Disease |
Hosts |
Botanical |
Symptoms |
Notes |
Control |
Anthracnose blight (1) |
Sycamores/ Plane trees |
Platanus species and hybrids |
Irregular-shaped spots on leaves, coalescing and running down the vein; leaves fall off, sometimes in large numbers. |
Common in April and May. Tree will drop many leaves, but will outgrow the disease. Resistant hybrids include Bloodgood and Columbia. |
No control. Feed the trees in late spring and fall to keep them growing vigorously. |
Anthracnose blight (2) |
Maples |
Acer species. |
Death of small, twiggy branches and eventually larger ones, apparently randomly through the tree. |
Attacks in spring and early summer. |
Prune out affected branches. Copper sprays may help prevent spread. |
Blossom-end rot |
Tomatoes, peppers, eggplants. |
Lycopersicon, Capsicum, and Solanum |
Rotten, discolored flesh on the bottom (the blossom end) of the young developing fruit. |
Long thought to be caused by a calcium deficiency, but actually just a symptom of fluctuating temperature or irregular watering causing damage to the root system. |
Common on the first fruit that sets due to changes in temperatures and soil moisture in spring. Water evenly and thoroughly. Pick off and discard the damaged fruit. No need for calcium supplements. The next fruit that sets will develop normally. |
Damping off of seedlings |
Seedlings grown indoors or densely planted bedding plants, or other bedding plants. |
NA |
Seedlings collapse and die rapidly; stems are brown and soft. White mold (downy mildew) will grow on dying seedlings. Young transplants die shortly after planting. |
Caused by Pythium or Rhizoctonia fungus, among others. Seedlings grown under low light conditions, too close together, or in overly rich soil may die suddenly. |
Move seedling trays outside during the day; spread the pots apart for better air movement. Thin seedlings as soon as they have produced true leaves (the second set of leaves to emerge). Avoid planting heat-loving summer annuals too early. |
Downy mildew |
Roses |
Rosa |
Yellow and black spots on leaves, coalescing into entire yellow areas, followed by defoliation. Purplish blotches on stems. Spreads very rapidly from leaf to leaf. |
Most damaging on overgrown or dense, leafy roses such as miniatures and climbers, or on plants that havent been pruned during the winter. Can entirely defoliate the plant. Disease stops with hot, dry weather. |
Liquid copper sprays will stop the spread, but will coat the plant and flowers with green residue (unsightly). Alliette is labeled for it. Blackspot of roses looks similar but doesn't invade the leaf vein and is far less common here. |
Early blight, bacterial speck |
Tomatoes |
Lycopersicon |
Spots on leaves of young plants, spreading up onto new growth; caused by two similar diseases. |
Common on bedding plants and will persist on young transplants. Stops spreading in hot dry weather. More of a problem in humid climates. |
Pick off affected leaves. |
Fireblight |
Members of the apple sub-family of the rose family, especially apples, pears, quince (fruiting); crabapples, hawthorns, loquats; Photinia, firethorn. |
Malus, Pyrus; Cydonia, Crataegus, Eriobotrya; Photinia, Pyracantha. |
Rapid dieback of flowering shoots and new growth. Leaves look burnt and don't fall off. Spreads rapidly down the plant stem. |
Narrow temperature range: 55 - 80F, but spreads rapidly when conditions are favorable. Spread chiefly by bees as they visit flowers; may also infect through pruning wounds and new growth. Very virulent bacterial disease; can kill the plant entirely. |
Prune out infected branches well below the dead portion. Copper sprays are used when the plants are blooming. Avoid pruning Photinia in the spring. |
Leaf curl of fruit trees |
Peaches and nectarines; plums, apples, cherries. |
Prunus and Malus species. |
Contorted, curled, discolored, swollen leaves on peaches and nectarines; leaves curled inward on other trees. |
Peach leaf curl is caused by a fungus and only affects peaches and nectarines; aphids cause curled leaves on the other trees. |
Dormant spray with copper sulfate or lime sulfur, especially in early February, for peach leaf curl. Treat for aphids as needed on other trees, and control ants. |
Leaf spot |
Ornamental members of the rose family--flowering pears, India hawthorn, Carolina cherry laurel, and more. Several different fungi cause similar symptoms. |
Pyrus kawakami; Rhaphiolepis; Prunus caroliniana. |
Dead spots on leaves. |
Don't plant Pyrus kawakami or Carolina cherry laurel. Leaf spot on India hawthorn is prevalent on nursery stock, especially from coastal growers, but usually goes away here unless the plants are constantly sheared, sprinkled overhead, or planted in |
Copper sprays on affected trees may help. Prune lightly; thin plants, don't shear them. |
Mosaic virus of roses |
Roses |
Rosa |
Leaves emerge with yellow mottling or striping. Growth may be stunted. |
Virus has been in the plant since it was propagated, even if the symptoms took years to be visible; wholesale growers try to work with only virus-free propagation stock. |
No control. You will not spread this on pruning shears; it is transmitted in grafting. |
Mushrooms in lawn |
Grow on organic matter that is decomposing. |
NA |
Familiar toadstool shaped mushrooms grow randomly in lawn, or in a line (following a decaying root). |
Harmless decomposers, doing their job recycling wood that was incorporated for the lawn or on decaying dying or dead trees. |
No control. May continue to sprout for years. Probably not toxic, but don't count on it. |
Powdery mildew |
Sycamores/Plane trees; Roses; Crepe myrtles; Japanese maples; lawns, and many more. |
Platanus, Rosa, Lagerstroemia, Acer, etc. |
White mildew growing on leaves, especially on new growth. Disease continues into summer, as it is tolerant of low humidity. |
'Columbia' is a resistant hybrid Plane tree. Hybrid crepe myrtles and many rose varieties are resistant. |
Spores can be blasted off the leaves with water early in the day. Copper and Neem sprays may help prevent the spread onto new growth; Bayleton also works. |
Rust of lawns. |
Lawns, especially Kentucky bluegrass. |
Poa species. |
Orange-red pustules on leaf blades, spreading to coat the entire leaf in mid-winter. |
Most visible on lawns that have a high percentage of bluegrass, and which were not fed in late fall. |
Nitrate-based fertilizers in November and January will help manage it. No fungicide is necessary. |
Rust of woody plants and perennials. |
Roses; snapdragons; hollyhocks; St. John's Wort, and more. |
Rosa, Antirrhinum, Alcea, Hypericum, etc. |
Red or black bumps (pustules) on the undersides of leaves, with a corresponding yellow spot on top. |
Each rust is host-specific; i.e., it lives only on the kind of plant you find it on, so the rust on your roses won't go on your lawn and vice versa. The spores are heavy, so they spread only by splashing water such as from windy rainstorms or sprin |
Dormant season pruning removes overwintering spores. Raking out leaves at that time is important. Picking off affected leaves helps. Sulfur or copper sprays may help prevent spread. Irrigation management is most important: use drip irrigation or soakers. |
Shothole fungus |
Fruit trees, esp. almond, nectarine, peach, and plum |
Prunus species. |
Holes in leaves that look like insect damage. Small tan, dead areas fall out to create holes. |
Not harmful at moderate levels, but may get worse without treatment. |
Dormant spray with copper sulfate or lime sulfur, especially in late November. |