The black spots are probably sooty blotch or flyspeck. Sooty blotch and flyspeck are two different fungal diseases that often occur together on apples. Sooty blotch appears as dark brown to black, ½ inch or larger smudges on the…
It would be best to place weeds that are producing seeds and diseased plant debris in biodegradable bags and have the material picked up and composed by a municipal or commercial composting facility. The temperatures in home compost piles…
Temperatures of 150 to 180 degrees Fahrenheit are required to kill most plant disease pathogens. Unfortunately, the internal temperatures of most home compost piles don’t reach this level and the disease organisms are not destroyed. For many home…
Phytophthora root rot can be a serious problem in poorly drained sites. Phytophthora root rot can be avoided by planting blueberries in well-drained soils. Outside of root rots, blueberries generally have few insect and disease…
Blackspot is a common fungal disease of roses. Symptoms of blackspot are circular black spots on the leaves. Infected leaves turn yellow and drop prematurely. Initially, symptoms develop on the lower leaves and gradually move…
Powdery mildew is a common disease of garden phlox (Phlox paniculata). The fungal disease produces a grayish white coating on the leaves. Infected leaves eventually turn yellow and then brown. Initial symptoms appear on…
Oak wilt is a serious disease that can infect many oak species. It is caused by the fungus B. fagacearum. Red and pin oaks are very susceptible to the oak wilt fungus and can die within 4 to 6 weeks. White and bur oaks…
Foliar diseases of tomatoes are a common problem in the home garden. Fungal diseases, such as early blight (Alternaria tomatophila and Alternaria solani), late blight (Phytophthora infestans), and…
Proper cleaning and sanitization of pruners and other garden tools is important to prevent the spread of disease issues. At minimum when removing disease-infected plant material, pruners should be disinfected between plants. Ideally,…
The orange color is likely due to rust. Rust is a fungal disease. It can be diagnosed by walking across the lawn in white shoes. As you walk across the lawn, bright orange spores of the rust fungus will rub off onto the shoes,…
The ‘Sunburst’ honeylocust has distinctive yellow-green foliage. Unfortunately, it is not a vigorous tree. It grows slowly and is susceptible to cankers and mimosa webworms.
Cankers, caused by fungal pathogens, are localized…
Magnolia scale is the largest scale insect in Iowa. Sap feeding by the scales causes stress to heavily infested plants and can result in stunted growth, yellowish foliage, branch dieback, or death of the plant. Magnolia scales produce…
The white, powdery material on the peony foliage is powdery mildew. Powdery mildew is a fungal disease. Powdery mildew occurs on a large number of plants (peonies, lilacs, viburnums, roses, garden phlox, bee balm, turfgrass, and many…
The sap oozing from the elm wound is probably due to bacterial wetwood or slime flux. Bacterial wetwood or slime flux is a common on elm, cottonwood, and mulberry. It also occurs on maple, birch, ash,…
The orange substance on your black raspberry leaves is orange rust. Orange rust occurs on black and purple raspberries and most varieties of blackberries. Orange rust does not occur on red raspberries.
The spotting and premature leaf drop on your dogwoods is probably due to Septoria leaf spot. Septoria leaf spot is a common fungal disease of dogwoods in Iowa. The disease typically causes irregularly shaped grayish spots with dark…
In Iowa, the foliage of the river birch (Betula nigra) often turns a sickly yellow-green. The yellow-green foliage is due to a deficiency of iron. The problem is referred to as iron chlorosis. (A close examination of chlorotic leaves…
The brown streaks in the apples are probably due to the apple maggot. The apple maggot is the most serious insect pest of apples in Iowa. Apple maggot damage appears as knobby, misshapen fruit with small pits or blemishes on the fruit…
The large, hard growth is probably crown gall. Crown gall is caused by the bacterium Agrobacterium tumefaciens. The bacterial disease can infect roses, grapes, apples, raspberries, willows, euonymus, and many other woody…
The problem may be sooty blotch and flyspeck. Sooty blotch and flyspeck are 2 different fungal diseases that often occur together on apples. Sooty blotch appears as dark brown to black, ½ inch or larger smudges on the surface of the…
Blossom end rot is probably responsible for the blackish spots on the tomato fruit. Blossom end rot is a common problem on tomatoes. It appears as a brownish black spot on the blossom end (bottom) of the fruit. Secondary…
Brown rot is a common fungal disease of peaches and other stone fruits. Affected fruits develop circular light brown spots that expand rapidly and rot the fruit. Sometimes the fungus that causes this rot is visible as ash-gray tufts.…
Pine wilt is a common disease that causes browning and death of pines, especially Scotch pine. Austrian, mugo, red, jack, and white pine may also be affected, but less commonly than Scotch pine. Affected trees turn brown and die within a few…
Cedar-apple rust is likely responsible for the yellow spots on the crabapple leaves. Cedar-apple rust is a fungal disease. The fungus requires both a crabapple or apple and a cedar (juniper) to complete its life cycle. Crabapple…
The hostas may have petiole rot. Petiole rot is a serious disease of hosta. It is caused by the fungus Sclerotium rolfsii var. delphinii. (Petiole rot can also affect daylily, peony, phlox, columbine, and other…
Dry, seedy, or crumbly raspberries usually result from poor pollination, leading to poor drupelet development. Each raspberry is made up of many small drupelets, and if some of the flowers are not adequately pollinated, portions…
A vascular wilt may be responsible for the wilting of the tomato plant. The initial symptoms of Verticillium and Fusarium wilts are wilting of the plant leaves during the heat of the day. Affected plants often recover in the evening…
