On Reconditioning an infested Rose Bed

19 years ago

A month or so ago we identified rose slugs on my roses. I had to travel on business and when I returned, I found that the gardener for the condo complex had pruned them, and that they are now growing back, just now budding, with beatiful healthy leaves. I asked him if he sprayed them with anything and he had not, thank goodness. I was surprised that simply pruning would achieve this effect. My roses were decimated by the slug (see earlier thread, "Something's bugging my roses"). My optimism is curbed by the fact that I know the slugs are still around...in fact, they have already gotten to work on one small stem on one bush. This is exactly how it happened before. Just a few leaves munched, and then, within two weeks, all six bushes were lace.

However, I am not one to treat symptoms when I can get at the cause. The plan I have so far is as follows:

1) Spray insecticidal soap (I've heard a mixture of dish soap and water works just as well) on all the bushes.

2) Dig up entire bed and mix in 12 bags of organic compost (scheduled for Tuesday 10/5) - re-do the drip system to accomodate roses' water needs.

3) Place beneficial nematodes in bed (have been purchased from Gardens Alive) to take care of larvae which I understand propogate in the soil.

Will this take care of the problem? The other issue is that my bed is adjacent to a neighbor's and she won't be reconditioning her soil. Will I be wise to add nematodes every year, or is it possible her soil is not contaminated with the larvae? She does not have a single rose bush.

The gardener, who is not organic, suggested fertilizing with a "systemic" brand - I cannot tell if it is organic...it basically fills the plant with insecticide as it feeds. Here is a link to it in case anyone can analyze it or knows about it. I would also appreciate other input on fertilizing.

http://www.ext.colostate.edu/psel/ps0103.html

I want to plant other things with the roses. There is a hibiscus that is doing nicely except that it has some kind of black dots that look like eggs on it. I'll take it to the local garden center to identify but if someone knows what it is, feel free to tell me. I am hoping insecticidal soap will take care of it. I am considering a gardenia bush, as they do well here, with the sun mitigated by ocean breezes - however, I would appreciate hearing about perennial items that are known to be resistant to bugs or even aid in ridding the plot of them.

I am a novice at taking care of roses, and "inherited" these by way of buying a condo. I appreciate any help while I give myself a "crash course" in organic rose maintenance.

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Comments (5)

User
19 years ago
You don't need to dig your roses up. Just topdress with the compost. The drip irrigation runs just under the mulch, so again, no reason to dig up your roses and totally set them back. If you only want to use organic methods, then of course you should not use a chemical fertilizer and insecticide combo. It's not terribly effective anyway. Just handpick and do the best you can. YOu can't grow perfectly spotless bug bite free roses without chemicals, so the first step in any organic program is learning to accept less than perfection. Learn to tolerate some damage. It'll be worse in some seasons than others. Do what you can with the tools you're willing to use, and don't sweat the rest. Roses are tough, as you've discovered. ANd, if you lose one flush, there's always another behind that one to take it's place.

As far as fertilizing, find some friends with horses. Clean the stalls. Horse manure makes great fertilizer. Ask them where they buy their alfalfa. Buy some for your roses. Alfalfa has a growth hormone in it in addition to being lots of yummy organic material for the soil microbes to break down. Place the manure and the alfalfa just at the drip edge of your roses 3-4 times a year and make sure they're watered well. Enjoy! That's all there has to be to it in a rose friendly climate like CA.

One of the best things you can do for your roses is to get a soil test and find out what type of nutrition your soil already has and what it's pH is. This is way important information and adding stuff without knowing that information would be like trying to make a cake from a boxed mix and assuming that all you needed to add was water, when it was brand X that required oil and eggs as well. Or, as in the case of the cake (and the soil), the even worse scenario of assuming that you needed to add everything from baking powder through the oil and eggs and flavoring when all you needed to do was add water. Some soils are already almost toxic in some macro and micro nutrients, and it's sure wise to know what you're starting out with to know where you need to end up.
Kimmsr
19 years ago
The "Bristly Rose Slug" is the larva of a sawfly and digging the bed and replacing the soil won't do much to keep them away. A soap and water spray, 1 percent soap or about 1 teaspoon of soap per quart of water (and it should be real soap not dish detergent since it is the fatty acids in that soap that do them in) works very well.
These guys seem to prefer my Hibiscus to the roses since I've not seen them on the roses since I've had the Hibiscus.
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michaelg
19 years ago
The advice above is all good.

The worms eating the leaves are the larvae. They come from eggs laid by winged adults on the leaves. The winged adults come from pupae that overwinter after the larval stage. At least one kind pupates in the soil under the plants where the nematodes might aid in control. Probably you would only install the nematodes once.

However, if you kill most of the larvae on the leaves, there will be few pupae in your soil. Next year, patrol the plants and either wipe them off or spray soap on the affected area (under the leaves) immediately when you see damage. You will have to check back in two days to see if the soap is in fact killing them. No need to spray the whole plant-- they don't move from where the eggs were laid until the area is defoliated.
michaelg
19 years ago
If I can re-emphasize-- the problem isn't infested soil. Rose slugs are normal in almost every rose garden, and the adults will seek out a new bed to lay eggs on the leaves. What is abnormal is the heavy damage you suffered. Usually it is minor as wasps and other predators pick off the larvae. If there are a lot of slugs and not enough wasps, you need to play that predatory role yourself. The slugs are sedentary on the chewed foliage and easy to find. In early stages they are quite small, though.
Chambray
Original Author
19 years ago
Thanks for the support - I am happy to report that the insecticidal soap is working well. Even the hibiscus is flourishing. There has been no further chewing on the one rose bush that was getting attacked during this "flush". Lots of buds. I'll just keep the spray handy - works well on ants too...