No. 7/June 5, 2012
Based on degree day base 50 degrees F, we still about three weeks ahead of schedule in southern Illinois, two to two and one-half weeks ahead in central Illinois, and two weeks ahead in northern Illinois. As described in earlier issues of this newsletter, most insect development proceeds at temperatures above approximately 50 degrees F. Bagworms and jumping oak galls are discussed.
Japanese beetle adults have emerged in southern Illinois, with reports of them being seen during the past week in Massac, Fayette, Madison, Jackson, and Effingham Counties. Thanks to Ron Hines, Robert Bellm, Steve Wunderle, and Kevin Black for their reports. They will probably emerge in central Illinois by June 10.
Hollyhock rust (Puccinia malvacearum)
Various Rust fungi infect a wide range of plant hosts. Hollyhock is commonly a host to the fungal rust Puccinia malvacearum. This rust pathogen is classified as an autoecious fungi, meaning the spore stages require only one host. Puccinia malvacearum is known to also infect several species of the mallow family (Malvaceae), which includes the common or roundleaf mallow (Malva rotundifolia), a common weed. Common mallow can act as a temporary site for the rust spore to reside before it infects hollyhock.
Reversion is a term used to describe when a cultivar, known for a particular leaf shape, color, or other characteristic, 'reverts' back to a different form found in the plant's parentage. The term is often used to describe a variegated shrub or tree that produces non-variegated shoots.
Poison Hemlock - Beautifully Poisonous
The ditches and roadsides of Central Illinois are showy right now with the white flowers of Poison hemlock (Conium maculatum). This plant is found statewide however in dense stands, and has been in greater abundance in recent years earning a spot on both a factsheet and a poster featuring exotic, invasive plants in Illinois habitats. This biennial is native to Europe, Western Asia, and Northern Africa and is commonly found in disturbed soils, pastures, meadows, roadsides, and along pond edges. Poison hemlock tends to prefer moist soils but can tolerate drier sites; it grows well in full sun or part shade.