The fungicides that can treat dollar spot and fusarium

Alistair Dunsmuir
By Alistair Dunsmuir February 26, 2012 17:11

The fungicides that can treat dollar spot and fusarium

Over the past few years, disease pressure has been very high throughout much of the country. This has led to some very severe outbreaks of disease, causing major problems both with playability and aesthetics on the golf course. Course managers have had to deal with numerous outbreaks of disease, such as microdochium patch (fusarium patch) on numerous occasions during the last year. Microdochium patch has been a long-established disease in the UK and Ireland. However, it seems to be becoming more and more difficult to manage efficiently. Outbreaks are more common and more damaging than ever before. Similarly, dollar spot is becoming more widespread across the UK and each year outbreaks are more damaging than in previous years. This is especially true where the full range of available fungicides is not employed effectively.

Fungicides fall into different categories, depending on their biochemical and physical modes of action. Their biochemical mode of action is dictated by the chemical family that they belong to. For example, azoxystrobin (Heritage), pyraclostrobin (Eland) and trifloxystrobin (in Dedicate and Scorpio) all belong to the strobilurins. This chemical family prevents electron transfer in mitochondria (the energy-producing organelles in the fungus), leading to insufficient energy production, therefore preventing growth. However, the physical mode of action differs between the three active ingredients. Azoxystrobin is an acropetal penetrant, which means that it is absorbed by the plant and moves within the xylem (the part of the plant that water moves in). Therefore, it will have upward movement in the plant. Pyraclostrobin and trifloxystrobin are both localised penetrants. This means they are not absorbed and move internally within the plant. Pyraclostrobin is tightly bound to the waxy cuticle and trifloxystrobin binds to the cuticle and can be redistributed by surface moisture and vapour phase activity over short distances in the leaf canopy.

The biochemical mode of action is important for resistance management. Active ingredients from different chemical families should be used in rotation to guarantee fungal resistance does not build up, by ensuring different biochemical processes within the fungal pathogen are disrupted with each fungicide spray. This should ensure we have effective fungicides for a long time to come. The biochemical modes of action of the other approved active ingredients are listed in the table opposite.

The third physical mode of action is contact. Chlorothalonil (in Instrata) is a contact fungicide. This active ingredient coats the outside of the plant preventing the pathogen from entering. The physical mode of action is important for the longevity of control. A contact active will give the shortest period of protection when grass is growing strongly, as the coated leaves will be cut and removed quickly. It will last longer when the grass is not growing or is growing very slowly. The protection provided by acropetal penetrants would last the longest in actively growing grass as they are incorporated in to the plant. However, the plant needs to be actively growing to take up the chemical. Therefore, the minimum soil temperature generally recommended for acropetal penetrant application is around 10ºC.

Timing of fungicide application is also important. In general, fungicides are best applied preventatively, when the disease pressure is high, but before symptom expression. For example, azoxystrobin, fludioxonil (Medallion) and tebuconazole (in Dedicate, Astute and Throttle) would all perform best if applied when disease pressure is high, but before mycelia growth has taken hold within the grass plant. This will keep golf greens clean, free from disease and well protected should snow fall leave the greens under very high pressure when curative fungicide treatments could not be applied. The benefits of preventative application of fungicides have been demonstrated in various trials at STRI. For example, preventative application of Heritage maintained clean turf, compared to a few blemishes remaining when treatments were applied curatively (at the very first sign of symptoms), although even this treatment was much better compared to not applying any fungicide in the untreated plot!

Iprodione (Chipco Green), a localised penetrant has good ‘knockdown’ activity at the very first sign of symptoms. However, remember that the grass still has to recover from the initial water-soaked symptoms. Once disease has taken hold, symptoms will have to grow out after control, potentially leading to long-term scarring if winter temperatures mean there is little or no growth.

Dr Ruth Mann BSc (hons), MSc, PhD, MBPR, FQA is the head of turfgrass protection at the STRI

Alistair Dunsmuir
By Alistair Dunsmuir February 26, 2012 17:11
Write a comment

3 Comments

  1. Arny February 21, 22:09

    How can your comments regarding Azoxystrobin as a tool to control Dollar Spot be reconciled with recent research producing evidence it actually enhances the disease?

    Reply to this comment
  2. (@PackLeader5) (@PackLeader5) February 26, 17:34

    Loads of golf courses hit by disease – always good when the STRI helps http://t.co/8NrMD1GX

    Reply to this comment
  3. (@GCM_mag) (@GCM_mag) February 26, 17:12

    The fungicides that can treat dollar spot and fusarium on golf courses http://t.co/HdLlcD4R

    Reply to this comment
View comments

Write a comment

Your e-mail address will not be published.
Required fields are marked*

Join Our Mailing List


Read the latest issues

Advertise With Us

To advertise in the magazine or online, contact:

Email marketing@thegolfbusiness.co.uk

Social media