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Spraying for Success
by Ryan Tilley
Although spring is still officially a month or so away, the notoriously mild weather that often accompanies February will no doubt put a touch of spring fever in all of us. It also does the same thing for our roses, causing buds to swell and canes to begin to grow. But as pleasing as it is to see our roses come back to life after a brief stagnant period, we have to be on our guard again for our roses' arch enemy fungus! In fact, late February and March are perhaps the most important time for us to keep disease spores out of our garden. The reason is that once a rosebush has been infected with blackspot spores, it may take months to completely get rid of it. Sometimes you may go the entire year and not get complete control of it. Prevention is the key, so let's see how you can keep your roses healthy and happy.
The first thing you need is the right equipment. If you have just a few roses, then one of the hand-held, one-gallon, pump-up sprayers will do the job nicely. If you have 30 or 40 roses, then you need a 2 or 3 gallon hand held sprayer so that you do not have to refill it in the middle of spraying. Once you get up around 80 or 90 roses, you may want to consider buying a power sprayer (see issue 11) to make the job faster and easier. Once you have your sprayer picked out, you will need a small bucket and a large spoon or something similar so you can mix your spray in the bucket and stir it so you have an even mixture. Protective clothing is also recommend since you do not want to be getting the spray all over yourself. Long pants, a long sleeved shirt, a hat, inexpensive paint goggles, pesticide resistant gloves, and a respirator will give you the best protection. This may seem like overkill, but better safe than sorry are good words to live by. I remember when I was a young boy and I would spray my parent's mountain ash tree with insecticide to kill beetles I did not even wear a shirt while I was spraying and the insecticide would get all over me. I shudder when I think about it now. Don't you try the same thing! Wear protective clothing.
Now that you have the proper equipment, it is time to protect your prized beauties. The main rose diseases include blackspot, powdery mildew, downy mildew, rust, and botrytis blight. Of these, blackspot and powdery mildew are the most serious. Blackspot occurs when the weather is warm and moist and can occur almost anytime of the year. Powdery mildew develops with warm dry days and cool moist nights and is most common in the spring and fall.
I like to get a jump on blackspot with a dormant spray anytime from late January through February. The spray consists of lime sulfur and dormant oil. The lime sulfur helps clean up disease spores and the dormant oil suffocates over-wintering insect eggs. Follow the directions on the label. Definitely wear protective gear when spraying this mixture since sulfur can stain clothing and it has a very distinctive odor. It will also leave a residue on the roses, which is normal. Be sure to spray all leaf surfaces as well as all the canes and bud union. I also like to spray the ground around the roses as well. Apply this spray when the temperatures are above 40 degrees for about 24 hours. It is best applied when the roses are dormant, but as we all know, roses do not always go dormant here in the south. So apply it when the roses are not actively growing. You can also wait until after the main pruning in late February or early March if the roses are not vigorously growing. Just spray it on the canes after pruning is done and the old leaves are removed from the canes.
Begin regular growing season spraying once your roses start growing vigorously in early March and keep at it. It is best to rotate fungicides on a regular basis so the fungi do not become resistant to any one fungicide. Funginex (triforine), Daconil, Benomyl, Manzate, Immunox, Benomyl, and Mancozeb are usually available at local nurseries. You may have heard that Triforine has been taken off the market and that is true. However, the more expensive Funginex that contains Triforine is still available. If you cannot find these materials, call you local rose society or county extension office for places to buy them. Mix all of these fungicides according to the directions on the label. Another fungicide, called Banner Maxx, is available from chemical wholesalers like Progress Grower's Supply and from some mail order companies.
Some fungicides can be combined with each other for more effective control. For instance,
Funginex, Immunox, Banner Maxx and penetrate the leaf and work to prevent fungus from reproducing. They are called single site or sterol inhibitors. They cannot be washed off. They will remain active for about 7 10 days and need to be re-sprayed at that interval. Banner Maxx has the added advantage of remaining active for up to 21 days. I would recommend spraying it at 14-17 day intervals for best results although you could wait 21 days.
Daconil, Manzate, Captan, and Mancozeb are multi-site, broad-spectrum fungicides and attack a fungus at several points in the fungus life cycle. These fungicides form a protective coating on the leaf and can be washed off, although some fungicides like Daconil Ultrex have a 'weather stile' compound to help is resist washing off during a rain. Cleary's 3336 and Benomyl are true systemic fungicides. They penetrate the leaf surface and actually get carried to all parts of the plant. Cleary's or Benemyl can be substituted for any of the sterol inhibitors.
A sterol inhibitor or true systemic can be combined with a broad-spectrum fungicide to provide even better protection. For instance, Funginex or Banner Maxx can be combined with
Daconil, Manzate, Captan, or Mancozeb. Normally these chemicals are sufficient to keep your roses looking great. However, if powdery mildew or botrytis blight is a serious problem, Rubigan can be used for powdery mildew and Ornalin can be used for botrytis. These products can be combined with any of the above products.
When you are spraying, be sure to get good coverage on all the leaf surfaces. Do not over spray your roses. Just apply enough spray until the leaves begin to drip and no more. Spray early in the morning or late evening to avoid burning the leaves in hot weather. Some fungicides like Daconil liquid contains oil that can injure or discolor leaves when the temperature gets above 80 degrees. Using
Fungi-Gard, which contains Daconil, is safer than just spraying Daconil. Daconil also comes in a wetable powder. I like to use Daconil Ultrex that does contain "weather
stik". It has a very low incidence of leaf injury and is very effective against
blackspot. Another good practice is to water your roses the day before you spray. This ensures that the leaves will be loaded with moisture when the spray hits them thus reducing the chance of chemical injury. Never spray on a windy day for the obvious reason of fungicide drift. For best results, begin spraying early March when new growth appears and continue to spray every 7-10 days (14-17 days for Banner
Maxx) at least until the end of November.
The key to getting good leaf coverage is to keep your sprayer highly pressurized. For a pump sprayer, pump it until it is very hard to pump, usually just before the pressure release goes off. Pump it again after every 5 or 6 roses to keep the pressure high. The mist should be very fine so the turbulence of the spray will quickly cover all leaf surfaces. This also helps you to use less spray. Younger, tender leaves are the most easily injured.
To help avoid injury, do not drench young leaves. Take a small stick or bamboo pole and lightly tap the excess spray off of the leaves after every 10 - 15 roses. This will help the leaves dry off more quickly and reduce the chance of injury. Also, keep your spray tank agitated. Wetable powders like Manzate
(Dithane M45) or Daconil WP will quickly settle to the bottom of the tank giving an uneven spray concentration to your roses. Shake your tank every 5 minutes or if you do get spray injury, you will most likely notice that the leaves will scrunch up a bit or show some discoloration. This injury will not hurt the rose, just the appearance of the rose with the foliage.
Up to this point, I have mentioned several fungicides. You may be wondering which ones to use. I recommend rotating your fungicides on a weekly or bi-weekly basis. This helps to avoid any build-up of resistance in the disease spores. For instance, you could start off with Funginex one week, and then use Immunox the next week. Adding a contact fungicide like Daconil or Manzate into the spray mixture further ensures that the spores won't mutate into a resistant strain. See what works for you. If disease does break out, try switching fungicides and shorten your spray interval to every 4 or 5 days to protect new foliage. It may take a month or so, but after you have regained control over the disease, resume your normal spray schedule.
Another very important aspect of spraying is making sure you do it when it will have time to dry. The fungicides will do no good if they are immediately washed off by a passing shower or thunderstorm. It is often said that the spray should dry on the leaf for 4 hours to be effective. I believe that as long as the Fungicide has fully dried on the all leaf surfaces, you will get benefit from the spray, as long as you have sprayed a sterol inhibitor or systemic fungicide. Remember that a sterol inhibitor or systemic fungicide penetrates the leaf surface and cannot be washed off. If it does rain before the spray dries, you will need to spray again after the rain ends.
So far, I have just talked about fungicides. What about insecticides? I recommend using insecticides sparingly because you kill the beneficial insects off as well as the bad bugs when you spray insecticides. And once the beneficial insects are killed, pests like spider mites flourish in our hot and dry summer weather. The only insects that I routinely spray for are
thrips. These critters affect the blooms by scraping the petals and sucking the juices out of them. Instead of spraying the entire plant, I simply mist the buds and blooms with a spray bottle full of Orthene or Cygon every 3 or 4 days. Lighter colored blooms are the most seriously affected. You must start by misting the buds when they show color to nip them in the bud. The first bloom cycle of the year is usually the one most affected, but thrips can be a problem anytime.
Aphids look bad, but are easily gotten rid of. Just spray them off with a garden hose or use a brand of insecticidal soap that has a low toxicity. Typically, aphids will only be a problem early in the year when there is plenty of young, succulent growth. There are almost no situations where you have to use a toxic spray like
Orthene, Sevin, or Malathion to get rid of aphids.
Insects such as Japanese Beetles can cause a lot of damage, but they are typically only a serious problem for 3 weeks. I pick off as many as I can, and then tolerate the rest until their feeding frenzy is through. If you must spray them, Sevin and Orthene are both effective. A better way to attack them is when they are just white grubs in the soil. Merit is a product that will kill the grubs and is a better alternative than
Dursban. Milky spore disease is a natural poison to beetle grubs and will not harm other living creatures. It takes about a year to establish, but lasts up to 15 years in the soil. It is probably the best and least toxic solution for beetles. Contact your county extension agent or local rose society to get the best times to use these products in your area.
Spider mites can be devastating to a rose. They multiply rapidly in hot dry conditions forming webbing between canes and leaves and causing distortion of growth in severe infestations. If you notice a dusty, dull yellow appearance on your leaves, you probably have spider mites and need to act quickly. Since insecticides do not affect mites you must either wash them off the plant by spraying a strong stream of water to the undersides or leaves for several days; or, use a miticide such as Avid once every two weeks. I find mites to be much worse than other insects, which is why I seldom use insecticides.
Midge can also be quite devastating to roses. They attack very young buds and the result is a cane with no blooms, only a small black leaf where the bud should have been. If you are sure you have midge, spreading Diazinon granules on the ground around the rose will break up the life cycle and Orthene will eliminate them on the rose.
A variety of caterpillars, beetles, borers, etc may pass through your rose garden during the year. Generally the damage from these pests is minor and not worth drastic measures, unless of course you plan on exhibiting your roses. If you want to make your spray work harder you, consider using a buffering agent like Indicate 5, which lowers the pH of your water to the optimum range for mixing most chemicals in. This helps to spread the spray more evenly on the leaves and can increase the time that the chemical remains active in your solution. Indicate 5 changes the water color to pink when the proper pH is reached, which eliminates the guessing that people used to do when they added vinegar to lower the water pH. There are also several sticker-spreaders on the market that will also help spread the spray more evenly and cause it to stick better on the leaf surfaces. These products do not lower the pH of the water.
When you are done spraying, be sure to clean your equipment thoroughly. Nothing gums up your sprayer like old spray residue. 5 minutes cleaning your sprayer is better than buying a new one several times a year. Also, do not save old spray mixtures. Mix a new batch each time you spray because the spray in your tank will only be effective for a short period of time. A good rule of thumb is never use spray that is over 4 hours old.
Finally, avoid using products that have both fungicides and insecticides in them. You generally do not need to use the insecticides each time you spray and you will be making your garden a friendlier place to be for friendly bugs and for you.