A B C
RESEARCH & EVENTS
Managing the risk of fungicide resistance in Australian almonds
Len Tesoriero 1 , Simone Kreidl 2 , Peta Faulkner 3 and Tonya Wiechel 2
1
Crop Doc Pty Ltd , Agriculture Victoria Research , 2 AgriBio Centre for AgriBiosciences , Bundoora , 3 Mildura SmartFarm
Introduction ALMOND production is affected by numerous fungal and bacterial diseases . If uncontrolled these can cause significant economic losses due to lower yields , reduced nut quality and decreased output over time through spur death , shoot dieback and tree death . Effective and practical disease management systems require integrated cultural , biological , and chemical strategies . The Australian almond industry currently has access to a range of fungicides used strategically to reduce disease risks and impacts ( Table 1 ).
What is fungicide resistance ? Fungicide resistance occurs via genetic changes in the fungal population leading to decreased sensitivity to a specific fungicide . Fungicide use selects for individuals which have developed mechanisms allowing them to survive . Inappropriate use may increase or accelerate this selection . With repeated exposure these will become the dominant pathogen population . There are four general mechanisms of resistance : 1 . Alterations that stop the fungicide binding to the target site . Continued page 41
Table 1 . Fungicide active ingredients registered or with permits for Australian almonds ( Jan 2024 ).
FRAC |
Chemical Family |
Active Ingredient |
Target Disease ( s )# |
Code |
|
|
|
2 |
Dicarboximide |
Iprodione |
BB , BR |
3 Demethylation Inhibitors ( DMIs )
A B C
Tebuconazole 1
BR , HR , R , Sh , Diplodia , Eutypa dieback
BB , BR , HR , R , Sh An , BB
|
|
Mefentrifluconazole |
|
|
|
Propiconazole * |
|
4 |
Phenylamide |
Metalaxyl-M ** |
Phytophthora |
7 |
Succinate |
Fluopyram 2 |
BB , HR , R , Sh |
|
dehydrogenase |
Fluxapyroxad 3 |
Al , An , BB , BR , HR , S |
|
inhibitors ( SDHIs ) |
Isopyrazam |
An , BB , HR , S , Sh |
|
|
Penthiopyrad |
BB , BR |
9 |
Anilinopyrimidine |
Cyprodinil |
BB , BR , R , Sh |
11 |
Quinone outside |
Azoxystrobin |
An , BB , BR , HR , R |
|
Inhibitors ( QoIs ), |
Azoxystrobin (+ fluopyram ) |
BR , HR , R , Sh |
|
Strobilurins |
Pyraclostrobin |
R |
|
|
Pyraclostrobin (+ |
Al , An , BB , BR , HR , R , S |
|
|
fluxapyroxad ) |
|
|
|
Trifloxystrobin (+ fluopyram ) |
BB , HR , R , Sh |
19 |
Polyoxin |
Polyoxin D zinc |
BB , HR |
P 07 |
Phosphonate |
Phosphorous acid |
Phytophthora |
M 01 |
Inorganic |
Copper hydroxide |
LC , Sh |
|
|
Copper oxychloride |
LC , Sh |
|
|
Copper ammonium complex |
LC , Sh |
|
|
Copper ammonium acetate |
LC , Sh |
|
|
Copper ( tribasic ) sulphate |
LC , Sh |
M 02 |
Inorganic |
Sulphur |
S |
M 03 |
Dithiocarbamate |
Mancozeb |
BR , R , S , Sh |
M 04 |
Phthalimide |
Captan |
An , BB , S , Sh |
M 05 |
Chloronitrile |
Chlorothalonil |
R , Sh |
* PER12989 until 30 / 11 / 25 ** PER94212 until 31 / 08 / 26 1 Registered only as a coformulation with either azoxystrobin or fluopyram . 2 Registered as a coformulation with either trifloxistrobin or tebuconazole . 3 Registered only as a coformulation with pyraclostrobin . # Al - Alternaria , An - Anthracnose , BB - Blossom blight , BR- Brown rot , HR - Hull rot , LC - Leaf curl , R - Rust , S - Scab , Sh- Shothole
Figure 1 . Fungal and bacterial diseases to be assessed for chemical resistance : A ) bacterial spot ( Xanthomonas arboricola pv . pruni ) B ) anthracnose ( Colletotrichum acutatum ), C ) hull rot ( Rhizopus stolonifer ).
40 In A Nutshell - Spring 2025 Vol 25 Issue 3