Gardening and Horticulture - Rosebush bug

In central Iowa, we have two different varieties of roses planted close to the house on the south side in full sunlight. I don't know the name of the roses, but one has very small blooms (about 1.5 " in diameter) and the other larger (about 2" in diameter). They both sit in a fairly large area with a large number of other flowers. The roses sit flat against the house and have been growing for about three years.

We started getting a lot of blooms from them the last two years and they have really looked nice in late spring to early summer. Then the leaves start dieing. They turn brown in small spots - it looks like a small lice or mite has eaten through the leaves to kill them. I can't find anything on them, but obviously something is killing the leaves. They get worse over the next month or so, then the leaves are pretty well gone.

Is there something I can put on them to stop this or anything I can look for to determine what is causing it?

Any help appreciated

Take a look here and see if this describes your problem.

http://www.ext.vt.edu/pubs/plantdiseasefs/450-617/450-617.html

Marbobj, scroll down here to 'Foilage and Leaf Pests' and click on Scarab Beetles, Rose Slugs/Rose Sawflies and Slugs and Snails for your leaf holes. You can then click on pictures of damage. You can also click on the different diseases at the bottom of that list.
http://www.sactorose.org/rosebug/irosepests.htm

Newt

Thanks so much for your replies and the site to go to for comparison.

I copied the links of pictures - our roses look just like these when they are on the way out.

http://www.sactorose.org/ipm/15coleops/15chineserosebeetle-dam2.jpg

http://www.sactorose.org/ipm/15coleops/15chineserosebeetle-dam1.jpg

I'm assuming ours may not be this particular beetle (we're in Iowa), but something similar?

Thanks a lot,

Bob

Brown spots on rose leaves could be spot anthracnose, a fungus, which can be controlled with fungicide. Small holes in leaves and leaf between veins disappears is a sign of rose slugs which feed on undersides of leaves. An insecticide can be used, taking care to treat undersides of leaves. If leaves appear to be bronze and dry with tiny specks on undersides and perhaps some webbing, spider mites have been busy. A miticide can be used for control.

You can post pictures at www.photobucket.com (http://www.photobucket.com) or other photo site with link here for all to see.

Thanks for the response twelvepole.

I found a few of the leaves still on the bushes. They have light brown spots of varying size with well defined borders. As that area dies, it falls out leaving a hole in the leaf which has the appearance of a leaf that has been eaten. More spots take over the leaf, die and fall out, leaving only the veins of the leaf.

I don't have a digital camera or I would post pictures for the forum to look at.

Thanks again

The spots from anthracnose have a dark circle around the outer edges of the spot and holes. You can see pics here.
http://www.sactorose.org/rosebug/irosepests.htm#ANTHRACNOSE

Is this what you see?

Newt

Newt:

No these are different. These are best described as take a perfectly green leave and draw a number of varying size, irregular spots (like small puddles) on them. Then color the inside your drawings with tan ink. Then on about half of the spots take a sharp knife and cut out the spot.

That's about what they look like. Past the edge of the spot = green leaf, until you get to the next spot. The edge of the spot is a very sharp well defined line.

Bob, it really sounds like rose slugs. Have you looked at the undersides of the leaves? Be sure to look a the pics too.

Newt

Newt:

You're right. I didn't look at that picture as closely as I should have. I thought I found a match with the Chinese bug. I've come up with some of those little green Bristly Rose slugs.

I never could find anything on these bushes, but maybe I was just looking at the wrong time and a lot of the leaves were completely gone. I guess I was thinking too much in terms of fungus.

Anyway, when I got the responses back from the forum, I sprayed these leftovers with Dursban. Some of those little green worms showed up on the ground. In one place where a branch of the rosebush was hidden under another flower, there were some undamaged leaves on the branch. After I sprayed, I dug those branches out and there were easily thirty to forty of those little critters on the ground - quite dead = Dursban cocktail.

The leaf damage on these is pretty bad. Do you think they will come back if the spraying gets rid of these things?

Bob, I'm sooo glad you've discovered who is the culprit! :thumbup:

If you give your roses all they need as to water and nutrients, you should see some new leaves. A foliar spray of compost tea should also help.

You might want to consider using Spinosad instead of diazinon, Dursban, orthene and the synthetic pyrethroids.
http://www.dirtdoctor.com/view_question.php?id=502

Newt

All the advice and help is much appreciated. I'll give that a try.

Last year I had the same thing, but instead of posting the problem I used a powder for a fungus, I believe. I wish I had posted it.

Thanks again to all of you.

Bob, you are so very welcome!

Newt