Monilia laxa in apricots seems to appear in already treated trees

Asked April 16, 2015, 3:36 PM EDT

Apricot trees started to bloom lately so I began with regular fungicide protection against monilia laxa. I used Chorus http://www3.syngenta.com/country/za/SiteCollectionDocuments/Fungicides/CHORUS%20-%20Eng_2014-04-25.p... I used it once and then I used it again after 10 days which was suggested by a person selling this product. That person also suggested that I should use Chorus.

Problem is that after 2 treatments there are still some trees which appear to be infected with monilia laxa, there are dried branches and dried flowers. Not too many of them but still they are present.

I also used Chorus just once this year in sweet cherries, sour cherries and plums but there are no signs of monilia in any of those. Only apricot.

My friend who is also having apricot orchard is experiencing the same problem. He used some other product (I can't recall the name) and he sprayed the trees way more frequently than me (3 times in under a week) yet he has the same problem.

Is this a problem with apricot? Problem with products that we use or is this some kind of new disease? Also I am worried by the fact that monilia might be getting resistant.

Thanks in advance for any kind of help.

Outside United States fruit trees fungicides horticulture

2 Responses

More than likely your problem is with the product that you used. I looked at the label that you have linked in your question. It mentions that resistance might be encountered. See section 3.

Fungi do develop resistance to fungicides if the same one is used continually. Large growers usually rotate the fungicides they use to slow down resistance development. See here for detailed information (http://oregonstate.edu/dept/NWREC/sites/default/files/upload/pubs/McReynolds_Robert/project26/Ocamb.pdf) and here (http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2317/F-7663web.pdf ).

I would advise you to use a different fungicide. The chemical name for Chorus is Cyprodinil. It’s a group 9 fungicide. Choose a fungicide that is not in group 9 to spray your tree. But please make certain that it is labeled for brown rot aka Monilinia on apricot. I suspect that you are living outside the United States. I am unaware of which chemicals are legal for use in your country. Look here for a chemical to spray instead, but make certain you read the label and check elsewhere if it is listed for your country. http://www.ipm.ucdavis.edu/PMG/r5100111.html

It's always a good idea to read the label, instead of just relying on a friend. I'm not sure if it’s illegal where you are at to spray without following the label’s directions, but it's illegal in the United States.

Apricot trees are very susceptible to blossom blight aka Brown Rot aka Monilinia spp. Because they are more sensitive to the disease, this might be why that tree got it, and the other one did not.

To decrease further infection, remove all dried fruit (also known as "mummies") from the tree. Cut off the dead stems. Don't drop them on the ground around the tree or compost them. Dispose of them in the trash.





Thank you for your help. I suspected that the disease already got resistant to cyprodinil so I asked some people to get help from them. There is an agricultural pharmacy near the town in which I live. I told the man working there about my problem and he said the same thing as you did. It is probably a resistance problem. He gave me two different products and instructed me to spray them with one week between spraying. The disease is gone now. It completely stopped monilia in its tracks. I also removed infected branches and burned them. Also worth to mention, I leave no mummies on the tree, when I harvest, I harvest every fruit and then check again for leftovers to remove everything. So yeah, you are right, cyprodinil is now useless as it seems because people around here also reported the same problem. All of them used Chorus. Thanks for that list of fungicides, I really needed something like that.