How often to spray for blackspot?

bgdug · Joined: 09 Apr 2007 Posts: 10 Location: Bedford,TEXAS

So I've seen plenty on what to use, but I've not seen how often to use it. I would assume, by the fact that I've had blackspot on my bushes for over a month, that it doesn't disappear with one spraying :shock: . It's probably been a month since I treated the roots with cornmeal/milk/compost/etc. and the plants have been growing back their leaves where the blackspot took them, which hopefully means the roots are getting back to full health. However, where the bushes haven't shed the infected leaves, the blackspot is still there.

So should I continue to spray until either a) the bush sheds the infected leaves or b) the blackspot starts to look different indicating that the infected spots on the leaves are no longer infected? If I should continue spraying, how often do I do it? daily? weekly? monthly? I've been using Garrett Juice mixed with potassium bicarbonate if that makes a difference on the frequency of spraying.

I'm new to disease management on plants so I'm just making guesses on my limited experience with gardening.

Tricky Grama · Posted: Wed May 30, 2007 7:10 am Post subject:

I would think that the rain would wash off treatments. It would not hurt to spray weekly but I don't think I'd do it more often.

Seems like you have a pretty good control on the blackspot, now have to wait for mother nature.

Patty

bgdug · Joined: 09 Apr 2007 Posts: 10 Location: Bedford,TEXAS

I figured once I saw the new foliage growing that the roots were getting back on track. However, the blackspot seems to be trying to spread to these new leaves, which concerns me. I'll keep spraying weekly and see what happens. Hopefully it'll make quicker progress once the rain stops and things dry up a bit.

khwoz · Joined: 10 May 2003 Posts: 777 Location: Weatherford,TX

Use the cornmeal juice, garlic juice or milk sprays instead of always potassium carbonate. I would start with the cornmeal juice at full strength & if you are spraying weekly, add the Garrett Juice 1/2 or 1/4 strength.

bgdug · Joined: 09 Apr 2007 Posts: 10 Location: Bedford,TEXAS

So after a couple months of trying to manage this disease on my shrubs, I've started to question whether it's blackspot or not. Here are a couple pictures I took. Does this look familiar to anyone? The leaves continue to fall off and the stuff is spreading to the new leaves as they start to grow. I've been spraying weekly or about every 5 days with either GJ, milk, and cornmeal juice or GJ and potassium bicarbonate. Early on when I first noticed the problem, I applied horticultural cornmeal to the soil and milk/GJ. It seemed to have started the healing process since new foilage had started to grow within 2 weeks. I added more cornmeal to the soil about a week ago, but I'm not sure the problem is the roots anymore.

So, by looking at the photos below (the first pic is existing leaves and the second pic is new leaves), can anyone verify whether the disease is blackspot or not? Also, I'm not sure what type of shrub this is, but I think it's a common one. Thanks.

khwoz · Joined: 10 May 2003 Posts: 777 Location: Weatherford,TX

I'm not sure but you may have a bug problem; some kind of piercing/sucking bug. Have you looked closely at the bottom of the leaves? Neem insecticide will control bugs & is good as a fungicide also. Maybe someone with more knowledge will respond.

bgdug · Joined: 09 Apr 2007 Posts: 10 Location: Bedford,TEXAS

I haven't noticed any bugs on the leaves during the day. I guess I could look tonight and see if there are some type of nocturnal bugs causing the problem. Thanks for the suggestion.

sandih · Joined: 04 Apr 2003 Posts: 1038 Location: Dallas,TEXAS

I don't think that's bug-related, it looks like a fungal disease to me. Looks exactly what I have on some of my phontinias (sp?)