Plant Health Problems
Diseases caused by Viruses:
Spotted wilt, virus, Impatiens Necrotic Spot Virus (INSV).
Symptoms can appear as a yellow line pattern on the leaves, as yellow ringspots or blotches, or as necrotic brown spots. Young plants may turn brown from the center out. This disease is transmitted by the western flower thrips.
Control of this disease is focused on prevention since once plants are infected, they cannot be cured. It is important to eliminate and remove infected plants as soon as they are recognized and to eliminate other symptomatic plants since this virus has a very broad host range. It is also critical to manage the thrips population.
Diseases caused by Nematodes:
Foliar nematodes, Aphelenchoides spp.
Black to brown V-shaped areas appear in the lower leaves, showing first at the bottom of the plant and working their way up the plant. These spots are bounded by veins at first but eventually may involve the entire leaf. The trouble is caused by microscopic eelworms which live in and destroy the leaf tissue. They come out of the leaf when the leaf surface and stems are wet with rain, dew, or syringing, and swim up the stem to infect the leaves above. The nematodes overwinter in plant debris in the soil.
This disease can be minimized by reducing leaf moisture and removal of infected tissues, debris, or plants.
Aphids, Myzus persicae and Neomyzus circumflexus.
The green peach and crescent-marked lily aphids attack gloxinia. Insecticidal soap or ultrafine horticultural oil, which are among the compounds registered for use against this pest in Connecticut, can be used for control if it is needed. Imidacloprid, applied as a soil drench, will provide season-long systemic control. Consult the labels for dosage rates and safety precautions.
Cyclamen mite, Phytonemus pallidus.
This translucent, microscopic mite often infests the new leaf and blossom buds, and can proliferate on spent blossoms. Characteristic injury includes dwarfed, thickened and wrinkled leaves. Infested plants do not bloom, or blossoms may be misshapen. Cyclamen mite is not easily controlled when mature plants are badly infested: effective miticides are not available to homeowners, so a commercial applicator may be required for effective miticide applications. Effective restricted use products include abamectin, dicofol, and endosulfan. Consult the labels for dosage rates and safety precautions.
Thrips, Frankliniella spp.
These small whitish insects feed on pollen and flower petals. The adults may have wings equal or greater than the body length. The four wings are veinless with long hairs on the leading and trailing edge. Plants are damaged when thrips pierce plant tissue and suck plant sap. They quickly scurry into hiding when the plant is touched or they sense changes in the environment. Thrips are readily detected by exhaling on a blossom held over your hand, or tapping the blossom onto a white sheet of paper. The carbon dioxide in the breath will cause the thrips to exit the bloom and fall into your hand. A sign of their presence is pollen spread downward from the anthers, spoiling the blooms. This is more noticeable on the darker-colored flower forms. Control in the home begins with buying clean plants and if needed, handpicking of infested blossoms. Spinosad is an effective product for controlling thrips. Consult the labels for dosage rates and safety precautions.