Status of Re-evaluation of Chlorothalonil

By Jim Ross

In February of this year, the Pesticide Management Regulatory Agency (PMRA) presented an amendment to a re-evaluation decision with regards to the fungicide, chlorothalonil.  This amendment would restrict the turfgrass use of this fungicide to a single fall application for the prevention of snow mould.  You can download a copy of the WCTA submission below. 

Currently, it is used to prevent a number of turf diseases and can be applied throughout the growing season.  More information can be found on the label http://pr-rp.hc-sc.gc.ca/1_1/view_label?p_ukid=68241114

In the turf industry this fungicide is either used as a single active (Daconil 2787, Daconil Ultrex, Equus 82.5) or as a multiple active formulation (Concert or Instrata).  It has been a very important fungicide in the turf industry for more than 45 years.

A recent webinar was held by the PRMA to inform user groups of the proposed amendment so that a more informed decision could be made about future use of this fungicide.  At this point, the proposed amendment is in the consultation phase where end users are asked to comment on the use patterns and the registrant can provide information on various aspects of the toxicology of the active ingredient.

A number of years ago legislation was enacted that stated that any pest control products licensed in Canada would have to go through an evaluation process every 15 years.  Chlorothalonil has been in use for many years and the review of this product was overdue.

As with any pest control product, it must be tested for its impact on those individuals and/or creatures that might come into contact with the product.  The main concern of the PMRA was for human exposure for those that apply the product and for those who may come into contact with it, i.e golfers.

The reason for the re-evaluation was that the PRMA felt that there was an underestimate of the length of time applicators and bystanders (golfers) might be exposed to the product.  Currently, some uses have worker exposure that is longer than 21 days per year and this was taken into consideration in the re-evaluation.  In addition, the uptake of the active ingredient was thought to be much higher than originally thought.

So,what needs to happen to ensure that the turf industry continues to have chlorothalonil?

First of all, there needs to be evidence that worker and bystander exposure is less than 21 days per year.  This is where the turf industry can provide some input such as how many times per year the product is applied and how frequently workers (other than applicators) and golfers might come into contact with the product during periods of time when residues might be dislodged and end up on the skin.  The WCTA will be compiling information for submission so do not hesitate to provide your input!

For the registrant, the information that was used to register chlorothalonil in the first place is very dated.  For instance, there was never any information presented on the dislodgeability of the active ingredient.  PRMA have used the formula that 25% of the product actually adheres to the leaves when sprayed and that only 10% will dissipate in a 24 hour period.  It is possible that this formula may be very different than what actually occurs.  Evidence needs to be brought forward from more recent information.

The GreenCast blog that Syngenta (the registrant) discusses provides considerable insight into what information that they will provide.  It and other updates can be viewed via the following link http://www.greencast.ca/Alerts/FeatureArticle.aspx?Paid=196818

As many of you know, iprodione is also up for re-evaluation.  I will provide an update in the next newsletter on the status of this important fungicide for the turfgrass industry.