Print
Parent Category: Buzz
Category: 2015 - June/July
Hits: 2795

It was in my Cape Town garden that I first noticed that the Agapanthus plants were dying back. On closer examination, I discovered that a caterpillar had burrowed into the base of each of them, that the leaves were dying from the outside in and that the fleshy bits at the bottom were rotting. [“Ah, a lotten lizome,” noted my Malawian gardener, Patlick!] I immediately consulted the fount of all knowledge – the Internet – and learnt that this nasty little creature, still unnamed, was a relatively new arrival in the Western Cape. It is thought to have originated in Gauteng and, omehow or other, had travelled the 15,000-odd kilometres to Cape Town. Constantia was the first suburb to be affected, but the infestation soon spread to other parts of Cape Town, where it is now a serious problem. For not only are thousands of gardens affected, but the huge plantations of Agapanthus that line the streets and highways are dying back – a tragedy if one considers how they contribute to the beauty of Cape Town when they flower in October and November.

A year ago, I noticed that the Agapanthus growing in my Betty’s Bay garden were similarly infected and this probably means that yours are too. Or if they are not, they soon will be. We all need to take urgent action if this scourge is to be halted.

a 032
A healthy plant.
a 033
Infested plant
a 034
Burrowing marks on the leaves
a 035
Caterpillar bores down into core
a 042
The culprit at close range

Luckily, it is very easy to get rid of the pest. You add a teaspoon of a poison called Ripcord ® to five litres of water in a watering can and water the plants with the solution. You then water them some more with the garden hose. The caterpillars will emerge and die and, in no time at all, your Agapanthus will be on the road to recovery. It is advisable to repeat the process two weeks later, to get rid of any newly-hatched caterpillars that might have appeared in the interim and then to give the plants a dose every couple of months as a prophylactic.

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 and it has been used as an insecticide for centuries and as a lice remedy in the Middle East called Persian Powder. Early history showed the Chinese used pyrethrum as a cure for tapeworms and other worms in human stomachs and intestines, with no deaths reported.

One of the advantages of pyrethrum and pyrethroids is that they are specific to insects and do not affect mammals or birds. However, they are toxic to aquatic organisms so be careful when you are applying poison near garden pools. Mammals and birds are able to quickly metabolise and get rid of pyrethrum; even very high doses are eliminated within 24 hours and no after-effects have been observed. In fact, many dogs are regularly bathed in pyrethrum washes and poultry and prized caged birds, which have a faster metabolism than mammals, are often completely submerged in a pyrethrum wash to kill mites and lice.

If you do not like using synthetic insecticides, there is an alternative. You can use Margaret Roberts’s Caterpillar Spray with equally good results. It contains Bacillus thuringensis,
a natural bacterium.