Spring weather promotes growth of trees, flowers, and lawns, but also spurs many diseases that attack the plants, said a University of Illinois Extension horticulture educator.

"None of these diseases is probably more noticeable and frustrating than shade tree anthracnose," said David Robson. "Anthracnose affects most of the major shade trees. However, while symptoms appear similar, different fungal organisms affect different plants."

Anthracnose thrives and develops when spring temperatures are on the cool side and moisture is adequate. The spring of 2008 has been ideal for this problem. The good news is that while disease symptoms increase as temperatures become warmer, when temperatures move into the 80s consistently the infections become less and less.

"The disease causes spots or lesions on leaves, flowers, twigs, and branches," said Robson. "Lesion colors range from tan to brown to olive green to black. Leaves curl, die, and fall off. Many trees appear defoliated or sparsely leafed out. Symptoms are noticeable during the latter part of May and into June.

"Trees usually affected include ash, birch, catalpa, dogwood, elm, hickory, linden, maple, oak, poplar (including cottonwood and aspen), tulip tree, and walnut."

However, he added, no tree gets hit as much as the sycamore, which has lived with the disease since records have been kept.

"Just looking at sycamore should give the gardener a clue as to the amount of damage to expect on other plants," he said.

In most cases, the disease starts out as small, irregular-shaped spots on the leaf, usually at the leaf margins or tips. Spots enlarge and leaves may curl. The oldest leaves appear infected first, but newer leaves can show symptoms if the weather is ideal.

"The color of the lesions varies," he said. "Dogwood exhibits a dark purple color. Elms show a gray to black color while lindens are light brown with some yellow."

Ash, maple, and sycamores are most often the hardest hit. Ash trees start with tan to brown lesions on the leaflets, usually at the margins or along the veins. Leaves curl, become distorted, and fall.

"Maple infections vary," Robson said. "Japanese maple shoots may turn black and shrivel. Purple or brown streaks develop along the veins of Norway maples, including the 'Crimson King' varieties. Greenish brown to reddish brown spots form between the veins of sugar maples. Spots merge as they get larger and leaves curl."

Sycamore anthracnose appears the most serious, though the trees recover easier than any others. Leaves develop brown lesions along the veins. Entire leaves then turn brown, curl, and fall. Sycamore anthracnose also attacks twigs and young shoots, girdling them, and causing them to die back and drop.

"Trees seldom die as a result of anthracnose," he said. "Most have the ability to produce new sets of leaves. Since environmental conditions are different in June and July, anthracnose fungal spores seldom infect new leaves and twigs.

"However, producing new leaves does limit the tree's growth and reduces the food reserves. Repeated infections over the years can reduce the plant's vigor and make it more susceptible to other disease and insect problems."

Control, Robson noted, is difficult. Protective fungicide sprays are usually too late and too costly to provide any acceptable control except on small trees.

"Sanitation is crucial for good control," he said. "Rake up fallen leaves and branches. Leaves may be composted to kill the disease spores if the compost pile reaches 140 degrees or more."

Trees should be fertilized in the late fall to maintain the plant's vigor. Watering may be necessary throughout the summer to reduce the tree's stress.

"Water thoroughly and deeply as opposed to small amounts daily," he said. "Make sure the tree is mulched with two to four inches of wood chips."

Source: David J. Robson, Extension Educator, Horticulture, drobson@uiuc.edu

Blossom-end rot is a summer disease very common in tomatoes and fruit vegetables such as peppers, eggplant, and sometimes melons and summer squash, said a University of Illinois Extension horticulture educator.

"It is a non-pathogenic disease, a physiological disorder," said Maurice Ogutu. "It is a symptom of calcium deficiency in the fruit. Calcium deficiency may be caused by low soil calcium, low calcium in maturing fruit, or fluctuating soil moisture. It is usually severe following extremes in soil moisture conditions--either too dry or too wet."

Calcium, he explained, is required in large amounts by fruits for normal cell growth. When a rapidly growing fruit is calcium-deficient, normal cell growth is interrupted and the tissues start breaking down. This leaves a characteristic dry, sunken lesion at the blossom end of the fruit.

"Blossom-end rot is induced when calcium demand exceeds supply," he said. "This may come as a result of low calcium levels or competition for calcium uptake with other mineral nutrients in the soil.

"The other factors that can predispose plants to blossom-end rot are very little moisture in the soil caused by drought stress, excessive soil moisture fluctuations which reduce uptake and movement of calcium into the plant, or rapid vegetative growth due to excessive nitrogen fertilization."

In tomatoes, the first visible symptom of this disorder is a small, darkened or water-soaked area around the blossom end of the fruit. The spot darkens, enlarges, and becomes sunken as the fruits mature. Larger lesions may show concentric rings. The affected tissue is leathery and firm unless invaded by secondary decay organisms.

"Blossom-end rot usually causes the fruit to ripen prematurely and it then becomes inedible," Ogutu said. "Sometimes the affected areas become infected with secondary pathogens which appear black on the affected areas. The affected area can be small or may cover most of the fruit.

"Blossom-end rot appears as tan in color in peppers and should not be confused with sunburn that appears whitish in color mainly away from the blossom end. It appears mainly on the first cluster of fruits in tomatoes and peppers."

The disease can be controlled by selecting sites with deep, well-drained soils where plants will develop well-formed root systems for optimal uptake of calcium and other mineral nutrients.

"Test your soil after every three years and lime it if needed," he said. "Avoid use of ammoniacal nitrogen fertilizers such as ammonium nitrate as the ammonium inhibits calcium uptake. Do not overfertilize the plants at planting.

Source: Maurice Ogutu, Extension Educator, Horticulture, ogutu@uiuc.edu

Photo: University of Illinois Extension