Hibiscus Diseases

Suggestions on dealing with Wilt and Dieback disease in Hibiscus

Author's note: Below is a description on Wilt and Dieback disease in Hibiscus plants and some suggestions on dealing with it. Mr. Charles Black of Hidden Valley Hibiscus provides this information.  He has graciously allowed us to use this information on our web site, for which I am grateful.

Wilt and Dieback can be prevented in many cases but only if one is willing to embrace an overall control strategy.  Here are a few techniques taken from a number of professional books I have plus some experience dealing with these problems at Hidden Valley Hibiscus. 

Hibiscus wilt: The cause

Hibiscus wilt disease is no different from wilts that affect many ornamental plants. It is caused by fungus with such intimidating names as Fusarium oxysporum and Vertocoium. This disease is often referred to as "root rot" but that is a misunderstanding of the problem.  What is actually happening is that pathogenic fungi are rapidly reproducing in the soil mix of the pot and entering the plant through roots.  The roots of such plants do not show any "rot" except possibly tnicillium the late stages of the disease if the plant survives that long.

Once inside the plant, the fungi disrupt the capillary system of the plants, preventing water and nutrients from circulating normally.  That is when yellow and or droopy leaves appear over the entire plant or over one side of the plant.  Do not confuse this with a few wilted leaves at the top of a stem (more on that later).  Also always check to be sure the plant has sufficient water as dryness is the most common cause of wilting.  If the plant remains wilted although there is ample water, read on……

What can be done?

  1. Prevention, before wilt occurs:
    • Keep your pots clean. Remove dead leaves and flowers from both the plat and the pot.
    • Control insects as tey can spread disease and make wounds in the plant that pathogens can enter.
    • When transplanting try not to wound the plant, as such wounds are entry points for pathogens.
    • Do not over fertilize when the soil mix is dry as this can burn the roots and make the plant more vulnerable to attack.
    • Adjust watering to match the season and the weather.  In the summer they need lots water often daily, but in cooler times reduce the frequency of watering so as not to create conditions that favor fungi growth.
    • Apply worm castings to the surface of the potting mix, working it into the mix as best you can.  Start with a layer that is ½" to 1" of castings on the surface of the potting mix.  This has reduced my problems with wilt of young transplants to almost zero the last several years.
    • Apply Rootshield/Plantshield beneficial fungi according to label directions.  This material is similar to the worm castings but perhaps mote potent and targeted to diseases problems.
    • Optional but recommended for those with continuing disease problems. In fall and again in spring drench your pots with fungicides.  Phyton (copper based), any product containing thiophanate methyl such as Cleary's 3336. Domain or Fungo or other fungicide recommended by your local Ag extension office (I like Medallion personally) will help to remove or suppress fungi.  Subdue Maxx is not recommended as it is specific for other types of fungi that do not usually cause the wilt disease nor the dieback disease in hibiscus (advise you might see elsewhere notwithstanding).
  2. Curative, after the wilt appears:
    • Immediately try an emergency save by mixing 1 pint of house bleach with 2 quarts of warm water and pouring the solution into the pot with the wilted plant, saturating all of the potting mix. This will kill off the fungi in the mix but will not affect the fungi already in the plant.  Sometimes the plant recovers after this, sometimes not.  If the plant is still alive a week later try adding Plantshield/Roorshield to the mix so that these beneficial and protective fungi will colonize the roots again.  A transplant shock treatment containing Vit B is also good, Superthrive being one such product.
    • Alternative to bleach, use the fungicides above as a drench in the potting mix.
    • Sometimes removing the wilted plant from the pot, removing as much soil as possible from the roots and then washing the toots with clean water can achieve a rescue. Afterwards repot in fresh clean soil mix in moist, but is not sopping wet potting mix.
    • While the plant is recovering keep it in the shade and do not over water it.  New leaves will appear after some days or even weeks if the plant is recovering. If no leaves appear, try scratching the bark on the main stem it see if there is green underneath. If not then the plant has died and should be disposed of the property place in plastic a bag and place in the trashcan is one method.
    • Wilt is a serious plant disease. Prevention is better than a cure as many plants will perish once they have it, no mater what type of "cure" is tried.

Hibiscus Dieback disease

This disease happens whenever fungi or bacteria enter a stem through a wound and causes a rot to begin at the point of entry.

The most common type occurs when a flower does not fall from the plant but remains attached to the peduncle (stem that attaches the flower to the plant). Both the old flower and peduncle are eventually invaded by fungi and or bacteria, and if left on the plant the infection spreads from peduncle and then into the plant where the peduncle attaches to the plant.

The second most common form happens when the flower falls off the peduncle but is caught in the stems and foliage of the plant and is held against on to the main stems. Here it will be attached be fungi such as Botrytis and as it molds and rots it passes this infection on to the stem is touching.

High humidity, clouds, and poor air circulation encourage dieback disease, which is why it is seen most often during periods when weather creates these conditions.

Another form of dieback can occur from internal infections of the plant similar to those that cause the Wilt Disease.  In the case of dieback the fungi or bacteria (Erwinia sp mostly) do not block the circulation of nutrients enough to cause wilt but instead accumulate at the very tips of the stems where they will sometimes appear to explode of the top of the branch.

  1. Prevention, before the dieback occurs:
    • Remove all spent blooms from the pants.
    • Remove the peduncle that was holding the flower. Do this carefully so as not to create a wound in the side of the stem.
    • Provide good air circulation with fans or plenty of vents if indoors.
    • Wet conditions will contribute to the problem. If there is anyway to prevent plants from being wet, particularly at night, do this.
    • Follow the same smart growing practices as outlined for wilt disease, such as cleanliness, insect control etc.
    • Promote a healthy soil using worm castings and or beneficial fungi.

  2. Curative, after the dieback appears:
    • Dieback is less often fatal than Wilt Disease if one acts quickly to control the problem.
    • The best way to deal with dieback is to cut away the infected part of the stem(s) from the plant. Find the source of the infection, which will appear as a dark of discolored area on the stem. Often there is wilting of leaves immediately above the infected area. Go down the stem one or two nodes and then cut the stem ¼ inch above the node, removing the infected area.  Dispose of the bad wood in the trash, not on the ground.
    • Next, look at the inner core of wood it has been cut.  It should appear clean and white. If there is dark streaking visible it is best to go a few more inches down the stem and cut again. Keep doing this until clean weed is found. It does not hurt to apply grafting wax to such cuts as this will help prevent re-infection thru the cut. Alternatively, painting the wound with Phyton (Copper biocide) diluted to label specified strength is a good idea, too.
    • Most Hibiscus will recover from Dieback if the infection is removed from the plant, if not removed it can spread to the entire plant and kill it. But often-older plants will stop the infection before that point. Still, it is best to remove the infected area, which also serves as a pruning for the plant, something the plant needs from time to time anyway.

Viruses

University researchers in Hibiscus have found a half dozen or so viruses. However, most commercial labs do not even have tests to detect them. There role in Hibiscus disease is poorly researched with little information available, but common diseases must Hibiscus growers will see have been diagnosed by labs as caused by fungus and sometimes by (Erwinia ct.). The symptoms are classic for these type of diseases and the prevention and cure of them is also well established as they are basically the same in all ornamental plants.

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