Copper Sulphate Fungicide
To prevent fungal disease in fruit trees, blight in potatoes and insects on any other flowering trees and plants, try this easy organic copper sulphate (bluestone) spray.
To prepare copper sulphate fungicide spray:
• Take 1 teaspoon of copper sulphate (bluestone) and wrap in an old panty hose stocking. Tie a knot in it so that the bluestone doesn’t escape and clog up the nozzle. Place the tied panty hose in a 1 liter plastic spray bottle.
• Take 2 teaspoons of hydrated lime and place it in the same bottle as the bluestone.
• Fill the 1 liter spray bottle close to the top of the rim with water.
• Agitate the ingredients in the bottle.
Now you are ready to spray your fruit trees, vegetables and anything else that you are growing in your garden. This will protect your plants during the cold winter months from many fungal problems such as downy mildew and rust, etc.
TIP:
• Prepare a fresh bottle of solution each time.
• Use the entire solution straight away, otherwise the bluestone settles to the bottom and hardens if left overnight.
• If you do not use the entire bottle contents – please discard safely. Do not tip it down your kitchen sink, as it will only clog up your pipes.
THE BORDEAUX FORMULA
Although there are many formulas for preparing Bordeaux mixture, generally a ratio of 10-10-100 works well for many disease-causing pathogens. The three hyphenated numbers represent the amount of each material to add.
The first number refers to pounds of copper sulfate, the second to pounds of dry hydrated lime, and the third to the total gallons of water. Thus a 10-10-100 Bordeaux mixture would be comprised of 10 pounds of copper sulfate, 10 pounds of lime, and 100 gallons of water.
A more manageable amount for the home gardener would be a 1-gallon mixture of 10-10-100 Bordeaux, which would contain 1/10th of a pound of each of the dry ingredients, which would be 3-1/3 tablespoons of copper sulfate and 10 tablespoons of dry hydrated lime in 1 gallon of water. You can purchase copper sulfate and hydrated lime at most garden centers.
THE MATERIALS
Copper Sulfate
Powdered copper sulfate, often referred to as “bluestone,” is a finely ground material that dissolves relatively quickly in warm water. Ordinary, lump copper sulfate isn’t satisfactory, because it is slow to mix into the solution. Store copper sulfate in a dry place. If it gets moist, it becomes lumpy and difficult to work with. Fixed copper fungicides shouldn’t be used in making up a Bordeaux mixture.
Lime
You can use either dry hydrated lime or slaked lime to prepare Bordeaux. The most important point is to use fresh lime. Don’t use lime from last season, and purchase only what you can use in the current season.
Hydrated Lime. Use only good quality hydrated lime (calcium hydroxide). The hydrated lime should be fresh and not carbonated by prolonged exposure to air. Hydrated lime is a dry product commonly used to make plaster and is readily available under several trade names. When mixing lime, protect your eyes, nose, and mouth by using a dust- and mist-filtering respirator.
Slaked Lime. Slaked lime is prepared by adding “quick” (hot, burned) lime (calcium oxide) to water to produce calcium hydroxide. Slaking quick lime in water can produce heat sufficient to boil the water, so regulate the amount of lime you add to the water at any one time, so the mixture doesn’t splash. Wear goggles or safety glasses to protect your eyes and stir the mix with a wooden stick while adding the lime to the water. The slaking chemical reaction takes 1/2 to 2 hours, so prepare the lime mixture before you plan to spray.
To make slaked lime add 1 pound of quick lime per gallon of water. This results in a mixture the consistency of milk. Slaked lime makes a superior suspension, but it requires more time, effort, and containers than prepared hydrated lime. If using slaked lime, follow the procedures in the Stock Solutions section below.
MAKING THE BORDEAUX MIXTURE
The effectiveness of a Bordeauxspray depends almost entirely on following the correct procedure for mixing. You can prepare Bordeaux directly in a spray tank equipped with an agitator, or if you don’t have a power sprayer, you can prepare smaller amounts for use in a hand sprayer. If you use a hand sprayer, you’ll first need to mix up stock solutions of lime and copper sulfate as described below. No matter how you mix the ingredients, you’ll need to use the spray solution soon after you prepare it, since the mixture will deteriorate upon standing.
Stock Solutions
The old-fashioned way of making a Bordeaux mixture is to prepare “stock” solutions of lime and copper sulfate that you later mix by pouring them into water in a sprayer. This method also works best for making small quantities of Bordeaux.
Using a plastic bucket, dissolve 1 pound of copper sulfate into 1 gallon of warm water. You can store this solution indefinitely in a stoppered, glass container.
For the lime, use the slaked lime suspension described above or mix a solution of 1 pound of fresh hydrated lime in 1 gallon of water. This mixture needs to stand for about 2 hours before use. You can store the lime mixture indefinitely as well in a stoppered container. Preparing a stock mixture of lime eliminates the need to obtain fresh hydrated lime each time you prepare a Bordeaux mixture.
Be sure to clearly label both stock solutions and store them where children can’t get into them, since these materials, especially the copper sulfate, are very toxic and corrosive.
To make 2-1/2 gallons of a 10-10-100 Bordeaux mixture, measure 2 gallons of water into a strong plastic bucket. Shake the copper sulfate solution vigorously before adding 1 quart of it to the 2 gallons of fresh water. Always add the copper to the spray water before adding the lime. Shake the lime mixture, and add 1 quart to the 2 gallons of water. Keep stirring the spray water mixture while adding the copper and the lime and continue stirring or shaking for several minutes before pouring it into the sprayer. The mixture now is ready to use.
Be sure to constantly shake the sprayer while using it to avoid clogging. Read the label directions carefully on the copper sulfate regarding the proper protective equipment to wear when preparing the stock solutions and when spraying. Bordeaux performs best if nothing is added to the prepared mix described above.
This formulation of Bordeaux mixture will be adequate for practically all home-garden, disease-protection needs. If you wish to maintain Bordeaux mixture on a tree throughout the entire winter rainy period, you can reapply the spray, or use a slightly stronger mixture—1-1/2 quarts of each stock solution to 2 gallons of water. In spring when buds are opening or on sensitive plants, use a slightly weaker mixture—1 pint of each solution to 2 gallons of water—or use a fixed copper spray.
Fungicide Rotations for Nursery,
Greenhouse, and Landscape Professionals
Janna Beckerman
Department of Botany and Plant Pathology, Purdue University
BP-71-W
Disease Management Strategies
Fungicides are important tools for managing ornamental plant diseases. There are
many different fungicides and numerous methods of classifying them. This publication
examines how fungicides are classified and recommends management practices to
prevent fungi from developing resistance to these products.
Fungicide Class
One way to classify fungicides is by their chemical structures or modes of action —
the specific ways the fungicides affect a fungus. Fungicides that share a common mode of
action belong to the same fungicide class (sometimes referred to as a fungicide family).
Unfortunately, if a fungus is resistant to a specific fungicide, it is usually resistant to all the
fungicides within that fungicide class.
Target Site
Fungicides are also characterized by their specificity.
Site-specific fungicides react with one very specific, very important biochemical
process, called the target site. For example, a fungicide target site could be the specific
proteins involved in cell wall biosynthesis, RNA biosynthesis, or cell division. Site-specific
fungicides target these specific processes, which prevents the fungus from growing and
ultimately causes its death.
Multi-site fungicides have multiple modes of action, so they affect multiple target sites,
and simultaneously interfere with numerous metabolic processes of the fungus.
Fungicide resistance occurs when a fungus develops a genetic mutation at the target
site that reduces its sensitivity to a specific fungicide. Because they affect multiple target
sites, multi-site fungicides have a very low risk of causing fungicide resistance because it
is highly unlikely for a fungus to simultaneously develop all of the mutations necessary
for resistance.
Site-specific fungicides, however, have a much higher risk of causing resistance because
a single genetic mutation at the target site can change a fungus’ biochemical process
so that it can still perform the needed biological function (cell division, membrane
biosynthesis, respiration). The result is a fungus strain that is less susceptible or no longer
susceptible to the site-specific fungicide.
If a single fungicide continues to be used, the fungicide-sensitive portion of the
population is suppressed over time, and only the fungicide-resistant portion of the
Disease Management Strategies Fungicide Rotations for Nursery, Greenhouse, BP-71-W Purdue Extension
and Landscape Professionals
population remains, which goes on to reproduce and make
up the majority of the population. Eventually, the fungicide is
ineffective because this majority of the fungal population is no
longer susceptible to it.
Minimizing Resistance
To minimize the possibility of fungicide resistance from
occurring, implement a comprehensive management strategy
before resistance develops. Some key tactics to include in your
management strategy include:
1. Follow good plant health practices.
Using disease-resistant cultivars, following proper planting
and fertilization techniques, and sanitizing equipment
reduce the reliance on fungicides, thereby reducing the
risk of their over-use and the development of resistant
populations.
2. U se the recommended doses as stated on fungicide labels.
Many fungicides have been extensively tested to identify the
optimal rate. Cutting the rate results in a sublethal dose that
is not only ineffective for disease management, but increases
the risk of resistance.
3. Minimize the number of fungicide treatments per season,
and apply only when necessary.
Excessive use of site-specific fungicides increases the
likelihood of resistance. By reducing the number of sitespecific
fungicide applications, you reduce the likelihood of
resistance development.
4. D o not rely solely on one fungicide with a site-specific
mode of action.
Use a diversity of fungicides with different modes of
action that provide broad-spectrum disease control.
There is no single, best fungicide. There are, however,
multiple fungicides with different efficacies for different
diseases. Many single-site fungicides are highly effective by
themselves, but you should tank-mix them with another
fungicide from a different family, or rotate or alternate
multiple fungicides to reduce the risk of resistance. The
important thing to remember is that you should avoid
consecutive applications of site-specific fungicides.
Tank-mixing and Rotating
There are two tactics that can reduce the risk of fungicideresistant
disease populations: tank-mixing and rotating
fungicides.
As the name suggests, tank-mixing consists of mixing a
fungicide with a high resistance risk with another fungicide
with a low or negligible resistance risk (Table 1).
Rotating fungicides involves alternating products that
have different modes of action so that you avoid back-to-back
treatments with any one site-specific fungicide.
Tank-mixing and rotating are important for two reasons.
First, both practices limit the amount of time fungi are exposed
to any one product. Second, other fungicides could potentially
suppress any resistant populations before they have a chance to
reproduce.
Selecting the proper tank mix or rotation partners in a
fungicide resistance management program is critical. To
develop an effective tank mix or rotation:
• Use fungicides with different Group Codes (Table 1), which
denote different fungicide families. Remember, fungicides
with different trade names can belong to the same chemical
family!
• Always partner site-specific products with a multi-site
inhibitor fungicide (Group Code M).
• Carefully read fungicide labels to determine if any
fungicides cannot be mixed or rotated together.
Fungicide rotations can be simple or complex, depending on
the problem and the pathogen that is causing it. For example,
you may control a Septoria, Myrothecium, or Alternaria leaf
spot by rotating a fludioxonil-based fungicide (Group Code
12) with a chlorothalonil-based fungicide (Group code M),
thereby minimizing the risk of resistance in the Group Code 12
fungicide.
Other diseases may require more elaborate rotations.
For example, downy mildew on snapdragon or lamium may
require:
• A dimethomorph-based fungicide (Group Code 40).
• And then, mancozeb or copper (both Group M).
• And then, a phosphorous acid-based fungicide (Group
Code M(33)).
• And then, mancozeb or copper again (Group M).
Furthermore, this rotation could only be repeated twice
with the Group 40 fungicide — it is limited to two applications
unless it is tank-mixed.
The bottom line is that tank-mixing or rotating fungicides
reduces the possibility of resistance development. This is
important as the labels on most newer, site-specific fungicides
have strict use recommendations to minimize the risk of
fungicide resistance, and protect the long-term efficacy of
the product. By carefully following these recommendations,
and using fungicides with different group codes, diseases and
fungicide resistance can be carefully and effectively managed.
Table 1. Fungicides Labeled for Use on Ornamentals. This table provides the common and trade names of selected fungicides currently
registered in the United States for use on ornamentals. It also provides the group code, major fungicide families and chemistries within these
groups, and the risk of resistance developing due to using these fungicides. Products set in italics indicate that they are prohibited from
greenhouse use. Products set in bold indicate that they are for greenhouse use only.
Group Code1 Fungicide Family2
or Class Common Name Example Trade Name Risk of Resistance3
1 benzimidazole or MBC thiophanate-methyl 3336,® Cleary’s 3336® high
2 dicarboximide iprodione Chipco 26GT,®
Iprodione Pro 2SE® medium to high
3 demethylation inhibitor (DMI)
triflumizole Procure,® Terraguard®
medium
triforine Funginex,® Saprol®
myclobutanil Eagle,® Systhane®
tebuconazole Folicur®
Banner Maxx,
Propiconazole Banner Maxx,® Propiconazole®
bayleton Bayleton®
4 phenylamide (PA) mefenoxam Subdue Maxx® high
7 carboximides
flutalonil Contrast® medium
boscalid Mix partner of Pristine®
11 quinone outside inhibitor
(QoI) — strobilurins
kresoxim-methyl Cygnus®
high
azoxystrobin Heritage®
trifloxystrobin Compass®
pyraclostrobin Insignia®
12 phenylpyrrole (PP) fludioxonil Medallion® low to medium
14
aromatic hydrocarbons dicloran Botran 70®
low
etridiazole Truban,® Terrazole®
17 hydroxyanilide fenhexamid Decree® low to medium
18 antibiotic streptomyces streptomycin Agri-Mycin,® Agri-Step® high
19 polyoxin polyoxin D Endorse® medium
21(P)4 host plant defense inducers,
systemic acquired resistance
(SAR)
acibenzolar-Smethyl
Actigard®
low
harpin Messenger®
M (33) multi-site activity phosphonate
fosetyl-aluminum Aliette®
low
phosphorous acid Alude,® BioPhos®
40 cinnamic acid dimethomorph Stature DM®, Stature SC® low to medium
M multi-site activity inorganics copper Kocide,® Champ® low
M multi-site activity inorganics sulfur Microthiol Disperss,® Sulfur low
M multi-site activity
dithiocarbamate
mancozeb, maneb,
dimethyldithio-carbamate Mancozeb,® Maneb,® Thiram® low
M multi-site activity
chloroalkythios captan Captan® low
M multi-site activity chloronitrile chlorothalonil Bravo,® Daconil 2787® low
U(28) unknown carbamate propamocarb Banol® low to medium
1 FRAC code is listed in parentheses under the EPA Group code when the codes differ. Neither system includes biofungicides.
2 For the sake of consistency, group codes, fungicide classes, fungicide names, and abbreviations are those used by the Fungicide Resistance Action Committee (FRAC) and
by the EPA Office of Pesticide Programs. This program is part of the pesticide classification system developed to assist growers in resistance management. Only fungicides
registered in the USA are included.
3 Resistance risk is considered high when resistance has already been reported, or a specific, single gene mode of resistance is known within a few years under commercial
use; Medium risk is associated with less frequent resistance development, or when more than one gene is involved, and the risk is considered low when the fungicide has
multi-site activity. Entries in this column were assigned by FRAC (www.frac.info). Labels for fungicides registered in the USA are accessible at www.greenbook.net and
www.cdms.net/manuf/manuf.asp.
4 Although similarly described, the modes of action are different.
