants will not tolerate freezing weather for any length of time.
	Agapanthus praecox is found in the winter rainfall area of the Western Cape and also in the all-year rainfall region of the Eastern Cape. Most of the cultivated varieties of Agapanthus that are so popular in gardens world-wide are derived from A. praecox.