No. 6/June 28, 2019

Modified Growing Degree Days (Base 50⁰ F, March 1 through June 27)
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 below with the degree day accumulations above to determine what insect pests could be active in their area.

Japanese Beetles on Ornamental Plants
They’re back!  Adult Japanese beetles (Popillia japonica) have emerged in Illinois and are beginning to feed on ornamental plants.  Japanese beetle adults have a broad host range, feeding on over 100 plants including linden, buckeye, rose, crabapple, apple, grape, and raspberry.  They may feed on the foliage, flowers, and fruits of their host plants, skeletonizing leaves so only the leaf veins remain.  Beetles tend to feed on and damage the upper portions of plants which can lead to heavy damage in the tops of trees.  In some cases, this means that the damage can go unnoticed by passers-by and may not require treatment.  While the damage can be unsightly, it does not usually result in dieback or the death of the plant.

Turf Weeds with Leaflets of Three
The Weed Gods have blessed us with several similar weedy trifoliate legumes. Then to make it more interesting, they threw oxalis (with its likeness of appearance) into the mix. It’s no wonder so many confuse these species. Fortunately, identification can be fairly simple if you know what to look for. The easiest identifiers are the flowers and leaves. Luckily, some of these are in bloom a little early this year.

Bacterial Leaf Spot on Oakleaf Hydrangea
This year’s frequent rain events have resulted in an abundance of leaf spot diseases. While fungal pathogens cause the majority of these leaf spots diseases, we occasionally see some caused by bacterial pathogens. Oakleaf hydrangeas, in particular, are known to develop leaf spots caused by the bacterial pathogen Xanthomonas campestris.

Hosta Petiole Blight
Hosta Petiole Blight, Hosta Crown Rot, and Southern Blight are common names for a fungal disease caused by Sclerotium rolfsii. Under favorable conditions, the pathogen can rapidly take-over and defoliate an otherwise healthy hosta. This disease is particularly devastating because of the pathogen’s ability to survive in the soil and on the soil surface from several months to years.  A tough, mustard seed-like overwintering structures, known as sclerotia (Image 1), contribute to the pathogen’s long-term survival.

Contaminated Neem Oil Products
On June 20th- The Oregon Department of Agriculture stopped the sale of 6 products containing neem due to pesticide contamination. According to the National Pesticide Information Center- Neem oil is a naturally occurring pesticide found in seeds from the neem tree. It is yellow to brown, has a bitter taste, and a garlic/sulfur smell. It has been used for hundreds of years to control pests and diseases. Neem oil is a mixture of components. Azadirachtin is the most active component for repelling and killing pests and can be extracted from neem oil. The portion left over is called clarified hydrophobic neem oil. The products tested in Oregon found malathion, chlorpyrifos, and permethrins.   These additional pesticides were not on the label and not approved for organic use, and therefore a statewide removal of these products was issued for Oregon.