It has been terribly hot here in Iowa...Temps at 98, heat index at 112 degrees for 7 days. No rain, but maybe some coming.
Here are some pictures of my new Knockout rose bushes I just planted this spring. This is my first experience with roses, and I read where Knockouts were free of diseases...now look. I have used a fungicidle spray on them just this week, but they continue to go bad. Someone told me to get rid of them, but I have some money in them and can't just throw them out...
Any and all suggestions are welcome as I am new at this.
Black spot will not kill them or even keep them from blooming, but Knockouts are supposed to be more resistant than average. I never spray any of my roses and they do lose some of their leaves to fungus, by fall they usually recover and bloom almost as well as in the spring. Many rose growers are able to keep their plants free of fungus by maintaining a spray schedule about every week or two. Don't give up on them!
Get rid of them??? Just because of a little black spot! Phshaw, I say! =)
It is probably just heat stress, probably aggrivated by the humidity, as you say. The real key to help guard against black spot is to have good air movement around the plants. That is a big help. The spray or a systemic will help the new leaves that will grow in (won't do much for the leaves already infected). I would go easy on the spraying with the Knockouts. You might also hit them with a strong spray from the hose to help knock off the diseased leaves. Be sure and pick or rake them out of the bed as those leaves left on the ground can just help to re-infest with the black spot. Burn or throw away the leaves, don't compost them.
You say that your roses are new (young)? There is a theory about that young roses are a little more susceptible to these things. Kind of like kids. They develop more immunity as they grow older. So, like every good Cub's fan knows, just wait 'till next year!
This is my first year gardening, and I am soooo anal about how everything is growing...I believe everything I read as I have absolutely NO experience, and if the plant doesn't do what the book says, I get worried...such as the knock-outs having disease resistantance. I figured that meant the NEVER get black spot, or powdery mildew!
That's why I rely on the expert gardeners...such a huge help!
I live in Michigan and black spot is an every year thing looks bad but dosent kill them just wait for it ot cool off and you will see I too belived every thing I read but have learned so much on here so now I can relax and enjoy my gardens in stead of being in a panic about it all which is more fun ;0)
LOL! I'm not an expert--you should see my roses right now. Two month with no rain and over two week of 100+ temps is really taking it's toll. I've done all I can do for them. I figure on losing a few. Its just that we all have been new gardeners at some point in our lives. We've all been where you've been, so hang in there!