Cereal Disease Control 2024 Part 3 Disease Control Stategies in Wheat Flashcards
Slide 3- Key Cereal Diseases – Infections through the leaf
Good diagram
Septoria tritici : a very complex disease
1- What happens during the season?
2- Can it be airborne?
3- Can they continuously develop?
4- What may the pathogen respond to overtime?
5- is this a simple or complicated disease?
1-* Sexual (ascospores) and Asexual (pycnidiospores)
reproduction during the season
2-* when airborne ascospores are active in the growing crop
then rainfall is not critical for infection spread
3-* hence there may be continuous development of the
sexual phase of this disease - the disease evolves over
time
4-* the pathogen may respond over time to selection exerted
either by the introduction of new cultivars or by the
application of site-specific fungicides (Hunter et al 1999)
5-* this disease is dynamic and changing over time
slide 6= lifecycle
Slide 8 The disease triangle
In the disease triangle, what are the 3 things effecting disease?
- Pathogen
-Environment
-Host
Septoria tritici - identify the
disease pressure risk
1- Host
2- Inoculum
3- Environment
*Host
Varietal resistance poor CROP
Inoculum
Early sowing, mild autumn,
long spray intervals DISEASE
Environment
Rainfall, leaf wetness,
multiple septoria episodes
WEATHER
Slide 10, 11, 12- fungicide chemistry that im not learning :)
2002 – Fungicide failure in the field - the emergence of Septoria tritici resistance to
strobilurin fungicides (QoI) was stunning and dramatic in Ireland
Read this
- 2002 was the highest disease
pressure year in at least a decade - disease control on wheat started very
well and finished very variably - high spend on strobilurin-based
fungicide programmes with over
90% of crops getting strob at T2 - uneven control of Septoria across
fields e.g. disease buildup in a very
unusual spatial pattern - unexplained differences in efficacy
of disease control between fields,
farms, localities, regions - Lab tests found a new disease strain
with a G143A mutation ( see next
slide)- look at slide 14,15,16,17,18,19,20
Properties of triazole-based fungicides:
(6)
- protective, eradicative and curative activity
- reliable systemic movement
- site-specific mode of action - DMI inhibitors
- good broad-spectrum activity
- good persistance of disease control ( 20-30 days )
- useful curativity on a number of key diseases like
Septoria , Rhynco / Net blotch / Rusts
Triazole Fungicides – Resistance Crisis
1- After analysis of experiments what do they show?
2- What is it due to?
3- What can still be achieved?
1- – analysis of experiments show that in last 2 decades
the field performance of triazole fungicides against
Septoria has been significantly poorer
2– due to the changing sensitivity to triazoles in the
Septoria population
3– Moderate Septoria control can still be achieved with
triazole fungicides but dose is more critical
Preventing Resistance Shifts in Triazole and other
Site-Specific Fungicides:
1- Recommended practices(3)
2- Farm Practice(3)
3- What is the key continuous issue?
1-* Recommend Practices
– Limit the number of applications
– To use the full-recommended rates
– To mix fungicides with different modes of action
2-* Farm Practice
– Limit the number of applications – to reduce cost
– To use appropriate rates – to optimise returns
– To mix fungicides with different modes of action –
to optimise control and to increase spectrum of
control
3- Dose rate
Use of Contact Fungicides – Chlorothalonil / Folpet:
1- What are they?
2- What sort of products are they?
3- How are they applied?
4- What is there some evidence to show?
5- What dod CTL not have?
1-* multi-site inhibitors hence chances of resistance developing
are very slight
2-* Preventative products with no curative activity
3- * Applied at 1.0-1.5 l/ha ( 500-750 grams of a.i.)
* If applied in a situation where curativity is required its effect
will be reduced
* To be effective as a partner in an anti-resistance strategy
contact products need to be applied preventatively
4-* There is some evidence of reduced triazole curativity when
chlorothalonil mixtures are used in a curative situation (9-12
days curative
5-* There are label restrictions and CTL did not have its licence
renewed in 2020 so its no longer on the market
‘Newer’ Carboxamide (SDHI) Chemistry
1- What sort of mode of action?
2- What is the risk of resistance?
3- How many mutations?
4- What are very important?
5- What is essential?
1- Single site Mode of Action - SDHI
2- Good efficacy but in partnership with existing chemistry at T1
and T2
- partner product is also critical
- uncertainty about optimum timing if only applying
once a season
3-What is the risk of resistance – medium-high
Mutations are found and well documented
79 and 152 mutations
4-Well integrated programmes are v important
5-Mixing options with other chemistry are essential
Disease Control Programmes - Winter Wheat:
Early season
Mid season
Late season
– early-season : GS 30-37 - CTL / triazole / SDHI
– T Zero and T1 – sprays at GS 30 and GS 32 expected
– mid-season : GS 37-50 - triazole / CTL / SDHI ( + triazole)
* split T2 application in difficult growing season
– late-season : GS 55-end – triazole (strob) ( + triazole)
– T3 ( ear spray)
What is off the market since 2021?
- CTL off the market in 2021 / replacement is Folpet ( cost-effect ??)
– SDHI resistance moved quickly to moderate resistance
– Current triazoles have moderate to high resistance
– A number of key market introductions 2020-2025 period :
– Revysol (BASF) – 2020 ‘designer’ triazole fungicide to which
current mutations are ‘sensitive’ – recently in 2023/2024 problem
mutations emerging
– Inatreq – 2021 : new mode of action fungicide from Corteva
Whats another SDHI option?
– ISY from Bayer – another SDHI option
– Pavecto 2027~ (Sumitomo/BASF) – novel QoI fungicide
– Adepidyn (Syngenta) – 2026 ? : 3rd Generation SDH
