Monday, February 25, 2013

Hazardous Roses 3: Spray Nothing Toxic?

Obviously, the best way to protect yourself from chemical fungicides and insecticides is not to use them.  But is that possible?  Well, yes and no and, if you subscribe to the idea of integrated pest management (IPM), you might say that "yes and no" is the only answer.  Or to put it another way,  it depends on which roses you plant, where you plant them and what your expectations are.

There are a number of very nice, exhibition-quality roses that are quite resistant to the dozen or so different races of black spot, as well as other funguses, such as anthracnose leaf spot.  In my experience, many of the Buck roses are very fungus resistant.  Good examples are Earth Song (grandiflora), Prairie Harvest (a shrub that looks like a hybrid tea) and Carefree Beauty (shrub).  Bailey's beautiful line of "Easy Elegance" shrub roses are bred for disease resistance, as are the very popular "Knock Out" shrubs.  Keep an eye on the "Earth-Kind" trials, that are regularly publicized in the American Rose magazine, for more ideas on  fungus-resistant roses.  Here is the Earth-Kind website:

If you take fungus-resistant roses and plant them among other perennial and annual flowers and shrubs, there is a pretty good chance that you will not often encounter rose funguses other than perhaps powdery mildew, which is easily treated with non-toxic baking soda (3 tbp per gallon of water).  While these types of flower beds are truly beautiful and largely carefree, most rose gardeners like to have lots of roses and, therefore, want to plant rose beds with multiple cultivars.  Unfortunately, the more cultivars you group together, the higher the probability of attracting one of the dozen or so races of black spot, or anthracnose leaf spot, even if all the roses you plant are fungus resistant.  One way of mitigating this problem is to have multiple small beds and plant only one kind of fungus-resistant rose in each bed.  For example, one of the most beautiful beds I have is a grouping of 15 highly disease resistant Buck Earth Songs and this bed is virtually fungus free, except for one brief encounter with anthracnose leaf spot last summer. Here's how that bed looks in summer:

Insects are another story altogether.  Spider mites, aphids, thrips and, worst of all, Japanese Beetles, are our biggest problems in the upper Midwest.  Once again, if you don't have a lot of roses and especially if you have them mixed in with other perennials and annuals, you may be able to get away without spraying insecticides, especially if you are willing to live with some damage.  Spider mites and aphids can be effectively controlled by washing your roses with sharp sprays of water every two or three days.  The frequency of washing is very important with spider mites because their eggs hatch every three or four days (depending on the temperature) so you have to wash consistently to control the generations.  The frequent washing takes care of  the aphids too, of course.  As you can see, however, washing a couple of hundred roses for spider mites every three or four days is a major undertaking that cries out for another solution, which, unfortunately usually becomes the use of miticides.  Of course, I should mention that washing your roses is tantamount to top watering, which is a no-no in controlling rose funguses (i.e. you can't win).  Just be sure that you wash your roses in the sunshine when they will dry quickly, i.e. never wash them when they will stay wet overnight.

Even in a large rose garden, thrips can often be controlled by early and consistent use of detergent soap sprays (one tablespoon per gallon of water).  The trick is to get started early before you actually see the telltale brown signs of thrips on your flower buds, which is when these virtually invisible little monsters have penetrated deeply inside of every bud.  At that point, you almost have to use an insecticide, like Conserve SC, (Spinosad) which is derived  from naturally occuring organisms found in soil. In a small garden, however, one could cut away all buds that are beginning to blossom and start spraying with soap before more buds form. So there is more than one way to skin this cat if you have only a few roses (perhaps fewer than 25).  If they're mixed in with other perennials and annuals, you may never encounter thrips.

Here is a good, completely non-toxic formula that you can use for everything we've talked about thus far.

In one gallon of water, mix:
One tablespoon liquid dish soap
1 cup cider vinegar (5%)
1  325 mg aspirin tablet (crushed)

I really like this mixture because you can spray it without worrying about getting it on you. The trick with this  is to get started early and use if often; perhaps every five days. (As I write this in late February I'm reminding myself to take my own advice this spring).

Japanese Beetles

And now, let's talk about the monsters of the garden: Japanese Beetles.  On the theory that a picture is worth a thousand words, here's what the JBs looked like on one of my Robusta shrubs last summer.

Actually, JBs are quite easy to control without chemicals until they reach infestation levels.  I strongly advocate knocking JBs off your plants into a can of soapy water. They don't sting and they have a natural dropping instinct, so even in large quantities you can knock them off into the water fairly easily.  This is especially true in the early morning and at dusk, when they are very slow moving.  I would take my nitrile-gloved hand, cup it over the blooms above and sharply push downward into the can, hitting the edge with the blooms, knocking the insects into the water.  The problem is, when there are so many, you won't get all of them and the next swarm will arrive as soon as you walk away.  If you have only a few roses, controlling JBs like this is fairly easy but, when infestation occurs in multiple beds with several hundred roses, it can become a nearly full-time job just knocking off the beetles.

Spraying is a last resort on JBs but, if it becomes necessary in a large garden, it is important not to spray something, like Sevin (carbaryl) or Merit (imidacloprid), that impacts the beneficials in the garden, especially the bees.  In short, I have found, through  experimentation last summer, that the pyrethroid, Demand CS, meets that requirement and actually has a deterrent effect on JBs for about a week, allowing you to go back to knocking a much reduced number of insects into soapy water.  I believe that this is how IPM should be practiced.

Please read the following articles that I have published on controlling JBs in the rose garden:

So, in conclusion, if you have a relatively small number of roses (25 or so), especially if they are planted in beds among other perennial flowers and shrubs, you can probably control fungal diseases and insects by natural, non-toxic means.  If you have a lot of roses in dedicated rose beds, like I do, you should practice integrated pest management as much as possible and never spray chemicals until you absolutely have to.  That means that no one should ever engage in  preventative spraying of fungicides and insecticides.  It is bad for the garden environment and bad for the gardener.

In my next installment of this series, I will deal with the best fungicides and insecticides to use, if you must, in an IPM program.

Jack Falker  E-mail:

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