Bean leaves with sunscald. Photo: Angela Schoenfeld, Master Gardener.

Bean Sunscald

Angela shared some images and asked, “My green beans are growing well but now some are getting dead looking blistered areas. [I am] not sure if this is nutrient deficiency, fungus or too much rain. Could you let me know what you think?” Angela has sunscald on her bean leaves. Sun scald is a non-pathogenic disease found on several plants, including ornamentals, vegetables, and fruits. This type of damage occurs when plants are exposed to too much direct sunlight. The injuries are more severe on stressed, weakened or recently transplanted plants. Kristine Lang, a Horticulture Specialist with South Dakota State University Extension, share this recommendation, “Once leaf tissue is scorched, the damaged areas will not recover; however, minor damage, while unsightly, will not kill the plant. Leaves with scorched margins may look unappealing, but they still help the plant with photosynthesis, creating food for new, undamaged leaves to emerge. Resist the urge to remove scorched leaves. Strange as it may seem, they provide some shade for the new growth and remaining green tissue can still contribute to photosynthesis for production of new leaves. The plant’s appearance will perk up when new growth begins, and once new leaves have emerged, you could gently remove the scorched leaves if they have not already fallen off naturally.”

A southern magnolia losing its leaves. Photo: Lyle Ross, homeowner

Ailing Magnolia

Lyle called the AgCenter to discuss his ailing magnolia tree. He sent a picture of his tree losing its leaves. AHA emailed Lyle with some thoughts about why this tree has a thin canopy, “ After seeing the top dieback on your magnolia, I am curious if you used a ‘weed and feed’ product. Sometimes these lawn products have an herbicide that can damage woody shrubs and trees. If you used this kind of product, what is the name of it? The reason I ask is because I was to read the label and see what herbicide was applied. Another possible reason for top dieback would be some kind of root disturbance including compaction by equipment, trenching, adding fill material, etc.”

A blackberry cane with dying flowers.

Blackberry Anthracnose

A gardener called to ask why his blackberry blooms were dying off. He later texted some pictures with the browning flowers. This blackberry plant probably has anthracnose. An AgCenter publication titled Growing Blackberries for Pleasure and Profit describes blackberry anthracnose, “Anthracnose is a common fungus disease that can attack both the canes and leaves. It is characterized by small, purplish, slightly raised spots on new shoots. These spots enlarge gradually and become oval with slightly raised purplish edges, and the center becomes grayish and sunken. Larger, irregular spots are formed as the small spots run together. Girdling may occur on some canes. Small, purplish-bordered spots occur on the leaves and can cause premature defoliation. Severe infections can reduce growth and yield of plants.

Providing good air circulation around plants and removing old and diseased canes can reduce anthracnose infections.” The infected canes prevent the flowers from developing normally, and the blooms die and turn brown.

This publication also discusses the application of fungicides for this disease, “Abound®, Pristine Switch®, Cabrio® or Captan 80WDG® are fungicides that can control Anthracnose when applied when the blossoms are in bud and the young canes are 8-10 inches long. A second application should be made 10-14 days later.”

Finally, the University of Arkansas Cooperative Extension Service also recommends sanitation for preventing the spread of this disease, “Infected floricanes should be pruned immediately after harvest and burned rather than being mulched in to weed free areas. This will remove much of the disease pressure in a field.”