Carefully read the product labels for additional information
- Copper Compounds are widely sold as fungicides for orchard and garden use. They can be highly phytotoxic (cause leaf burn) to many fruit crops and must be used with extreme care. Read the label of the product you intend to apply to determine the type of copper, the percentage of the active ingredient, and any cautions that accompany its use. Copper was first used in the mid-1800s in grape vineyards in France to discourage theft of the grapes. Copper sulfate and lime were mixed in a slurry and spread over the grapevines. In 1882, a French scientist observed that this anti-theft treatment was effective in reducing a disease called downy mildew. Copper sulfate and lime became known as Bordeaux Mixture.
- Copper sulfate is readily soluble in water and can burn foliage and fruit (phytotoxicity). Fixed coppers have been developed that are relatively insoluble and therefore less toxic to plants, however, fixed coppers can also result in phytotoxicity under certain conditions. Fixed coppers include basic copper sulfate, basic copper chloride, copper oxides, and copper hydroxide.
The fungicidal activity of copper is based on its ability to destroy proteins in living tissue. Thus, copper fungicides may also injure fruit and foliage. Ideally, the copper concentration on the leaf surface should be high enough to kill the fungus but so high as to harm the leaf tissue. Never apply copper to strawberries, because severe phytotoxicity will result under almost any conditions.
- Lime Sulfur is good for pre-bloom powdery mildew control on apples and for leaf curl control on peaches and nectarines during the dormant season. High rates will also control scale insects on stone fruit trees. It can also help control several fungal diseases that affect the foliage and stems of raspberry and blackberry Several formulations are available; some contain horticultural oil and are designed for dormant season use.
- General Purpose Mix, GPM (home orchard spray) usually contains an insecticide, typically a pyrethrum, and the fungicides, sulfur, and copper. Can be purchased as a dust or spray. Even though this is considered organic GPMs generally are not recommended, especially early in the season. During the bloom period, a fungicide may be needed but GPMs always contain insecticides. Pyrethrums are broad-spectrum insecticides that are especially harmful to honeybees, other pollinators, and natural enemies. Sulfur is very effective against powdery mildew of apples and cherries, and scab on peaches and nectarines. Some cultivars are easily injured by sulfur applications. Jonathan and Cortland apples are more tolerant than Stayman and Delicious. Rome Beauty is intermediate. Micronized sulfur formulations can be used in seasonal programs on apples without injury. The finer the particle size, the more effective the spray will be. Allow at least 7 days between oil and sulfur applications when made during the growing season. Sulfur is not considered very effective against black rot disease on grapes.
- Captan is effective in apple orchards against scab, black rot, white rot, bitter rob, Brooks spot, and blossom end rot. It is effective against sooty blotch and flyspeck if the last spray application is not more than 30 to 40 days before harvest. It is not effective against the rusts, fire blight, or powdery mildew.
Where the early-season apple scab control program fails and scab becomes established in the trees, Captan at low rates cannot be expected to provide control. This fungicide is highly effective, however, in reducing spore germination.
On stone fruits, Captan is a good fungicide for the control of brown rot and scab, when adequate spray schedules are followed. Captan plus wettable sulfur can be used on peaches when brown rot, scab, and mildew are present. Captan is effective against cherry leaf spot and brown rot on tart cherries if the diseases are at a low level and the spray intervals do not exceed 2 weeks.
On apples, Captan can cause a necrotic spotting, yellowing, and dropping of leaves when used under poor drying conditions or in combination with sulfur, especially on Delicious and Stayman varieties. Dead spots on fruit and foliage have occurred on both plums and prunes when Captan is used from petal fall until the fruit begins to ripen. Captan is not registered for use on pears. The leaves of some sweet cherry varieties may be injured by repeated Captan applications.
Captan has few spray incompatibilities, but it should not be used with oil, lime, or other alkaline materials. The use of Captan within 1 to 2 weeks either before or after an oil application may result in leaf injury on apple trees. Combinations with sulfur might result in increased injury under high temperatures and high relative humidity.
- Chlorothalonil (Daconil 2787) is a broad spectrum, non-systemic fungicide. It is labeled for a small number of fruits including peaches, cherries, and plums. Helps control several early-season diseases. Read the product label for further information.
- General Purpose Mix, GPM (home orchard spray) contains both a fungicide and an insecticide to control a range of insects and diseases. Captan is usually the fungicide. Methoxychlor, malathion or Carbaryl (Sevin) are the insecticides. There are newer GPMs on the market with the active ingredients lambda-cyhalothrin (pyrethroid-insecticide), pyraclostrobin (fungicide), and boscalid (fungicide). GPMs generally are not recommended, especially early in the season. During the bloom period a fungicide may be needed but GPMs always contain insecticides. Carbaryl (Sevin) is a broad-spectrum insecticide that is especially harmful to honeybees and kills spider mite predators, thus encouraging large spider mite populations.
- Immunox (myclobutanil) is a fungicide with some systemic action. It is labeled for use on apples to control powdery mildew, rust, and scab, on stone fruits to control powdery mildew, and brown rot, and on grapes to control powdery mildew and black rot. Be careful not to purchase Immunox Plus, which is mixed with an insecticide and is not labeled for edible plants.