Petrobia latens: a good mite gone bad.Petrobia latens: A good mite gone bad Drought conditions plaguing north central Montana for most of the past five years may be triggering more than the obvious problems for farmers there, plant pathologists report. Petrobia latens, a tiny spider mite found on cereal crops during stretches of dry weather but never before implicated im·pli·cate tr.v. im·pli·cat·ed, im·pli·cat·ing, im·pli·cates 1. To involve or connect intimately or incriminatingly: evidence that implicates others in the plot. 2. in the spread of disease, now appears responsible for a new disease in barley. Researchers at Montana State University Montana State University, at Bozeman; land-grant; coeducational; chartered 1893. It is primarily a technical institution specializing in agriculture, engineering, and applied sciences. The Museum of the Rockies is there. in Bozeman have been searching since 1983 for the cause of the disease, first recognized in a Montana barley field in 1982. It has since infected crops in five contiguous counties. They report in the May 27 SCIENCE discovering long, filamentous filamentous /fil·a·men·tous/ (fil?ah-men´tus) composed of long, threadlike structures. filamentous composed of long, threadlike structures. virus-like particles (VLPs) in diseased leaves from infected barley plants, and provide evidence the particles are transmitted by the brown wheat mite. The scientists previously ruled out aphids, leaf hoppers and thrips thrips, minute, agile insects of the order Thysanoptera. Thrips have piercing-and-sucking mouthparts and cup-shaped feet from which bladderlike adhesive organs may be extended. Some species are wingless, but many have four narrow, featherlike wings fringed with hairs. -- all known to transmit plant viruses -- as carriers of the new disease. But electron microscopy of ultrathin ul·tra·thin adj. Very thin. of similar VLPs in the mites' digestive tracts. presence of similar VLPs in the mites' digestive tracts. Although viruses of similar length (4,000 nanometers) have been identified in animals and insects, such long viruses have not previously been reported in plants, the researchers say. Indeed, they suggest, since the VLPs most resemble certain enveloped en·vel·op tr.v. en·vel·oped, en·vel·op·ing, en·vel·ops 1. To enclose or encase completely with or as if with a covering: "Accompanying the darkness, a stillness envelops the city" , filamentous viruses found in the animal kingdom, they may have originated in mites before developing their new penchant for residing in plants. The researchers report mites can transmit the disease to healthy plants after feeding on leaves from a diseased plant, but not if they have fed previously only on healthy leaves. They also found young mites hatched from eggs of infected adults can transmit the disease -- even if these youths never fed on diseased plants. This implies the VLPs may be passed to mite offspring via an infected mother's eggs, and that mite eggs may serve as an overwintering o·ver·win·ter·ing n. The persistence of an infectious agent in its vector for an extended period, as in the cooler winter months, during which the vector has no opportunity to be reinfected or to infect another host. host for the disease-causing agent. |
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