Alternaria Leaf Spot on Geraniums

Alternaria Leaf Spot

• Alternaria leaf spot disease makes small blisters appear underneath leaves. These brown blisters sink into the leaf overtime and produce yellow halos around the spots. Eventually, these spots appear on the top of geranium leaves. Leaf yellow or cholorosis may appear near these spotted areas. Leaves that fall underneath the geranium harbor fungal spores, which continually infect the plant. Without proper treatment, the disease may spread or cause your geranium to decline in health.

Pruning

• Prune off diseased areas from your geranium plant. Make sure that you use a pair of sharp sterilized bypass shears to trim diseases leaves and stems. Dull bypass shears can cause tears, which create wounds for other fungal diseases to enter. Clean up all diseased debris around your geranium plant. Throw away or burn your plant debris, but do not place in the compost. Anytime you place fungal diseased debris in your compost you run the risk of spreading the fungal spores over the entire yard.

Fungicides

• Fungicides are used to control severely infected geranium plants. Use a fungicide that contains mancozeb, as suggested by the University of California. When using a fungicide on your geranium plant, keep up the watering schedule. Fungicides cause harm to water-stressed geranium plants. Water your geranium in the morning or before 11 a.m., as suggested by the University of Georgia. Avoid any overhead watering. Moisture left on the leaves prolong, encourage and cause fungal diseases such as alternaria leaf spot.

Prevention

• As gardeners you can prevent alternaria leaf spot by proper spacing the geranium plants or encouraging air flow. Plant geraniums 12 inches apart from each other. Choose places to plant them that receive full sunlight and has proper drainage. When growing a geranium in a pot, keep a saucer with 1/2 an inch of pea gravel underneath the plant to encourage drainage. Apply water to the plant until you see it flow from the draining holes on the bottom of the pot.