Greater Gwinnett Rose Society



Fungicides for Newbies!Now that you have all these new roses and you want them to look great for the season, or you’ve had roses for a while and had issues with fungal diseases and want to start a spray program, what should you do? In our area, Northeast Georgia, the pressure for fungal diseases is very high. High humidity and the possibility of rain at any time create a perfect breeding ground for blackspot and other fungal diseases. It can be daunting for the new rose grower to understand why roses have disease and what can be done about it. How you deal with disease is totally up to you. No one needs to use fungicides or any pesticide if they don’t want to. However, if left unabated in susceptible roses, blackspot and other fungal diseases can cause failure to thrive. Blackspot will not kill a rose outright, but if the rose is constantly defoliated, it will not be able to supply energy from the leaves to the rest of the plant and will be more susceptible to other diseases or weakened to cold damage. A few facts:Fungal disease are always around. They live in the air. They will bloom when the conditions are right. A rule of thumb is that the spores will activate when they are wet for a number of hours. If you have rain, especially at night, and the leaves don’t have a chance to dry off, you will have blackspot on susceptible roses. Since fungal spores can over winter in rose canes and leaves, it is important to remove all old leaves from the rose when doing your spring pruning. Older leaves will be more susceptible to disease and will spread it to the rest of bush. Also, any leaves that fell to the ground should be removed and fresh mulch spread on top to stop the fungal spores from splashing up onto the bush with watering or rain. Air circulation is important, so spacing of roses apart and pruning to allow air circulation is key. Planting roses in full sun, while important for growth and flowering, will help the roses dry off before blackspot can take hold.Some roses are more susceptible to fungal diseases. Hybrid Teas, the fancy roses with the big blooms are usually more susceptible. They are bred for bloom form, color, size and not disease resistance. David Austin’s, very popular English type roses with lots of petals, dramatic colors and fragrance are also not very disease resistant, at least not in our climate. The Rose Industry has created some resistant varieties, Knockouts, now available in different colors, are extremely resistant to black spot (notice I did not say immune!). Newer rose varieties are coming out every year touting disease resistance. However, some of the testing is done in places like California and Arizona, which certainly don’t have the same conditions that we have. So, your mileage may vary.If you want some of the less resistant roses, you will likely need a spray program. It can be tailored to your yard, your roses and your tolerance to disease.I Don’t Want Yucky Chemicals in my Yard! (or the organic approach)There are a many new options for the organic gardener for fighting fungal diseases. First, the rose selection, spacing and pruning/bed cleaning process mentioned above are more important in the organic garden. These practices will cut down on the diseases you will need to deal with.The Organic Spray Program:Dormant Spray (also part of the chemical spray program): as we noted above, fungal spores can over winter on roses and in rose beds. When roses are dormant (anytime after a hard frost to beginning to bud out in the late winter/early spring) you can apply dormant sprays. Lime Sulphur and Horticulture Oil are two of the types of dormant sprays you can use. These are sprayed on the roses and the rose beds. Lime-sulfur: is a form of sulfur mixed with lime (calcium hydroxide), and is mostly used as a dormant spray, meaning it should not be applied to plant foliage. Lime-sulfur is more effective than elemental sulfur at lower concentrations; however, its strong, rotten-egg odor usually discourages its use over extensive plantings.Horticultural oil: can be beneficial in smothering insects that also harbor in the soil over winter. Oils effectively manage powdery mildew on many plants, but are significantly less effective against other leaf spot diseases.During the growing season:Neem oil: is pressed from the fruit and seeds of the neem tree (Azadirachta indica). At a 70 percent concentration, neem oil kills powdery mildew spores, virus vectors (such as aphids and white fly), and the eggs of numerous insect pests. It is less effective against rose black spot (caused by Diplocarpon roseae) and other fungal diseases. Copper: Liquid Copper Fungicide helps control powdery mildew, downy mildew, black spot, peach leaf curl, rust, and many other listed diseases.?Copper?is a naturally occurring chemical which makes it a great option for use on all of your plants. It is approved for Organic Gardens.Sulphur: Sulfur is the oldest recorded fungicide and has been used for more than 2,000 years. Early in agricultural history, the Greeks recognized its efficacy against rust diseases on wheat.Although few homeowners grow their own wheat, sulfur can be a preventive fungicide against powdery mildew, rose black spot, rusts, and other diseases. Sulfur prevents fungal spores from germinating, so it must be applied before the disease develops for effective results. Sulfur can be purchased as a dust, wettable powder, or liquid. Do not use sulfur if you have applied an oil spray within the last month — the combination is phytotoxic (plant-killing). Likewise, do not use sulfur when temperatures are expected to exceed 80°F to reduce the risk of plant damage.Bicarbonates: Baking soda (sodium bicarbonate) has been used as a fungicide since 1933. Recent research has demonstrated that although baking soda can be effective against plant diseases when used with oil, its sodium component can build up and become toxic to plants.I don’t care, I want pretty roses and no disease (or the Chemical approach)There are many different types of fungicides available if you want to go the chemical route. You don’t need to be a chemist to understand fungicides, but it’s important to know a few things: Mode of Action is very important. Mode of Action is how the chemical works on the fungus. Many commercially available fungicides are actually the same chemical or have the same MOA , so using just one or the same MOA may lead to resistance by the fungal disease or not getting complete coverage. Systemic or Contact: Most rose growers who use chemicals use a combination of a systemic and a contact fungicide. A systemic is what it says, it will enter the plant system and protect from the inside. A contact fungicide will kill spores on the surface for a period of time. Both will need to be re-applied every 7-14 days to be totally effective. You will have to base your spray program on the number and type of roses you have. For the small garden under a dozen roses, you can probably get by with a RTU (ready to use ) spray that is already mixed, you just buy in the store and spray on your roses bushes according to the directions. For larger gardens, it’s recommended to use concentrates that you then mix with water in a pump sprayer. You can also combine two different fungicides in the mix, one systemic and one contact to get a double whammy on the blackspot (check product labelling on mixing with other chemicals).For Roses, we have a few MOA groups that we use. Most use MOA 3, the chemicals known as either Propiconazole or Tebuconazole. These are systemic fungicides that are available in big box stores like Home Depot and online from Rosemania and other suppliers. I’ve listed some of the brand names in the table.Trade nameActive ingredientFungicide groupTypeOrganic?HeritageAzoxystrobin11SystemicNoCaptan 50 WP, Captan 50 W, Captec 4LCaptanM4ContactNoSpectro 90 WDGChlorothalonil + thiophanate-methylMS + 1CombinationNo Daconil, Bonide Fung-onilChlorothalonilMSContactNoDithane 75 DF Rainshield, Manzate MaxMancozebM3ContactNoBanner Maxx, Honor Guard, Bonide InfusePropiconazole3SystemicNoBayer Advanced Disease ControlTebuconazole3SystemicNoCleary's 3336Thiophanate-methyl1SystemicNoImmunoxMyclobutanil3SystemicNoBonide, Southern Ag Liquid CopperCopper hydroxide + Copper oxychlorideM1SystemicYesNeem OilNeem Oil46ContactYesMontery Complete Disease ControlBacillus amyloliquefaciens strain D747*44SystemicYesMilstoppotassium bicarbonate?ContactYesVariousSulphurMO2ContactYesIn addition to MOA 3 fungicide, many of us add in a contact M3 fungicide such as Manzate or Manzecob. These are also available in retail or online.It is also recommended to alternate your MOA to prevent resistance. So instead of a MOA 3 you can use a MOA 1, brand name Cleary’s. You can also switch your M3 for MS or M4.In my garden, I have over 180 roses, so I’ve long grown out of the ready to use products. I alternate between generic Propiconazole mixed with Manzate and Cleary’s Thiophanate-methyl. I usually spray every other Sunday, weather permitting, from the time the rose leaves emerge to first hard frost in the fall. Safety First!When using chemicals (even organic fungicides are chemicals and can be harmful to you), safety precautions must be taken.Personal Protection:You will need to protect yourself from exposure to the various chemicals. Water proof gloves must be worn. Nitrile or latex gloves work well and are thin enough to allow you great dexterity. Eye protection is also important. Safety glasses or goggles will prevent any spray blow back from getting in your eyes. Some people use a face shield. A mask or respirator can also be used. Long sleeve shirt, long pants, closed toe shoes will also offer you the maximum protection. A hat will keep the sun out of your eyes and protect your head. You should have your protective gear on from the moment you reach for your bottles of chemicals, as the most dangerous time is when you are handling the concentrated chemicals and mixing them.Proper Tools:You should have a dedicated sprayer for fungicide only. Don’t use it for herbicides or insecticides. Label it with a marker so everyone knows what it’s for. A pump sprayer is fine, you can also get an electric sprayer. Hose end sprayers are not recommended as they spray indiscriminately and you can’t be precise with the dilution. You should also have measuring tools that are for garden use only! Keep your chemicals in proper storage in a shed, garage or basement, preferably in a cabinet where children cannot reach them. Some chemicals can degrade with age or if kept in places where the temperatures can get high. Therefore, it is not recommended to buy in large quantities for more than one or two growing seasons.Other Considerations:Children and pets should be inside while you are mixing and spraying and up to 2 hours after as the spray dries. Do not eat, drink or smoke while spraying. Weather conditions such as wind and rain must be taken into consideration when spraying. Also, time of day. Sprays can react with sunlight or high temperatures and burn the leaves of your roses. It is recommended to spray as early in the morning as possible, or in the evening when the sun is setting and the temps are cooler. Roses should be well watered before applying fungicides. Watering the day before you spray is fine.Ok I’m ready! How to Spray:Gather your materialsGet your chemicals, your sprayer and your mixing tools out (you of course already have your protective gear on and your pets and kids are inside). Refer to the product label as to the amount of chemical you need based on your sprayer and how many gallons you are spraying (more on this below). Fill your sprayer half way with water. Measure out your chemical and pour into the sprayer. Fill the sprayer with water. Close tight, and pump (if necessary). Make sure you agitate the mixture when filling the sprayer to ensure proper mixing.Spraying your rosesStart with the closest rose (since your sprayer is very heavy when at its fullest). Use the spray wand to get underneath the leaves and spray up . Then spray the tops of the leaves. The spray should be just about dripping off the leaves. Then proceed to the next rose. If you are using a pump sprayer, re-pump as needed. A fine spray is preferable.Clean UpWhile still wearing your protective gear, open the sprayer (if a pump sprayer, be careful opening or release the pressure by holding down the button until the pressure is low). Rinse out the sprayer and then fill with water. Pump up the sprayer and spray until the water coming out of the sprayer is clear. Then empty the sprayer and allow it to dry and store it for next time. Then remove your protective gear and either dispose of (gloves) or rinse with the hose. Your clothes should be removed and washed. And you should take a shower.Read the label!Most chemical bottles will have labels with tiny print. If you are like me and are sight challenged, you will need an alternative. Luckily, we now have the internet. All chemical labels are available online in PDF Format that you can zoom in on and print for your own use. I recommend you do this to read it before using the first time. I keep a copy of a label of each chemical I use in a binder so I can refer to it when I need to.What’s on the label?? Trade name or brand name ? Active ingredients and their percentage by weight ? Types of plants or sites where pesticide may be used ? Pests targeted ? How much to use ? How and when to apply ? Required protective clothing and equipment ? Signal words ? Precautionary statements defining hazards to people, domestic animals, or the environment ? Emergency and first aid measures to take if someone has been exposed ? Proper storage and disposal of the pesticide and empty containersHow much do I need?Many of the labels are confusing and can have mixing directions by acre or a percentage of. It will also list uses for Turf Grasses and other plants. So, figuring out what to use for roses can be a bit of a mystery. Luckily, we have Rosemania to thanks for this fabulous chart:How many gallons you will need depends on the number of roses and how large they are. For under 50 roses, one gallon should suffice. From there you can go to 1 ? gallon or two. Try not to mix more spray than you can use. It cannot be stored and you don’t want to have to dump it out. I have 180 roses and I use a 4 gallon backpack sprayer. What else on the label is important?You will notice on the Rosemania chart that there is a column labeled Category. It’s actually the ‘Signal Word’. Each chemical is assigned a Signal Word based on toxicity. The lower the number, the more toxic the chemical is. Most are labelled Caution but some are Warning or Danger. The more toxic the chemical is, the more vigilant you will need to be when using it. Or decide to use chemicals that are less toxic. If all this sounds like a lot of work, well it can be. However, once you get the process down, it shouldn’t take you longer than 2 hours from start to finish, depending on how many roses you have. You’ll be more familiar with your sprayer, how much of the chemical to mix and how you will go about your yard spraying. You can also add in some items to the spray that will be beneficial to your roses. One item I use is Nature’s Magic, a combination humic acid and seaweed extract. It does double duty as coloring the water in the tank so I can easily see when the mix is at the level I want, and it gives a great dose of vitamins and minerals plus humic acid to my roses. Something you don’t want to add is any beneficial fungal products. Wait at least one week after spraying a fungicide to use those products.You can also tailor your spray program for conditions. Lots of rain, you will want to spray more often. Hot dry weather, such as July and August, you may be able to get away with not spraying. Some people spray only 3-4 times a year, when the roses first leaf out and then a few times during the year. You don’t have to spray every rose. I have some roses that never get disease. I don’t spray them. New roses that I buy that may have good disease resistance I don’t spray and observe to see if they will need to be sprayed going forward. You can do a combination of organic and chemical. It’s all up to you.A word about combination products with fungicide/insecticide/fertilizer. I personally don’t recommend them. I never want to apply insecticide unless I absolutely need to. And the six-week interval is not enough to prevent black spot on most of my roses. These products are also relatively expensive and unless you have a small garden, not cost effective. Once you start your program your way, you can make adjustments as necessary. Gardening is a constant adaptation to conditions. But they do work, that is why serious rosarians use them. You will be rewarded with beautiful healthy roses, more blooms, bigger plants, longer flowering season. It is worth it if you love roses. As with all things, if you have questions, our Consulting and Master Rosarians are available for questions. ................
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