We had significant anthracnose fruit rot issues in some fields last year, and we now have confirmed reports of anthracnose on ‘Farthing’, with unconfirmed reports on other varieties.  Symptoms appeared very early – even on green fruit, which is unusual.  The expectation is that the fruit will turn blue before you see the anthracnose symptoms. Unfortunately, if producers have not sprayed well up to this point, especially on southern highbush blueberries, the disease may be firmly rooted for the season.  Rain splash can quickly spread spores from infected berries to healthy ones, and infection can occur throughout the season.

We can’t say for sure why we are seeing more anthracnose issues, but one possibility could be fungicide resistance. In particular, the strobilurin fungicides (e.g. Pristine and Abound) may have developed resistance, as this has been confirmed in Florida blueberry production. These fungicides generally have excellent activity against anthracnose, but if resistance has developed, producers might as well be spraying water.

Dr. Phil Harmon (University of Florida) has graciously agreed to test blueberry anthracnose samples for resistance to strobilurin fungicides.  As mentioned, in Florida, he has found resistance to this fungicide class. If you find fruit with anthracnose, take 20-30 samples to the local county agents office for shipment to Dr. Harmon’s lab. Spores should be examined in the county agents office to confirm anthracnose before shipment to Dr. Harmon. Symptomatic fruit with confirmed anthracnose (10-15) should be individually placed in small snack bags (ziplocks) and then collectively sealed in a larger ziplock (quart or gallon freezer) for transit to Florida.  Don’t crush (obviously), and overnight shipment is best.  Give enough information in an accompanying note for Dr. Harmon to track the samples (producer, site, county agent name and all contact information for producers and county agents).  Dr. Harmon will then process the samples and let us know the results.

I hope we don’t have resistance, but after over ten years of strobilurin use, I would not be surprised to find that we do – at least in some locations. If you observe anthracnose, take advantage of this free service from Florida. If we send lots of samples, it may not be free for long!


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