Garden mums are most often produced outdoors and can be subject to weather conditions favorable for pests and diseases. Some of the more common problems occurring on garden mums are caused by Pythium and Fusarium. Both of these pathogens are likely to emerge under higher temperatures and moisture conditions.

Left uncontrolled, Pythium can cause root and stem rot, sometimes resulting in wilt and leaf rot (Figure 1 and 2), and it can spread in water and potting medium as well as by tools and worker handling. Apply fungicides early in the crop to avoid any losses to Pythium, and use good sanitation practices for the most effective preventive treatment. Growing media with high soluble salts can cause root burn and make the plants more susceptible to Pythium attack. Plant protection products for Pythium include: Subdue Maxx^® (mefenoxam), Segway™ (cyazofamid), or Terrazole^® (etridiazole) fungicides. As with all plant protection products, follow all label recommendations.

Fusarium problems occur more frequently when the plants are stressed, so attention to proper growing practices is essential. Wilt, stem rot and root rot can occur with a Fusarium infection (Figure 3), and plants are often infected simultaneously by Fusarium and Pythium. Fusarium can travel by soil, water or air. Plant protection products effective for Fusarium include:Heritage^® (azoxystrobin) and Medallion^® WDG (fludioxonil) fungicides. Tank mixes to address both Pythium and Fusarium can be appropriate. Use Heritage + Subdue Maxx for prevention of both Pythium and Fusarium.

Another problem for garden mums grown outdoors is bacterial leaf spot (BLS), caused by Pseudomonas cichorii. This bacterium causes black spots on foliage and can also affect flower buds (Figure 4). Overhead watering and rainy periods in warm weather favor this disease. Free water must be on the leaf surface for the disease to develop. Drip irrigation or irrigating early in the day may decrease disease probability. There are no effective bactericides; some copper compounds may help in preventing some spread, but the best bacterial control measure is sanitation. Remove affected plants to reduce inoculum spread.

Occasional pests on garden mums include aphids, two-spotted spider mites, thrips and whiteflies. Flagship^® 25WG insecticide is effective against aphids, thrips and whiteflies and should be used in a rotation schedule with Avid^® 0.15EC. If garden mums are being grown in the greenhouse, there are biological control agents available.

Controlling thrips and aphids can prevent the spread of viruses. Thrips act as a vector for the tospoviruses: Impatiens Necrotic Spot Virus (INSV) and Tomato Spotted Wilt Virus (TSWV). Aphids can spread Chrysanthemum Virus B (CVB). There are no chemicals that control viruses, so vector control is critical.

Finally, Chrysanthemum White Rust (CWR) can destroy your crop, so prevention is vital in areas where this disease has been found.

©2013 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties. Please check with your local extension service to ensure registration status. Flagship^® , Heritage^® , Medallion^® , Subdue Maxx^®  and the Syngenta logo are trademarks of a Syngenta Group Company. Segway™ is a trademark of FMC Corporation. Terrazole^® is a registered trademark of Chemtura Corporation.