What's eating my arum lilies?
Summer is settling in, we've had good rain, plants are recovering, birds are singing, butterflies are flitting – did I say 'butterflies'?
Butterflies and moths, as innocent as they appear, have a definite sting in the tail. To have them we have to live with their myriad offspring which chomp, chew and generally deface our carefully raised beds of whatever it is we are growing. One of the most voracious of these is the caterpillar of the hawk moth, which is particularly partial to arum lily leaves, and a couple of them can strip a plant of all its leaves in a matter of days.
The eggs are laid individually, each under it's own leaf. Look for a spherical, yellowish ball about the size of a small bead. These hatch out into pale green caterpillars about a centimeter long. They hide under the leaves during the day but eat ravenously and grow at an alarming rate at night. As they grow their colour darkens and they lie along the upper stem of the arum where they blend perfectly. A week or so later the teeny weeny, cute little caterpillar is a staunch 7 or 8 centimeters long, it turns brown and descends to the base of the plant where once again it blends perfectly with its surroundings.
Eventually it will have eaten its fill and will make a rudimentary shelter at the base of the plant to await metamorphosis. The only damage to the arum lily is the loss of its leaves and it will recover. To save your arums, visit them regularly and check for eaten leaves, under which you will find the culprits. You may decide to pick them off and destroy the lot, but bear the results of this action in mind: birds will go hungry, night blooming flowers will not be pollinated and bats will be deprived of a protein packed 'snack on the wing'.
It's all about balance. Three seasons back, in my innocence and to my shame, I eradicated every hawk moth egg and caterpillar I came across, so decimating the population of hawk moths in my garden that I found none last season and only five this season, of which three disappeared before reaching maturity - presumably eaten by birds. This season I sacrificed a few of my arum lilies to protect next season's generation of hawk moths and with the exception of slugs and snails, snout beetles in my aloes (indestructible at best) and anything that attacks my food, I have learnt to live and let live.
I took the following series of pictures from the beginning of June until the middle of July 2011. The caterpillar ate its way through three bags of smallish arum lilies before it was ready to pupate. I hope to add pictures of the eggs, the hatchlings and the moth itself - if only I can find them! It's scary how long it takes for a species to renew itself after the damage is done!
Comments
Caterpillars
Your blog and pictures are so explanatory. I have seldom seen hawk months, but find them wonderful as well as the very large green caterpillar which I imagine to be a hawk month's. I write now to say that if one sees the whole metomophosis from egg to caterpillar to crysillis to moth is quite important. I kept some of the amaryllis caterpillars in a box with crinum leaves as food (I have many mooreii) until they became crysillus and then moth and eggs. Now I know what they all look like and can take action. I dont believe that these caterpillars are eaten by birds as they are yellow and black and as such tell birds etc they are poisonous. I found some cryssilus under the crinums today and could kill them.
Amaryllis caterpillars
Amaryllis caterpillars or Brithys crini pancratii are a scourge. I agree with you that birds and other vertebrates do not eat them - according to Wikipedia they are in fact poisonous. This pest is also known as the Lily borer and attacks crinums, clivia, scadoxus and haemanthus. I have had huge infestations of them and have been forced to use Blue Death. I have not really studied them and would like to know what the moth looks like. Could you perhaps describe it?
Amaryllis caterpillars
I replied as above and dont really have much to add. The moth of the Amaryllis caterpillar only likes the amarylidacea family not arums on which to lay its eggs and is a reasonably large one, very dark wings that fold back rather than spread sideways. I found a couple in my lounge the other night and they got squashed. The green caterpillars may be hawk moth caterpillars. I have seen some that are not so green, but may have been older. I wish I knew what nibbles the edges of yellow Arums. The hybrid coloured arums and white are not so attractive to whatever it is. My Crinum moorei are just starting to bud so they got a dose of Karbaspray. Sometimes I just powder all the plants and then water, but now I sprayed the flowers very specifically. I have a lot of crinums - 4 varieties.
Amaryllis caterpillars
As much as I like the hawk moth, I loathe the caterpillars! I may be acting really un-PC and ungreen, but I kill the buggers. Birds do not eat them. In two days I killed six which between them virtually destoyed my arums. Well, there are just about no leaves left on my plants.I am also not very keen on them attacking my clivias. Maybe I should resort to blue death as well, although I never use poisons of whatever nature in my garden.
Arum lily devastation
Hi Dudley I avoid using poisons in the garden at all but the pots in the nursery are terribly vulnerable and when an entire generation of 5 year old crinum bulbs is at risk of being annihilated, there's not much else to do. I have not had the hawk moth larvae attack my clivias yet - the amaryllis caterpillars enjoy them though. Perhaps give the arums a dressing of compost and water them regularly. They'll soon have a new lease on life.
CATERPILLARS
I must be lucky in only seeing one Hawkmoth caterpillar in my garden. I thought it very beautiful; did not kill it, just took a couple of pictures. What I did to was to collect about 10 of the amaryllis caterpillars and grow them on to see what the crysillus looks like and then the moth. During the time it took - about 2 weeks - for the stages to take place I found that the caterpillrs preferred the leaves of Crinum moorei to the crinum. In the new bulb book by Graham Duncan it is also stated that crinum leaves are their preference. It is not surprising that the crysillis is never seen - blends in with the soil. The moth tho is more obvious in that it is fairly large and nearly black. During the past few weeks I have killed off quite a few of these monsters. The amaryllis caterpillar likes all the amaryllis family which include nerines and cyrthanthus so if you are like me and like bulbs then it is best to control these horrors. I have managed to have quite a number of Crinum moorei flowering at the moment having sprayed the buds as they emerge. Not much in the way of leaves now as they die off and then reappear later. My Nerine masoniorum are just starting to flower so need attention.
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