By: Teo Spengler
Chrysanthemumplants are among the easiest perennials to grow in your garden. Theirbright and cheerful flowers will bloom through the first hard frost. However,mums are not immune to diseases, including collar and stem rot ofchrysanthemums. Read on for information on these chrysanthemum issues as wellas tips for mum rot treatment.
Collar and stem rot of chrysanthemums are caused by severaldifferent fungi. These include Fusarium, Pythium and Rhizoctonia.
When Fusarium fungus causes the rot, the disease is alsocalled fusariumwilt. You’ll notice that the plants wilt, as if they need water. However,water won’t help with fusarium wilt, and the plants soon turn brown and die.When Fusarium enters through the soil line, it is called chrysanthemum collarrot. It can also enter through the roots of the plant. The diseasedchrysanthemum can die stem by stem or it may die all at once.
The fungi, Rhizoctoniaand Pythium, also cause chrysanthemum stem rot and collar rot. Rhizoctoniausually occurs when you get hot, dry weather on the heels of very wetconditions. When it is Pythium fungus causing the collar or stem rot, itusually results from poor drainage combined with heavy irrigation or rain.
The fungus causing collar and stem rot of mums spreadseasily, making it harder to control. Your plants can get the fungal diseasefrom containers, tools, or anything used to transfer soil or growing media.Note that the fungus produces spores which can live in the soil for longperiods of time.
If you want to limit these fungal rots in your chrysanthemumplants, use sterilized soil in your flower beds. It also helps to make sureyour cuttings don’t carry a fungus. Propersoil drainage is essential.
Is there any mum rot treatment? If you find that your plantshave collar or root rot, stop irrigating them immediately and allow the soil todry out. You can also apply appropriate fungicides,but this usually works best if applied quickly after transplant.
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Chrysanthemum sp. (Shasta daisy) can get Alternaria leaf spot that causes concentric rings of light and dark. Septoria leaf spot usually causes brown along the margins and tips of leaves. Botrytis may cause flowers to brown and die early as well as cause irregular brown spots on leaves and shoots. Fungicides and sanitation are helpful.
Chrysanthemum sp. (mums) may get Botrytis on buds, flowers, leaves, and stems. Infected areas are brown to dark brown in color (the gray fuzzy appearance requires proper moisture conditions). Infections start as small spots and rapidly expand to encompass the entire bud or flower. Sometimes mums get rust diseases that can be whitish or brownish in appearance. Fungicides and sanitation are helpful.
Fusarium wilt is also a possibility. Fusarium may enter through roots or at the soil line (collar rot). Plants wilt, then turn brown and die. Plants may go "piece meal" or all at one time. Rhizoctonia and Pythium can cause root rots and collar rots. Pythium occurs when soils drain poorly or are kept wet by over watering. Rhizoctonia may occur when soils are wet followed by hot dry conditions. Control is to fix drainage problem, reduce watering and then treat the soil with the correct fungicide.
Written by James Schuster, Extension Educator, Horticulture, and reviewed by Bruce Paulsrud, Extension Specialist, Plant Pathology and Phil Nixon, Extension Entomologist, University of Illinois at Urbana-Champaign.
Mix together 1 pound of dry copper sulfate with 1 gallon of warm water in a plastic bucket and stir with a long plastic spoon or other plastic utensil.
Combine 1 pound of fresh hydrated lime with 1 gallon of warm water in a plastic bucket using a plastic spoon or other plastic stirring utensil. Allow the lime mixture to stand for two hours.
Pour 2 gallons of water in a plastic bucket. Stiry the copper sulfate solution well and add 1 quart of it to the water. Agitate the lime solution vigorously and add 1 quart of it to the water.
Stir the mixture and pour it in the tank of a pump or backpack sprayer. Shake the tank between sprays to prevent clogging the nozzle. Discard any leftover Bordeaux mixture after using.