Hello there,

Recently, I started maintaining a condo complex in CT. They have many purple plum trees infected with Black Knot. I know it is not an easy disease to eradicate but I want to try.
This year, I did some research and made some inquiries and was told that a chemical called, 'chlorothalonil' was recommended for black knot. (under the common name Manicure)
I sprayed the trees 3 times during bud break, flowering and pedal fall.
Continuing this program next season and the season after, tree health may not show for two or three years, but then again, some trees may not come around at all.

My question is, has anyone used anything else to combat this disease? Had it worked? Any recently published info on the best way to control the fungus? ( Besides pruning, fertilizing and maintaining moisture)Any suggestions?

My trees range from very large trees to small and most of them are infected.

Thanks,
Kim

Reply to post by Kim, on November 15, 2000 at 18:55:53:

I looked into it a while back and found the consensus be that survival rates not worth the expence of treatment product.

Here in S/E Wisconsin most prunus are very short lived due to the variouse cankers that they get. I usualy recomend that one prune out the cankers until the aesthetic threshhold is hit then replace. In the case of Blacknot I will usualy recomend a genus with similar charicturistics, or just to be preopared for replacing in 6-10 years.

Reply to post by Kim, on November 15, 2000 at 18:55:53:

This confirms JPS'comment:

Reply to post by JPS, on November 15, 2000 at 18:55:53:

I find that Black Knot reoccurances are primarily due to the close proximity to native stands of Prunus and/or Amelanchier, both of which are highly susceptible and unmanaged. Any buffer strips or wild stocks nearby?
DgM

Reply to post by DgM, on November 15, 2000 at 22:04:02:

Our plum tree has died of black knot, Now the two Hawthone trees on either side of the plum tree are infected - Any suggestions?