Kousa Dogwood (Cornus kousa)

Powdery mildew is a common fungal disease caused by various fungi species including Erysiphe, Podosphaera, Oïdium, and Leveillula. It affects over 10,000 plant species worldwide. The disease thrives in warm, dry climates with high humidity and appears as a distinctive white powdery coating on plant surfaces.

Septoria leaf spot is a destructive fungal disease caused by Septoria lycopersici, particularly devastating during seasons of moderate temperature and abundant rainfall. The disease starts on lower leaves and progresses upward, causing small circular spots with tan to gray centers and dark brown margins. If left untreated, it can dramatically reduce plant yields and cause complete leaf blight.

Scale insects are small sap-sucking pests that appear as brown, shell-like bumps on plant stems and leaves. There are over 25 species, divided into armored (hard) and unarmored (soft) scales. They feed by piercing plant tissue and extracting sap, which weakens the plant and can lead to yellowing, stunted growth, and even death if left untreated. They also excrete honeydew, which attracts ants and promotes sooty mold growth.

Caterpillars are the larval stage of moths and butterflies that feed voraciously on plant foliage, stems, flowers, and fruits. Common species include cabbage loopers, tomato hornworms, armyworms, and cutworms. These pests can cause extensive damage by consuming large amounts of plant tissue in a short time. They vary in size from small (1/4 inch) to large (5 inches), with colors ranging from green to brown, often featuring stripes or spots. Caterpillars are highly mobile and can quickly spread throughout gardens, making them one of the most destructive common pests.

Sunscald is physical damage that occurs when intense sunlight and heat strike plant tissues that are not acclimated to such exposure. It typically follows heatwaves, heavy pruning, transplanting, the removal of shade, or intense winter sun followed by freezing nights. On fruits such as tomatoes, peppers, cucumbers, apples, and pumpkins, it manifests as pale, bleached, or whitish patches that later become tan or brown, sunken, and occasionally leathery or blistered. Leaves may appear scorched at the margins, but the primary diagnostic sign is light-bleached, papery, or corky areas on the side facing the sun. On young trees (such as maple, birch, and various fruit trees), the bark on the south or southwest side may darken, crack, or scale following sunny winter days and cold nights.

Water deficiency occurs when a plant cannot absorb enough moisture to meet its transpiration and metabolic demands. Also known as drought stress or underwatering, this condition deprives cells of turgor pressure, leading to wilting, leaf scorch, and — if prolonged — permanent root and tissue damage. It is one of the most common causes of houseplant decline and is fully reversible when caught early.