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Boxwood Blight

information from September city meeting

Understanding Boxwood Blight

. Found in Europe in 1990's. Introduced into U.S. in 2011.

Only affects plants in the Buxaceae family including Buxus (boxwood), Sarcococca (sweet box), and Pachysandra (spurge). Spores are heavy and sticky and are moved on plants or by people, equipment, and splashing water. Fungus appears as brown or black spots on foliage with yellow or brown rings. After defoliation, infected areas usually have black streaks in the stem. Fungus is fast moving in wet and mild temperatures (65-75° F is ideal). In prolonged dry, hot, or cold weather, the fungus goes dormant only to reappear in wet, mild temperatures. Fungus can survive for years in infected debris either on the plant or in the soil. Once in the landscape, the fungus can be suppressed in some cases but not eliminated. Current chemical options can kill active spores but not the disease. The best control measure is to plant tolerant cultivars.

Optimal Conditions for Boxwood Blight

Fungus must be present. Continual wet foliage from irrigation, rain, or high humidity.

Temperatures of 60-80degrees F (Ideal range of 70-75degrees F)

• Little air movement.

Prevention and Control of Boxwood Blight

Educate yourself and others who garden. Purchase boxwood from educated and prepared suppliers. Use landscapers and lawn care companies who are aware of and educated about the disease and use practices to prevent introducing or spreading the disease. Clean tools and equipment regularly, and launder clothes daily. Lessen or eliminate sharing of tools across other landscapes. Prune and plant boxwood to promote good airflow in and around the plant. Avoid overhead irrigation. Dry foliage is important. Choose cultivars carefully, based on desired size and tolerance to boxwood blight. Mulch to lessen water splash.

Cleanup of Boxwood Blight If suspected:

. Consult your Extension office for recommendations on taking and sending samples to a lab for analysis and limit

access to area until results are obtained. If confirmed:

Take great care not to further spread disease. Do cleanup on dry, sunny days when foliage is not wet. Consider fungicide applications before and during cleanup to lessen sporulation. Consider wearing rubber boots and disposable clothing during cleanup to lessen contamination of clothing and shoes. Cut and place the infected plants in a plastic bag and take care to catch as much leaf litter as possible. After cleaning up of leaf debris, remove roots. Debris should be burned or taken to landfill with care not to let the leaves escape. After cleanup, wash skin, launder or dispose of outer clothing, and wash boots. Increase airflow in and around remaining plants by thinning and removing lowest limbs. All tools and equipment should be thoroughly cleaned when moved between different gardens or areas. Be sure to mulch to lessen the splashing of spores. Replant boxwood that are tolerant of boxwood blight. Monitor boxwood in times of optimal conditions for new infections and flare-ups.

Saunders Brothers Boxwood Summary Sheet

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+

Blight Zone | Exposure | Tolerance

6-8 SU, PS, SH 5-8 SU, PS, SH

SU, PS, SH 6-8 PS, SH

SU, PS, SH

5-8 PS, SH

6-8 SU, PS, SH

+

6-8

+

+

+

+

+

+

6-8

PS, SH

6-8

+

5-8

+

5-8

+

SU, PS, SH SU, PS, SH SU, PS, SH

SU, PS, SH

PS, SH SU, PS, SH

5-8

+

5-8

5-8

I

Cultivar Buddy Chicagoland GreenTM Dee Runk Elegantissima Fastigiata Franklin's Gem Golden Dream Grace Hendrick Phillips Green Beauty Green Gem Green Mound Green Mountain Green Pillow Green Velvet harlandii

insularis Nana Jensen Jim Stauffer John Baldwin Justin Brouwers Little Missy Morris Dwarf Morris Midget Richard sempervirens (American) Suffruticosa (English) Vardar Valley Winter Gem Wintergreen

7-9

PS, SH

+

6-8

PS, SH

+

6-8

+ +

PS, SH SU, PS, SH SU, PS, SH SU, PS, SH

6-8

+

6-8

I

5-8

SU, PS, SH

+

+

6-8

PS, SH

6-8

PS, SH

PS, SH

+

+

7-9

5-8

SU, PS, SH

6-8

PS, SH

5-8

SU, PS, SH

SU, PS, SH

5-8

+

+

5-8

SU, PS, SH

+

+

Exposure Key

++

Boxwood Blight* Tolerance Key Very Tolerant Somewhat Tolerant Variable Tolerance/Susceptibility Somewhat Susceptible Very Susceptible

SU- Sun PS- Part Sun SH-Shade

*Boxwood blight tolerance data based on multiple tests and observations from Saunders Brothers 2012-2017.

Based on Data from 5th Edition Boxwood Guide March 2018