No. 15/September 7, 2016
Tubakia Leaf Spot
Tubakia leaf spot was briefly mentioned in the last issue. We continue to receive samples infected with this disease. 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.
White Mold (AKA Southern Blight)
The common fungal pathogen Athelia rolfsii (syn. Sclerotium rolfsii) causes a basal rot to stems and petioles of herbaceous plants. We've seen a few samples of hosta and anemone infected with this disease so far this year.
We have reports of white grub infestations throughout the state. Most of these appear to be Japanese beetle grubs as their numbers have rebounded from being severely reduced by the droughts of 2012 and 2013, and the severe winter that followed. Thanks to Harold Enger of Spring-Green, and others that provided information.
Emerald Ash Borer
Emerald ash borer continues to spread through the state. Several months ago, the Illinois Department of Agriculture (IDA) deregulated the insect, lifting restrictions on movement of firewood and other materials that might contain emerald ash borer within the state due to it being widespread in Illinois.
Woolly aphids typically feed on two hosts during a 1-year period, with most species apparently having to switch hosts. This host-switching occurs in various species from late June to late July, and fuzzy adult females that look like flying lint seemingly drifting on the wind are their means of getting to the other host.