Plant Health Problems
Diseases caused by Fungi:
Verticillium wilt, Verticillium albo-atrum.
This disease is responsible for the death of many street trees but it can also kill forest trees growing in poor sites. The fungus enters the tree through the roots and spreads throughout the tree. Dark streaks can occasionally be seen in the vascular system by cutting away the bark. Wilting and defoliation are followed by general decline and death of the tree. The fungus may infect susceptible species planted as replacements, and care should be taken to use only resistant trees such as conifers, gingkos, beech, sweet gum, and willows.
Maintaining tree vigor with adequate water during dry seasons and applications of fertilizer in the spring can help the trees resist the pathogen or prolong the life of the tree once it is infected.
Powdery mildews, Microsphaera alni var. vaccini and Phyllactinia guttata.
White or gray powdery appearance of the leaves late in the season results in some foliage damage, but usually does not do serious harm to the tree. This disease is favored by hot, humid weather.
Rake and dispose of fallen leaves to reduce the chance of infection in the following season. Although this disease is widespread and common, it is rarely serious enough to warrant chemical control.
Catalpa leafminer, Agromyza clara.
This leafminer starts a serpentine mine, which later becomes a blotch mine that often involves the entire leaf. Acephate, which is among the compounds registered for use against this pest in Connecticut, can be applied when there are early stage mines. Imidacloprid may be used as a soil-applied systemic to provide season-long control. Abamectin is an effective restricted use product. Consult the labels for dosage rates and safety precautions.
Catalpa sphinx, Ceratomia catalpae.
The caterpillars of this pest grow to 3" long, are yellow and black, and chew leaves. The moth is grayish-brown and has a 3" wingspread. The pupae overwinter in the ground. Malathion, spinosad, and Bacillus thuringiensis var. kurstaki, which are among the compounds registered for use against this pest in Connecticut, sprayed early in May and again in mid-August, will control this pest. Consult the label for dosage rates and safety precautions.
Comstock mealybug, Pseudococcus comstocki.
The whitish powdery deposit in the crevices of the bark in the axils of the twigs and leaf stems and on the underside of the leaves may contain the adult females, nymphs, and eggs, together with abundant wax secretion. There are two or three generations each year, and treatment is often necessary. Good control has followed sprays of malathion, horticultural oil or insecticidal soap, which are among the compounds registered for use against this pest in Connecticut. Imidacloprid may be used as a soil-applied systemic to provide season-long control. Consult the label for dosage rates and safety precautions.