With the final use-up date for chlorothalonil rapidly approaching, arable growers will need to consider switching to folpet to maintain effective protection against cereal diseases such as septoria in wheat and rhynchosporium and ramularia in barley.
As a multi-site fungicide which targets multiple metabolic sites within a pathogen, chlorothalonil (CTL) has been the ‘go-to’ multi-site fungicide for many years thanks to its ability to perform two important functions: providing effective control of key wheat and barley diseases, and reducing the risk of further resistance to at-risk single site actives.
Unfortunately, CTL can’t be used beyond the 20th May after the EU voted to revoke its license, prompting some within the industry to wonder if it is feasible to choose simply not to replace the multi-site component of their crop protection programmes.
Omitting a multi-site fungicide would be a dangerous backward step as it would put crops at increased risk of infection and heighten the resistance risk for other modes of action.
Growers are therefore urged to switch to Arizona (500 g/L folpet) as an alternative to chlorothalonil: Arizona is flexible enough to be used at T0, T1 and T2 (at a maximum individual application rate of 1.5 L/ha and a total application rate of 3 L/ha) to protect wheat against septoria and barley against rhynchosporium and ramularia.
Arizona also provides some activity against yellow rust in wheat, and offers the additional advantage of not interfering with the curative kickback activity of azoles: an important factor where active rust is present.
Folpet acts on multiple bio-chemical pathways making it less susceptible to resistance.