Good practice I Rhizoctonia

The fungus Rhizoctonia ssp. can be combated by means of good practices which, if taken into account, will save a lot of headaches. Symptoms of Rhizoctonia development can be the Brown patch, Large patch or Yelow patch,

Rhizoctonia can present itself in different forms in the field, such as the famous "Brown Patch" or the "Yelow Patch" or the "Large Patch".

• Brown patch, caused by Rhizoctonia solani, develops in warm and humid weather. The fungus becomes active at times when the air temperature does not fall below 15ºC and the soil temperature does not fall below 18ºC. But generally, no major problems are seen until air temperatures above 25°C are reached in combination with a relative humidity of 95% for more than 10 hours. Such high humidities are easily reached at ground level with dew or heavy watering.

• Large patches develop during dormancy periods of C4 species due to Rhizoctonia solani. They are large patches that can develop in the same places every year. It is estimated that the temperature of thatch should be between 10 and 21°C and a high relative humidity. In many cases, infection occurs in autumn and symptoms appear in the spring of the following year. As in the Brown patch, it is important to keep the leaves and collars of the plants as dry as possible.

• Yelow patch occurs in areas with warmer temperatures than brown patch as it can be problematic from 20°C and is also combated by keeping the turf at low humidity. It is common in the transitions from autumn to winter and from winter to spring.

The appearance of the spots is favoured by any factor that does not make it easier for the leaves not to dry out, such as excessive shading, lack of ventilation or drainage. Excessive nitrogen or the use of mulch that has not completed its composting process correctly also encourages the fungus.

The combination of heat and humidity is often the trigger for most fungi affecting plants.

Knowledge is essential to define effective good practice:

To control their impact, there are techniques that encourage long, infrequent irrigations to minimise water-leaf contact. Shifting irrigation to the morning to eliminate large spray and droplets and to encourage rapid drying of small spray droplets has a good effect. Early in the morning, mowing with a mower, a roller or a bar over the surface removes the dewdrops.

-Excess nitrogen means that natural defence mechanisms are not triggered, and plant growth occurs with soft tissue that is easy for fungi to invade. Nitrogen doses during hot periods should be low.

-Poor drainage prevents the turf from drying out quickly, so dethatching and thatch removal will be a good remedy for brown patch.

The fungus does not normally kill the crop and will recover as soon as the fungus is no longer active.

-Watering in the late afternoon so that the leaves do not remain wet for too long during the hot summer nights. Refreshing watering usually has little impact because the heat of the day dries the grass quickly.

-Remove vegetation from areas of low sunlight or ventilation, and in high maintenance areas forced ventilation and artificial lighting can be installed to help keep the turf dry and healthy.

-The scheduled preventive use of chemical fungicides such as Azoxystrobin, Fenarimol, Flutolanil, Mancozeb, Myclobutanil, Propiconazole, Triadimefon (It is important to know which are valid in the area of use) are a valid strategy to assist all the above good practice techniques. When the impact of Rhizoctonia is intermittent, fungicides can be used in a curative way to minimise the impact on the environment.

Gutation is the exudation of xylem sap droplets at the tips or edges of leaves of some vascular plants, such as grasses.

The impact of Rhizoctonia can be controlled very efficiently, although it will be impossible to eliminate the fungus 100%. Field knowledge and experience are invaluable tools. Many greenkeepers carry out these walks hand in hand with moisture measuring instruments like POGO o TDR to finally take advantage of the reconnaissance and gather more information on the state of the field.

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