Leaves Discolored, Fall Prematurely; Stems Woody Means Water Problems
Mums growing in poorly drained or heavy soil, or that are getting too much water, start to drop their leaves because their roots are drowning. Move the plants to a better-drained site and improve the original soil by mixing in lots of sand, peat moss 6 75 100 and other organic materials to increase its ability to drain excess water. Conversely, if garden mum plants are consistently underwatered, they’ll develop woody stems and lose many of their lower leaves. Water more frequently, and see that the water soaks through the mulch layer instead of running off. Water more frequently during droughts.
Lanky, Flopping Stems Are Caused By Too Much Shade
Garden mums need at least 5 hours of sun daily; even more is better. If they do not receive this, either clear away any neighboring plants or branches which are shading the maturing mums, or move the mums to a sunnier location. If sun is scarce in your yard, plant mums in containers that can be moved into the sun.
Leaves Are Curled And Distorted By Aphids
Aphids, also called “plant lice,” are soft-bodied, pear-shaped sucking insects about the size of the head of a pin. They often gather in large, visible groups on tender tips of stems and buds of garden mums. Their feeding distorts plant growth. Chrysanthemum leaves may turn yellow or brown. They wilt under bright sunlight, or sometimes curl and pucker. Often this problem is most easily eliminated by simply pinching off the infested tender tips and discarding them--aphids and all--in a plastic bag in the trash. Since mums respond well to pinching of their tips anyway, this does them no harm. If aphids return, then spray them with an insecticidal soap product according to label directions. Check to see if the plant is stressed in some way that makes it vulnerable to insect infestation.
For more information see file on Dealing with Aphids.
Leaves Blotched With White Trails Caused By Leafminers
Chrysanthemum leafminers are tiny white maggots that feed on the soft tissue between the upper and lower leaf surfaces, leaving distinctive light-green to brownish serpentine “mines” visible in the leaves. After about 2 weeks, large areas of leaf blades become discolored and collapse. The larvae pupate just outside the mines, in brown seedlike cases which are often attached to the leaf. After another 2 weeks they emerge as small 2-winged flies. Pick off and destroy all infested leaves. Prune stems down to healthy growth. Larvae can be repelled by spraying plants with a commercial insecticidal soap product in late June or early July.
For more information see file on Dealing with Leafminers .
Plant Grows Poorly Because of Mealybugs
Mealybugs are 1/5 to 1/3 inch long, oval, flattened, covered with white waxy powder and adorned with short, soft spines around their margins. They suck plant sap, then the honeydew secretions from their feeding encourage mold growth on the chrysanthemum leaves and attract ants. Mealybug-infested plants look unsightly and grow poorly. They may die if severely infested. Control mealybugs by spraying them directly with insecticidal soap.
For more information see file on Dealing with Mealybugs.
Stalks Break Off Due To Feeding Of European Corn Borer
Caterpillar larvae of the European corn borer are grayish-pink, with spots on each segment and a dark head. They may burrow into chrysanthemum stems, hollowing them out and causing them to break off easily. Corn borers are easier to prevent than to control once they appear. Spray any mum leaves hosting visible young, feeding caterpillars with Bacillus thuringiensis (Bt). They will ingest this bacteria, become ill, stop eating and die in a matter of days. A thorough fall garden cleanup and rotation of the plants in the garden are the best long-term controls. Some mum varieties, such as ‘Fireside Cushion’, ‘Buckeye’, ‘Grenadine’, and ‘Viking’ are relatively resistant to these borers, probably because they have thinner stems than more susceptible varieties.
For more information see file on Dealing with Corn Borers.
Ragged Holes In Leaves Are Chewed By Slugs Or Snails
Slugs are essentially snails without protective shells. They are usually 1 to 2 inches long (some species grow up to 8 inches). They may be white, gray, yellow, brown or black. Mums attacked by slugs and snails suffer large ragged holes in their leaves and stems. Slugs and snails are attracted to moist, well-mulched gardens and acidic soil. They are active at night, rasping holes with their file-like tongues in leaf and stem surfaces. They hide under boards or leaf litter during the day. Trap them in a commercial slug trap or in shallow plate baited with beer and set in the garden. The pests are attracted to the yeast in the beer, climb in, and drown. Begin trapping within the first three to four weeks after the last frost. The more you catch early, the fewer there will be to reproduce over the season.
For information see file on Dealing with Snails and Slugs.
Leaves Are Mottled, Blotched By Botrytis Gray Mold
This fungus attacks chrysanthemum leaves in cool, damp environments or if they have too much shade. Control it by thinning plants to improve air circulation, moving them to a sunnier location, or improving soil drainage. Pick off damaged leaves and dust uninfected leaves with garden sulfur to prevent the spread of the fungus. Dig up and discard individual plants that seem to catch this disease year after year.
For more information see file on Dealing with Fungal Disease.
Leaves Covered With White Powder Have Powdery Mildew
Powdery mildews are caused by fungi that live on the surface cells of the plant, not inside them. Infected leaves are covered with a white or ash-gray powdery mold. Badly infected chrysanthemum leaves become discolored and distorted, then drop off. Powdery mildews thrive in both very humid or very dry weather. They are not life threatening, but they are unsightly. If it is not possible to ignore the mildew, spray healthy leaves on affected plants and healthy neighboring plants thoroughly with garden sulfur to prevent the spread of the fungus. Follow the instructions on the product label. Allow ample spacing between plants to promote air circulation and collect and discard all aboveground refuse in the fall.
For more information see file on Dealing_with_Fungal_Disease.
Plant Blooms and Stem Tips Eaten Might Be Deer
Deer will eat many ornamental plants in the home landscape and chrysanthemums are a favorite snack. For complete information go to the file Dealing With Deer