Garden Petunia: How to Care for Petunia x hybrida

Bacterial wilt is a fatal vascular disease caused by bacteria (Erwinia tracheiphila, Ralstonia solanacearum, Xanthomonas spp.) that infects the water-conducting tissue of plants. The bacteria multiply and block the flow of water and nutrients, causing rapid wilting and plant death within 1-2 weeks.

Gray mold, caused by the fungus Botrytis cinerea, is one of the most common fungal diseases in plants. It affects over 200 plant species, including ornamentals, vegetables, fruits, and houseplants. The disease thrives in cool, humid conditions with poor air circulation, causing grayish spots and soft rot on infected tissues.

Southern blight is a devastating soilborne fungal disease caused by Athelia rolfsii (formerly Sclerotium rolfsii), affecting over 500 plant species including vegetables, ornamentals, and fruit crops. The fungus survives in soil through resting structures called sclerotia that resemble mustard seeds and can remain viable for years.

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.

Downy mildew is a fungal-like disease caused by oomycetes (water molds) that thrives in cool, wet conditions. It affects a wide range of plants, causing yellowing leaves with fuzzy white-gray growth underneath, leading to defoliation and reduced yields if left untreated.

Aphids are small, soft-bodied, pear-shaped insects (1/16 to 1/8 inch long) that feed by sucking nutrient-rich sap from plants. They reproduce rapidly and can quickly weaken plants, causing distorted growth and transmitting plant viruses. Aphids come in various colors including green, black, red, yellow, brown, and gray. They secrete honeydew, a sticky substance that attracts ants and encourages sooty mold growth.

Spider mites are tiny arachnids (less than 1/20 inch long) related to spiders and ticks that feed on plant sap. They thrive in hot, dry conditions and can cause significant damage to ornamental and vegetable plants. During severe infestations, crop losses can reach 14% or higher as these pests disrupt vital plant processes including photosynthesis, carbon dioxide absorption, and transpiration.

Thrips are tiny cigar-shaped insects (1/25-inch long) that damage plants by sucking plant juices and scraping at fruits, flowers, and leaves. With over 6,000 species and rapid reproduction (lifecycle as short as 14 days), they can quickly infest plants and transmit viruses like tomato spotted wilt virus.

Whiteflies are small, soft-bodied, winged insects closely related to aphids and mealybugs. They are moth-like in appearance, about 1/16 inch long, triangular in shape, and gray-white in color. These sap-sucking pests feed on plant tissue, causing yellowing, stunted growth, and wilting. They also excrete honeydew, which attracts ants and promotes sooty mold growth. Whiteflies can transmit serious plant viruses.

Flea beetles are small, jumping insects that feed on the leaves of many vegetable crops. They chew numerous small, circular holes, creating a characteristic 'shothole' appearance. While established plants can often tolerate the damage, young seedlings are highly susceptible and can be stunted or killed if the infestation is severe.

Slugs and snails are mollusks that feed on plant tissue, causing irregular holes in leaves and damage to young seedlings. They are most active at night and in moist conditions, leaving characteristic silvery slime trails. These pests can quickly devastate gardens, especially during wet seasons.

Leafminers are the larvae of various insects including flies, moths, sawflies, and beetles that tunnel between leaf surfaces, creating distinctive serpentine trails or blotchy patches. While primarily cosmetic, severe infestations can weaken plants by reducing photosynthesis capacity and making them susceptible to secondary infections.

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.