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Plant NameTypeDescription 
Bacterial blightGeraniumDiseaseBacterial blight (leaf spot and stem rot) arises due to a bacterium that can survive in soil for more than 6 months. These bacteria cannot survive in soil after the plant decomposes. They are readily spread by physical contact, irrigation water, rain, tools, and insects. Bacteria are not contained in seed. Sudden black rotting may start at the base of cuttings, and blue-black rotting emerges on stems. Leaves drop, then stems partially recover and produce new leaves at the terminals. Depending on the variety, either round spots or angular dead areas develop on leaves. Spots initially appear as translucent pustules similar to those of oedema. Round spots are dark green to black, about 0.1 inch in diameter, and sunken. The arrival of angular dead areas is often accompanied by the wilting of leaf edges. Ivy geranium foliage loses luster and shows symptoms suggesting nutrient deficiency or mite infestation. Some regal or Martha Washington cultivars are extremely resistant, although leaf spots have been observed. Hardy, perennial geraniums can be carriers of the bacteria without showing any symptoms.
Botrytis leaf spot and blossom blightGeraniumDiseaseBotrytis is a fungus which thrives under mild environmental conditions. Brown, water-soaked areas appear on leaves and petals. The spots soon dry out and become covered with gray-brown masses of fungal growth. Flowers wilt and drop. Brown leaf lesions often result after petals drop on leaves. Stock plants may show a stem blight.
OedemaGeraniumDiseaseOedema is a physiological problem that occurs when the soil is warmer than the air, soil moisture is high, and relative humidity is also high. Lower transpiration rates coupled with increased water absorption causes cell pressure to increase, erupting epidermal cells and allowing inner cells to bulge and protrude. Symptoms usually occur on lower leaf surfaces and appear as watery blisters or galls, which eventually turn dark brown, yellow, or rust and give the appearance of a rust or bacterial infection. Cells die and discolor, giving the impression of a parasitic infestation. Insect feeding (especially aphids and thrips), mechanical injury, chemicals, and windblown particles produce a similar effect.
RustGeraniumDiseaseRust is caused by a fungus that lives on plants and plant debris. This disease can spread by wind-blown spores or infected cuttings. Infections occur easily if leaves are wet for 5 to 6 hours in mild temperatures (55 to 75 degrees). Both leaf surfaces first develop white or yellowish spots, which enlarge and become blisterlike. The brown powdery pustules are often in target-like arrangement. The pustules occur mostly on leaves and less frequently on stems. Severe infection causes yellowing and defoliation. Cultivars range widely in genetic variation of resistance, from highly susceptible to immune.
Tobacco budwormGeraniumInsectTobacco budworm larvae attack several ornamental flowers including petunia, rose, geranium, and nicotiana. They feed primarily on buds, petals, and developing seed pods, but will feed on shoot tips and foliage if flower buds are not available. On most hosts, larvae prefer to tunnel into buds, but they will also feed on the petals of opened flowers (especially on petunia). Damaged buds fail to open, resulting in loss of color in floral plantings. If buds open, flowers and leaves appear ragged or tattered. The adult is a greenish-brown moth with cream-colored bands on the wings. It is about 3/4 inch long with a wingspan of about 1 1/2 inches. Eggs are laid on blossoms, fruit, or shoot tips of plants. Very young larvae are yellowish or light yellow-green, but the color of older larvae is variable. Mature larvae may be light to dark green, brown, tan, or reddish. These older larvae usually have stripes along the sides and a brown head. Mature larvae drop to the ground and pupate in the soil around host plants. There are typically two or more generations per year. Tobacco budworm overwinters as pupae in the soil.