| What Pest Is That? WOOD LICE |
| Woodlice are of the Order Arthropoda (Arthropods, which means segmented body & jointed appendages), Class Crustacea, Order Isopoda (isos meaning equal & podes meaning feet), Suborder Oniscidea., and share with insects and Arachnids (Spiders and Scorpions etc) and Myriapods (Millipedes and Centipedes) a hard exoskeleton and jointed limbs. The fact that they are members of the Class Crustacea means that they are closely related to crabs and prawns. The ones that concern us the most are of the genera Armadillidium, & are also known as Pill Bugs & Slaters. These are generally greyish brown in color although their coloring can vary right through to oranges & indeed they do look like miniature Armadillos. These Wood Lice are capable of rolling themselves up into a ball, this is a defence against desiccation as well as against predators, & if you disturb them, you will no doubt see them doing this. They prefer to live in sheltered areas that are damp & have plentiful decaying vegetation, such as under pots or bricks etc, but much like our orchids they do not like conditions that are too wet. These bugs, even though we class them as pests, cause little or no evident damage in small numbers, but if they are plentiful enough, damage to your orchid roots can be quite serious. The Life Cycle.........MATING Mating occurs at night, and is therefore hard to see, so I'll describe the process for you. The male climbs onto a receptive female, licks her head and drums on her back with his legs for about five minutes (this save having to give flowers or taking her out for a meal). He then shifts to a diagonal position on the females back and passes sperm to her left side genital opening from his right hand stylets. He then changes his position to the opposite diagonal and deposits sperm in her right hand genital opening from his left hand stylet. Sperm transfer takes about 5 minutes for each side. The female will then produce the eggs, generally one brood a year into her 'marsupium'. The eggs take from 3 to 9 weeks to hatch and the young spend from 3 to 9 weeks to hatch and the young spend from 3 to 9 nine days in the brood pouch. When Woodlice are born & for the first part of their lives, they are vulnerable to desiccation or drying out, so they spend this period in the brood pouch underneath their mother. This pouch is composed of plates on the underside of segments 2-5, and is called a 'marsupium' and is grown especially by pregnant females for this purpose. At this age a young woodlouse is called a 'manca', but I don't think they mind if you call them Jack or John. At this stage it only has 6 pairs of legs, but after its first moult it gains its 7th pair of legs and leaves the marsupium. After leaving the pouch & the first moult the young are classed as juveniles. Juveniles moult at regular intervals until they reach sexual maturity, usually within a year, when they become adults, & away we go again. GROWING UP Like all other arthropods, growth can only occur at times of moult, but unlike the others, Woodlice only shed half their skin at a time. When approaching the time to moult a Woodlice will stop eating for a few days, then its skin splits around its middle and it sheds the back half of its skin, and then a few days later it sheds the front half. The woodlice will then often eat their own shed skin. The Woodlouse is very vulnerable during this time, and often seek a spot away from its fellows for the duration of its shedding. DAMAGE Nearly all Woodlice are herbivores and feed on dead and rotting vegetation, or more correctly the microbial flora that infests such material. Woodlice will also feed on their own faeces, this is quite natural, what they are actually eating is the fungi and bacteria that are living on the faeces. The damage caused to the roots of your precious orchids is a result of the woodlice grazing on the fungi & micro organisms that inhabit the root surfaces. Hence as they chew on their food source, a certain amount of the root tissue also gets chewed up. CONTROL The best way is to ensure that pots are raise off the ground slightly, & the bark media is kept fresh, decaying media creates a great food supply for these little guys. The other options are chemicals along the lines of Diazinon, or the prills that kill grass grub etc in lawns sprinkled through pots. This should soon cure any infestations that may have taken up residence around the roots of your orchid plants. |
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