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The smart way to manage disease

Features, News, Research / 6th October 2017

Improving your turfgrass management skills is an important part of career progression in the turf industry. Here, STRI’s head of research, Dr Ruth Mann, gives an insight into the significance of Integrated Pest Management, which form part of STRI’s Autumn training courses.

As part of a good Integrated Pest Management (IPM) strategy, we must make the best use of those fungicides we have and ensure that we keep the active ingredients working as efficiently as possible without encouraging field resistance in our pathogen populations.

IPM strategies will not only reduce the chance of resistance occurring but may also reduce the amount of plant protection products required providing environmental and financial benefits. An IPM strategy consists of:

Cultural Practices

Disease Resistance

Biological Control

Plant Protection Products

 

Good IPM starts long before a disease is ever encountered – we would call it traditional greenkeeping methods. In the IPM strategy it is termed cultural practices. By this we maintain the turf as healthily as possible. There is no exact recipe that can be followed by everyone. Each aspect of your management strategy depends on what you are trying to achieve in the long term and what the problems are to begin with.

 

Cultural control

This includes using adequate fertiliser to keep the grass growing but never lush, appropriate fertiliser (such as acidifying fertiliser like ammonium sulphate to discourage alkaline conditions that may encourage certain diseases) and fertilising at the correct times. Returning clippings is also a form of fertilising as the nutrients within them can be broken down and reused. However, they also form food sources for earthworms and many pathogenic fungi and so should be avoided on greens.

Irrigation and drainage are other important issues. If the rootzone of your greens is sandy, suffers dry patch and drought is a problem you will need to irrigate and perhaps use wetting agents. This leads to ensuring that your irrigation water is not alkaline (and so may encourage take-all) or that the salinity is not too high. However, on wet, water retentive rootzones the issues for concern are different. The most important issue is to improve drainage. In the long term this may mean installing drains. In the short term surface drainage can be improved by aeration. This will also help keep the rootzone aerobic and decrease thatch accumulation, which can further exacerbate problems of surface drainage. Thatch layers can encourage the formation of wet surfaces in the winter and dry hydrophobic surfaces in the summer. Thatch can also be the primary source of many fungi that spend most of their time growing saprophytically on the thatch, becoming pathogenic and causing the disease when the environmental conditions favour their growth. Thatch should, therefore, be kept to a minimum.

 

Thatch

Thatch

 

Airflow over greens is important for the removal of surface water. Many of the pathogens that affect turf require water for spore germination and infection. By decreasing the length of time the surface stays wet you can reduce the amount of spores that germinate and infect the grass. Removal of surface water can be done by switching and by increasing the airflow over greens by judiciously pruning trees or shrubs that surround the area. Shading by trees and shrubs may increase the length of time for greens to dry due to lack of direct sunlight. Some diseases are also more prone to occur under low light intensities.

The cutting height should be appropriate for the grass species that you are growing. Leaving grass too long can encourage a microclimate more suitable for the pathogenic fungi. However, too short a cutting height leads to stressed grass plants that are also more susceptible to disease. The incidence of anthracnose has increased rapidly over the past few years. Part of the reason for this may be due to the concurrent lowering of cutting height. This may have lead to stressed annual meadow grass plants that are more susceptible to anthracnose.

 

Anthracnose

Anthracnose

 

Disease Resistance

Some species of grass are not susceptible (or less susceptible) to certain pathogens. Fescues are not affected by Gaeumannomyces graminis (the pathogen that causes take-all). If take-all becomes a problem and is killing bentgrass, the area could be oversown with fescue to keep grass cover and prevent the ingress of annual meadow grass or broad leaved weeds.

Some cultivars are more susceptible to certain diseases. This may be important in the case of red thread for example. Normally, red thread is associated with low fertility and would be controlled by the application of a nitrogenous fertiliser. However, we are observing red thread that is not controlled by increasing the fertility and requires the application of a fungicide. Tables in Turfgrass Seed show varieties of bent and fescue that are not as affected by red thread.

 

Red thread

Red thread

 

Biological Control

Biological controls consist of using antagonistic fungi and bacteria to compete with or parasitise the pathogenic fungi. In a sense, traditional greenkeeping methods help to enhance the biological profile within the rootzone encouraging a natural biological control. The use of applied biological controls can be complicated. The applied fungi or bacteria must be able to establish and persist in the rootzone. They must have activity against local isolates (products with good efficacy in the USA may not be as effective on our pathogens). All applied fungi and bacteria needs to be compatible with fungicide use.

 

Plant protection products

A particularly prolonged period of conducive conditions can increase the disease pressure to the extent that the amount of disease on greens becomes unacceptable despite the employment of all of the above non-chemical control methods. Plant protection products then become an essential part of an IPM strategy.

The pathogen must be correctly identified before any fertiliser or plant protection product is used. Some diseases can be encouraged by fertiliser application. If the identification is wrong and a fertiliser is applied, it may make matters worse. Similarly, some diseases are not controlled by certain fungicides. Applying the wrong one will cost a lot of money and it was never going to make any difference. Seek confirmation if you are not 100% sure.

When you know what the pest or disease is, application of any plant protection product should be carried out according to the manufacturers recommendations on the product label. Remember that all persons applying plant protection products should have the correct training (NPTC certificates) and that you always adhere to the recommendations on the label of the particular product and ensure COSHH regulations are applied.

 

Resistance management

In order to reduce the chance of resistance occurring in our pathogen populations you need to be aware of the properties of the products that are approved. Some fungicides work better on certain pathogens, some provide better control when applied to protect the plants from disease spread whereas others can cure established infections.

With all fungicides, applying the same active ingredient continuously in any one year, or over a few years will increase the potential for resistance to occur. Once we have widespread resistance (especially in populations where the resistant isolates are as fit for survival as the sensitive isolates) we have effectively lost that group of fungicides from our armoury. This reduces the number of effective fungicidal active ingredients that we have left. To prevent this occurring the Fungicide Resistance Action Group (FRAG-UK) suggests the following:

1. Avoid prophylactic treatments (always treat at the first sign of disease rather than preventatively).

2. Avoid repeated applications of fungicides from the same GROUP.

3. For control of red thread and rusts, make full use of disease resistant varieties.

4. Pay attention to guidelines on labels for maximum dose rates, maximum number of treatments, rotation of fungicidal groups, recommended mixes or approved tank mixes.

 

Remember that an apparent loss of efficacy of a certain product does not immediately imply field resistance as incorrect identification, incorrect dose rates and inclement weather conditions directly after application may all contribute to ineffective control. By following a good IPM strategy, personalised for your grass type, soil type and conditions, greens may be kept disease free most of the time. However, when the pathogens are winning, the implementation of IPM will also keep the fungicides working effectively, providing the last line of defence.

 

If you would like to learn more about Integrated Pest Management and want to gain formal qualifications in Amenity Horticulture why not speak to STRI about our foundation courses, recognised by BASIS.

We will be running a Foundation Course in Amenity Horticulture from Tuesday 31st Oct to Thursday 2nd Nov 2017.

For more details or to book your place on the course click here, call 01274 565131 or email enquiries@strigroup.com

 

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