Plant Health Problems
Diseases caused by Fungi:
Botrytis blight or Gray mold, Botrytis cinerea.
Infected flowers develop tan, papery patches and are often covered with gray, fuzzy masses. Senescing flowers are particularly susceptible. Tan to brown spots with a target-like appearance can also develop on the leaves. These patches are often associated with flowers which have dropped onto the leaf surface.
Good sanitation practices including grooming the plants and removing spent or senescing flowers can minimize the potential for infection. These affected tissues should be carefully removed and discarded when they are dry. It is also important to avoid wetting the flowers when watering and crowding plants. Adequate spacing between the plants can promote good air circulation. Control can also be achieved with the use of fungicide sprays applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut are mancozeb, chlorothalonil, copper sulphate pentahydrate, and thiophanate-methyl. Consult the label for dosage rates, safety precautions, and indoor use.
Whiteflies, Trialeurodes vaporariorum.
The greenhouse whitefly, Trialeurodes vaporariorum, the sweetpotato whitefly, Bemisia tabaci, and silverleaf whitefly, Bemisia argentifolii, commonly infest fuchsia, as well as many other kinds of plants, under glass and are often carried into the field where they may persist on the plants. The life cycles of these species are similar. The tiny, white moth-like adult has a mealy appearance due to the small particles of wax that it secretes. It lays groups of eggs on the underside of leaves. The eggs hatch into small oval crawlers, which then settle down and become scale-like nymphs that suck sap from stationary locations on the leaves. These then spend about 4 days in an immobile pupal stage before becoming adults. About 5 weeks are required to complete the life cycle in the greenhouse.
Yellow sticky traps are an effective way to monitor populations of whiteflies, and may even be attractive enough to reduce minor infestations. Biological controls can also be effective against whiteflies, especially in a greenhouse environment. The predatory ladybeetle, Delphastus pusillus, specializes in whiteflies and feeds on all three whitefly species. The parasitoid, Encarsia formosa, can control the greenhouse whitefly, but not the other species, in the greenhouse. Another parasitoid, Eretmocerus californicus, attacks all three species and can assist in controlling minor infestations in the greenhouse. Insecticidal soap or ultra-fine horticultural oil, which are among the compounds registered for control of this pest in Connecticut, sprayed on the undersides of leaves, can be used against whiteflies in the greenhouse or the field. When applied at a low, half-percent concentration, soap is selectively toxic to whiteflies rather than parasitic wasps. Azadiractin (neem), or fenoxycarb, also directed to the undersides of the leaves, act as insect growth regulators and can also be used. Repeat applications of sprays will probably be needed because some stages in the life cycle are dormant and not affected by insecticides or other sprays. Consult the label for dosage rates and safety precautions. Chemical control using conventional insecticides is difficult because of widespread insecticide resistance. Imidacloprid, applied as a systemic to be taken up by the roots, provides season-long control.
Mealybugs, Planococcus citri.
The common mealybug and probably other species infest fuchsia. White cottony masses appear on leaf surfaces, in leaf axils and sheaths. These insects damage plants by sucking plant sap. Among the compounds registered for control of this pest in Connecticut are insecticidal soap, ultrafine horticultural oil or resmethrin. These products are most effective against crawlers. Because of overlapping life stages in a home environment, multiple applications will be needed to control this pest. Spray needs to contact the insect. Imidacloprid, applied as a systemic to be taken up by the roots, will also provide season-long control. Consult the label for dosage rates and safety precautions.