Tuesday, February 28, 2012

Agapanthus borer

Klein Constantia wine estate

It is hard to explain just how deep agapanthus run in the veins of South African horticulturists. Their blood is blue.

Kirstenbosch Botanical Garden

When I was little there was one kind of agapanthus (probably straight A. praecox) - big, pale blue, like the ones above - blooming over the December and January school holidays. So associated with South African summers that we called them Christmas flowers. Ooh, look, Mommy, Christmas flowers! The lagoon at Knysna ringed with them, beside the other ubiquitous holiday plant, hydrangea. Great pink and lilac mopheads gradually paling under the hot southern sun. Years that felt like lifetimes.

Agapanthus were the plants you forgot about. They bloomed, no matter what you did or didn't do to them. So they were planted en masse, beside highways and  in parking lots and on sidewalks.

Kirstenbosch

Then came the breeding boom. And agapanthus are now not only the pale blue moons of my childhood. They are fat and round, graceful and pendulous, deep purple, black and bright lilac. Bi-coloured and statuesque, pure white and tiny, whispering with blue ruffles or singing with intense sapphire. The hybrids are endless. They are highly collectable. They are everywhere.

My mother's garden

Before the bust comes the bubble, right?

Kirstenbosch

Enter the agapanthus borer, family unknown. That's right. It is nameless. So far.


It started with a bud, last December. The green wasting from it, the colour turning yellow, the sap drying up so that the plump point became soft. Soon, other buds began to droop. On closer inspection, a black hole in the bud or at its base. A bruise on the stem. Violence had occurred.


Snap it off and the hole extends into the long stem. Cut the stem open lengthwise and is revealed a striped caterpillar, entombed. Bud after bud succumbs.


It is hard to not to be filled with revulsion at a creature whose only purpose in life seems to be to destroy beauty. An army of one (by one, by...). The caterpillars are the offspring of a moth.

I started searching the web. Nothing. Except a discussion in June 2011 in a Cape Horticltural Society newsletter where Mike Picker, who wrote the book on insects (literally - The Field Guide to Insects of South Africa, published by Struik) writes:

“I have noticed it in my own garden as well, and as you have no doubt observed, it attacks both the buds, stems and rhizomes of Agapanthus. It is a moth larva, and it’s the first time I have seen it, so I suspect that it has just appeared/spread this year [2011]. It may represent a species from another part of SA, as many insects have moved southwards recently. I think it might turn out to be a real problem, although insects are very sensitive to short-term climate variations, and this summer was very unusual in that regard.I have done a quick scan on the net, and there appears to be nothing on them. I can't be certain of the family, although they are probably Noctuidae (same family as the Crinum borer, Brithys crinii).”

He then invites members to bag suspects and drop them in his mailbox!

But if you do have the borer, please take a picture of it (in focus!) and please write to Dr Picker, indicating your suburb, and evidence of the borer (description of affected plants, lack of flowers, rotting of central leaves and rhizome, and possible observation of the caterpillar). Include the date when it was noticed.

Send observations to :  mike.picker (at) uct.ac.za

The signs of a borer attack are yellow and brown central leaves in an agapanthus clump, that pull away easily from the plant. The caterpillars generally enter the flower bud and eat their way downwards through the flower stem into the rhizome, partially destroying it. The result is a lack of flowers on most agapanthus. The caterpillars are found on and in rhizomes that are dug up, or in stems, and are cream with black spots.


And I, alarmist that I am, connector of crawling dots, photographed these disas on Table Mountain (where Agapanthus africanus occurs naturally) and suggested on iSpot that this may be evidence of the borer. Botanical firebrand Dr Tony Rebelo's response was dismissive (correctly so, if we're talking science): "Did you dissect the parasitized buds? What on earth makes you suspect Agapanthus Caterpillars?: Why not Arum Lily Borers or Fig Tree Borers? Get us a critter and we will try and identify it without prejudice or preconception. Something has to stop the world being covered sky high in Disa uniflora!!"

So the man has a sense of humour.

Disa bud, Table Mountain

Fine, all true. But as a non bona fide botanist I was not about to start picking Disa uniflora in the national park.

But circumstantially? It ain't no fig tree borer. Why would it be? And arums don't grow that high. Though it's a possibility. But agapanthus abound. And the modus operandi looks. just. the. same.

Maybe the disas will make people sit up and take notice. Because right now they think it's just some gardening ladies in the suburbs crying, Worm! I'm curious about when it will begin to affect growers and nurseries.


Once the caterpillar works its way down the stalk, having destroyed the bud and turned it into black mush, it heads for the crown of the plant at soil level, there to pupate, and begin again. So far, the only solutions are to remove it mechanically (meaning find and handpick it out), or to douse the crown of the plant in poison. Poison, being posion, kills everything in its path. Dead zone. Ferndale, a local nursery in Constantia recommends poison. They even have a designated poison person selling poisons, whose personality matches the product. I am not a fan.

So. In my mother's garden, the agapanthus are being inspected and cut down and divided. Some of them have been doused. Those big blue swathes are now empty brown patches.

The only upside, at the moment, is that this creates room for improvisation. Meaning: new plants.

When in doubt, shop.

*** If anyone is able to photograph this caterpillar, please do. Check your agapanthus. My image is not very helpful for ID purposes, and if you are able to send me a better one we can post it to iSpot so that the pros are able to observe it better.

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