Utah Pests News Spring 2007

click here for pdf version

Plant Disease Diagnoses, 2006

There were 149 samples diagnosed for plant diseases or abiotic stress in the 2006 season.  Many were diagnosed with abiotic stress and chemical injury.  Turf was at the top of the frequently submitted category at 31 entries total.  Of the turf samples, fading out (Curvularia spp.) and Fusarium spp. were the most frequently isolated.  Other common turf pathogens were snow mold (Michrodochium nivale) and take-all (Gaumanomyces spp.).  Dothistroma needle blight is present in Utah and has shown up on a couple of Austrian pines (see below).  The UPPDL had one greenhouse sample test positive for impatiens necrotic spot virus.  Viral diseases can be difficult to recognize, so be on the lookout to spot them in commercial greenhouses.

The Unusual Suspects

The 2006 season brought about some interesting pathogens and symptoms on host samples submitted to the UPPDL.  A peppermint grower submitted a sample that was infected with a pathogen and was thought to be Verticillium wilt but was not.  The UPPDL diagnoses found that it was a Phoma sp. Verticillium in peppermint can ruin a grower’s ability to produce the crop.

Honeylocust tree branches were submitted having large swellings around the nodes. There is much controversy nationwide and internationally whether this is due to a bacterial infection or other causal agent. The issue remains unresolved.

A Photinia fraseri plant was submitted from a nursery to the UPPDL to screen for sudden oak death (Phytophthora ramorum).  The sample was tested using ELISA and found negative.  For verification it was sent to Oregon State University for PCR (polymerase chain reaction) testing.  The PCR test was also negative.  The UPPDL’s diagnosis was confirmed as Entomosporium leaf spot.  It is not known if this disease has been reported in Utah. 

Pandora's Box

The UPPDL has initiated long-term storage of pathogens that were positively identified in submitted samples.  Among these are an Alternaria sp., Bipolaris spp., Curvularia spp., Fusarium spp., and a Verticillium sp. (all are fungi).  This is a plus for research in that the location information is recorded in the database and can be traced directly to the isolate.  The cultures will serve as a reference collection and for future research.

Disease Profile: Dothistroma Needle Blight

Common name: Dothistroma needle blight or red band disease.

  Dothistroma blight on pine.
Scientific name: Mycospharella pini is the perfect state.  Dothistroma pini is the imperfect or conidial state.

Host Range: Susceptible hosts include Austrian, Lodgepole, Mugo and Ponderosa Pines.  Less susceptible hosts are Douglas-fir, European Larch, and Sitka Spruce. 

Symptoms: Symptoms on needles appear as yellow bands that progress to red.  The color change is due to the fungal production of a toxin called dothistromin.  Once the fungus has girdled the needle, the upper portion turns brown while the base remains green.  Rarely will you will see black fruiting bodies called stromata that develop in the dead needles.  Trees can lose their needles.  Disease progression will be from the lower branches upward.  Pathogen development is where humidity is highest.  Dothistroma attacks first, second, and third year growth.  Stress predisposes the trees to the disease.
Management: Clean up debris when feasible since spores are harbored in the needles.  Remove weeds from the base of the tree to help reduce humidity.  Sprinkler irrigation will contribute to the spread of Dothistroma.  Regular wetting of the foliage provides moisture for sporulation as well as spread of the disease.  Promote plant health with adequate water and fertilization.  Bordeaux can be applied as a protectant, although it can be toxic to newly formed needles.  Follow the recommended guideline on the label for application and rates. Two applications per season are the most effective.  Apply once before bud break and then 3 to 4 weeks later (to avoid harming newly formed needles).  This is a preventative fungicide and will not cure those needles that have already been infected.  It is also important to make sure that you get good coverage.  Any healthy needles that are not protected will become infected.

-Julie Jenkins, Plant Disease Diagnostician

Insect Diagnoses

  Striped mealybug - a new insect to Utah 

2006 was a busy time for insect and arthropod-related submissions, with more than 100 submissions. Our Insect Diagnostician, the late Alan Roe, communicated with USU Extension personnel and individual homeowners about identification and management options.  Alan was an excellent taxonomist and readily answered hundreds of email and phone inquiries every year.

Most of the specimens were submitted by individuals via USU Extension Agents.  Nearly every county submitted at least one specimen in 2006 (22/29 counties).  Counties most likely to submit a sample to the UPPDL include: Cache (26), Davis (18) and Washington (17).  We had several new state and county records in 2006, including the Japanese beetle (Popillia japonica) on wisteria in Utah County; a mealybug, (Ferrisia gilli) on honeylocust; an armored scale, yet to be identified, on Austrian pine in Salt Lake County; a flatheaded cedar borer (Chrysobothris nixa) from creeping juniper in Cache County; and an exotic wood borer (Bostrychoplites cornutus), from a wooden drum in Washington County.

There were also several exotic beetles identified from a CAPS survey: an elm borer (Saperda tridentate) in Morgan County; a bark beetle (Gnathotrichus pilosus) in Iron, Davis, and Weber Counties; a bark beetle (Hylastes rubber) in Box Elder County; and a buprestid beetle, yet to be determined, in Iron County.

Alan’s experience and knowledge will be sorely missed, but we are attempting to refill his position by the June 2007.  If you know of someone who might be interested in the Insect Diagnostician position, please go to http://utahpests.usu.edu/insects for a full job description.  In the meantime, please be patient with the UPPDL, as Diane Alston and I attempt to diagnose incoming specimens and make management recommendations.

-Erin Hodgson, Extension Entomologist (No longer at USU)

Spreading the Word About Collecting Insects

As a new member of the Utah Plant Pest Diagnostic Lab, I would like to briefly introduce myself.  Since first arriving in March 2006, I have been very busy trying to meet with USU Extension personnel, various commodity groups and individuals throughout the state.  My Extension duties are vast, and include field/forage crops, landscape/ornamental plants, nuisance/household pests, health-related issues like West Nile Virus, and youth programs.  My research programs will focus on IPM in alfalfa and turfgrass.  I am also the State Survey Coordinator for the CAPS (Cooperative Agriculture Pest Survey) Program and coordinate exotic pest surveys throughout Utah.  I have always been interested in outreach education, especially getting children excited about science; entomology can be a great hands-on tool to teach basic scientific concepts.

I think youth programs, like 4-H, can help children start to learn about science in a fun, social setting.  To help promote Utah 4-H programs, I would like to donate two insect collecting kits to every county as a way of encouraging youth to participate in a project.  Each kit includes a sweep net and various pinning supplies needed to preserve insects. Kits will be distributed to Extension Agents at the Annual Conference in March 2007.  I am relying on Agents to distribute the kits to children in their respective counties.

Two kits per county is certainly not enough for every child that might want to start an insect collection.  But my hope is that this small token can help a child that might not otherwise be able to afford a 4-H project.  The overall goal is not only to have more insect collections submitted as 4-H projects, but to increase the overall quality and diversity of specimens prepared.  I would be happy to help out with any questions you may have about collecting or preserving insects.  I can’t wait to see the insect collections get bigger and better at upcoming 4-H events.

-Erin Hodgson, Extension Entomologist (No longer at USU)