Common Disease Problems
Cercospora Leaf Blight: Small flecks which develop a yellowish halo appear on the leaves and turn brown and coalesce. They cause the leaves to wither and die. Burpee Recommends: Remove infected plants and destroy all plant debris. Rotate crops.
Leaf Scorch: The margins of the leaves turn red to brown and appear burnt. Burpee Recommends: This is not a disease but comes from hot, dry, windy conditions. Make sure the plants are properly sites in partial shade in moisture retentive soil.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and keeping weeds under control. Contact your Cooperative Extension Service for fungicide recommendations.
Root Knot Nematodes: Microscopic worm-like pests that cause swellings (galls) to form on roots. Plants may wilt or appear stunted. Burpee Recommends: Remove infected plants and do not plant in the soil for at least a year. Try planting in containers.
Virus (Various causes): Plants may have a yellowish tone and become stunted. Burpee Recommends: Remove infected plants.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps which feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Asiatic Garden Beetle: Velvety, cinnamon-brown beetle that looks like a coffee bean. The grubs eat the roots and the adults attach the foliage and blossoms. Burpee Recommends: Night time picking. Prevent by cleaning up fall debris. Check with your Cooperative Extension Service for pesticide recommendations.
Slugs: These pests leave large holes in the foliage or eat leaves entirely. They leave a slime trail, feed at night and are mostly a problem in damp weather. Burpee Recommends: Hand pick, at night if possible. You can try attracting the slugs to traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.
Tarnished Plant Bug: These insects cause distorted leaves and flower buds. The adults are about ¼ inch long, oval shaped and flat. They are greenish brown with reddish brown markings on their wings. There is a small but distinct yellow tipped triangle in the center of the back behind the head. Burpee Recommends: Introduce beneficial insects to your garden. Traps are available. Try insecticidal soap.
Vine Weevil: This insect cuts irregular notches in leaf margins and grubs feed on plant roots, sometimes causing the death of the plant. Adults are approximately 5/16 inch long, dull black with dirty yellow marking on the wing cases. The grubs are c-shaped, 3/8 inches long, with light brown heads. Burpee Recommends: Handpick adults at night, shake the plants over newspaper to dislodge them. Check under pots where they hide during the day. Check with your Cooperative Extension Service for pesticide recommendations.
Can I grow astilbe in a container? Yes astilbe is fine for containers. Be sure to use a commercial potting mix and do not allow it to dry out.
Is astilbe deer resistant? Yes, astilbe tends to be resistant to deer and rabbits.
What are some good plants to combine with astilbe? Astilbe looks great with other shade loving perennials such as heuchera, hosta and hakonechloa, which contrast with its ferny foliage.
Can I grow astilbe under a black walnut tree? Astilbe is more resistant to the toxin in black walnut roots than other plants, but if planted too close to it they may wilt.
Does astilbe attract pollinators? Yes, astilbe attracts bees, butterflies and moths.