Interestingly, Foc was not recovered from soil that was treated with urea and the urea/lime combination. Foc was however recovered from soil treated with lime only, proving the application of lime on its own as ineffective at reducing inoculum levels.
Lab trial results have shown that both urea and the combination of urea and lime at the specified rates are effective at killing the spores that cause Panama disease race 1.
These investigations showed that urea applied at 0.062 kg/m2 or greater prevented Foc recovery from soil. All the other chemical alternatives were not effective at reducing the recovery rate of Foc.
Additional trials have investigated the effectiveness of different urea rates (between 0.031 and 0.062 kg/m2) and further explored alternative sources of ammonium. This time the effect of urea, ammonium nitrate + potassium hydroxide and aqueous ammonia were assessed. The trial showed that ammonia (NH3) from any source that produces a concentration equal to or above 2500 ppm was effective at preventing Foc from being recovered from the soil.
These lab trials show the current methods for dealing with infected plants using urea (1 kg per square metre) would significantly help in reducing the amount of inoculum in infested banana paddocks. The trials further show that ammonia, rather than other gasses produced during the breakdown of urea, is likely to be responsible for the toxic effect on the fungus.
For more information about this work contact our better bananas team on 13 25 23 or email: betterbananas@daf.qld.gov.au