WhatFinger


November Gardening

Are There Zombies in Your Garden?



Halloween may have come and gone, but there are still could be some weird and wonderful happenings lurking there, waiting for another season. As for elsewhere, well, you had to ask, didn’t you?
That dinky little ladybug, or what our Brit cousins call a ladybird, either way is an entomological puzzle. For the creature is neither true bug nor, certainly, avian, but belongs to the Coleoptera, or true beetles. Busy as a bee, to mix metaphors, ladybugs feast on many a foe. Indeed they have become the very personification of natural control in the garden. Alas, as the 19th-century mathematician Augustus de Morgan so astutely observed:
Great fleas have little fleas upon their backs to bite ‘em, And little fleas have lesser fleas, and so ad infinitum

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The ladybug is in its turn, preyed upon by an insidious wasp, the minute Dinocampus cocconellae. Upon hatching from an egg of this member of the Hymenoptera, the larvae burrows through the ladybugs internal organs, feasting and fattening but not killing – it needs the unfortunate victim for more gruesome purposes. Ready to pupate, the wasp larvae forces its way out of the underside of the ladybug, there to build its cocoon. Meanwhile the partially paralyzed ladybug may twitch when disturbed, protecting it from yet other predators. De Morgan would have been delighted. Happier for the home gardener is the recent revealing that an attack of a virulent baculovirus turns gypsy moth caterpillars into zombies. The virus, utilizing a gene dubbed LdMNPV, manipulates the infected caterpillar, encouraging it to climb high up in the tree it infests. There it dies and deliquesces, falling upon the rest of the family feasting below. They too, in turn, will be doomed to follow the same fatal trail. Entomophthora fungi create a similar set of conditions when the spores infect their housefly hosts. Keeping their carriers alive while the feed within them, when the fungus reaches maturity, it releases mind-manipulating chemicals, noted a recent issue of New Scientist, which somehow force the fly to seek out an exposed location in which to die. This puts the fungus in an ideal position from which to shoot spores out into the air and infect yet more flies. Most fungi, however, do best under the hot, humid conditions of the tropics. Those in the Ophiocordyceps genus, for example, infect many insects. In a study published in the journal PLoS One, researchers found four different species of ‘zombie fungus’ in the Atlantic Brazilian rain forest. These feed in an ant until close to entering into its fruiting stage, when it takes over the ant’s brain, forcing it to climb high above a popular ant congregating point. There the victim bites down onto the underside of a leaf. The fungus’ fruiting body gruesomely emerges from the head of the ant to spread spores on its companions below. A similar parasitic fungus, Cordyceps sinensis, infects ghost moth caterpillars as they hibernate in alpine meadows in the Himalayas. Unfortunately it may be doomed in itself – It is prized above any of the other 400-odd species of Cordyceps for supposedly effectively treating a vast range of diseases and conditions, including the inevitable sexual dysfunction. According to the journal Science, China’s harvest alone for the past three years has been a staggering 100 tons each year. The year 1984 may have been ominous, thanks to science-fiction fanatics, but it provided better news thanks to mycologist Chris Prior. He discovered it was possible to suspend Ophiocordyceps spores in vegetable oil, retaining their viability when used as a spray against locusts in West Africa and Australia. Notwithstanding the unfortunate wasp-parasitized ladybug then, zombies might be jolly good things at the bottom of your garden. “With most insecticides you have to worry about getting the toxin inside the insect,” says Andrew Read, an evolutionary biologist at Pennsylvania State University told Matt Kaplan from New Scientist. “These fungi are great. They readily attack passing insects all on their own, doing the hard work for us.”


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Wes Porter -- Bio and Archives

Wes Porter is a horticultural consultant and writer based in Toronto. Wes has over 40 years of experience in both temperate and tropical horticulture from three continents.


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