Fungal Diseases of Plants

Taphrina Leaf Curl

• Taphrina leaf curl, also referred to as oak leaf blister, is caused by the Taphrina group of fungi. The disease is more prevalent during wet weather and the fungi are likely to affect a wide range of tree species. Taphrina leaf curl is characterized by the appearance of galls, or raised plant tissue areas, on the foliage, accompanied with leaf curling and dropping. The upper surfaces of the foliage also start to bulge. Taphrina leaf curl is best managed by ensuring that trees and plants are in vigorous health by ensuring adequate watering and fertilizing. Weaker plants are most susceptible to a number of diseases.

Rots

• The fungi from the Phytophthora group are likely to cause rotting plant crowns and roots. Symptoms of Phytophthora rot include wilting and discoloration of foliage. The leaves are stunted in growth and start to fall prematurely. Trunks of infected trees often display vertical cankers, streaks or stains. Inspection reveals dark gray or light brown discoloration on trunk wood under the bark. There is often a red or black secretion from the infected bark area. As the disease progresses, the entire plant health is affected with branch and twig dieback and eventual death. Management includes improving drainage in poorly drained sites. Avoid planting in compacted soil, and use resistant varieties in areas with known cases of Phytophthora.

Scab

• Scab is caused by the Spilocaea and Venturia group of fungi. The diseases have a wide range of potential host plants. Spilocaea most commonly infects pear and apple trees, while the Venturia fungi frequently invades cypress, poplar, cotoneaster and willow trees. The presences of scab is characterized by the appearance of round, black, scab-like or velvety spots on foliage. As the disease progresses, the spots turn yellow or red and there is premature leaf drop. The spots, shriveled and cracked, also appear on the fruit of fruit trees. Management includes pruning and disposal of all infected tree areas. Chemical control options includes weekly applications of sulfur and Bordeaux mixtures. Keep plants in good health for better disease resistance.