No. 5/May 26, 2015
Modified Growing Degree Days (Base 50°F, March 1 through May 21)
Insect development is temperature dependent. We can use degree days to help predict insect emergence and activity. Home, Yard, and Garden readers can use the links in this article with the degree day accumulations listed to determine what insect pests could be active in their area.
Illinois Invasive Plant Phenology Report for May 18, 2015
Several invasive plant experts from around the state are continuing their series of reports focusing on the phenology of invasive plants in Illinois. The intent of these reports is to provide an update on the development of invasive plants across the state of Illinois – what plants are in bloom, leafing out, setting seed, or senescing in different areas of the state.
Rhizoctonia on Turfgrass
Brown Patch, a common disease of turf, is caused by the fungus Rhizoctonia solani. It is a warm-season disease which affects the leaf tissue of infected plants. However, there is a much milder cool-weather Rhizoctonia disease called Yellow Patch which bookends summer Brown Patch in the spring and fall. With the cloudy, wet spring in the Midwest, a few samples have shown up at the Plant Clinic.
Witches'-broom of Hackberry
Witches' brooms are diseases known to affect a variety of deciduous and evergreen hosts. They cause a dense clustering of shoots originating from a single point on a stem. A lack of apical dominance essentially causes all the shoots to develop equally. Affected branches have short internodes resulting in broom-like or dense clusters of branches. Depending on the host, the witches' broom may be caused by insects, fungi, viruses, or phytoplasmas.
Periodical cicadas have emerged in southern Illinois. This is a 13-year brood referred to as Marlatt's Brood XXIII or the Lower Mississippi River Valley Brood. This brood touches only small portions of Illinois, emerging in western Kentucky and Tennessee, southeastern Missouri, eastern Arkansas, most of Mississippi, and the eastern half of Louisiana. It emerges in southeastern Illinois in Crawford, Lawrence, and Wabash counties; in southwestern Illinois, in Alexander, Pulaski, Union, Jackson, southeastern Perry, and the western edges of Williamson, Johnson, and Massac counties. This brood emerged in early May and will be present for 6 to 8 weeks.
There are many species of the genus Phyllophaga, also known as true white grubs or May beetles that occur in Illinois. Their larval stage is one of the genera known as white grubs that feed on turfgrass roots. While Japanese beetle, Popillia, and masked chafer, Cyclocephala, larvae or white grubs feed only on the roots of grasses, true white grubs also feed on dead organic matter. For that reason, they are commonly found in flower beds, under dead logs, and in mulch causing no apparent damage.