Plant Health Problems
Diseases caused by Fungi:
Leaf spots, Cercospora, Phyllosticta.
These diseases are recognized as spots of dead tissue scattered over the leaf surface. Most have distinct margins but the size, shape, and color can vary. Several fungi cause leaf spots although they are usually not serious except during periods of extended leaf wetness and humidity. Some defoliation can occur when infection is heavy.
Leaf spots can be managed by raking and removing fallen leaves to eliminate the source of overwintering inoculum and by maximizing plant vigor by following good cultural practices. Although usually not necessary, control can also be achieved with the use of fungicide sprays applied when new growth emerges in the spring. Several applications may be necessary, especially when wet weather persists. Among the compounds registered for use in Connecticut are chlorothalonil and thiophanate-methyl. Consult the label for dosage rates and safety precautions.
Powdery mildew, Erysiphe, Microsphaera.
White powdery spots or patches develop on the leaves, usually during mid- to late summer. Leaves are usually not obviously curled or deformed and although some defoliation can occur, this disease is not considered a serious problem.
Disease can be minimized by carefully picking off affected leaves as soon as symptoms are evident and by raking and removing fallen leaves to reduce the amount of overwintering inoculum. This disease is generally not serious enough to warrant chemical control although fungicide sprays can be applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut are potassium bicarbonate, thiophanate methyl, and sulfur. Consult the label for dosage rates and safety precautions.
Planthoppers, Metcalfa pruinosa and Anormensis septentrionalis.
These sucking insects damage plants as adults and nymphs. The green nymphs do not do much damage but cover themselves with white cottony strands, which makes them very noticeable. Grayish-black, 1/4 to 1/3" (6-8 mm) long females lay eggs singly inside twigs of host plants where they overwinter. In the spring, after hatching, the nymphs feed on developing leaves and shoots. Control is seldom necessary.
Occasionally, the olive parlatoria scale infests trumpetvine. If control is needed, ultrafine horticultural oil can be applied in late winter or during the growing season; malathion can also be applied during the growing season. Both products are registered for use against this pest in Connecticut. Consult the label for dosage rates and safety precautions.
If conditions are right, whitefly may become a problem on trumpetvine. The greenhouse whitefly,Trialeurodes vaporariorum, the sweetpotato whitefly, Bemisia tabaci, and silverleaf whitefly, Bemisia argentifolii, commonly infest many kinds of greenhouse-grown plants, which subsequently are often carried into the field where they may persist. 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 on the undersides of leaves and become scale-like. These insects 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. 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. Azadiractin (neem), also directed to the undersides of the leaves, 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. Chemical control using conventional insecticides is difficult because of widespread insecticide resistance. Season-long control can be achieved with imidacloprid applied as a systemic taken up by the roots. Consult the label for dosage rates and safety precautions.