Sparganothis Fruitworm Moth

2012 August 29

This moth was drawn to our porch light on August 1, 2010, and obligingly hung out on our house siding.

This looks to me like a Sparganothis Fruitworm moth, Sparganothis sulfureana. These have the right shape, are often that particular shade of yellow, and have that dark “X” pattern running across the backs of the wings.

The larvae look to be thin, pale caterpillars that hide out in rolled-up leaves that they tie together with silk. They eat lots of different broad-leaved plants, but they are a particular pest of cranberries. It seems that they have two generations per year. The caterpillars of the first generation in the spring eat the cranberry leaves and blossoms, which is bad enough. But the second-generation caterpillars actually burrow into the fruit.

Controlling these moths on cranberry farms is complicated by two problems: (1) they live on a lot of common wild plants too, like goldenrod and aster and loosestrife, so even if you knock them back from your cranberry field there is still a big supply from outside; and (2) they are becoming resistant to the more common chemicals used for their control.

As an alternative to conventional insecticides, there are pheromone lures available for these moths. These are chemicals that draw the male moths into traps. The beauty of pheromone lures is that they are fantastically selective, generally getting only the exact species that you want to control. And yet, there is some difficulty in getting them – many possible pheromone-based insecticides have been proven to work in studies, but they are not commercially available even though there is no fundamental reason why they cannot be manufactured. This is because of the basic problem with this type of insecticide.

The problem with pheromone lures is that they are fantastically selective, which means that a manufacturer of pheromone lures has to have a separate lure compound for each pest. See, if you have a broad-spectrum insecticide that will kill pretty much any pest, then you can sell it to all sorts of markets, from corn, to soybeans, to cranberries, to apples. This gives you a big economy of scale, and ensures that you will have a constant demand. But, if you are selling a pheromone lure for, say, Sparganothis fruitworm, then your only market is cranberry farmers. This is a much smaller market, and so you only sell a little bit of it per year, which means that you have a much harder time covering your capital costs. And on top of that, the farmers mainly buy it when there is an outbreak, which means the manufacturer has to go through a lot of boom-and-bust cycles when trying to match production to the demand.

Which is a long-winded way of saying, sometimes life just can’t be easy. And some things are both a blessing . . . and a curse.

2 Responses
  1. August 29, 2012

    What a nice looking moth!


  2. August 31, 2012

    This Sparganothis fruitworm moth has a neat name and looks rather familiar to me. In fact, it resembles the many rubber dinosaurs that I bought for the boys that now occupy a bin in our basement.

    It also reminds me of the many cockroaches in Kuwait that I would find on the bedroom or kitchen floor at night or swarming in the morning over our bed like missiles thrown from an unkind god.

    They made crunchy corn flakes sounds when I’d step on them at night when I would go to the kitchen to get a glass of water. This may be the reason why I am so sensitized to the sight/feel of bugs now. If you only you could have seen them marching like battalions of tiny warriors deserting the battlefield! They were rather like a moving escalator of brown soldiers running off when the light of the sun god came on (the kitchen light). Even when it was during the day, they would be frantic about. We never knew where they hid out. Once —-my mum made a pot of tea and offered it to guests—- and it was only later—when we had to empty the pot that we noted it was full of these darling cockroaches (my mum had just thrown in the tea leaves into the pot without checking for lurking victims inside). You can imagine the trauma this type of encounter with bugs caused to a sensitive child like myself (yes I was a sensitive child). No amount of fumigation got them out of the house and we eventually had to move to another house to keep ourselves intact. It was either that or leave Kuwait prematurely.

    But your moth. Although I admit the X on the back makes it look slightly raffish and debonair (forbidden fruit and all that) I see why these moths need a pheromone to mate. I can’t see why any decent female moth would date such a rubbery male moth—much less mate with one. The one depicted has a slightly mad scientist looking expression on his face.

    But I must not be mean. Let me say something complimentary about the wild looking thing.
    I like the frugal aspects of this bug that you mentioned—how it uses leaf detritus and tidily ties up the entire with silk— to make small packages for safekeeping. They seem to make parchments out of their abodes. Are they poets?

    As usual, my comment is here and there and overlong but at least I managed to get through it without being excessive and I will now go back to Thoreau where he says “It is individuals that populate the world.” And it is individual insects that populate your blog—each of them memorable creatures. I’d best stop yapping now and go work on Thoreau.

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