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Western Plant Diagnostic Network First Detector News Western Plant Diagnostic Network1 First Detector News A Quarterly Pest Update for WPDN First Detectors Winter 2015 edition, volume 8, number 1 In this Issue Page 1: Editor’s Note Dear First Detectors, Where do insects go for the winter? Miami? Actually some insects move south for the winter, Pages 2 - 3: Insects in winter such as the famous migration of monarch butterflies to Pages 4 – 5: Phytophthora Mexico and dragon flies to warmer areas. An interview with tentaculata found in CA a specialist in insects at low temperature, Dr. Brent Sinclair, answers this question in the lead article. Two plant Pages 6 - 8: Swede Midge pathologists at the California Department of Food and Agriculture, Drs. Cheryl Blomquist and Suzanne Rooney- Page 8: NPDN online Latham, have identified a new nursery-associated Phytophthora species, P. tentaculata. A new invasive insect Pages 9 - 10: Pale cyst in Canada and the NE US, the swede midge, is a very small nematode spreads in ID and persistent pest of all Brassica crops. Cornell University Page 10: Red palm weevil has assembled a team to study the biology and control of eradicated in CA this midge: Cornell University SWEDE MIDGE Information Center for the U.S. Learn about it so you will be able to Contact us at the WPDN Regional identify the symptoms if the swede midge keeps migrating Center at UC Davis: westwards. Finally, in Pest Updates there is some bad news Phone: 530 754 2255 and some good news. Email: [email protected] Web: https://wpdn.org Editor: Richard W. Hoenisch @Copyright Regents of the Please find the NPDN family of newsletters at: University of California All Rights Reserved Newsletters Western Plant Diagnostic Network News 2 Photo courtesy of Flickr of Photo courtesy Altizer Sonia Photo by Photo courtesy of Flickr of Photo courtesy Monarch butterflies migrating A wooly bear caterpillar Goldenrod gall flies Where do insects go in the winter? From an interview with Brent Sinclair, Ph.D., Western University, London, Ontario, by Business Insider When temperatures drop, icicles form, and parkas come out of storage, the bugs seem to vanish completely from the chilliest corners of the world — until months later, like some kind of magic trick... they reappear, as if they'd been there all along. One reason most people are mystified by the fate of insects in the winter is because there is not a simple answer. Some survive as eggs, larvae, or pupae, while others make it through the winter as fully-grown adults. 1. Avoid the cold The first strategy is perhaps the most straightforward. Many insects survive the cold winters by simply avoiding them, employing what Sinclair dubs "the snowbird approach. “ Some, like butterflies and dragonflies, migrate much like songbirds do, heading south en masse as soon as the cold sets in. (Researchers have actually attached tiny radio transmitters to dragonflies to track these migration patterns.) North American monarch butterflies, the most famous migrating insects, make a long and somewhat miraculous journey to central Mexico each winter. (Swallowtail butterflies do no such thing, sticking out the winter safely encased as a chrysalis instead.) For other insects, avoiding sub-zero temperatures means a journey of inches, not miles. Many aquatic insects wait out the winter at the bottoms of ponds, where they can remain relatively comfortable even when the surface freezes. Others do the same in the soil, burrowing deep below the frost. Different types of mosquitoes have different winter survival strategies, but some are able to survive cold temperatures by hiding out in sheltered places like "inside the envelope of a house or under a bridge," where they lay in wait in a state called "quiescence." Their next meal won't come till springtime. 2. Carry on as usual While insects seem scarce when December rolls around, some — a rare and hardy few — continue doing their thing, just like those headstrong outdoorsmen who go camping in the dead of winter. "If you were to put a little trap underneath the snow, you would find some small primitive insects," Sinclair tells us. Some crawl within warm pockets carved out by grass and leaves, while others survive on the surface. 3. Freeze! It's called diapause a dormant, semi-frozen state some insects enter until they thaw out in the spring and crawl off as if nothing had happened. (Despite our fantasies of full-body cryogenics, humans definitely can't do that yet — though some mosquitoes pull off something a lot like it.) The emerald ash borer , a tree-killing invasive species in North America, enters diapause in the winter, which (unfortunately for the northern regions it's infested) means it can survive freezing temperatures. In this state of suspended animation, "they don’t do anything," Sinclair says, "They don’t develop. They just sit under the bark of trees where they’ve been feeding all summer." Western Plant Diagnostic Network News 3 The environmentally damaging creatures are able to stay unfrozen and alive in the cold because a high concentration of their blood is made up of something called glycerol , which acts as an antifreeze. Woolly bear caterpillars, meanwhile, actually freeze into tiny statues but still live through the winter. "Ice forms inside their bodies — you tap them and they’re solid," Sinclair explains. "It's an amazing trick." They can survive, Sinclair has found in his lab, at temperatures well below anything found on Earth. A lot of body processes shut down so they aren't injured in the meantime. (Goldenrod gall flies perform a similar stunt.) 4. The undead invasion Many insects actually do die in the winter, leaving nothing but eggs behind. That means they are replaced by an entirely new generation in the spring. "You know the crickets that you hear singing in the fall? Those adults that are singing are all going to die in the winter," Sinclair explains. "They lay eggs in the soil, and those hatch in the spring." One problem with our warming winters — yes, parts of the US are experiencing a cold snap, but nationally it's one of the warmest winters ever recorded — is that insects that are supposed to die off don't, and those that normally can't survive in the coldest areas are moving in and setting up shop. "If you have more and more warm winters, you can get invasive species moving further up and into cold areas," Sinclair says. And all that's stopping non-invasive species, like the mountain pine beetle, "from eating eastern North America," is the blistering cold of the Rockies — something we may not be able to rely on for long. "Elevated temperatures at high elevations across western North America have allowed mountain pine beetle populations to develop in a single year in areas where two or more years were previously required," noted a report from the US Forest Service. Photo courtesy of Growing with Science Photo by Dean by Dean Photo Photo by Photo Robert Gorman Robert Stables A praying mantis egg case 1. 1. Ladybugs overwintering Photo from Photo Anise swallowtail in a seed pod chrysalis the A complimentary article to the Dr. Sinclair’s is Minitab Blog Minitab Insect Winter Ecology. His full interview with Business Insider can be found at: What happens to insects in winter? Caddisfly larva with portable case of rock fragments Dr. Brent Sinclair is an associate professor in Western Plant Diagnostic Network News the Department of Biology at Western University in London, Ontario. His research focus is “Insects at Low Temperatures.” New Species of Phytophthora found in California 4 Phytophthora tentaculata, Kröber & Marwitz (1993) Twenty years ago, scores of trees began visibly dying off around the San Francisco Bay Area, in what turned out to be the advent of Sudden Oak Death. The cause was a microscopic parasite, Phytophthora ramorum . Phytophthora comes from Greek and means “plant destroyer.” Whereas fungal cell walls are made primarily of chitin, Phytophthora cell walls are constructed mostly of cellulose. Of its many relatives, perhaps the best known is Phytophthora infestans , noted for causing the Irish Potato Famine. It is a genus of plant-damaging Oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, as well as environmental damage in natural ecosystems. An extensive USDA study on the many species of pathogenic Phytophthora species can be found at Emergency Manual of Phytophthora species. As you page down in the document, there are excellent photos and descriptions of the many plant pathogenic Phytophthora species, including P. tentaculata. The species name, tentaculata (tentacle like), perhaps comes from the spider-like mycelium when grown in culture (1). Phytophthora tentaculata has been detected in several California native plant nurseries and restoration sites. These are the first detections of P. tentaculata in the U.S. It was known previously in China, Germany, Italy, the Netherlands, and Spain. It was first isolated in 1993 in a nursery in Germany infecting Chrysanthemum , Verbena, and Delphinium ajacis. P. tentaculata was initially noticed in a native plant nursery causing a severe root and crown rot in sticky monkey flower, Diplacus aurantiacus subsp. aurantiacus (family Scrophulariaceae ) in Monterey County, CA, in October 2012. Nearly all the M. aurantiacus plants grown in a nursery for a restoration project were stunted and had dull, yellowish leaves. Roots and stem collars had necrotic, sunken lesions with few feeder roots. Thirty percent of the plants had died. Since then it has been detected in four additional nurseries in three counties in CA in addition to three restoration sites where out planted stock was found to be infected. Other plant species known to be susceptible are, Chrysanthemum spp., rocket larkspur (Delphinium ajacis), African daisy ( Gerbera jamesonii), oregano, Verbena, and lavender cotton (Santolina chamaecyparissus ).
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