All posts

All things White Rot

31 July 2013

At conference in Wellington at present, have to say a topic being spoken to me the most is White Rot and chemical programs for White Rot.

Be great to have your thoughts on what is being applied, how big the problem is (of which I knkow it is a HUGE problem)

I have to say it is a most important issue / challenge for the onion industry. There is only a certain amount of chemistry available, of which must be used sustainably and responsibility to give us efficacy for many years to come...

With Luna Devotion, Pristine and Cereous registered, we need to use these products responsibly, so as they are available to use into the future.

Be great to hear your thoughts and comments

Below is a post from another onion thread by Bharat Jivan:

There appears some resistance building up against our traditional whiterot control. Would be great to see chemical companies get their heads together collectively and sort out a whiterot control strategy for the industry.

Early infection coming through in young onions - Thank you for the picture Bharat Jivan


PristineOnionsVegetables


Comments 8

  • Fenton Hazelwood (Moderator) 31 Jul 2013

    I have asked Grant Hagerty, our Tech Lead / R&D to give some thoughts on programs...

    Stand by

    • Grant Hagerty 31 Jul 2013

      Fenton is right, we have only 2 strong fungicide modes of action against onion white rot (OWR), these are either DMI’s, triazoles like Cereous, or SDHI’s in mixtures like Pristine or Luna Devotion.  All are at risk from resistance developing if abused.  Cereous has been the cornerstone, and only player, in the OWR programme for far too long.  Pristine and Luna Devotion offer a new mode of action (SDHI) against OWR but this MUST be protected from overuse if they are to last.

       

      I would say growers have been very lucky Cereous has been as robust as it has.  8 applications per crop cycle and rates of use 2-4 time label rates have occurred.  This sort of abuse will break the SDHI’s and once broken there is no replacement on the immediate horizon.

       

      A resistance strategy specifically for OWR management is not currently published.  The labels for all products have limitations on the frequency of use per crop cycle and sequential use.  These are:
      Pristine -  2 applications (SDHI + QoI)
      Luna Devotion - 2 applications (SDHI + DMI)
      Cereous -  3 applications. (DMI)

       

      So programmes following resistance management must be limited to no more than 3 SDHI per crop cycle and 3 DMI per crop cycle.  E.g. DMI/DMI/SDHI/SDHI/DMI/SDHI giving 6 possible spray options.  Unfortunately the maximum possible combination is 5 sprays, Pristine & Luna Devotion are each limited to 2 applications and Luna Devotion contains both of the critical modes of action so counts as 2 applications..  The following are possible.

       

      #1 Cereous/Cereous/Pristine/Pristine/Cereous

      #2 Cereous/Pristine/Cereous/Pristine/Cereous

      #3 Cereous/Pristine/Pristine/Cereous/Luna Devotion

      #4 Luna Devotion/Cereous/Pristine/Cereous/Pristine

      #5 Cereous/Luna Devotion/Pristine/Cereous/Pristine

      #6 Cereous/Pristine/Luna Devotion/Cereous/Pristine

      #7 Pristine/Pristine/Cereous/Cereous/Luna Devotion

      #8 Pristine/Cereous/Pristine/Cereous/Luna Devotion

       

      From our trial work we believe the best programmes start with Cereous so we eliminate options #7 & #8.  Option #4 is also eliminated as the rate of DMI in Luna Devotion is lower than the full dose of Cereous.  All of the remainder are viable.  My preference is #6 as it starts strong with a full dose of DMI, swaps to a copletely non-DMI product and finishes with Pristine as it has label claims for both OWR and Downy mildew.

      We cannot let the SDHI group be abused because they are the best products available now and for the future.

       

  • Bharat Jivan 01 Aug 2013

    Thanks for that advice Grant. Last season I applied #4 program still had whiterot show up. This year I made the call to apply Pristine first. My thoughts were that maybe the triademenol was not not working at the early part of the crop. We have been told in the past that the first application is critical and sets up the W.R. Program. I was going to use a triademenol next but will now consider pristine....

    • Grant Hagerty 01 Aug 2013

      Hi Bharat
      I make the call that Cereous should go first based on a number of trials we did, unfortunately, in 1999-2006 and in those times Cereous was a serious OWR product.  It was consistantly ahead of Pristine, but both products still did great jobs.  The key for us was the industry needed alternate chemistry and Pristine was certainly good enough for that.  It was similar to the situation with Ascend on onion Thrips, we could never beat endosulfan but that became irrelivant as endosulfan was withdrawn.

      Anyway data I just got from three trials in Pukekohe in 2012/13 seems to point that both Pristine and Cereous are about equal ..

      Product

              

      mean of 3 trials

      Untreated    11.9% plants infected
      Cereous      3.9% plants infected
      Pristine        4.2% plants infected.

      So your choice (#4) may be the best option after all - just rotate the chemistry and close up the gaps.

      • Rob Cox 17 Sep 2013

        I'm a wee bit late joining this guys but in my opinion programs 3,7 & 8 won't work in a commercial situation due to the witholding periods of Luna Devotion. Even programs 4,5 & 6 are likely to be a bit of a struggle with the slightly shorter witholding period of Pristine.  

        • Fenton Hazelwood (Moderator) 18 Sep 2013

          Take those thoughts on board Rob.

          It is going to be a challange to work towards getting a full program in, then getting WHP's down pat. Especially on the early maturing onion crops...

          With the moisture levels and warmer temperatures present, it to me could well be a perfect storm for white rot...

          My thoughts on programs would be to go Cereous, Pristine, Pristine, Cereous...

          Not an easy one all round

  • Bharat Jivan 17 Sep 2013

    Been out there today and found some whiterot on small onions. Not a good sign....

    • Fenton Hazelwood (Moderator) 18 Sep 2013

      I think it will be a common thing to see infected plants start showing up...

      Getting white rot sprays on in good conditions is vital also

 
Page Functions