Her previous jobs include reporter, photographer and editor for a weekly newspaper. Spider mites are a red, yellow or green pest about the size of a pinhead that create webbing on the leaves and stems of the verbena. A small infestation of aphids generally doesn’t cause major damage. Although lantana and verbena can survive most pests, you may need to intervene if the plant is attacked heavily. Sticky traps will help control adult thrips while Neem oil applied to the verbena will control the insect’s larvae. Horticultural oil, Neem oil and insecticidal soaps will kill the mealy bugs. A small number of spider mites is generally just an annoyance. Also, place yellow sticky cards around the plant to catch flying adult mealy bugs. Verbenas have a key position among bedding, hanging basket and container crops. Small infestations are generally controlled by removing infected leaves and hosing down the plant with a water hose. They bloom from spring to summer but may not flower as heavily during periods of extreme heat. Remove any infected plant parts and debris from around plants and destroy. Whiteflies resemble white moths that congregate on the underside of the verbena leaves. Diseases of Verbena (Verbena × hybrida Groenl. Verbena is rarely affected by diseases, and if properly cared, it will never happen at all. There may be a yellow halo or concentric rings around the spots. Some varieties of Verbena are resistant to powdery mildew, such as the Aztec, Laskar and Tukana series. They provide pure, bright colors or delicate, pastel shades and generally grow like gangbusters. Learn which plants thrive in your Hardiness Zone with our new interactive map! This will result in stunted plants, discolored leaves and premature leaf dropping. Black root rot Thielaviopsis basicola (Berk. As the spots mature, they begin to sink and turn brown. She currently works as a writer and copy editor. Another option is to introduce green lacewings to your garden. But if there is an excessive watering or summer is wet and hot, the plant can be affected by powdery mildew that is treated with sulfur or fungicides. Black root rot Thielaviopsis basicola Chalara elegans [synanamorph] . The best defense against caterpillars is prevention and handpicking the insects off the plants. Pests Of Verbena. There may be a yellow halo or concentric rings around the spots. This variety originated from South America where it is a common sight in most of the warm regions of … The fungus Alternaria causes small water-soaked spots on the lower, older leaves of Verbenas. Plan the perfect garden with our interactive tool →. Shaking the plant lightly will result in a cloud of whiteflies flying off the plant. This article is a list of diseases of verbena (Verbena × hybrida).. Fungal diseases. Tiny, soft-bodied insects covering the buds and underside of leaves, aphids suck the plant’s fluid by piercing stems and leaves with their slender mouths. These common pests are not insects and are in fact a part of the arachnid family. Some thrips are beneficial insects and feed on pests that can damage plants. Galls look like colorful or distorted swellings on the verbena. Verbena boasts an impressive list of 250 species that include perennial, shrubs and herbaceous annuals. Verbena boasts an impressive list of 250 species that include perennial, shrubs and herbaceous annuals. Alternaria Leaf Spots. Both flowers and leaves will become stiff and discolored. The best treatment against broad and cyclamen mites is predatory insects that feed on them. As the spots merge, the leaves become chlorotic and fall off. They appear raised as spores are produced. The spots may merge into a V-shaped area. Large infestations of whiteflies are difficult to control even with yellow sticky cards, horticultural oil and insecticidal soap. Spider mites are most prevalent in dry, hot locations and tend to attack water-stressed plants. Cercospora is a fungus that causes light-green sunken spots on the leaves of Verbenas. Most of the insect and mite pests that affect lantana and verbena are similar. This fast-growing plant produces butterfly-attracting flowers in various colors including coral, blue, salmon, lavender, rose and red. Yet, there is one pathogen group that takes advantage of perfectly healthy plants, … Mealy bugs are a common problem on houseplants and appear as small pieces of cotton on leaves and stems. The spots merge into large areas of necrotic tissue. Fungal diseases are the most common diseases that affect Verbenas. All Rights Reserved. & Broome) Ferraris Chalara elegans Nag Raj & Kendr. The leaves turn yellow, become necrotic and fall off. However, larger infestations will lead to twisted leaves, stunted growth and cover the plant with a sticky substance -- called honeydew -- that encourages powdery mildew growth. The spots merge into large areas of necrotic tissue. If thrips are infesting the verbena, some pests will land on the paper. Controlling these pests with insecticides is difficult since they feed on the plants buds and inside distorted plant tissue. The gall midget is a tiny fly that resembles fungus gnats. This innate vigor protects them from some of the disease problems that require a debilitated host. Botrytis blight Some gall midgets are actually beneficial and feed on aphids. Treat leafminers will beneficial predator insects such as ladybugs, and prevent further infestation with proper plant care and removing older infected leaves. The mites can also cause stunted growth and premature dropping of leaves and buds. Sometimes a plant can get attacked by aphids or … The adult leafminer is a small black or gray fly with a yellow stripe and clear wings. Powdery mildew, as the name suggests, resembles a white, powdery coating on leaf surfaces. Other species of gall midgets bore into the plant’s tissue. Leaves, stems and buds grow distorted as the disease progresses and the plant becomes distorted. Margery Daughtrey, collator (last update 5/25/00) FUNGAL DISEASES Alternaria leaf spot Alternaria sp. Verbenas are annual or perennial plants with purple, pink, red or white flowers. Use at the rate recommended by the manufacturer. This will lead to defoliation and twig or branch dieback. So, the powdery mildew on your cucumbers may not be the same species as the one affecting your phlox. Disease Symptoms Pathogen/Cause Management; Botrytis Blight: Tan spots develop on leaves. Established plants rot at the crown. Avoid overhead watering, or water in early morning to allow plants to dry before damp evening hours. The first signs of powdery mildew on Verbenas are dusty gray or white circular patches on the lower leaves. Amanda Flanigan began writing professionally in 2007.