How To Control Root Rot In Landscape Plants | Maintaining Lawns And Gardens

How To Control Root Rot In Landscape Plants | Maintaining Lawns And Gardens

In humid climates such as Queensland, and even in locations such as Sydney, root rot can be a major problem for certain plants.

Disease Causing Organism: The primary pathogenic fungi causing this problem is Phytophthora (Root Rot Fungus). A fungus with a well publicised history. Once the plant is in a weakened state, other pathogenic fungi i.e. Rhizoctonia, Colletotrichum, Fusarium can invade to complete the continuing decline of the plant.

Symptoms: The first visual symptoms are that the plant ‘appears’ to be dry. The leaves are curled inward and hanging limply on the plant. A simple test to you can do is to gently tug the central leaves. If the disease is well advanced, these leaves will come away and have blackened, smelly ends. If doesn’t pull away, have a close look at the crown for black discolouration.

There are ways to avoid the problem in the first place. One is to use better plant varieties that have resistance to these root diseases. For example, use resistant varieties of Lomandra longifolia such as Tanika or Katrinus, rather than the common form. With the common form you never know what you’ll get, for instance a third may be resistant and the other two thirds may be prone. You might even get sand dune varieties, which will quickly die when exposed to root rot in heavy soils. Another suggestion is to reduce the conditions which cause root rot.

Causes:

  • Planting too deep. Many grasses, grass like plants, and numerous other forms of plants have only one growing point (the crown). If this is buried too deep and covered with soil, problems will arise.
  • Mulching practices. The number 1 cause. Covering the foliage and crown with mulch. Mulch should be kept away a min. of 75 mm away from the crown of plant and under the foliage. Keep the mulch out of the foliage. Try to use mulch that is of a coarse grade with no fines, such as hard wood chip. Mulch with a lot of leaf litter or fines, become a haven for such diseases, and when they get wet they tend to not breathe, and act as a breeding ground for root rot.
  • Over-watering after planting. This disease spreads via ‘free’ water. Over-watering with irrigation systems coupled with poor drainage particularly along garden edges during the establishment phase generally leads to soggy areas in the gardens. Ideal breeding grounds for this disease particularly in the hot, summer months

Simple Management Tips: Check for the above causes and undertake ‘fix-up’ program. One of the best and most cost effective chemicals is Phosphoric acid, which will help with Phytophthora. Another safe chemical program that can be used to overcome the disease is two applications of a heavy drench of Fosject and Thiram mixed together at recommended rates, five days apart. Apply to the crown and foliage to the point of run off.

If the problem is Fusarium or Rhizocktonia, Baycor from Nuturf is a good option. Often it is necessary to alternate between different treatments to achieve the desired results. Root rot generally occurs in the first summer after planting, and generally as a result of bad planting practices, so by following these guidelines, you should be able to solve or avoid the problem.
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