Boxwood Blight

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Boxwood Blight

  1. 1. Boxwood Blight First Detector Training October 31, 2013 Tracey Olson PA Dept. Agriculture Harrisburg, PA (717) 783-9636 tolson@state.pa.us
  2. 2. Boxwood Blight (Cylindrocladium pseudonaviculatum) S.M. Douglas, Connecticut Exp. Station
  3. 3. Boxwood Blight (BWB) • Caused by the fungus Cylindrocladium pseudonaviculatum. • = Cylindrocladium buxicola. • = Calonectria pseudonaviculata (teleomorph has never been observed). • Also called: • Box blight. • Boxwood leaf drop. • Blight disease of Boxwood. S.M. Douglas, Connecticut Exp. Station
  4. 4. Terminology Sporodochium = fruiting structure Microsclerotia = resting/over-wintering structure (Joseph Bischoff, USDA-NIS) Conidia = infective spore
  5. 5. Best months for detection are July - October
  6. 6. Historical Background • 1994 – Boxwood Blight first detected in United Kingdom. • 2002 – BWB found in New Zealand, reported as Cylindrocladium pseudonaviculatum . • Now widespread throughout UK (reported as C. buxicola) and European Countries. (not regulated, but “disease of concern”). • October, 2011 – First detected in U.S. in NC and CT. • January 2012 - PA • Detections in North America (2011 – present) – 13 States – AL, CT, DE, MA, MD, NC, NJ, NY, OH, OR, PA, RI, and VA, USA – BC, ON, QC, Canada.
  7. 7. Origin of Boxwood Blight Fungus • Geographic origin is not known. • Not known how or when the pathogen was introduced into the U.S.
  8. 8. Hosts in Family Buxaceae • Buxus sempervirens ‘suffruticosa’ • “English Boxwood” • Buxus sempervirens • “Common Boxwood” S.M. Douglas, Connecticut Exp. Station • Sarcococca spp. • “Sweet-box” • Pachysandra spp. • “Japanese spurge” • “Allegheny spurge” S.M. Douglas, Connecticut Exp. Station
  9. 9. BWB symptoms • • Tracey Olson, PDA Active infection period starting in July through October. Start as leaf lesions/stem cankers. July 22, 2013 July 22, 2013 Tracey Olson, PDA Tracey Olson, PDA July 22, 2013
  10. 10. S.M. Douglas, Connecticut Exp. Station • • Lesions progress to leaf blight. Sporulation may be visible on undersides of infected leaf during moist conditions. Tracey Olson, PDA Tracey Olson, PDA
  11. 11. Cylindrocladium sporulation white color. Tracey Olson, PDA Volutella sporulation salmon color.
  12. 12. Stem lesions Kelly Ivors, Box blight, NC State University Kelly Ivors, Box blight, NC State University
  13. 13. S.M. Douglas, Connecticut Exp. Station Blight and defoliation starting in July - Oct
  14. 14. BWB symptoms October through June * • • • • Defoliated interior of plant. “Healthy” foliage at tips of branches. Stem cankers may still be visible. * Samples submitted during this period should include stems with cankers, as well as leaves that have dropped. Tracey Olson, PDA
  15. 15. Disease Cycle • • • • Can be rapid, completed in one week. Temperatures between 41-86 0F. Optimum temperature 77 0F. Infections occur quickly under warm(64-77 0 F), humid conditions (July-October). • Spores germinate and penetrate leaves within 5 hours. No wound necessary. • High humidity or leaf wetness required for infection.
  16. 16. Transmission • Short distances, within a nursery or landscape: – Splashing conidia from rain and irrigation. – Conidia can be wind disseminated. – Conidia can be carried on clothing, implements, hands, animals. – Diseased plant debris. – Microsclerotia in Soil. • Long distances: – Movement of infected plants.
  17. 17. • PA Department of Agriculture has declared Boxwood Blight to be a “Regulated Pest”. • Goal is to stop artificial spread by human activities such as: – Propagation of infected material. – Distribution of infected plant material.
  18. 18. Control (BMP’S) 1. Avoidance • • • • • • Use less susceptible varieties. Routine scouting – inspect new shipments. Segregate shipments. Minimize movement of plants/people/animals. Keep foliage dry – spacing and watering. Fungicides as preventive. 1. Management • • • • Early detection/interception. Plants that defoliate in July-October (Contact PDA). Destruction of infected plants. Thorough “decontamination” of affected area.
  19. 19. Other Boxwood Diseases Volutella blight (Volutella pachysandrae) Tracey Olson, PDA Phytophthora root rot (Phytophthora parasitica) Tracey Olson, PDA
  20. 20. Winter burn Tracey Olson, PDA Macrophoma leaf spot (Macrophoma candeolei)
  21. 21. Tracey Olson, PDA Boxwood leafminer (Monarthopalpus flavus)
  22. 22. Important points • New disease to the U.S. – Landscapes with this disease likely had boxwoods planted in last few years. • Disease active July – October. – Rapid progression of blight and stem cankers. – May be extended in hoop houses. • Disease dormant November – June. – Look for defoliated plants. – Sample must include defoliated leaves. • Dwarf English boxwood most susceptible.

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