Fungicide essentials for spring protection

Dr Simon Watsonin Pests & Diseases

Today's players have increasingly high expectations of playing surface quality. Most golfers picture themselves on the perfect putting greens of Augusta, even in the depths of winter. Sunday league pub sides and schoolboy teams expect Premiership pitches.

Dr Simon Watson explores proactive, preventative applications and suggests that 'going early' not only achieves longer lasting results, but also considerable savings in time and cost

Today, there is zero tolerance for disease and turf loss, at a time when greater extremes in weather conditions are making it ever more difficult.

The only realistic way to achieve this, without resorting to a routine prophylactic programme of fungicide every four to six weeks, is with proactive preventative applications. That means targeting appropriate treatments during periods of high disease risk. We know that all fungicides work most effectively when applied preventatively, and give the greatest level of protection in the first weeks after application.

Factors you need to consider in assessing risk include:
• Prevailing weather conditions and forecasts
• Existing turf health or stress
• Previous disease incidence
• Turf conditions conducive to disease
• Previous fungicide treatments

Proactive prevention

Proactive application just ahead of disease attack can prevent infection from breaking out. Working on the development of the GreenCast website disease forecasting system, it has been proven that greenkeepers could maintain higher playing surface quality from more effective timing of applications based on disease risk, compared to treatment at the first signs of disease or routine applications (see graph).

Furthermore, by focusing applications during risk periods, control was achieved from the same or fewer treatments - in this case two proactive treatments, compared to four applications at monthly intervals. Even where the same number of applications was used, better risk-based timing led to better results.

The advantage of going early at low disease levels and reducing pathogen risk has also been highlighted in Medallion TL trials this season. Early treatment, to knock-out existing Microdochium (Fusarium) Patch spores in the thatch and keep the leaf clean, left less than 1% disease infection seventy-five days after treatment. When application was later and disease was already present on up to 8% of the surface, disease was successfully checked, but was clearly more evident thirty days after treatment. The lesson is there for the importance to go early to get longer lasting results.

Disease breakout

But, what if you already have disease present? A fungicide application is not going to cure visible disease on the leaves that have already been affected. However, you can still help to stop the spread onto surrounding turf and to limit the extent of any damage, as well as providing clean conditions for the affected plants to recover.

If disease lesions are visible in some leaves, there is a very high chance that other surrounding plants have already been infected by the pathogen; the mycelia will be spreading through the leaves, although the effects will not yet be visible. In these instances you need a fungicide that will quickly move around within the leaf, to seek out and stop the infection.

The timescale for action does depend on the level of infection, the virulence of the pathogen, the health of the turf plant and the prevailing weather conditions but, generally, we are talking hours or, at best, a couple of days. It demands genuine systemic movement from an active that can be taken up and move around within the plant leaf. If you applied a contact or local penetrant at this stage, it would primarily only target pathogen activity on the leaf surface. This can effectively protect from new infection from spores landing on the leaf, but offers little recourse to disease activity already in the plant.

Also, consider the speed of the active uptake and how quickly it can move through the leaf - especially in cooler spring conditions. All systemic actives need some growth to aid movement but some, such as propiconazole, are taken up and move faster than others in cool weather.

Furthermore, if you get an active that is taken up by the roots and crown, it can give a continuous resupply of fungicide through the plant for weeks. Indeed, any active that subsequently exudates from the leaf tip after cutting may be washed down and reabsorbed to recycle the fungicidal properties, such as azoxystrobin in Heritage Maxx and Headway.

In trials, azoxystrobin treated bentgrass and fescue turf has been shown to retain consistent high levels of active in clippings removed for six weeks or more after application, which demonstrated the fungicide was being replenished through the leaf throughout this period. In comparison, trifloxystrobin was present in the clippings at only low levels for only six days after application, and no evidence in new growth thereafter. Biokinetic studies have shown up to 98% of trifloxystrobin was locked into the lipophilic wax layer on the plant leaf surface, with minimal local movement through the leaf, whereas true systemic actives move smoothly and consistently through the leaf.

Contact cut off

With contact products bound onto the leaf surface, as the leaf grows and is cut off, the fungicide protection is removed. With a fine turf surface cut at 4mm, for example, spring growth of 0.5mm a day could see 50% of the product applied cut off in four days, and all removed in just a week. Furthermore, as the plant puts on new growth from the base of the leaf, the new growth will be completely unprotected - where disease can be most prevalent and where damp conditions are conducive to infection.

When we look at appropriate fungicide actions for different periods of the year, then it points towards systemic in the summer when the turf is growing and contact+ activity in the winter, when it's not. But, to refine that recommendation, we are seeing good results from assessing soil temperatures as a guide to growth potential and fungicide selection.

When soil temperatures are consistently less than 7°C, growth will typically be slow or zero and you will get the best out of contact+ activity to give long-lasting results. As temperatures rise above 7°C and turf begins to grow in the spring, or slows down in the autumn, a cool weather systemic will provide the necessary movement to protect the slow growing turf. As temperatures continue to warm up, and when they reach 12°C or more, you can also employ the full systemic actives to maintain clean surfaces right through the season.

Covering a multitude of conditions

Weather conditions in early spring and late autumn often pose a real dilemma for fungicide selection. Warm days that get plants photosynthetically active, are often followed by cold and even frosty nights. That puts extra stress on turf and that can make it more vulnerable to disease infection.

It's a time of the year when multi-active fungicides can have a highly effective role to cover all the eventualities of changeable conditions. The key is to ensure that you have both the systemic and contact facets required in the one product; two relatively immobile contact or local penetrant actives won't give the systemic movement required when the turf starts to grow.

Also, ensure that the multi-active as a whole is providing more active and protection than if the individual components were used alone. When conditions are tough and stressful, it is even more important to have sufficient fungicide on and in the leaf to prevent attacks.
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Pests & diseases