- Reducing spore population around the plant<\/li>
- Reducing spore population on the plant<\/li>
- Defending and protecting the plant on the outside from new pathogen<\/li>
- Getting into the plant and killing the pathogen<\/li>
- Getting into the plant and defending from new infection<\/li><\/ul>\n\n\n\n
How much of each of the above is happening, and how long it goes on happening, doing depends on:<\/p>\n\n\n\n
- Timing of application \/ stage of disease<\/li>
- Active ingredient applied<\/li>
- Disease pressure<\/li>
- Growth conditions<\/li><\/ul>\n\n\n\n
In its simplest form, experience indicates you can rest easy and expect the fungicide to perform for:<\/p>\n\n\n\n
- August – 10 days<\/strong><\/li>
- September – 14 days<\/strong><\/li>
- October – 21 days<\/strong><\/li>
- November – 30 days<\/strong><\/li><\/ul>\n\n\n\n
After that point it’s time think carefully about what’s next. Hopefully that’s been enough to get you through the pressure period and you’ve moved into a better window with some cool temperatures, high winds or low humidity.<\/p>\n\n\n\n
However if you’re still in those horrible humid conditions that you know result in Microdochium pressure on your site, you’ll know it’s time for action. Furthermore, these figures will vary a bit up and down the country as they are so climate related, so maybe we need to look at something better.<\/p>\n\n\n\n
Lesson 1 – Fungicides do not necessarily last for 30 days<\/h4>\n\n\n\n
The effectiveness of a fungicide will reduce over time and the speed of that breakdown is related to:<\/p>\n\n\n\n
- Exposure to light<\/li>
- Plant absorption<\/li>
- Microbial activity<\/li>
- pH<\/li>
- Plant metabolism<\/li>
- Temperature<\/li><\/ul>\n\n\n\n
Lesson 2 – How can I make it last longer?<\/h4>\n\n\n\n
Fungicide longevity can be improved by:<\/p>\n\n\n\n
- Better applications <\/li>
- Reducing drift <\/li>
- Choosing the correct water volume<\/li>
- Selecting the right nozzles<\/li>
- Ensuring good plant health<\/li>
- Preventative applications rather than curative<\/li>
- Good management afterwards<\/li><\/ul>\n\n\n\n
So how do I time my next application?<\/h4>\n\n\n\n
Growing Degree Days for decision support<\/h4>\n\n\n\n
There is a growing trend towards using GDD to help guide you with your fungicide timings. <\/p>\n\n\n\n
I know several people who are using 130 GDD to guide their applications. It’s a much better system than a monthly calendar approach, but it’s only a guide and you have to be aware of the limitations.<\/p>\n\n\n\n
![\"\"](\"https:\/\/greencastadvisory.com\/wp-content\/uploads\/2020\/10\/image-9.png\")
<\/figure><\/div>\n\n\n\nThe challenge with using GDD is that according to the results calculated above<\/strong> applications made at the end of September in some parts of the country would take around 2 months to reach 130 GDD, and by early November that could be 3 months! Yorkshire in November can be a very high period of disease pressure and to expect 3 months control from an application is just crazy.<\/p>\n\n\n\n
- September – 14 days<\/strong><\/li>
- August – 10 days<\/strong><\/li>
![\"\"](\"https:\/\/greencastadvisory.com\/wp-content\/uploads\/2020\/10\/image-7.png\")
<\/figure><\/div>\n\n\n\n