Post-bloom fungicide choices in blueberries
Controlling different diseases calls for a change in fungicide choice.
Early in the season, blueberry growers focus on controlling mummy berry and Phomopsis. Dormant and delayed dormant sprays of Lime sulfur or Sulforix aimed at these diseases also serve to reduce inoculum of fruit rot pathogens overwintering on infected twigs and remnants of last year’s fruit clusters.
Before and during bloom, fungicide protection is focused on preventing mummy berry flower infections. After bloom, there is no risk of further mummy berry infection. However, some of the fungicides used against mummy berry also have efficacy against fruit rots. In addition, bloom to early fruit set is also good time for management of anthracnose fruit rot because the pathogen becomes active at that time.
After bloom, the disease control strategy changes to protecting green fruit and young shoots. Later in the summer and early fall, protecting leaves may also be needed for controlling leaf rust.
Green fruit are susceptible to fungal diseases such as anthracnose, Phomopsis and Botrytis, the latter if the weather is excessively wet with high humidity. With respect to anthracnose fruit rot, some cultivars are resistant to the disease, e.g., Elliott, Draper, Liberty and Legacy, and won’t need as much protection as susceptible cultivars (e.g., Bluecrop, Bluetta, Blueray, Jersey).
Alternaria fruit rot becomes more of a concern when berries start to ripen, particularly in the cultivar Bluecrop. Be sure to change the mode of action of your fungicides to include these diseases and reduce the likelihood of fungicide resistance occurring in blueberries.
A recent survey has shown evidence of strobilurin resistance in the anthracnose fruit rot pathogen in Michigan. Thus, it is important to alternate fungicides with different modes of action and not rely solely on strobilurins for anthracnose fruit rot control. The anthracnose fruit rot prediction model on the Michigan State University Enviroweather website can also help improve fungicide spray timing.
|Fungicide efficacy against fruit diseases in blueberries|
|Trade name||Active ingredient||FRAC||Phomopsis||Anthracnose||Alternaria||Botrytis|
|Abound||azoxystrobin||11||Fair||Good / Excellent*||Good||Poor|
|Pristine||pyraclostrobin + boscalid||11/7||Good||Excellent*||Good||Good*|
|Quilt Xcel||azoxystrobin + propiconazole||11/3||Good||Good||Unknown||Unknown|
|Quash||metconazole||3||Good / Excellent||Good||Good||Fair|
|Proline||prothioconazole||3||Good / Excellent||Fair||Unknown||Fair|
|Inspire Super||difenoconazole + cyprodinil||3/9||Good||Unknown||Unknown||Good|
|Luna Tranquility||fluopyram + pyrimethanil||7/9||Unknown||Fair /Good||Fair / Good||Excellent|
|Switch||cyprodinil + fludioxonil||9/12||Poor/Fair||Good||Excellent||Excellent|
|Aliette||fosetyl-Al||33||Fair / Good||Good||Good||Unknown|
|Phostrol||phosphorous acid||33||Fair / Good||Fair / Good||Fair / Good||Unknown|
|Double Nickel||Bacillus amyloliquefaciens||44||Fair||Unknown||Unknown||Fair|
|Serenade||Bacillus subtilis + terpene-based sticker- extender||44||Fair||Poor||Poor||Fair|
|Oso or PhD||polyoxin-D zinc salt||19||Unknown||Poor||Poor||Good|
|Copper (various products)||copper||M1||Poor / Fair||Poor / Fair||Poor / Fair||Poor / Fair|
|Captan||captan||M4||Fair||Fair / Good||Poor||Fair|
|Protectant and systemic mixtures|
|CaptEvate||captan + fenhexamid||M4/17||Fair||Fair||Poor||Good / Excellent|
*If fungicide resistance is present, this product may be less effective than indicated.
See related MSU Extension articles
- The challenges of disease control during rainy spells
- How to get the most out of your fungicide sprays
- Protect against blossom blights in blueberries
- Anthracnose fruit rot prediction model to assess risk of infection in blueberries
Dr. Schilder’s work is funded in part by MSU‘s AgBioResearch.