Plant Health Care Report August 24, 2012

Tagged as: bur oak blight, downy mildew on impatiens, boxelder bugs, Index, Needle Drop, watering

 

 

Aug 24, 2012                                                                                         Issue 2012.17
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Our report includes up-to-date disease and insect pest reports, as well as color images, for northeastern Illinois. You'll also find a table of accumulated growing degree days throughout Illinois, precipitation, and plant phenology indicators to help predict pest emergence. The report is published bi-weekly on Fridays in April and August, and weekly May-July.

Arboretum staff and volunteers will be scouting for insects and diseases throughout the season.  We will also be including information about other pest and disease problems based on samples brought into the Arboretum's Plant Clinic from homeowners and professionals.

This is our final issue of the season.

If you prefer a PDF version of the PHCR, please click here to download and print.

Quick View

What’s in bloom at the Arboretum? 

Cup plant (Silphium perfoliatum) is in bloom (figure 1).

 

Accumulated Growing Degree Days (Base 50):  2578 (as of Aug 23)
Accumulated Growing Degree Days (Base 30):  5990 (as of Aug 23)

Insects:

• Boxelder bugs

  Figure 1  Cup plant (Silphium perfoliatum)

Diseases:

• Bur oak blight (BOB)
• Downy mildew on impatiens

Miscellaneous:

• Watering into autumn
• Fall needle drop

 

2012 index

 

 

 

 

 

 

 Degree Days and Weather Information

As of Aug 23, we are at 2578 base-50 growing degree days (GDD), which is 355 GDD ₅₀ ahead of 2011 at this time. We have had 1.41 inches of rain so far in Aug and 15.62” for the year (compared to 30.05” last year at this time).

Location	B50 Growing Degree Days Through Aug 23, 2012	Precipitation (in)
Aurora, IL*	2929	--
Carbondale, IL*	3922	--
Champaign, IL*	3315	--
Chicago Botanic Garden**	2652.5 (as of 8/20)	.73 (8/14-20)
Crystal Lake, IL*	2804	--
Harvard, IL*	2746	--
Kankakee, IL*	3073	--
The Morton Arboretum	2578	.81 (8/10-23
Northbrook**	2826 (as of 8/22)	.44 (8/15-21)
O'Hare*	2965	--
Peoria, IL*	3381	--
Quincy, IL*	3639	--
Rockford, IL*	2895	--
Springfield, IL*	3579	--
Waukegan, IL*	2639	--

**Thank you to Mike Brouillard, Northbrook Park District and Mike Annes, Chicago Botanic Garden, for supplying us with this information.

*We obtain most of our degree day information from the GDD Tracker from Michigan State University web site. For additional locations and daily degree days, go to http://www.gddtracker.net/

 

 

Pest updates: insects

Boxelder bugs

Figure 2 Boxelder bug nympn (top) and adult (bottom)

Fall is just around the corner and already the boxelder bugs (figure 2) (Boisea trivittata) are making a return engagement in many homes in the area. The Plant Clinic has already received a few reports of this nuisance pest. These sap-feeding insects feed on sap of seeds, flowers, and leaves of boxelders (Acer negundo). Their feeding causes little damage to the tree. They are considered to be nuisances when large numbers of them appear in homes, especially in fall and spring. Nymphs are bright red when they first hatch, developing black wing pads over time. Adults are about ½ inch long, have three red or orange lines in back of their heads, and have black wings with red lines and a red abdomen. Generations seem to overlap; that is, now we're seeing both adults and nymphs at the same time. Boxelder bugs overwinter as adults in protected sites. Since they consider your house to be a protected site, if you have cracks in your foundation or around your windows, they will enter your house through those cracks in fall to overwinter. They do no harm in the house but are very annoying.

Management: To manage the insect while it is on the boxelder tree, spray the foliage of the tree with carbaryl. As the insects gather on the outside of your home, they can be sprayed with insecticidal soap. Do not use insecticides inside the home. Caulk around doors and window to minimize entry by the insect. Keep screens in good repair. Boxelder bugs that do enter the home can be removed with a vacuum or manually. Do not crush them as they can leave a stain.

Good website: http://ccesuffolk.org/assets/Horticulture-Leaflets/Boxelder-Bug.pdf

 

Pest updates: diseases

Bur oak blight (BOB)

 

The University of Illinois Plant Clinic has confirmed a case of bur oak blight (BOB) in Lake County, Illinois.  There have been isolated cases of this disease previously discovered in Illinois.   This disease has also been seen in Iowa, Wisconsin and Minnesota for at least 6 or 7 years.  It is thought that BOB might have been in those areas for as long as 20 years.   For a full account of the recently confirmed case and photos go to http://hyg.ipm.illinois.edu/article.php?id=420

Good websites: http://na.fs.fed.us/pubs/palerts/bur_oak_blight/bob_print.pdf

http://dnr.wi.gov/topic/UrbanForests/documents/insider/BOB120208.pdf

 

Downy mildew on impatiens

Downy mildew on impatiens (Plasmopara obduscens) is a relatively new disease in our area, showing up in various locations in Illinois and Indiana in the last year and a half. Mike Annes, Plant Health Care Specialist at the Chicago Botanic Garden, reports that they have seen some of this recently in a couple of their impatiens beds, and the plants were defoliated in a few days. This disease seems to be limited to garden impatiens (Impatiens walleriana). New Guinea impatiens seems to be resistant, and the disease does not seem to affect other garden plants.

Now that our weather is starting to change we are seeing conditions that are favorable to this disease: wet foliage, cooler temperatures and moist air. The disease is also promoted by poor air circulation and heavy shade.

There are a number of symptoms associated with this disease including yellowing and downward curling of the leaves, distorted leaves and stunted growth. Eventually a white to light gray downy layer of spores will form on the underside of the leaves. Defoliation can occur.

Management: Although this disease does not seem to affect other garden plants, diseased impatiens (including the roots) should be removed from the garden and destroyed, not composted. There is some concern that the disease organism may over-winter in debris. When planting impatiens, select areas with good air circulation and lighter shade. Avoid over-head watering, especially late in the day when it may be more difficult for leaves to dry off. Inspect plants regularly, especially the undersides of the leaves, for symptoms.

Good websites: http://www.state.nj.us/agriculture/news/hottopics/approved/topics120706.html

http://hyg.ipm.illinois.edu/article.php?id=354

 

Miscellaneous

Watering into autumn

The drought has certainly been a problem this season and we continue to see the effects of it even as we go into autumn. In late summer, we saw some rain come into our area, but we are still several inches below normal at this time. As autumn comes on and the temperatures cool, there is often the assumption that the growing season is over and we can put the garden hose away. That really is not the case, even in a 'normal' year. In a drought year, it is even more important to continue watering into autumn.

With autumn, we will start to see plants go dormant and perennials will even start to die back. The root systems of all are plants are still quite active and watering will help to keep them in good health. You can continue to water until the soil freezes. Pay special attention to evergreens. Since they retain their needles year round, they can continue to lose water. Make sure that all evergreens go into winter fully hydrated. If you are planting bulbs like tulips or daffodils, they will also need to be watered. When bulbs are planted, they need to grow a root system in the fall. That can be difficult to do if the soil is too dry.

 

Other areas that would need special attention are newly seeded or sodded lawns and any newly planted trees, shrubs or perennials.  All these plants will need a good supply of water to help them become established.

If we start to get rain on a regular basis, we will be able to modify our watering practices.  Consider purchasing a rain gauge for your yard so you can accurately determine how much rain you are receiving.  Storms can be deceiving.  A heavy storm may give the impression that a lot of rain fell, but a rain gauge will let you know how much rain really fell.

Fall needle drop

 Coming soon to an evergreen near you:  fall needle drop (also known as normal needle

Figure 3 Normal needle drop (photo credit: Sharon Yiesla)

drop).  In autumn, many evergreens will drop older needles.  This is a normal process.  Needles on an evergreen live for a limited number of years.  At the end of their lives, these needles will turn brown and eventually fall off.  On some evergreens, such as white pine or arborvitae, this process can be very dramatic, making the evergreen look like it is dying.  To determine if your tree has a disease or is going through normal needle drop, check the location of the browning.  Trees going through normal needle drop will have a fairly uniform brown appearance in the interior of the tree (figure 3)  since this is where the oldest needles are located.  After a few weeks the brown needles will fall off leaving the tree looking normal and healthy.  Trees with a disease may have brown needles in various areas of the tree, depending on the disease, but the appearance will not be as uniform as that of needle drop.  Diseased needles may eventually fall off, but the tree won’t look healthy

 2012 index

 

 

Ailanthus webworm ................................... 10, 16

Annual cicadas ................................................ 12

Anthracnose, ash............................................... 4

Anthracnose, birch .......................................... 12

Anthracnose, lily-of-the-valley .......................... 16

Anthracnose, maple........................................... 4

Anthracnose, oak............................................... 4

Anthracnose, sycamore...................................... 7

Anthracnose, walnut ........................................ 11

Aphid, balsam twig ....................................... 5, 11

Aphid, spiny witch hazel ..................................... 4

Aphid, woolly alder....................................... 1, 10

Apple scab......................................................... 8

Article: So what are degree days and why do

 we care about them anyway.............................. 1

Ash-lilac borer ................................................... 3

Aster yellows .................................................. 14

Bacterial blight ……………………………………………………9

Bagworm........................................................ 11

Bald Cypress rust mites .................................... 13

Bedstraw or cleavers ......................................... 6

Black knot ........................................................ 3

Black spot, rose ................................................ 7

Black vine weevil ............................................... 6

Blossom end rot .............................................. 10

Borers ............................................................ 13

Boxelder bugs ................................................. 17

Boxwood psyllid ................................................ 1

Brown rot of stone fruit...................................... 3

Bulls-eye leaf spot ........................................... 12

Bur oak blight (BOB) ........................................ 17

Canker, Botryiosphaeria ................................... 11

Canker, Cytospora ........................................... 13

Canker, Phomopsis .......................................... 14

Canker, Seiridium .............................................. 5

Canker, Thyronectria........................................ 10

Cankerworm...................................................... 2

Carpenter bees ................................................. 4

Cercospora leaf spot .......................................... 7

Chlorosis........................................................... 9

Currant spanworm ............................................ 4

Diplodia tip blight............................................. 10

Downy leaf spot................................................. 6

Downy mildew on impatiens ............................. 17

Drought stress ................................................. 12

Drought tolerant trees ....................................... 9

Dutch elm disease.............................................. 5

Earwigs........................................................... 12

Eastern spruce gall .......................................... 10

Eastern tent caterpillar....................................... 1

Emerald ash borer.............................................. 4

Entomosporium leaf spot ................................. 11

Fall webworm.................................................. 16

Filbert blight.................................................... 12

Four-lined plant bug .......................................... 3

Frog-eye leaf spot ............................................. 4

Gall, ash flower ................................................. 5

Gall, buttonbush .............................................. 14

Gall, erineum..................................................... 3

Gall, fragrant sumac ........................................ 14

Gall, gouty vein gall ........................................... 9

Gall, hackberry nipple......................................... 6

Gall, hedgehog .................................................. 5

Gall, hickory midge............................................. 8

Gall, jumping oak............................................... 8

Gall, maple bladder............................................ 3

Gall, oak apple............................................... 2, 6

Gall, Phylloxera.................................................. 8

Gall, spindle....................................................... 3

Gall, vein pocket................................................ 6

Gall, wool sower leaf......................................... 5

Genista caterpillar ........................................... 11

Grubs in lawns ................................................. 14

Guignardia leaf blotch........................................ 8

Gypsy moth....................................................... 1

Head blight on Silphium .................................... 14

Hemlock rust mite.............................................. 2

Honey locust plant bug................................... 2, 3

Japanese beetles................................................ 9

Juniper webworm.............................................. 1

Larch casebearer............................................... 1

Leafhoppers ..................................................... 8

Leafminer, alder........................................... 3, 11

Leafminer, arborvitae......................................... 3

Leafminer, columbine......................................... 8

Leafminer, elm............................................... 3, 6

Leafminer, hawthorn ......................................... 6

Leafminer, shothole .......................................... 6

Leafroller .........................................................  2

Leafroller, oblique banded ................................. 4

Leaf spots (general) .................................... 13, 15

Lichens ............................................................. 1

Linden looper.................................................... 2

Maple petiole borer ........................................... 8

Measles on peony ............................................. 8

Milkweed bugs ................................................ 13

Milkweed tussock moth ................................... 14

Mulch volcanoes ............................................. 11

Needle drop .................................................... 17

Oak leaf blister............................................... 2, 4

Oak wilt ............................................................ 7

Peach leaf curl.................................................. 2

Pear leaf blister mite ........................................ 13

Pestalotiopsis .................................................... 1

Pesticide recommendations ............................... 5

Physiological yellowing of tuliptree ................... 10

Phytophthora root rot........................................ 5

Pine bark adelgid................................................ 1

Pipevine swallowtail caterpillar........................... 8

Poison Hemlock ................................................ 8

Polyphemus moth caterpillar ............................ 14

Powdery mildew................................................ 7

Red milkweed beetle ....................................... 10

Remontant flowers.......................................... 11

Rhizosphaera needle cast................................... 1

Rose curculio .................................................. 12

Rose rosette...................................................... 3

Rust, buckeye ................................................... 7

Rust, cedar.................................................... 1, 5

Rust, cedar quince............................................. 9

Rust, crown on buckthorn................................... 2

Rust, hollyhock ................................................. 7

Rust, lawn ....................................................... 11

Rust, rose.......................................................... 7

Sawfly, roseslug................................................. 5

Sawfly, European pine........................................ 1

Sawfly, larch ..................................................... 7

Sawfly, oak slug .............................................. 11

Scale, azalea bark .............................................. 4

Scale, euonymus ............................................... 9

Scale, European elm .......................................... 2

Scale, juniper .................................................... 3

Scale, Lecanium................................................. 8

Scale, magnolia ............................................... 12

Scale, pine needle ............................................ 11

Scorch, abiotic and bacterial............................. 12

Seed crops, heavy ............................................. 2

Septoria leaf spot............................................. 14

Slime mold ...................................................... 13

Slugs................................................................. 4

Smooth patch ................................................. 15

Sooty mold...................................................... 12

Spider mites, spruce .......................................... 2

Spiny elm caterpillar ........................................ 11

Spittle bug......................................................... 3

Squirrel damage .............................................. 10

Stinkbugs......................................................... 10

Strange winter and spring .................................. 1

Sycamore lace bug........................................... 10

Tachinid fly ..................................................... 16

Taphrina fungus ................................................ 2

Tarnished plant bug............................................ 7

Tar spot of maple ............................................ 12

Thrips................................................................ 7

Tortoise beetle ................................................ 14

Treehopper, two-marked ................................... 6

Tree selection ................................................. 15

Tremella mesenterica ........................................ 4

Twig pruners and girdlers ................................. 15

Two-spotted spider mites................................. 13

Viburnum leaf beetle ....................................... 13

Virus ...................................................... .6, 9, 14

Watering ................................................. 5, 9, 17

Weevil, European elm flea ................................. 2

Witches broom ................................................. 8

Zimmerman pine moth....................................... 1

 

 

________________________________________

The Plant Health Care Report is prepared by Sharon Yiesla, M.S., Plant Clinic Assistant and edited by Stephanie Adams, M.S. Research Specialist (Plant Heath Care); Fredric Miller, Ph.D., research entomologist at The Morton Arboretum and professor at Joliet Junior College; Doris Taylor, Plant Information Specialist, and Carol Belshaw, an Arboretum Volunteer. The information presented is believed to be accurate, but the authors provide no guarantee and will not be held liable for consequences of actions taken based on the information.

Thank you...I would like to thank the volunteers that scout for us and who found most of the insects and diseases that are in this report. The Scouting Volunteers include: Davida Kalina, Ann Klinglele, LeeAnn Cosper, Bill Sheahan, Kathy Stephens, and Loraine Miranda. Your hard work is appreciated. Thanks also to Donna Danielson, who teaches at The Morton Arboretum and shares her findings when she scouts for her classes.

Literature recommendation:

Indicator plants are chosen because of work done by Donald A. Orton, which is published in the book Coincide, The Orton System of Pest and Disease Management. This book may be purchased through the publisher at: http://www.laborofloveconservatory.com/

 

The 2010 Commercial Landscape & Turfgrass Pest Management Handbook, for commercial applicators, and the 2012 Pest Management for the Home Landscape for homeowners from the University of Illinois, are available by calling (800-345-6087).

This report is available on-line at The Morton Arboretum website at http://www.mortonarb.org/tree-plant-advice.html

For pest and disease questions, please contact the Plant Clinic at (630) 719-2424 between 10:00 and 4:00 Mondays through Saturdays or email This e-mail address is being protected from spambots. You need JavaScript enabled to view it . Inquiries or comments about the PHC reports should be directed to Sharon Yiesla at This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Copyright © 2012 The Morton Arboretum

Not printed on recycled paper, or any paper for that matter.

 

 

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