As the fickle Victorian weather attempts to break into some sort of spring, air and soil temperatures are beginning to rise.  While this may enhance root and shoot growth, it also encourages other factors that are detrimental to turf health. As temperatures reach between 24 °C and 32 °C, we enter the optimum range for disease infection and development of Rhizoctonia solani.  Being a Facultative Parasite, Rhizoctonia solani can survive on things like thatch and organic matter in the soil before attacking a living host when conditions are ideal.  Brown Patch infects both cool and warm season grasses in turf.  Symptoms on closely mown turf appear as small circular or irregular patches of blighted leaf tissue ranging from 5cm to 60cm in size.  In dewy or very humid conditions, these patches sometimes produce a dark brown or grey “smoke ring” which indicates active fungal growth on the foliage and imminent development of the disease.  In higher cut situations, patches are usually larger and more circular in appearance with turf in the centre being less affected or having a faster rate of recovery. While the optimum temperature range suggests that late spring to early autumn will be the active infection period, turf growing at its optimum i.e. Couch will often outgrow infections in the summer period.  When optimum temperature and leaf tissue wetness are coupled with high fertility and poor drainage you have a very conducive conditions for disease infection.   Cultural Controls  Apply nitrogen in slow release forms and reduce excessive upfront applications.  Maintain a well-balanced nutrition program ensuring good plant health.  Reduce leaf tissue wetness by removing dew and irrigating early morning rather than in the evening.  Some penetrants can assist with keeping dew to a minimum.  Keep thatch levels below about 20mm to aid in surface moisture control. Chemical Controls Registered control for Rhizoctonia include:  Thiram  Mancozeb  Propoconizole  Chlorothalonil  Iprodione  Azoxystrobin  Trifloxystrobin/Tebuconazole. The key to controlling any disease is to firstly identify the pathogen, select the appropriate fungicide, and apply the fungicide correctly.  It is imperative to read the label and apply the fungicide as the label suggests.  With Rhizoctonia solani in most cases the fungicide needs to be irrigated into the root zone where the hyphae are attacking.  By Lee Govan Turf Diagnostic Solutions