Spring is on its way and with that comes the list of spring chores. Some can be left undone or put off to a later date with very little consequence, but there are chores that need to be done on time in
order for them to be affective.
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Pruning is one chore that needs to be done on time, and another that is essential in a tree/shrubs health is applying lime sulphur and dormant oil, which is a combination spray that kills many overwintering insects and disease.
This is important, as many of the chemicals that were available years ago to treat tree/shrub problems are no longer available, and so you want to be able to prevent any problems from arising as they could be harder to treat later in the season.
Lime sulphur and dormant oil is applied to all deciduous shade trees, fruit trees, small fruits, flowering and ornamental shrubs and roses.
Apply in the early spring before the tree/shrub break into leaf. I like to tell people to apply the oil after you have finished pruning as there is no need to treat the branches that are going to be removed.
Timing is important when using this combination spray. Plants need to be dormant as the oil can cause damage if used when the leaves break out. This is why it is called dormant oil.
Temperature also plays an important role in when to apply the spray. It has to be a mild day with temperatures staying above freezing. Apply early in the day so that there is enough time for the spray to dry.
Considered organic by some gardeners because both the lime sulphur and dormant oil occur naturally. Oils have been used by farmers and gardeners for hundreds of years before chemical pesticides were ever available.
Oil is a contact insecticide meaning that it has to have contact with the insect or egg as it suffocates the eggs and overwintering insects. Insects including the beneficial ones that migrate to the tree/shrub later will not be affected.
The lime sulphur helps kill or prevent the spread of fungal spores that lead to disease.
To make it easy the spray comee in a box labelled Dormant Spray Kit.
The bottle of lime sulphur is twice the size of the horticultural oil because when you mix the two together you mix one part oil to two parts lime sulphur and then the water.
Only mix what you are going to use, and use it immediately after it has been mixed because it will separate. Any type of
sprayer will work.
When spraying, start from the top and work down, making sure that all surfaces of the plant are coated. It is always important to follow the instructions given by the manufacturer when using any product.
You want to be careful by never spraying on a windy day and to always wear protective clothing, goggles, and gloves. You also want to be careful when spraying around pavement and other structures as this
product can cause stains.
Protect all your deciduous trees and shrubs by applying Dormant oil and Lime Sulphur over the next couple of weeks. Being proactive now will save you from being reactive later.
Reminder: The 31st annual tree pruning clinic is being held at Art Knapp Plantland, Kimball road location only. Saturday March 31, 10 a.m and Sunday April 1, 12 p.m. There is a $10 charge which will be donated to the Child Development Center.
- Using Lime Sulfur In Gardens: When And How To Use Lime Sulfur
- What is Lime Sulfur?
- How and to Use Lime Sulfur
- Even with effective synthetic alternatives Sulfur remains a relevant tool for controlling powdery mildew
- Powdery Mildew on Hops
Using Lime Sulfur In Gardens: When And How To Use Lime Sulfur
Fungus happens. Even the most experienced and dedicated gardeners will experience fungal disease on plants at some point. Fungus can affect plants in any climate and hardiness zone because, like plants, certain fungal spores grow better in different climates. Even new disease resistant varieties can suffer from these issues. As gardeners, we can choose to spend a fortune on different chemicals that can have residual effects to treat different symptoms or we can use a natural based product that has been used by growers and breeders for hundreds of years. Continue reading to learn about using lime sulfur in gardens.
What is Lime Sulfur?
Lime sulfur is a mixture of calcium hydroxide and sulfur. In horticultural dormant sprays, lime sulfur is usually mixed with an oil, like mineral oil, to make it stick to plant surfaces. These horticultural oil sprays contain a high concentration of lime sulfur that is only safe to use on plants that are dormant because the sulfur can burn leaf tissues.
Lime sulfur can also be mixed in much weaker concentration with water for use when plants have leafed out. Even in lower concentrations and diluted with water, it is important not to spray lime sulfur on plants during hot, sunny days, as the sulfur can cause sunscald on plants.
With warnings like this, you may wonder is lime sulfur safe? When used properly, lime sulfur is a safe and effective treatment of fungal diseases such as:
- Powdery mildew
- Black spot
- Black rot
As a horticultural dormant spray, lime sulfur is safe to use even on fruits that include:
Lime sulfur is also used to treat fungal diseases of ornamental plants like:
Additionally, lime sulfur can be an effective treatment for certain pests.
How and to Use Lime Sulfur
Fungal disease spores can overwinter in cracks or fissures on plants or in soil and garden debris. For this reason, lime sulfur is used in high concentrates mixed with oil as a horticultural dormant spray. When to use lime sulfur this way is in late winter or early spring before the plant begins to leaf out. It is also a good idea to spray the soil around plants that have been previously infected or are prone to infection.
For perennials or plants that are showing new signs of fungal diseases, lime sulfur can be mixed with water and sprayed on plants anytime except for hot, sunny days. The mixing ratio is 1 tsp. per gallon of water. Spray all surfaces of the plant thoroughly. Allow the mixture to sit on the plants for 15-20 minutes. Then thoroughly rinse the plants with just clear water.
Occasionally, you will notice the bottom portion of tree trunks covered with white latex paint. Sometimes, this contains a diluted mixture of lime sulfur.
Dormant oil is a combination of horticulture oil and lime sulphur that when sprayed on dormant plants, kills and protects them from many damaging insect and fungal problems. It is especially useful on fruit trees.
What are the benefits?
This spray can be used on fruit trees, roses and many deciduous ornamentals. It is especially useful in killing off overwintering insects and fungal disease. By killing these pests before they get a chance to become a big problem this growing season, you’ll help your plants out immensely.
The oil will help control overwintering insects such as: blister and rust mites, red mite eggs, aphid eggs, scale insects, twig borer, plum black knot, peach leaf curl, as well as overwintering fungal diseases.
Some plants are however sensitive to this oil, so it is best not to use it on: Colorado blue spruce, butternut, Japanese maple, sugar maple, beech, hickory, holly, walnut, or Douglas fir.
When to spray
Now is the time to apply your fruit trees with dormant oil. For most trees, this application should be done before the buds break open, as application after bud break can damage leaves. Usually February through early April is a good time to apply.
You’ll want to apply it on a day that is 0 degrees Celsius or above (so that the oil can dry and not freeze). Apply it early in the morning so the oil has a chance to dry during the course of the day. It is also important that there is no precipitation for at least 24 hours after application, you don’t want your oil to be washed away before it dries!
A day with low wind is better, higher winds mean less of the spray will adhere to the trees.
Once the plants have broken dormancy; some species can tolerate applications of horticultural oil (but not the mixture of horticulture oil and lime sulphur). Always follow the instructions on the product packaging. If you have a plant and you are unsure if it can tolerate the oil, spray some on a test leaf. If the plant cannot withstand the oil, leaf damage will show in 24 hours. If the test leaf is damaged, do not spray the entire plant.
How to spray
Mix the lime sulphur and horticulture oil according to package directions. We have it available for sale as a kit. You’ll also need some means of spraying the mixture. A handheld mister bottle or pump sprayer is useful for small applications. A large tank sprayer, or a dormant spray applicator that attaches to your garden hose are better for larger jobs.
Regardless of what applicator you’re using, start spraying at the top of the plant. Continue spraying until the oil just begins to drip off the branches. Move downward until your plant is coated with oil.
For roses, spraying the soil around the base of the plant can be helpful in controlling powdery mildew and black spot.
- Always read and follow the instructions on the product label.
- Mix only what you can use; the mixture of horticulture oil and lime sulphur cannot be stored for later use.
- For spraying any pesticide, wear protective clothing. Wearing a long sleeved shirt, hat, chemical resistant gloves and goggles would be ideal.
- Wash hands and face after application.
- It’s important to note that the lime sulphur can permanently stain wood, stone, pavement etc. If you are spraying in close proximity to one of these surfaces, be sure not to get it on any on them. Laying down a plastic sheet to prevent splash/spray can also be beneficial.
Lime-sulfur: A fungicide used to control a variety of diseases
by Don Janssen, Extension Educator
Lime-sulfur, a fungicide composed of inorganic sulfur and lime, is commonly used today to control a variety of diseases such as plum pockets, black knot, black spot of rose, and a number of raspberry diseases. Lime-sulfur was originally developed in 1851 by Grison who was the head gardener at the vegetable houses in Versailles, France. Grison boiled “flowers of sulphur”, freshly slaked lime, and water for 10 minutes, drew off the clear liquid and mixed it with water. He then used this solution to protect plants against mildews. The solution was originally known as the “Grison Liquid” or “Eau Grison”. In 1886, lime-sulfur was used to control peach leaf curl in California.
Sulfur is the only ingredient in the mix that is toxic to pathogens. It is able to kill pathogens through direct contact or fumigation (sulfur vapors). The vapor action of sulfur allows the fungicide to be effective from a distance and is important in killing spores of powdery mildew. Once taken up by the fungus, sulfur disrupts the transfer of electrons causing the reduction of sulfur to hydrogen sulfide (H2S), which is toxic to most cellular proteins.
Sulfur itself is also toxic to certain plant species and is capable of causing a phytotoxic reaction. As a result, lime has been added to the mix to reduce the phytotoxicity of sulfur. The more lime added to the mix the less phytotoxic. In general, lime is considered a “safener” for the plant.
According to the label, lime-sulfur can be applied as a dormant season fungicide or as a growing season spray. Dormant season applications need to be applied in late winter or early spring when temperatures are above freezing, but before leaves are present on the plant. Growing season applications can be made after leaves are present on the plant, but should be applied in the early morning or late afternoon to avoid burning. Plant damage caused by lime-sulfur is most severe during dry weather when temperatures reach 80 degrees to 95 degrees F. Lime-sulfur is corrosive to the eyes and harmful if swallowed, inhaled, or absorbed through the skin. Appropriate precautions according to the label should be taken when applying lime-sulfur. Thoroughly read the label before purchasing, handling, or applying lime-sulfur.
Return for more resources – http://lancaster.unl.edu
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office
Even with effective synthetic alternatives Sulfur remains a relevant tool for controlling powdery mildew
California growers were using sulfur to battle powdery mildew before the first synthetic fungicides were introduced to control the disease in the early 1980s. But, that doesn’t make this elemental material any less relevant for containing outbreaks of the disease today.
In fact, sulfur remains the go-to natural choice of organic growers for limiting powdery mildew damage, says Larry Bettiga, University of California Cooperative Extension viticulture advisor for Monterey County.
“The synthetic fungicides, especially the current ones, work quite well in controlling powdery mildew,” he says. “But sulfur still has a big role to play in protecting conventional vineyards from the disease.”
Unlike synthetic materials, natural sulfur carries no risk of disease-causing fungi developing resistance to it, Bettiga notes. And, it costs considerably less than synthetic products. As a result, sulfur offers an affordable option where resistance may be developing in a vineyard.
“If you’re seeing some slippage in effectiveness of a synthetic fungicide, especially in the case of an older product, including sulfur in your powdery mildew program may help control those more resistant isolates of the fungi,” Bettiga says.
In some cases, sulfur may have proven beneficial for growers who relied heavily on synthetic fungicides to control last year’s unusually high powdery mildew pressures, he notes. “Along with additional leaf pulling and canopy hedging to improve air circulation and treatment coverage, adding sulfur to the tank may have improved control where growers experienced some decline in effectiveness of a synthetic product,” Bettiga adds.
Recent research by scientists at Cornell University refute the contention of some in the wine industry that excess levels of sulfur residue on the fruit at harvest can disrupt the fermentation process, producing sulfides that harm the quality of the wine.
These studies show that when sulfur is used only up until veraison, the point where increasing sugar levels begin to inhibit development of powdery mildew, any sulfides in the wine are often caused by poor nutrition of the must. This stresses the yeasts, which can cause them to produce sulfides, Bettiga said.
When sulfur use stopped after veraison, the level of elemental sulfur in must was found to be below the 10 mg/L threshold. That threshold is the level at which the potential for sulfide production resulting from applications of sulfur increases, Bettiga said.
Like any fungicide, except oil, sulfur is best used by applying it in advance of any outbreak of powdery mildew to protect against the disease rather than to eradicate it after the disease has already infected the vines, Bettiga notes.
Also, as with other soft chemistry materials, intervals between sulfur applications need to be reduced when disease pressure is high to maintain disease control. “Sulfur can maintain disease control if applied frequently enough with good coverage,” he says.
Sulfur kills the disease-spreading spores by disrupting respiration within their cells. It does this either by residual action or, at higher temperatures, by volatilization. Residual action requires direct contact with the spores.
What’s more, contrary to what some growers may think, researchers at Cornell University and in Australia found that sulfur does help control powdery mildew during the colder temperatures of spring.
“The key to using sulfur effectively under these conditions is to increase application rates and improve coverage of the green tissue you’re trying to protect,” Bettiga says. “If you do that, sulfur is still pretty effective at lower temperatures.”
Sulfur is available as a dust or in such sprayable forms as a wettable powder, a liquid flowable and a micronized dry flowable.
Of these, the dust form is the most economical treatment, Bettiga notes. He estimates the application cost of a dust treatment at about $8 per acre compared to around $17 to $20 per acre for a spray application.
“You can treat a lot more acres in the same amount of time using a duster rather than spraying a liquid, because a sprayer requires a slower ground speed to get the same degree of coverage as a duster,” Bettiga says “Also, you can get better coverage in thick canopies where leaves are shingled with the dust than a spray.”
The dust form, supplemented with synthetic fungicides from bloom to fruit set, tends to be more popular for vineyards with lower profit margins, he notes. Use of the more expensive synthetic products is greater in the higher-value grapes.
One advantage of micronized dry flowable sulfur products is the smaller and tighter range of size of the particles compared to wettable powders. Sulfur dust has the largest average particle size.
“The smaller the sulfur particle size the more activity along the leaf surface of the vine,” Bettiga says.” Also, smaller particle sizes volatize at a little higher rate than larger ones.”
More information on using of sulfur and other fungicides, as well as the Powdery Mildew Risk Index, for controlling powdery mildew, is available at www.ipm.ucanr.edu
Powdery Mildew on Hops
This study highlights the need to consider the sometimes complex bio-systems present in the hopyard when making pest management decisions. Natural predators play a huge role in any integrated pest management, so special care must be given to maintain these beneficial populations and it’s important to consider how management decisions aimed to control one pest may affect another down the road. Frequent sampling for target pests as well as beneficial insects, before and after making spray applications of any kind can help a grower get a better idea of the full picture of his crop, and will encourage better pest management decisions. In this case, growers of hops in the Pacific Northwest may choose alternate fungicides to sulfur, or adjust to lower rates in order to preserve beneficial insect populations and help control two-spotted spider mites later in the season.
Effects of powdery mildew fungicide programs on twospotted spider mite (Acari: Tetranychidae), hop aphid (Hemiptera: Aphididae), and their natural enemies in hop yards
Plant Management Network, 2008