No. 13/August 3, 2015

Aster Yellows
Aster Yellows is a disease commonly found on members of the Asteraceae (Compositae) family, including Aster, Chrysanthemum, marigold (Tagetes), Zinnia and coneflowers (Echinacea). However, you can find the disease on other plants such as carrots and onions.

Rusts on Apple and Hawthorn
We're finally seeing some beautiful weather for this time of year, with days full of sunshine and moderate temperatures. We're not the only ones enjoying the outdoors; we share it with animals, insects, plants, and of course, plant pathogens. One common problem that's rearing its ugly head is rust on apple trees and hawthorns.

Tubakia Leaf Spot
Tubakia leaf spot has been observed on many oak samples this year. The disease is caused by the fungal pathogen, Tubakia dryina. All oak species are susceptible to this disease, but those within the red oak group are more commonly affected. This leaf spot is often associated with stressed trees, especially pin oaks with symptoms of iron chlorosis. Other potential hosts include maple, hickory, chestnut, redbud, ash, black tupelo, sourwood, sassafras and elm.

Emerald Ash Borer
Emerald ash borer has been found in white fringetree in northern Illinois. Research conducted by Don Cipollini, Wright State University, Dayton, OH found characteristic exit holes, larval tunneling damage, or other symptoms in 7 of the 16 white fringetrees, Chionanthus virginicus, inspected at the Morton Arboretum on May 29, 2015. Dr. Cipollini conducted previous research in Ohio that proved by taxonomic examination and DNA analysis that emerald ash borer is able to infest and complete its life cycle in white fringetree.

White Grubs
Populations of adult Japanese beetle continue to be light in most of Illinois. Although leaf feeding damage on linden, crabapple, rose, and other trees and shrubs is obvious in some areas, the amount of damage is less than in most years and not as widespread.