The IPM group in RustWatch carried out field trials and tested alternative chemistries effect on yellow rust in 2019.  

Four field trials were carried out in four different countries screening for alternative chemistries for control of yellow rust in 2019. The trials were carried out by JKI in Germany, NIAB in UK, Arvalis in France and AU in Denmark. The protocol included untreated and eight common treatments, as well as room for one local adapted treatment. Among the tested products were six alternative products. These substances have not previously been specifically tested for their efficacy for control of yellow rust. However, the substances have been recognized for providing low to moderate levels of disease control against some other pathogens.

The alternative products included two biological control agents (BCA) (Tricoderma and Bacillus subtilis) as well as four alternative products (phosphonate, Sulphur, combinations of the two and Chitosan). Two chemical references were used at low rates (10% rate of pyraclostrobin and 25%  rate of tebuconazole) representing traditional chemistry, known to provide effective control of yellow rust.

Three of the trials with moderate to severe attack of yellow rust showed all very clear differences between control from different treatments with BCA and alternative chemistries providing inferior control to traditional fungicides. The French trial developed severe attack of yellow rust and very low levels of control from alternatives (0-10%). This was in contrast to 99% control from the chemical reference using 4 x quarter rate of tebuconazole. The trial in UK showed 0-13% control from alternative chemistries and 100% control from the tebuconazole solution.  The Danish trial developed moderate attack and alternatives provided 0-50% control, but again the reference tebuconazole similarly to the other two countries showed 100% control.

The two trials, which provided usable yield data did not show significant yield responses from the six alternative substances tested. In the French and UK trials’ the reference with tebuconazole increased yields by 44 dt and 32 dt/ha respectively compared with untreated.

The data from 2019 create the basis for next years’ IPM trials, which will focus on different alternative measures for control of yellow rust including the use of resistant cultivars, cultivar mixtures and DSS.